Baron Services DSSR-250C Pulsar Digital Solid-State Radar System User Manual

Baron Services Inc Pulsar Digital Solid-State Radar System

TTY Nonvolatile Setups

RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–13. TTY Nonvolatile SetupsThe RVP8 provides an interactive setup menu that can be accessed either from a serial TTY, orfrom the host computer interface. Most of the RVP8’s operating parameters can be viewed andmodified with this menu, and the settings can be saved in non-volatile RAM so that they takeeffect immediately on start-up. This permits custom trigger patterns, pulsewidth control,matched FIR filter specs, PRF, etc., to be configured by the user in the field.The TTY menu also gives access to a collection of graphical setup and monitoring proceduresthat use an ordinary oscilloscope as a synthesized visual display. The burst pulse and receiverwaveforms can be examined in detail (both in the time and frequency domain) and the digitalFIR filter can be designed interactively to match the characteristics of the transmitted pulse.3.1 Overview of Setup ProceduresThis section describes basic operations within the setup menus such as making TTY connections,entering and exiting the menus, and saving and restoring the configurations.The setup TTY menu can be accessed by executing the following command:$dspxYou will then be prompted by the following:$dspxDigital Signal Processor ’Chat’Checking for code upgrades...Okay(Type ^C to exit Chat Mode)The interactive setup menu is invoked by pressing the Escape key on the TTY. If that key cannot be found on the keyboard, you can sometimes use Control “[” to generate the ESC code.The RVP8 then responds with the following banner and command prompt. SIGMET Incorporated, USARVP8 Digital IF Signal Processor V3.9(Pol) IRIS 8.03.6––––––––––––––––––––––––––––––––––––––––––––––––––––––RVP8>The banner identifies the RVP8 product, and displays the RVP8 software version (e.g., V3.9)and IRIS software version (e.g., IRIS 8.03.6). This information is important whenever RVP8support is required, and it is also repeated in the printout of the “V” command (See below).The “Q” command is used to exit from the menus and to reload the RVP8 with the (possiblychanged) set of current values. It is important to quit from the menus before attempting toresume normal RVP8 operation. Portions of the RVP8 command interpreter remain runningwhile the menus are active (so that the TTYOP command works properly), but the processor as awhole will not function until the menus are exited.From the command prompt, typing “help” or “?” gives the following list of availablecommands.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–2Command List: F: Use Factory Defaults S: Save Current Settings R: Restore Saved Settings M: Modify/View Current Settings Mb – Burst Pulse and AFC Mc – Overall Configuration Mf – Clutter Filters Mp – Processing Options Mt<n> – Trigger/Timing <for PW n> Mz – Transmissions and Modulations M+ – Debug Options P: Plot with Oscilloscope Pb – Burst Pulse Timing Ps – Burst Spectra and AFC Pr – Receiver Waveforms P+ – Visual Test Pattern V: View Card and System Status ?: Print all Menu Commands (this list)?? – Print all Current Setup Settings *: Sample Receiver Noise Levels @: Display/Change the Current Major Mode ~: Swap Burst/IF Inputs on IFD Q: Quit3.1.1 Factory, Saved, and Current SettingsThe current settings are the collection of setup values with which the RVP8 is presentlyoperating; the saved settings are the collection of values stored in non-volatile RAM. The savedsettings are restored (made current) each time the RVP8 starts. The “S” command saves thecurrent settings into the non-volatile RAM, and the “R” command restores those non-volatilevalues so that they become the current settings. The “F” command initializes the current settingswith factory default values. Thus, “F” followed by “S” saves factory defaults in non-volatileRAM, so that the RVP8 powers up in its original configuration as shipped.The RVP8 retains all of its saved settings when new software releases are installed; the newversion of code will automatically use all of the previous saved values. However, if the RVP8detects that the new release requires a setup parameter that did not exist in the previous release,then a factory default value will automatically be filled in for that parameter. A warning isprinted whenever this occurs (See also, Section 3.1.2).There is also support for intermediate minor releases of RVP8 code. Each software release has amajor version number (the one that it always had), plus a minor version number for intermediate”unofficial” releases. The minor number starts from zero at the time of each ”official” release,and then increments until the next ”official” release. The RVP8 includes the minor releasenumber (if it is not zero) in the printout of the ”V” command. Likewise, the minor release
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–3number of the code that was last saved in the nonvolatile RAM is also shown. This is animprovement over having to check the date of the code to determine which minor release wasrunning.Note that the RVP8 does not actually begin using the current settings until after the “Q”command is entered, so that the processor exits the TTY setup mode and returns to normaloperation.3.1.2 V — View Card and System StatusThe “V” command displays internal diagnostics. This information is for inspection only, andcan not be changed from the TTY. The view listing begins with the banner:Configuration and Internal Status–––––––––––––––––––––––––––and then prints the following lines:RVP8 Digital IF Signal Processor V3.10(Pol) IRIS–8.04This line shows the revision level of the RVP8 software, the IRIS version.Settings were last saved using V3.10This line tells which version of RVP8 code was the last to write into the non-volatileRAM. It is printed only if that last version was different from the version that iscurrently running. The information is included so that a “smart upgrade” can oftenbe done, i.e., values that did not exist in the prior release can be filled in with a guessthat is better than merely taking the factory default.RVP8 started at: 13:07:33 3 NOV 2003Current time is: 13:14:03 3 NOV 2003These lines provide information about when the RVP8 was started, the current systemtime, and implicitly, the uptime.CPU–Type: Pentium(R) IIIThis line displays processor information.IPP–Library: ippsa6 v2.0 gold SP1 2.0.6.39This line displays information about the Intel libraries used for RVP8 processing.Physical hardware inventory: Found PCI Card RVP8/Rx – Rev.A Serial:1628 Code:14(/dev/rda/rvp8rx–1) Found PCI Card RVP8/Tx – Rev.B Serial:1887 Code:9(/dev/rda/rvp8tx–0) Found PCI Card I/O–62 – Rev.B Serial:1841 Code:19(/dev/rda/io62–0) \––> IO62CP Backpanel – Rev.B Serial:1822 Code:3The physical hardware inventory provides information about the system hardwarebeing used by the RVP8. This list ONLY displays hardware that is being used, not allhardware in the system (i.e., an RCP8 could be present in the same chasis, but theRCP8 hardware would not be included in this list).
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–4Diagnostics: PASSIf errors were detected by the startup diagnostics then an error bitmask will be shownon the first line. The word “PASS” indicates that no errors were detected.Processes and Threads: RVP8Proc–0 – PID:28503 Priority:10 Policy:RealTimeRRThe “Process and Threads” list displays RVP8 processes and their related priority.All RVP8 processes/threads should be running under RealTimeRR policy toguarantee adequate attention from the processors.Shared library build dates:This section provides RVP8 developers with information about code resources.Front panel display: +––––––––––––––––––––––+ | 0.00 AZ/EL 0.00 | | FFT 100B 1000Hz x1 | +––––––––––––––––––––––+The front panel display mirrors the display on the front of the RVP8 chasis. This ishelpful if you are at a remote location using DspExport.Tx/Clk:Okay TrigRAM is 99.0% free, TrigCount:378921The Tx/Clk field displays information about the RVP8/Tx clock (if applicable).TrigRAM provides resource information for those who are implementing customwaveforms.IFD:Okay Link: Delay = 0.541 usec, Jitter = 0.014 usecThis first section of this line summarizes the receiver status and Burst input signalparameters. The status may show:Okay RVP8/IFD and connecting cables are all working properlyDnErr Problem in DownLink connection from RVP8/IFD ––> RVP8UpErr Problem in UpLink connection from RVP8 ––> RVP8/IFDNoPLL RVP8/IFD PLL is not locked to external user-supplied clock referenceDiagSW RVP8/IFD test switches are not in their normal operating positionThe section second describes the IFD link status. During startup the RVP8 measuresthe round trip delay along 1) the uplink to the receiver module, 2) the pipeline delayswithin the receiver module, 3) the downlink, and 4) pipeline delays in the datadecoding hardware. The time shown is accurate to within 14ns, and is used internallyto insure that the absolute calibration of trigger and burst pulse timing remainsunaffected by the distance between the main card and the receiver module. You mayfreely splice any lengths of cable without affecting the calibrations; the delay timewill change, but the trigger and burst calibrations will remain constant.The standard deviation of the measured delay is also shown. If the link to the IFD isworking properly this variation should be less than half the period of its acquisitionclock. Larger errors may indicate a problem in the cabling. A diagnostic error bit isset if the error is greater than two acquisition clock periods.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–5AFC:0.00% (Disabled), Burst Pwr:–48.6 dBm, Freq:30.000 MHzAFC indicates the level and status of the AFC voltage at the RVP8/IFD module. Thenumber is the present output level in D-Units ranging from –100 to +100. Theshorter “%” symbol is used since percentage units correspond in a natural way to theD-Units.Burst Pwr indicates the mean power within the full window of burst samples. DCoffsets in the A/D converter do not affect the computation of the power, i.e., the valueshown truly represents the waveform’s (Signal+Noise) energy. Freq indicates themean frequency of the burst, derived from a 4th order correlation model.For more information refer to Chapter 4.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–63.2 View/Modify DialogsThe M menu may be used to view, and optionally to modify, all of the current settings. Thecurrent value of each parameter is printed on the screen, and the TTY pauses for input at the endof the line. Pressing Return advances to the next parameter, leaving the present one unchanged.You may also type U to move back up in the list, and Q to exit from the list at any time.Typing a numeric or YES/NO response (as appropriate to the parameter) changes theparameter’s value, and displays the line again with the new value. All numbers are entered inbase ten, and may include a decimal point and minus sign. In some cases, several parameters aredisplayed on one line, in which case, as many parameters are changed as there are new valuesentered. In all cases, the numbers are checked to be within reasonable bounds, and an errormessage (listing those bounds) is printed if the limits are exceeded. Note that changes to thesettings (generally) do not take effect until after the Q command is typed, at which point theRVP8 exits the local TTY menu and resumes its normal processing operations.The M menu provides access to a large number of configuration settings. As a result, all of theM menu commands begin with the letter “M” and are followed by a lower case letter whichrepresents a subcategory, i.e., Mb (Burst Pulse and AFC), Mc (Overall Configuration), Mf(Clutter Filters), Mp (Processing Options), Mt (Triggers and Timing), Mz (Transmissions andModulations), M+ (Debug Options). The ?? command by itself prints the entire set ofquestions so that you can make a hard copy.The M menu always works from the current parameter values, not from the saved values innon-volatile RAM. If the host computer has modified some of the current values, then you willsee these changes as you skip through the setup list. However, typing S at that point would saveall of the current settings and would, perhaps, make many changes to the original non-volatilesettings. In general, to make an incremental change to the saved settings, first type R to restoreall of the saved values, then use the M menu to make the changes starting from that point, and Sto save the new values.A listing of the parameters that can be viewed and modified with the M menu is detailed in thefollowing subsections. In each case, the line of text is shown exactly as it appears on the TTYwith the factory default settings. A definition of each parameter is given and, if applicable, thelower and upper numeric bounds are shown.3.2.1 Mc — Top Level ConfigurationThis set of commands configure general properties of the RVP8/IFD and RVP8 cards.Acquisition clock: 35.9751 MHzThis is the frequency of the acqusition sampling clock in the IFD module. This willgenerally be in the 72MHz range for the RVP8 CAT-5E IFD, and in the 36MHz rangefor the legacy RVP7 IFD. If you are locking the IFD to an external reference, thecenter frequency of the installed VCXO is entered (see section 2.2.12).Limits: 33.33 to 80 MHz
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–7Live Angle Input – 0:None, 1:Sim, 2:TAGS, 3:S/D : 2This setting is used to configure the input of live angles. In most situations, theangles will be coming in from the RCP via TAGS. The S/D option provides directconversion of 3–wire synchro waveforms for the AZ and EL position angles. Youmay directly hookup AZ/EL synchros to the 12–pin input connector on teh IO–62standard backpanel when you choose S/D.Primary RVP8/Rx PCI Card (–1:None) : 0This setting configures which RVP8/Rx card will be used by the RVP8.Primary RVP8/Tx PCI Card (–1:None) : –1This setting configures which RVP8/Tx card will be used by the RVP8.Primary I/0–62 PCI Card (–1:None : 0Run I/0–62 external line powerup tests:NOThis setting configures which RVP8/Rx card will be used by the RVP8. The I/O–62external line powerup tests are used for debugging the backpanel and should beturned off during normal operation. When enabled, the backpanel receives a spreadof signals which could cause problems in an operational environment (.i.e. firing ofthe transmitter).Provide IRIS RPC network status server: NOThe default value is NO in order to reduce network security concerns. Whenenabled, it opens up a network port.PWINFO command enabled: NoThe “Pulsewidth Information” user interface command can be disabled, thus furtherprotecting the radar against inappropriate combinations of pulsewidth and PRF. Thisis a more safe setting in general, and is even more important when DPRT triggers arebeing generated. It can also be useful when running user code that is not yet fullydebugged.TRIGWF command enabled: NOThe “Trigger Waveform” user interface command can be disabled if you want toprevent the host computer from overwriting the RVP8’s stored trigger specifications.This is the default setting, based on the assumption that the built-in plottingcommands would be used to configure the triggers. Answering “YES” will allownew waveforms to be loaded from the host computer.Fundamental RVP8 Operating Mode: 0The RVP8/IFD and RVP8/Rx cards can operate in one of several fundamental modesfor the acquisition of (I,Q) timeseries data. Please see Section 5.1.2 for details.Important: The receiver mode is chosen in the “Mc” menu, but changes do nottake effect until they are saved and the RVP8 is restarted.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–83.2.2 Mp — Processing OptionsWindow- 0:User, 1:Rect, 2:Hamming, 3:Blackman : 0Whenever power spectra are computed by the RVP8, the time series data aremultiplied by a (real) window prior to computation of the Fourier Transform. Youmay use whichever window has been selected via SOPRM word #10, or force aparticular window to be used.R2 Processing- 0:Never, 1:User, 2:Always : 1Controls R0/R1 versus R0/R1/R2 processing. Selecting ”0” unconditionally disablesthe R2 algorithms, regardless of what the host computer requests in the SOPRMcommand. Likewise, selecting ”2” unconditionally enables R2 processing. Thesechoices allow the RVP8 to run one way or the other without having to rewrite theuser code. This is useful for compatibility with existing applications.Clutter Microsuppression- 0:Never, 1:User, 2:Always : 1Controls whether individual “cluttery” bins are rejected prior to being averaged inrange. Same interpretation of cases as for ”R2 Processing” above.2D Final Speckle/Unfold – 0:Never, 1:User, 2:Always : 1The Doppler parameter modes (PPP, DFT, etc) include an optional 3x3 interpolationand speckle removal filter that is applied to the final output rays. This 2-dimensionalfilter examines three adjacent range bins from three successive rays in order to assigna value to the center point. Thus, for each output point, its eight neighboring bins inrange and time are available to the filter. Only the dBZ,dBT,Vel, and Width data arecandidates for this filtering step; all other parameters are processed using the normal1-dimensional (three bins in range) speckle remover. See Section 5.3.3 for moredetails.Unfold Velocity (Vh–Vl) – 0:Never, 1:User, 2:Always : 0This question allows you to choose whether the RVP8 will unfold velocities using asimple (Vhigh – Vlow) algorithm, rather than the standard algorithm described inSection 5.6. Bit-11 of SOPPRM word #10 is the host computer’s interface to thisfunction when the “1:User” case is selected (See Section 6.3).Note: This setup question is included for research customers only. The standardunfolding algorithm should still be used in all operational systems because of itslower variance. For this reason, the factory default value of this parameter is“0:Never”.Process w/ custom trigs – 0:Never, 1:User, 2:Always : 0This question allows you to choose whether the RVP8 will attempt to run its standardprocessing algorithms even when a custom trigger pattern has been selected via theSETPWF command. Generally it does not make sense to do this, so the defaultsetting is “0:Never”. Bit-12 of OPPRM word #10 is the host computer’s interface tothis function when the “1:User” case is selected (See Section 6.3).Use High–SNR 16–bit packed timeseries format: YesThis parameter provides an additional 6dB of SNR. It can be disabled to providecompatibility with legacy systems.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–9Minimum freerunning ray holdoff: 100% of dwellThis parameter controls the rate at which the RVP8 processes free-running rays. Thisprevents rays from being produced at the full CPU limit or I/O limit of the processor(whichever was slower); which could result in highly overlapping data being outputat an unusably fast rate. Note that this behavior will only occur when runningwithout angle syncing, such as during IRIS Manual and RHI scans.To make these free-running modes more useful, you may establish a minimumholdoff between successive rays, expressed as a percentage of the number of pulsescontributing to each ray. Choosing 100% (the default) will produce rays whose inputdata do not overlap at all, i.e., whose rate will be exactly the PRF divided by thesample size. Choosing 0% will give the unregulated behavior in which no minimumoverlap is enforced and rays may be produced very quickly.Limits: 0 to 100%Linearized saturation headroom: 4.0 dBThe RVP8 uses a statistical saturation algorithm that estimates the real signal powercorrectly even when the IF receiver is overdriven (i.e., for input power levels above+4dBm). The algorithm works quite well in extending the headroom above the topend of the A/D converter, although the accuracy decreases as the overdrive becomesmore severe. This parameter allows you to place an upper bound on the maximumextrapolation that will ever be applied. Choosing 0dB will disable the algorithmentirely.Limits: 0 to 5dBApply amplitude correction based on Burst/COHO: YES Time constant of mean amplitude estimator: 70 pulsesThe RVP8 can perform pulse-to-pulse amplitude correction of the digital (I,Q) datastream based on the amplitude of the Burst/COHO input. Please see Section 5.1.7 fora complete discussion of this feature.Limits: 10 to 500 pulsesIFD built–in noise dither source: –57.0dBmThis question will only appear if the processor is attached to a Rev.D RVP8/IFD thatincludes an out-of-band noise generator to supply dither power for the A/Dconverters. The available power levels are { Off, –57dBm, –37dBm, –32dBm,–27dBm, –22dBm, –19dBm }. The closest available level to your typed-in value willbe used. You can observe the band-limited noise easily in the Pr plot to confirm itsamplitude and spectral properties.For standard operation, we recommend running at –57dBm. The problem higherlevels of dither level is that, for certain choices of (I,Q) FIR filter, the stopband of thefilter may not give enough attenuation to preserve the RVP8/IFD’s inherent noiselevel. For example, the factory default 1MHz bandwidth Hamming filter has astopband attenuation near DC of approximately 43dB. You can see this graphically atthe right edge of the Ps menu. The in-band contribution of dither power is thereforeapproximately (–37dBm) – 43dB = –80dBm, which exceeds the A/D converter’s1MHz bandwidth noise of –81.5dBm.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–10IFD Wide Dynamic Range Parameters Channel separation: 20.00 dB, 0.0 deg Maximum deviation : 0.50 dB, 5.0 deg Overlap/Interpolate interval: 30.00 dBThe Channel Separation and Overlap/Interpolate Interval should be determinedfrom the Pr printout described below. Sweep a SigGen across the shared powerregion of the two channels to determine a representative channel separation, alongwith the size of the overlap region at the top of the HiGain channel within which thatseparation remains steady and constant, i.e., unaffected by eventually approaching thenoise floor of the LoGain channel.The RVP8 continually measures and updates the complex channel separation duringnormal operation. Ratios of echoes that fall within the overlap/interpolate intervalare averaged over several minutes, thereby tracking gain and phase variations thatoccur with temperature changes and component aging. If the channel separation everexceeds the specified maximum deviation, the GI4S_IFDCHANERR bit (11) will beset in GPARM Immediate Status Word #4.TAG bits to invert AZ:0000 EL:0000TAG scale factors AZ:1.0000 EL:1.0000TAG offsets (degrees) AZ:0.00 EL:0.00The incoming TAG input bits may be selectively inverted via each of the 16-bitwords. The values are displayed in Hex. Setting a bit will cause the correspondingAZ (bits 0–15) or EL (bits 16–31) lines to be inverted. Note that the SOPRMcommand also specifies TAG bits to invert. Both specifications are XOR’ed togetherto yield the net inversion for each TAG line.The overall operations are performed in the order listed. Incoming bits are firstinverted according to the two 16-bit XOR masks. This yields an unsigned 16-bitinteger value which is then multiplied by the signed scale factor. The result isinterpreted as a 16-bit binary angle (in the low sixteen bits), to which the offset angleis finally added.As an example, suppose that the elevation angle input to the RVP8 was in anawkward form such as unsigned integer tenths of degrees, i.e., 0x0000 for zerodegrees, 0x000a for one degree, 0x0e06 for minus one degree, etc. If we apply ascale factor of 65536/3600 = 18.2044 to these units, we will get 16-bit binary anglesin the standard format. If we further suppose that the input angle rotated“backwards”, we could take care of this too using a multiplier of –18.2044.Interference Filter – 0:None, Alg.1, Alg.2, Alg.3: 1 Threshold parameter C1: 10.00 dB Threshold parameter C2: 12.00 dBThe RVP8 can optionally apply an interference filter to remove impulsive-type noisefrom the demodulated (I,Q) data stream. See Section 5.1.5 for a complete descriptionof this family of algorithms.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–11Provide WSR88D legacy BATCH major mode: YES Maximum range to unfold: 600.0 km Low–PRF bins range averaged on each side: 2 Overlay power – Refl:5.0dB Vel:8.0dB Width:12.0db LowSamps = ( 0.00000 x HiSamps ) + 6.00 : LowPRF = ( 0.00000 x HiPRF ) + 250.00 :This is actually a fully general implementation of a Lo/Hi Surveillance/Doppler PRF unfoldingscheme that provides all of the legacy features as special cases. The parameters are defined asfollows:SThe maximum range to unfold is given in km. This allows you to set an upper bound onhow many Doppler trips will be unfolded according to the echoes seen in the surveillancedata.SThe surveillance data set uses very few pulses and therefore is somewhat noisy. You maychoose the number of bins that will be range averaged from both sides of these bins toprovide a lower variance power estimate. A value of zero means “No averaging”, avalue of one would average three points total, etc.SThe unfolding algorithm flags obscured range bins according to three different powerthresholds for reflectivity, velocity, and width, and outputs these bits in the DB_FLAGSdata parameter. Each of these thresholds is specified in deciBels.SThe fundamental RVP8 operating parameters (PRF, Sample Size, etc) all apply to thehigh PRF portion of the BATCH trigger waveform. The low PRF rate and sample sizeare derived from these high values using a slope and offset. In the example shownabove, the slopes are both zero, so that the surveillance data will be fixed at 6-pulses and250-Hz. Making the slopes nonzero would cause the low-PRF parameters to varyautomatically if desired.These setup parameters are accessible through the DSP driver using the new entry pointsdspw_batchSetup() and dspw_batchSetup(). These use the custom opcode that is definedseparately by each major mode, so you may find customUserOpcode_batch() to be a usefulmodel for how to build such things.Polarization Params – Filtered:YES NoiseCorrected:YESPhiDP – Negate: NO , Offset:0.0 degKDP – Length: 5.00 kmT/Z/V/W computed from: H–Xmt:YES V–Xmt:YEST/Z/V/W computed from: Co–Rcv:YES Cx–Rcv:NOThe first question decides whether all polarization parameters will be computed fromfiltered or unfiltered data, and whether noise correction will be applied to the powermeasurements.The second and third questions define the sign and offset corrections for FDP and thelength scale for KDP.The fourth and fifth questions control how the standard parameters (TotalReflectivity, Corrected Reflectivity, Velocity, and Width) are computed in a multiplepolarization system. Answering YES to H-Xmt and/or V-Xmt means that data from
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–12those transmit polarizations should be used whenever there is more than one choiceavailable. Thus, these selections only apply to the Alternating and Simultaneoustransmit modes. Likewise, answering YES to Co-Rcv and/or Cx-Rcv means to use thereceived data from the co-channel or cross-channel. The receiver question will onlyappear when dual simultaneous receivers have been configured.A typical installation might use H-Xmt:YES,V-Xmt:YES,Co-Rcv:YES,Cx-Rcv:NO.This will compute (T/Z/V/W) from the co-polarized receiver using both H&Vtransmissions. Including both transmissions will decrease the variance of (T/Z/V/W);although some researchers prefer excluding V-Xmt because that is more standard inthe literature. Also, if your polarizations are such that the main power is returned onthe cross channel, then you will probably want Co-Rcv:NO and Cx-Rcv:YES.DualRx – Sum H+V Time Series: NOIn dual-receiver systems, you may choose whether the (H+V) time series data consistof the sum of the “H” and “V” samples or the concatenation of half the “H” samplesfollowed by half the “V” samples. The later is more useful when custom software isbeing used to analyze the data from the two separate receive channels.3.2.3 Mf — Clutter FiltersResidual clutter LOG noise margin: 0.15 dB/dBWhenever a clutter correction is applied to the reflectivity data, the LOG noisethreshold needs to be increased slightly in order to continue to provide reliablequalification of the corrected values. The reason for this is that the uncertainty in thecorrected reflectivity becomes greater after the clutter is subtracted away.For example, if we observe 20dB of total power above receiver noise, and then applya clutter correction of 19dB, we are left with an apparent weather signal power of+1dB above noise. However, the uncertainty of this +1dB residual signal is muchgreater than that of a pure weather target at the same +1dB signal level.The “Residual Clutter LOG Noise Margin” allows you to increase the LOG noisethreshold in response to increasing clutter power. In the previous example, and with thedefault setting of 0.15dB/dB, the LOG threshold would be increased by 19x0.15 = 2.85dB.This helps eliminate noisy speckles from the corrected reflectivity data.Spectral Clutter Filters––––––––––––––––––––––––Filter #1 – Type:0(Fixed) Width:1 EdgePts:2Filter #2 – Type:0(Fixed) Width:2 EdgePts:2Filter #3 – Type:0(Fixed) Width:3 EdgePts:3Filter #4 – Type:1(Variable) Width:3 EdgePts:2 Hunt:3Filter #5 – Type:2(Variable) (Gaussian Model) Spectrum width: 0.200 m/secFilter #6 – Type:2(Variable) (Gaussian Model) Spectrum width: 0.300 m/secFilter #7 – Type:2(Variable) (Gaussian Model) Spectrum width: 0.500 m/secThese questions define the heuristic clutter filters that operate on power spectraduring the DFT-type major modes. Filter #0 is reserved as “all pass”, and cannot bere–defined here. For filters #1 through #7, enter a digit to choose the filter type,followed by however many parameters that type requires. The three filter types areall described in detail in Section 5.2.5.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–13Fixed Width Filters (Type 0)These are defined by two parameters. The “Width” sets the number of spectral pointsthat are removed around the zero velocity term. A width of one will remove just theDC term; a width of two will remove the DC term plus one point on either side; threewill remove DC plus two points on either side, etc. Spectral points are removed byreplacing them with a linear interpolating line. The endpoints of this line aredetermined by taking the minimum of “EdgeMinPts” past the removed interval oneach side.Variable Width, Single Slope (Type 1)The RVP8 supports variable-width frequency-domain clutter filters. These filtersperform the same spectral interpolation as the fixed-width filters, except that theirnotch width automatically adapts to the clutter. The filters are characterized by thesame Width and EdgePts parameters in the Mf menu, except that the Width is nowinterpreted as a minimum width. An additional parameter Hunt allows you to choosehow far to extend the notch beyond Width in order to capture all of the clutter power.Setting Hunt=0 effectively converts a variable-width filter back into a fixed-widthfilter.The algorithm for extending the notch width is based on the slope of adjacent spectralpoints. Beginning (Width–1) points away from zero, the filter is extended in eachdirection as long as the power continues to decrease in that direction, up to adding amaximum of Hunt additional points. If you have been running with a fixed Width=3filter, you might try experimenting with a variable Width=2 and Hunt=1 filter.Perhaps the original fixed width was actually failing at times, but you were reluctantto increase it just to cover those rare cases. In that case, try selecting a variableWidth=2 and Hunt=2 filter as an alternative. In general, make your variable filters“wider” by increasing Hunt rather than increasing Width. This will preserve moreflexibility in how they can adapt to whatever clutter is present.Gaussian Model Adaptive Processing (GMAP) (Type 2)This type of processing is the most advanced form of clutter filtering and momentestimation (see Section 5.2.5 ). For GMAP processing, the only thing that needs bespecified is the spectrum width of clutter. Note that the algorithm is not too sensitiveto the exact value of this. Several widths should be configured to cover the antennarotation rates that are commonly used. It is useful to turn off clutter filtering (selectthe all pass filter #0) and then look at actual measurements of the clutter width whilethe antenna is rotating, e.g., using the ascope utility or application software such asthe SIGMET IRIS system.Whitening Parameters for Tx:Random––––––––––––––––––––––––––––––––––Secondary SQI Threshold Slope:0.50 Offset:–0.05The two values in this question define a secondary SQI threshold that is used toqualify the LOG data during Random Phase processing. The secondary SQI level iscomputed by multiplying the primary user-supplied SQI threshold by the SLOPE,and adding the OFFSET. See also Section 5.7.3.Limits: SLOPE: 0.0 to 2.0, OFFSET –2.0 to 1.0
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–143.2.4 Mt — General Trigger SetupsThese questions are accessed by typing “Mt” with no additional arguments. They configuregeneral properties of the RVP8 trigger generatorPulse Repetition Frequency: 500.00 HzThis is the Pulse Repetition Frequency of the internal trigger generator.Limits: 50 to 20000Hz.Transmit pulse width: 0Limits: 0 to 3Use external pretrigger: NO PreTrigger active on rising edge: YES PreTrigger is synchronous with IFD AQ clock: No PreTrigger fires the transmitter directly: NOWhen an external pretrigger is applied to the TRIGIN input of the RVP8, either therising or falling edge of that signal initiates operation. This decision also affectswhich signal edge becomes the reference point for the pretrigger delay times given inthe “Mt<n>” section.Answer the second sub-question according to whether the radar transmitter is directlyfired by the the external pretrigger, rather than by one of the RVP8’s trigger outputs.In other words, answer “YES” if the transmitter would continue running fine even ifthe RVP8 TRIGIN signal were removed. This information is used by the ”L” and”R” subcommands of the ”Pb” plotting command, i.e., when slewing left and right tofind the burst pulse, the pretrigger delay will be affected rather than the start times ofthe six output triggers.Number of user–defined output triggers: 6This setting defines the number of user–defined output triggers.Limit: 12 (including polarization output controls)Number of polarization output controls: 2This setting defines the number of polarization output controls.2–way (Tx+Rx) total waveguide length: 0 metersUse this question to compensate for the offset in range that is due to the length ofwaveguide connecting the transmitter, antenna, and receiver. You should specify thetotal 2-way length of waveguide, i.e., the span from transmitter to antenna, plus thespan from antenna to receiver. The RVP8 range selection will compensate for theadditional waveguide length to within plus-or-minus half a bin, and works properly atall range resolutions.POLAR1 is high for vertical polarization : NOPOLAR2 is high for vertical polarization : NOThese questions define the logical sense of the two polarization control signalsPOLAR1 and POLAR2. In a dual-polarization radar POLAR1 should be used toselect one of two possible states (nominally horizontal and vertical, but any other
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–15polarization pair may also be used). The control signal will either remain at a fixedlevel, or will alternate from pulse to pulse with a selectable transition point (SeeSection 3.2.5). POLAR2 is identical to POLAR1, but may be configured with adifferent polarity and switch point. This second signal could be used if the radar’spolarization switch required more than one control line transition when changingstates.Quantize trigger PRT to ((1 x AQ) + 0) clocksIt is possible to control the exact quantization of the PRT of the internal triggergenerator. Normally the trigger PRT is chosen as the closest multiple of AQ (theacquisition clock period) that approximates the requested period. This questionallows the possible PRT’s to be constrained to ((N x AQ) + M) clock cycles. Thisfeature can be useful for synchronous receiver systems in which the trigger periodmust be some exact multiple of the COHO period.Blank output triggers within AZ and EL sectors: NO Sector #1 – InUse:NO AZ: 0.0,0.0 EL: 0.0,0.0 Sector #2 – InUse:NO AZ: 0.0,0.0 EL: 0.0,0.0 Sector #3 – InUse:NO AZ: 0.0,0.0 EL: 0.0,0.0 Sector #4 – InUse:NO AZ: 0.0,0.0 EL: 0.0,0.0 Sector #5 – InUse:NO AZ: 0.0,0.0 EL: 0.0,0.0 Sector #6 – InUse:NO AZ: 0.0,0.0 EL: 0.0,0.0 Sector #7 – InUse:NO AZ: 0.0,0.0 EL: 0.0,0.0 Sector #8 – InUse:NO AZ: 0.0,0.0 EL: 0.0,0.0These settings can be modified to reduce erroneous transmissions into physicalobstructions.Blank output triggers via softplane sTrigBlank : NO Blank triggers 1:YES 2:YES 3:YES 4:YES 5:YES 6:YESThese questions control trigger blanking based on the TAG0 input line. You firstselect whether the trigger blanking feature is enabled; and then optionally choose thepolarity of TAG0 that will result in blanking, and which subset of the six userdefinable triggers are to be blanked.Blank output triggers during noise measurement : NOThe RVP8 can inhibit the subset of blankable trigger lines whenever a noisemeasurement is taken. This will be forced whenever trigger blanking (based onTAG0) is enabled, but it can also be selected in general via this question. Since noisetriggers must be blanked whenever trigger blanking is enabled, this question onlyappears if trigger blanking is disabled.This question permits the state of the triggers during noise measurements to beconsistent and known, regardless of whether the antenna happens to be within ablanked sector; and you have the additional flexibility of choosing blanked noisetriggers all the time.Rx–Fixed Triggers: #1:N #2:N #3:N #4:N #5:N #6:N P0:N P1:N Z:NYou have explicit control over which RVP8 trigger outputs are timed relative to thetransmitter pre-fire sequence, versus those which are relative to the actual receivedtarget ranges. Triggers in the first category will be moved left/right by the “L/R”
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–16keys in the Pb plot, and will also be slewed in response to Burst Pulse Tracking.Triggers in the second category remain fixed relative to “receiver range zero”, andare not affected by the “L/R” keys or by tracking.This question specifies which triggers are Tx-relative and which are Rx-relative.Answer with a sequence of “Y” or “N” responses for each of the six trigger lines, forthe two polarization control lines, and for the timing of the phase control lines. Youshould answer No for any trigger that is involved with the pre-fire timing of thetransmitter. If you enable the Burst Pulse Tracker (Section 5.1.4) you will probablywant to assign a Yes to some of your triggers so that they remain fixed relative to theburst itself.It is very helpful to have these two categories of trigger start times. Triggers that firethe transmitter, either directly or indirectly, should all be moved as a group whenhunting for the burst pulse and moving it to the center of the FIR window. However,triggers that function as range strobes should be fixed relative to range zero, i.e., thecenter of that window, and the center of the burst. This distinction becomesimportant when the transmitter’s pre-fire delay drifts with time and temperature.Merge triggers to create composite waveforms: YES Merge Trigger #1 into : #1: #2: #3: #4: #5: #6: Merge Trigger #2 into : #1:N #2: #3: #4: #5: #6: Merge Trigger #3 into : #1:Y #2: #3: #4: #5: #6: Merge Trigger #4 into : #1: #2:Y #3: #4: #5: #6: Merge Trigger #5 into : #1: #2:Y #3: #4: #5: #6: Merge Trigger #6 into : #1: #2: #3: #4: #5: #6:These questions allow you to merge the six user triggers together; resulting in triggerpatterns that can be much more complex. In this example, Trigger #3 will be mergedinto Trigger #1; Trigger #3 will be unaltered, and Trigger #1 will be the “OR” ofitself with Trigger #3. Likewise, Triggers #4 and #5 will be merged into Trigger #2so that the later will contain three distinct pulses within each PRT. Answer eachquestion with a sequence of up to six “Y” or “N” responses in order to set the mergeddestinations for each trigger line.Note that the six triggers are still defined in the usual way in the Mt<n> menu, i.e.,start time, width, etc. The only change is that you may now combine these individualpulse definitions into a more complex composite output waveform.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–173.2.5 Mt<n> — Triggers for Pulsewidth #nThese questions are accessed by typing “Mt”, with an additional argument giving the pulsewidthnumber. They configure specific trigger, transmit waveform, and FIR filter properties for theindicated pulsewidth only.Trigger #1 – Start: 0.00 usec #1 – Width: 1.00 usec High:YESTrigger #2 – Start: 0.00 usec + ( 0.500000 * PRT ) #2 – Width: 10.00 usec High:YESTrigger #3 – Start: –3.00 usec #3 – Width: 1.00 usec High:YESTrigger #4 – Start: –2.00 usec #4 – Width: 1.00 usec High:YESTrigger #5 – Start: –1.00 usec #5 – Width: 1.00 usec High:YESTrigger #6 – Start: –5.00 usec + (–0.001000 * PRT ) #6 – Width: 2.00 usec High:NOThese parameters list the starting times (in microseconds relative to range zero), thewidths (in microseconds), and the active sense of each of the six triggers generated bythe internal trigger generator. Setting a width to zero inhibits the trigger on that line.The Start Time can include an additional term consisting of the pulse period times afractional multiplier between –1.0 and +1.0. This allows you to produce triggerpatterns that would not otherwise be possible, e.g., a trigger that occurs half waybetween every pair of transmitted pulses, and remains correctly positioned regardlessof changes in the PRF Enter this multiplier as “0” if you do not wish to use this term,and it will be omitted entirely from the printout..In the above example, Trigger #2 is a 10.0 msec active-high pulse whose leading edgeoccurs precisely halfway between the zero-range of every pair of pulses. Likewise,Trigger #6 is a 2.0 msec active-low pulse whose falling edge is nominally 5.0 msecprior to range zero, but which is advanced by 1.0 msec for every millisecond oftrigger period. All other triggers behave normally, and have fixed starting times thatdo not vary with trigger period.Some subtleties of these variable start times are:SThe PRT multipliers can only be used in conjunction with the RVP8’s internaltrigger generator. The PRT-relative start times are completely disabled wheneveran external trigger source is chosen from the Mt menu.SWhen PRT-relative triggers are plotted by the Pb command, the active portion ofthe trigger will be drawn cross-hatched and at a location computed according tothe current PRF. The cross-hatching serves as a reminder that the actual locationof that trigger may vary from it’s presently plotted position.SThe PRT multiplier for a given pulse is applied to the interval of time betweenthat pulse and the next one. This distinction is important whenever the RVP8 isgenerating multiple-PRT triggers, e.g., during DPRT mode, or during Dual-PRF
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–18processing. Multipliers from 0.0 to +1.0 are generally safe to use because theyshift the trigger into the same pulse period that originally defined it. Forexample, a start time of (0.0 msec + (0.98 * PRT)) would position a trigger 98%of the way up to the next range zero. But, if –0.98 were used, and if the period ofthe previous pulse was shorter than the current one, then that shorter period wouldbecome incorrect (longer) as a result of having to fit in the very early trigger.A small but important detail is built into the algorithm for producing the six usertrigger waveforms. It applies whenever a) the trigger period is internally determined,i.e., the external pretrigger input is not being used, and b) the overall span of the sixtrigger definitions combined does not fit into that period. What happens in this caseis that any waveforms that do not fit will be zeroed (not output) so that the desiredperiod is preserved. This means that you can define triggers with large positive starttimes, and they will pop into existence only when the PRF is low enough toaccommodate them.For example, if Trigger #2 is defined as a 200.0msec pulse starting at +400.0msec,then that trigger would be suppressed if the PRF were 2000Hz, but it would bepresent at a PRF of 1000Hz. Whenever a trigger does not completely fit within theoverall period it is suppressed entirely. Thus, even though the +400.0msec start timeis still valid at 2000Hz, the entire 200.0msec pulse would not fit, and so the pulse iseliminated altogether.Start limits: –5000 to 5000 msec. Width limits: 0 to 5000 msec.Maximum number of Pulses/Sec: 2000.0 Maximum instantaneous ’PRF’ : 2000.0 (/Sec)These are the PRF protection limits for this pulsewidth.The wording of the “Maximum number of Pulses/Sec” question serves as a reminderthat the number shown is not only an upper bound on the PRF, but also a duty cyclelimit when DPRT mode is enabled.The “Maximum instantaneous ’PRF’” question allows you to configure the maximuminstantaneous rate at which triggers are allowed to occur, i.e., the reciprocal of theminimum time between any two adjacent triggers. This parameter is included so thatyou can limit the maximum DPRT trigger rate individually for each pulsewidth.Note that the maximum instantaneous PRF can not be set lower than the maximumnumber of pulses per second.PRF limits: 50 to 20000Hz.External pretrigger delay to range zero: 3.00 usecRange Zero is time at which the signal from a target at zero range would appear at theradar receiver outputs. This parameter adjusts the delay from the active edge of theexternal trigger to range zero. It is important that this delay be correct when theRVP8 is operating with an external trigger, since the zero range point is a fixed timeoffset from that trigger. When the transmitter is driven from the internal triggersignals, those signals themselves are adjusted (see Burst Pulse alignment procedures)to accomplish the alignment of range zero.Limits: 0.1 to 1000 msec.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–19Range mask spacing: 125.00 metersThe range resolution of the RVP8 is determined by the decimation factor of thedigital matched FIR filter that computes “I” and “Q”. This decimation factor is theratio of the filter’s input and output data rates, i.e., the output rate is some integerdivisor of the IFD Acquisition Clock (See Mc Section). For the legacy RVP7 IFDoperating at its standard frequency of 35.9751MHz, the available range resolutions(in meters) are: 25.0, 28.3, 36.7, 50.0, 58.3, 66.7, 75.0, 83.3, 91.7, 100.0, 108.3,116.7, 125.0, and 133.3. The RVP8 IFD operating in the 72MHz range providestwice the resolution between steps, and four times the number of steps.The ranges that are selected by the bit mask in the LRMSK command are spacedaccording to the range resolution that is chosen here. Also, the upper limit on theimpulse response length of the matched FIR filter (see below) is constrained by therange resolution. If you choose a range resolution that can not be computed at thepresent filter length, then a message of the form: “Warning: Impulse responseshortened from 72 to 42 taps” will appear.Limits: 25 to 1000 meters.FIR-Filter impulse response length: 1.33 usecThe RVP8 computes “I” and “Q” using a digital FIR (Finite Impulse Response)matched filter. The length of that filter (in microseconds) is chosen here.The filter length should be based on several considerations:SIt should be at least as long as the transmitted pulsewidth. If it were shorter, thensome of the returned energy would be thrown away when “I” and “Q” arecomputed at each bin. The SNR would be reduced as a result.SIt should be at least as long as the range bin spacing. The goal here is to choosethe longest filter that retains statistical independence among successive bins. Ifthe filter length is less than the bin spacing, then no IF samples would be sharedamong successive bins, and those bins would certainly not be correlated.SIt should be “slightly longer” than either of the above bounds would imply, sothat the filter can do a better job of rejecting out-of-band noise and spurioussignals. The SNR of weak signals will be improved by doing this.In practice, a small degree of bin-to-bin correlation is acceptable in exchange for thefilter improvements that become possible with a longer impulse response. The FIRcoefficients taper off to zero on each end; hence, the power contributed byoverlapping edge samples is minimal. SIGMET recommends beginning with animpulse response length of 1.2–1.5 times the pulsewidth or bin spacing, whichever isgreater.The maximum possible filter length is bounded according to the range resolution thathas been chosen; a finer bin spacing leaves less time for computing a long filter. Forthe RVP8 Rev.A processor, the filter length must be less than 2.92 msec at 125-meterresolution; for Rev.B and higher this limit increases to 6.67 msec.NOTE: Cascade filter software is being contemplated that will extend the maximumimpulse response length to at least 50 msec. This is of interest when very long(uncoded CW) transmitted pulses are used.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–20Burst Freq Estimator– Length: 1.33 usec, Start: 0.00 usecThis estimator is mostly used with the Pb (plotting commands) and can be referencedin Section 4.3.2.FIR-Filter prototype passband width: 0.503 MHzThis is the passband width of the ideal lowpass filter that is used to design thematched FIR bandpass filter. The actual bandwidth of the final FIR filter will dependon 1) the filter’s impulse response length, and 2) the design window used in theprocess. The actual 3dB bandwidth will be:SLarger than the ideal bandwidth if that bandwidth is narrow and the FIR length istoo short to realize that degree of frequency discrimination. In these cases it maybe reasonable to increase the filter length.SSmaller than the ideal bandwidth if the FIR length easily resolves the frequencyband. This is because of the interaction within the filter’s transition band of theideal filter and the particular design window being used. For example, for aHamming window and sufficiently long filter length, the ideal bandwidth is anapproximation of the 6dB (not 3dB) attenuation point. Hence, the 3dB width isnarrower than the ideal prototype width.This parameter should be tuned using the TTY output and interactive visual plot fromthe “Ps” command. The actual 3dB bandwidth is shown there, so that it can becompared with the ideal prototype bandwidth.Limits: 0.05 to 10.0 MHz.Output control 4–bit pattern: 0001These are the hardware control bits for this pulsewidth. The bits are the 4-bit binarypattern that is output on PWBW0:3Bit Limits: 0 to 15 (input must be typed in decimal)Current noise level: –75.00 dBmPowerup noise level: –75.00 dBm–or–Current noise levels – PriRx: –75.00 dBm, SecRx: –75.00 dBmPowerup noise levels – PriRx: –75.00 dBm, SecRx: –75.00 dBmThese questions allow you to set the current value and the power-up value of thereceiver noise level for either a single or dual receiver system. The noise level(s) areshown in dBm, and you may alter either one from the TTY. The power-up level(s)are assigned by default when the RVP8 first starts up, and whenever the RESETopcode is issued with Bit #8 set. Likewise, the current noise level is revisedwhenever the SNOISE opcode is issued. These setup questions are intended forapplications in which the RVP8 must operate with a reasonable default value, up untilthe time that an SNOISE command is actually received. They may also be used tocompare the receiver noise levels during normal operation, which serves as a checkthat each FIR filter is behaving as expected when presented with thermal noise.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–21Transmitter phase switch point: –1.00 usecThis is the transition time of the RVP8’s phase control output lines during randomphase processing modes. The switch point should be selected so that there isadequate settling time prior to the burst/COHO phase measurement on each pulse.This question only appears if the PHOUT[0:7] lines are actually configured for phasecontrol (See Section 3.2.1).Limits: –500 to 500 msec.Polarization switch point for POLAR1: –1.00 usecPolarization switch point for POLAR2: 1.00 usecThe RVP8’s POLAR1 and POLAR2 digital output lines control the polarizationswitch in a dual-polarization radar. During data processing modes in which thepolarization alternates from pulse to pulse, the transition points of these controlsignals are set by these two questions. The values are in microseconds relative torange zero; the same units used to define the start times of the six user triggers. Thelogical sense of POLAR1 and POLAR2 is set by questions described in Section 3.2.4.Limits: –500 to 500 msec.3.2.5.1 Special Options for Tx SynthesisSeveral of the dialogs described in the previous section will be modified when the RVP8 isequipped with an RVP8/Tx Digital Transmitter Card that has been configured for Tx waveformsynthesis in the Mz menu. In this case, each of the RVP8’s four “pulsewidths” can select anentirely different type of transmit waveform and associated matched receiver.For example, PW-0 and PW-1 could transmit conventional 0.5msec and 2.0msec CW pulses thatare received using the bandpass filters described in Section 3.2.5. But within this same system,PW-2 and PW-3 could be further configured as, perhaps, 20msec and 40msec compressednon-linear FM waveforms. This makes it very easy for application software such as ascope totransparently switch between radically different Tx waveforms simply by requesting a different“pulsewidth” for each one.The following questions will appear in the Mt<n> menu (immediately after the Range MaskSpacing question) when digital Tx waveforms are being synthesized.Tx Waveform – 0:CWPulse, 1:LinFM, 2:NLFM : 2The RVP8 supports three standard Tx waveforms: a conventional fixed-frequencyCW pulse, a linear FM chirp, and non-linear FM. The CWPulse can be used as apulsed Doppler waveform in all the same ways that a Klystron or Magnetron systemhaving a traditional pulse forming network would be used. The linear and non-linearFM waveforms, however, are compressed pulses that are intended to be transmittedby a wide-bandwidth Klystron/TWT/SolidState amplifier.Note: The RVP8 internal APIs permit code developers to create arbitrary waveformsfor transmission. The three types mentioned above are the out-of-the-box selectionsthat are standard on all RVP8 processors.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–22Bandwidth of transmit pulse: 3.25 MHzPulselength of transmit pulse: 15.00 usecThese questions select the bandwidth and pulse length of the Tx waveform. Thebandwidth value represents the true spectrum width of the complete waveform, i.e.,including all the effects of whatever frequency modulation and amplitude modulationthe waveform happens to use. Thus, a spectrum analyzer (or the RVP8’s Ps plot)would show an overall spectrum width equal to this desired value.Likewise, the pulse length value represents the entire time duration of the waveform,including whatever amplitude modulations may be included at the tails.Zero offset of transmit pulse: 0.00 usecThe Tx waveform is normally synthesized with its center lined up with range zero. Ifthe radar’s high-power amplifier had zero delay, this would serve to define the middleof the transmit pulse as range zero, which is the usual RVP8 convention. This offsetquestion is provided so that the RVP8/Tx output waveform can be shifted in time tocompensate for whatever delays are present in the radar’s IF/RF electronics.Note: This transmit pulse timing offset is typically checked via the Pb plot by makingsure that the Tx burst is centered within the FIR data window.TxWave MIN tuning params: 0.0000, 0.0000, 0.0000TxWave MAX tuning params: 1.0000, 1.0000, 1.0000TxWave tuning parameters: 0.9500, 1.0000, 0.0490The RVP8 uses three real-valued tuning parameters to make the synthesis of complexwaveforms more flexible. Each waveform class can be altered and fine tuned with upto three degrees of freedom, making it possible for a single class (e.g., the non-linearFM class) to generate a huge variety of actual waveforms. These adjustable constantsalso form the basis of the automatic waveform optimization procedure described forthe Pa command in Section 4.6.2.Each of the three parameters has a minimum value, a maximum value, and a currentvalue, all of which can be changed from this menu. The Min/Max limits are usedwithin the Pa command to maintain sensible bounds as the parameters are adjusted.In general, the Min/Max values will be entered from the Mt<n> menu, but the actualvalues will be tuned using either manual or automatic procedures found in the Pacommand.The CWPulse class of waveforms do not use any of the tuning parameters becausethe Tx waveform is completely determined by the desired bandwidth and pulsewidth,i.e., there are no remaining degrees of freedom to adjust. Thus, these three questionsdo not appear in the CWPulse case.The linear FM class is also entirely specified by just the bandwidth and pulsewidthvalues, and does not reference any of the tuning parameters. However, the non-linearFM class is the most flexible of all, and references all three tuning parameters asfollows:SParameters #1 and #2 are the (X,Y) location of the non-linear “breakpoint” forthe FM curve. Referring to the white plot line in Figure 4–9, the Time/Frequencybehavior of the pulse can be drawn in a coordinate system whose abscissa ranges
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–23from –1 to +1 over the complete time duration of the pulse, and whose ordinateranges from –1 to +1 over the complete frequency span of the pulse.SThe class of non-linear FM curves always pass through the points (–1,–1),(0,0), and (1,1), i.e., they begin at the lowest frequency at the start of the pulse,end at the highest frequency when the pulse completes, and pass through theorigin (to maintain symmetry across both halves of the pulse). Between thepoints (0,0) and (1,1) the curves also pass through the tunable (X,Y) “breakpoint”defined by the first two parameters. In other words, the positive-time portion ofthe FM curve consists of two linear segments; one from (0,0) to (X,Y), and theother from (X,Y) to (1,1). By tuning the breakpoint we create a diverse class ofFM modulations, but all of them adhere to the physical bandwidth and pulsewidthlimits imposed by the earlier setup questions. Note that to maintain symmetry,the breakpoint is also mirrored on the negative-time side as line segments from(–1,–1) to (–X,–Y), and from (–X,–Y) to (0,0).SParameter #3 specifies the X location of the start of the amplitude taper of thenon-linear FM waveform. For example, setting X to 0.95 will result in a pulsehaving full amplitude over the middle 95% of its duration, but then having raisedcosine amplitude weighting applied to the leading and trailing 5% of its edges.Some examples may be helpful:P1 = 0.0, P2 = 0.0, P3 = 1.0P1 and P2 place the FM breakpoint at the origin. But the FM curve passes throughthat point anyway, so the response reverts to linear FM. P3 indicates that amplitudemodulation should not be applied until the very end of the pulse, and thus will notoccur at all. The resulting waveform is therefore linear FM having abrupt On/Offtransitions.P1 = 0.9, P2 = 0.7, P3 = 1.0During the middle 90% of the waveform’s duration the frequency chirp uses 70% ofits available bandwidth. Then, within the 10% pulse tails, the remaining 30% of thebandwidth suddenly gets covered. No amplitude modulation is applied. Pulses ofthis type have been studied theoretically, but do not perform very well for a giventotal bandwidth that includes the leading/trailing “ears”.P1 = 0.9, P2 = 1.0, P3 = 0.8The entire frequency band is chirped within the middle 90% of the pulse duration, sothat the frequency remains constant in the 10% pulse tails. An amplitude modulationis also applied over 20% of the pulse tails, i.e., encompassing both the ends of thechirp and the entire constant frequency intervals. Pulses of this type have superiorsidelobe behavior and fit very neatly within their prescribed bandwidth limits. Werecommend using non-linear FM waveforms that combine chirp limits and amplitudemodulation in this manner.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–243.2.6 Mb — Burst Pulse and AFCThese questions are accessed by typing “Mb”. They set the parameters that influence the phaseand frequency analysis of the burst pulse, and the operation of the AFC feedback loop.Receiver Intermediate Frequency: 30.0000 MHzThis is the center frequency of the IF receiver and burst pulse waveform.SWith the legacy RVP7 IFD, the RVP8 can operate at an intermediate frequencywithin any of the alias bands 22–32MHz, 40–50MHz, and 58–68MHz.SWith the CAT-5E IFD, the RVP8 can operate at an intermediate frequency withinany of the alias bands 8–32MHz and 40–68MHzThese bands are delineated by 4MHz safety zones on either side of integer multiplesof half the IFD’s sampling frequency. The value entered here implicitly defines theband being used.Limits: 6 to 72 MHz.Primary Receiver Intermediate Frequency: 30.0000 MHzSecondary Receiver Intermediate Frequency: 24.0000 MHzThese alternate questions will replace the previous question whenever the RVP8’sdual-receiver mode is selected. You should enter the two intermediate frequenciesfor your primary and secondary (nominally horizontal and vertical polarized)receivers. Note that you can easily swap receiver channels merely by exchanging thetwo frequency values.IF increases for an approaching target: YESThe intermediate frequency is derived at the receiver’s front end by a microwavemixer and sideband filter. The filter passes either the lower sideband or the uppersideband, and rejects the other. Depending on which sideband is chosen, an increasein microwave frequency may either increase (STALO below transmitter) or decrease(STALO above transmitter) the receiver’s intermediate frequency. This questioninfluences the sign of the Doppler velocities that are computed by the RVP8.PhaseLock to the burst pulse: YESThis question controls whether the RVP8 locks the phase of its synthesized “I” and“Q” data to the measured phase of the burst pulse. For an operational magnetronsystem this should always be “YES”, since the transmitter’s random phase must beknown in order to recover Doppler data. The “NO” option is appropriate for nonphase modulated Klystron systems in which the RVP8/IFD sampling clock is lockedto the COHO. It is also useful for bench testing in general. In these “NO” cases thephase of “I” and “Q” is determined relative to the stable internal sampling clock inthe RVP8/IFD module.Minimum power for valid burst pulse: –15.0 dBmThis is the minimum mean power that must be present in the burst pulse for it to beconsidered valid, i.e., suitable for input into the algorithms for frequency estimationand AFC. The reporting of burst pulse power is described in Section 4.3; the valueentered here should be, perhaps, 8 dB less. This insures that burst pulses will still beproperly detected even if the transmitter power fades slightly.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–25The mean power level of the burst is computed within the narrowed set of samplesthat are used for AFC frequency estimation. The narrow subwindow will containonly the active portion of the burst, and thus a mean power measurement ismeaningful. The full FIR window would include the leading and trailing pulse edgesand would not produce a meaningful average power. Since radar peak power tends tobe independent of pulse width, this single threshold value can be applied for allpulsewidths.Limits: –60 to +10 dBm.Design/Analysis Window– 0:Rect, 1:Hamming, 2:Blackman : 1You may choose the window that is used in 1) the design of the FIR matched filter,and 2) the presentation of the power spectra for the various scope plots. Choices arerectangular, Hamming, and Blackman; the Hamming window being the best overallchoice. The Blackman window is useful if you are trying to see plotted spectralcomponents that are more than 40dB below the strongest signal present. It isespecially useful in the “Pr” plot when a long span of data are available. FIR filtersdesigned with the Blackman window will have greater stopband attenuation thanthose designed with the Hamming window, but the wider main lobe may beundesirable. The rectangular window is included mostly as a teaching tool, andshould never be used in an operational setting.Settling time (to 1%) of burst frequency estimator: 5.0 secThe burst frequency estimator uses a 4th order correlation model to estimate thecenter frequency of the transmitted pulses. Each burst pulse will typically occupyapproximately one microsecond; yet the frequency estimate feeding the AFC loopneeds to be accurate to, perhaps, 10KHz. Obviously this accuracy can not beachieved using just one pulse. However, several hundred of the (unbiased) individualestimates can be averaged to produce an accurate mean. This averaging is done withan exponential filter whose time constant is chosen here.Limits: 0.1 to 120 seconds.Lock IFD sampling clock to external reference: NOThis question determines the usage of the shared SMA connector that is labeled“AFC/(CLK)” on the RVP8/IFD. It is generally not necessary to phase lock the IFDsampling clock to the radar system clock, since very good stability is obtained fromthe burst phase measurements during normal operation. However, two cases thatbenefit from clock locking are 1) using the RVP8 in a klystron system where anexternal trigger is provided, and 2) dual-receiver systems in which computation ofFDP is important.The following two questions will appear only if you have requested that the IFDsampling clock be locked to an external clock reference. See Section 2.2.12 for adescription of the hardware setups that must accompany this selection.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–26 PLL ratio of (1/1) ==> Input reference at 17.9876 MHzThe VCXO phase-locked-loop (PLL) in the RVP8/IFD can work with any inputreference clock whose frequency is a rational multiple (P/Q) of half the desiredsampling frequency, i.e., the center frequency of the VCXO that is entered in the“mc” command (Section 3.2.1). This question allows this ratio to be established. Ingeneral, the best PLL performance will be attained when the ratio is reduced tolowest terms, e.g., use a ratio of 6/5 rather than 12/10. For example, assume:VCXO center frequency fsamp = 36 MHzReference clock frequency fref = 10 MHzfref +PQĄfsamp2ĄĄĄ ;ĄĄĄ PQ+2Ąfreffsamp+2@10ĄMHz36ĄMHz +59In this case enter the numbers “5 9”. The proper input reference frequency (e.g.,10.0000 MHz) should be displayed after you enter the values. The “v” command canbe used to verify that the PLL is “Okay”.Limits: 1 to 128 for both numerator and denominator. VCXO has positive frequency deviation: YESMost VCXOs have positive frequency deviation, i.e., their output frequency increaseswith increasing input control voltage. This question will generally be answered“yes”, but is included to accommodate the other case as well. The PLL will not lock,and will be completely unstable, if the wrong choice is made.Enable AFC and MFC functions: YESAFC is required in a magnetron system to maintain the fixed intermediate frequencydifference between the transmitter and the STALO. AFC is not required in a klystronsystem since the transmitted pulse is inherently at the correct frequency.The following rather long list of questions will appear only if AFC and MFCfunctions have been enabled. AFC Servo– 0:DC Coupled, 1:Motor/Integrator : 0The AFC servo loop can be configured to operate with an external Motor/Integratorfrequency controller, rather than the usual direct-coupled FM control. This type ofservo loop is required for tuned magnetron systems in which the tuning actuator ismoved back and forth by a motor, but remains fixed in place when motor drive isremoved. These systems require that the AFC output voltage (motor drive) be zerowhen the loop is locked; and that the voltage be proportional to frequency error whiletracking. Please see Section 3.2.6.1 for more details. Wait time before applying AFC: 10.0 secAfter a magnetron transmitter is first turned on, it may be several seconds or evenminutes until its output frequency becomes stable. It would not make sense for theAFC loop to be running during this time since there is nothing gained by chasing thestartup transient. This question allows you to set a holdoff delay from the time thatvalid burst pulses are detected to the time that the AFC loop actually begins running.Limits: 0 to 300 seconds.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–27 AFC hysteresis -- Inner: 5.0 KHz, Outer: 15.0 KHzThese are the frequency error tolerances for the AFC loop. The loop will applyactive feedback whenever the outer frequency limit is exceeded, but will hold a fixedlevel once the inner limit has been achieved. The hysteresis zone minimizes theamount of thrashing done by the feedback loop. The AFC control voltage willremain constant most of the time; making small and brief adjustments onlyoccasionally as the need arises. AFC outer tolerance during data processing: 50.0 KHzIn general, the AFC feedback loop is active only when the RVP8 is not processingdata rays. This is because the Doppler phase measurements are seriously degradedwhenever the AFC control voltage makes a change. To avoid this, the AFC loop isonly allowed to run in between intervals of sustained data processing. This is fine aslong as the host computer allows a few seconds of idle time every few minutes; but ifthe RVP8 were constantly busy, the AFC loop would never have a chance to run.This question allows you to place an upper bound on the frequency error that istolerated during sustained data processing. AFC is guaranteed to be appliedwhenever this limit is exceeded.Limits: 15 to 4000 KHz. AFC feedback slope: 0.0100 D-Units/sec / KHz AFC minimum slew rate: 0.0000 D–Units/sec AFC maximum slew rate: 0.5000 D-Units/secThese questions control the actual feedback computations of the AFC loop.The overall span of the AFC output voltage is set by Gain and Offset potentiometerson the RVP8/IFD module (See Section 2.2.11). The control level that is applied tothe AFC’s 16-bit Digital-to-Analog converter is specified here in “D-Units”, i.e.,arbitrary units ranging from –100 to +100 corresponding to the complete span of theD/A converter. Since the D–Unit corresponds in a natural way to a percentage scale,the shorter “%” symbol is sometimes used.AFC feedback will be applied in proportion to the frequency error that the algorithmis attempting to correct. The feedback slope determines the sensitivity and timeconstant of the loop by establishing the AFC’s rate of change in (D-Units / sec) perthousand Hertz of frequency error. For example, a slope of 0.01 and a frequencyerror of 30KHz would result in a control voltage slew of 0.3 D-Units per second. Atthat rate it would take approximately 67 seconds for the output voltage to slew onetenth of its total span (20 D-Units / (0.3 D-Units / sec) = 67 sec). AFC is intended totrack very slow drifts in the radar system, so response times of this magnitude arereasonable.Keep in mind that the feedback slew is based on a frequency error which itself isderived from a time averaging process (see Burst Frequency Estimator Settling Timedescribed above) . The AFC loop will become unstable if a large feedback slope isused together with a long settling time constant, due to the phase lag introduced bythe averaging process. Keep the loop stable by choosing a small enough slope thatthe loop easily comes to a stop within the inner hysteresis zone.See Section 3.2.6.1 for more information about these slope and slew rate parameters.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–28 AFC span– [–100%,+100%] maps into [ –32768 , 32767 ] AFC format– 0:Bin, 1:BCD, 2:8B4D: 0, ActLow: NO AFC uplink protocol– 0:Off, 1:Normal, 2:PinMap : 1The RVP8’s implementation of AFC has been generalized so that there is nodifference between configuring an analog loop and a digital loop. The AFC feedbackloop parameters are setup the same way in each case; the only difference being themodel for how the AFC information is made available to the outside world. Manytypes of interfaces and protocols thus become possible according to how these threequestions are answered. AFC output follows these three steps:SThe internal feedback loop uses a conceptual [–100%,+100%] range of values.However, this range may be mapped into an arbitrary numeric span for eventualoutput. For example, choosing the span from –32768 to +32767 would result in16-bit AFC, and 0 to 999 might be appropriate for 3-digit BCD; but any otherspan could also be selected from the full 32-bit integer range.SNext, an encoding format is chosen for the specified numeric span. The result ofthe encoding step is another 32-bit pattern which represents the above numericvalue. SIGMET will make an effort to include in the list of supported formats allcustom encodings that our customers encounter from their vendors.SAvailable formats include straight binary, BCD, and mixed-radix formats thatmight be required by a specialized piece of equipment. The “8B4D” formatencodes the low four decimal digits as four BCD digits, and the remaining upperbits in binary. For example, 659999 base-10 would encode into 0x00419999Hex.SFinally, an output protocol is selected for the bit pattern that was produced byencoding the numeric value. The bits may be written to the eight RVP8backpanel RS232 outputs, or sent on the uplink as a value to be received by theRVP8/IFD and converted to an analog voltage. Yet another option is for the bitsto be sent on the uplink and received by the DAFC, which supports arbitraryremapping of its output pins.To summarize: the internal AFC feedback level is first mapped into an arbitrarynumeric span, then encoded using a choice of formats, and finally mapped into anarbitrary set of pins for digital output. We are hopeful that this degree of flexibilitywill allow easy hookup to virtually any STALO synthesizer that one might encounter.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–29 PinMap Table (Type ’31’ for GND, ’30’ for +5) ––––––––––––––––––––––––––––––––––––––––––––– Pin01:00 Pin02:01 Pin03:02 Pin04:03 Pin05:04 Pin06:05 Pin07:06 Pin08:07 Pin09:08 Pin10:09 Pin11:10 Pin12:11 Pin13:12 Pin14:13 Pin15:14 Pin16:15 Pin17:16 Pin18:17 Pin19:18 Pin20:19 Pin21:20 Pin22:21 Pin23:22 Pin24:23 Pin25:24 FAULT status pin (0:None): 0, ActLow: NOThese questions only appear when the “PinMap” uplink protocol has been selected.The table assigns a bit from the encoded numeric word to each of the 25 pins of theRVP8/DAFC module. For example, the default table shown above simply assigns thelow 25 bits of the encoded bit pattern to pins 1-25 in that order. You may also pull apin high or low by assigning it to +5 or GND. Note that such assignments produce alogic-high or logic-low signal level, not an actual power or ground connection. Thelatter must be done with actual physical wires.One of the RVP8/DAFC pins can optionally be selected as a Fault Status indicator.You may choose which pin to use for this purpose, as well as the polarity of theincoming signal level. Note that the standard RVP8/DAFC module only supports theselection of pins 1, 3, 4, 13, 14, and 25 as inputs. This setup question allows you tochoose any pin, however, because it does not know what kind of hardware may belistening on the uplink and what its constraints might be. Burst frequency increases with increasing AFC voltage: NOIf the frequency of the transmit burst increases when the AFC control voltageincreases, then answer this question “Yes”; otherwise answer “No”. When thisquestion is answered correctly, a numerical increase in the AFC drive (D–Units) willresult in an increase in the estimated burst frequency. If the AFC loop is completelyunstable, try reversing this parameter. Mirror AFC voltage on– 0:None, 1:I, 2:Q : 0AFC/MFC can be mirrored on a backpanel output of the main chassis using thisquestion. When either “I” or “Q” is selected, the AFC/MFC voltage will be presenton the corresponding BNC output, and the other output will be used for scopeplotting. This configuration would be useful, for example, in a dual-receivermagnetron system that needs a phase locked acquisition clock in the RVP8/IFD, butalso needs an AFC tuning voltage to control the transmit frequency. When “None” isselected, scope plotting will revert to its normal “Q” output.The voltage range of the “I” and “Q” outputs is approximately 1 Volt, and is notadjustable. When AFC/MFC is mirrored on these lines, you will probably need toadd an external Op-Amp circuit to adjust the voltage span and offset to match yourRF components. We also recommend that you add significant low-pass filtering(cutoff at 3Hz) to remove any power line noise or crosstalk that may be originatingwithin the RVP8 chassis.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–30Enable Burst Pulse Tracking: YESThis question enables the Burst Pulse Tracking algorithm that is described in Section5.1.4. Remarkably, for such an intricate new feature, there are no additionalparameters to configure. The characteristic settling times for the burst are alreadydefined elsewhere in this menu, and the tracking algorithm uses dynamic thresholdsto control the feedback.Enable Time/Freq hunt for missing burst: No Number of frequency intervals to search: 5 Settling time for each frequency hop: 0.25 sec Automatically hunt immediately after being reset: YES Repeat auto hunt every: 60.00 secThese questions configure the process of hunting for a missing burst pulse. Thetrigger timing interval that is checked during Hunt Mode is always the maximum+20msec; hence no further setup questions are needed to define the hunting process intime. The hunt in frequency is a different matter. The overall frequency range willalways be the full –100% to +100% AFC span; but the number of subintervals tocheck must be specified, along with the STALO settling time after making each AFCchange. With the default values shown, AFC levels of –66%, –33%, 0%, +33%, and+66% will be tried, with a one-quarter second wait time before checking for a validburst at each AFC setting.You should choose the number of AFC intervals so that the hunt procedure candeduce an initial AFC level that is within a few megaHertz of the correct value. Thenormal AFC loop will then take over from there to keep the radar in tune. Forexample, if your radar drifts considerably in frequency so that the AFC range had tobe as large as 35MHz, then choosing fifteen subintervals might be a good choice.The hunt procedure would then be able to get within 2.3MHz of the correct AFClevel. The settling time can usually be fairly short, unless you have a STALO thatwobbles for a while after making a frequency change. Note that hunting in frequencyis not allowed for Motor/Integrator AFC loops, and the two AFC questions will besuppressed in that case.The RVP8 can optionally begin hunting for a missing burst pulse immediately afterbeing reset, but before any activity has been detected from the host computer. Thismight be useful in systems that both drift a lot and generally have their transmitterOn. However, this option is really included just as a work around; the correct wayfor a burst pulse hunt to occur is via an explicit request from the host computer which“knows” when the pulse really should be present. Blindly hunting in the absence ofthat knowledge can not be done because there are many reasons why the burst pulsemay legitimately be missing, e.g., during a radar calibration.The automatic hunt for the burst pulse will always run at least once whenever thefeature is enabled. The automatic hunting ceases, however, as soon as any activity isdetected from the host computer. Only use this feature on radars with a serious driftproblem in their burst pulse timing.Simulate burst pulse samples: NOThe RVP8 can simulate a one microsecond envelope of burst samples. This is usefulonly as a testing and teaching aid, and should never be used in an operational system.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–31A two-tone simulation will be produced when the RVP8 is setup in dual-receivermode. The pulse will be the sum of two transmit pulses at the primary and secondaryintermediate frequencies. To make the simulation more realistic, the two signalstrengths are unequal; the primary pulse is 3dB stronger than the secondary pulse. Frequency span of simulated burst: 27.00 MHz to 32.00 MHzThe simulated burst responds to AFC just as a real radar would. The frequency spanfrom minimum AFC to maximum AFC is given here.3.2.6.1 AFC Motor/Integrator OptionThe question “AFC Servo– 0:DC Coupled, 1:Motor/Integrator” selects whether theAFC loop runs in the normal manner (direct control over frequency), or with anexternal Motor/Integrator type of actuator. The question “AFC minimum slewrequest:...” provides additional control when interfacing to mechanical actuatorswhose starting and sustaining friction needs to be overcome.The DC-Coupled AFC loop questions (changes shown in bold) are:AFC Servo– 0:DC Coupled, 1:Motor/Integrator : 0Wait time before applying AFC: 10.0 secAFC hysteresis– Inner: 5.0 KHz, Outer: 15.0 KHzAFC outer tolerance during data processing: 50.0 KHzAFC feedback slope: 0.0100 D–Units/sec / KHzAFC minimum slew rate: 0.0000 D–Units/secAFC maximum slew rate: 0.5000 D–Units/secand the Motor/Integrator loop questions are:AFC Servo– 0:DC Coupled, 1:Motor/Integrator : 1Wait time before applying AFC: 10.0 secAFC hysteresis– Inner: 5.0 KHz, Outer: 15.0 KHzAFC outer tolerance during data processing: 50.0 KHzAFC feedback slope: 1.0000 D–Units / KHzAFC minimum slew request: 15.0000 D–UnitsAFC maximum slew request: 90.0000 D–UnitsNotice that the physical units for the feedback slope and slew rate limits are differentin the two cases. In the DC-Coupled case the AFC output voltage controls thefrequency directly, so the units for the feedback and slew parameters useD-Units/Second. In the Motor/Integrator case, the AFC output determines the rate ofchange of frequency; hence D-Units are used directly.The above example illustrates typical values that might be used with aMotor/Integrator servo loop. The feedback slope of 1.0 D-Units/KHz means that afrequency error of 100KHz would produce the full-scale (100 D-Units) AFC output.But this is modified by the minimum and maximum slew requests as follows:SA zero D-Unit output will always be produced whenever AFC is locked.SWhen AFC is tracking, the output drive will always be at least 15 D-Units.This minimum non-zero drive should be set to the sustaining drive level of themotor actuator, i.e., the minimum drive that actually keeps the motor turning.SWhen AFC is tracking, the output drive will never exceed 90 D-Units. Thisparameter can be used to limit the maximum motor speed, even when thefrequency error is very large.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–32The AFC Motor/Integrator feedback loop works properly even if the motor hasbecome stuck in a “cold start”, i.e., after the radar has been turned off for a period oftime. The mechanical starting friction can sometimes be larger than normal, andadditional motor drive is required to break out of the stuck condition. But once themotor begins to turn at all, then the normal AFC parameters (minimum slew,maximum slew, feedback slope) all resume working properly. The algorithmoperates as follows:SWhenever AFC correction is being applied, the RVP8 calculates how long itwould take to reach the desired IF frequency at the present rate of change. Forexample, if we are 1MHz away from the desired IF frequency, and the measuredrate of change of the IF burst frequency is 20KHz/sec, then it will be 50 secondsuntil the loop reaches equilibrium.SWhenever the AFC loop is in Track-Mode, but the time to equilibrium is greaterthan two minutes, then the “Minimum Slew” parameter will be slowly increased.The idea is to gradually increase the starting motor drive whenever it appears thatthe IF frequency is not actually converging toward the correct value, i.e., themotor is stuck.SAs soon as the frequency is observed to begin changing, such that the desired IFwould be reached in less than two minutes, then the ”Minimum Slew” parameteris immediately put back to its correct setup value. The loop then continues to runproperly using its normal setup values.Manual Frequency Control (MFC) operates unchanged in both of the AFC servomodes. Whenever MFC is enabled in the Ps command, it always has the effect ofdirectly controlling the output voltage of the AFC D/A converter. The MFC modecan be useful when testing the motor response under different drive levels, and whendetermining the correct value for the minimum slew request.3.2.7 M+ — Debug OptionsA collection of debugging options has been added to the RVP8 to help users with thedevelopment and debugging of their applications code. For the most part, these options shouldremain disabled during normal radar operation. These questions are included so that the RVP8can be placed into unusual, and perhaps occasionally useful, operating states.Noise level for simulated data: –50.0 dBThis is the noise level that is assumed when simulated “I” and “Q” data are injectedinto the RVP8 via the LSIMUL command. The noise level is measured relative to thepower of a full-scale complex (I,Q) sinusoid, and matches the levels shown on theslide pots of the ASCOPE digital signal simulator.Limits: –100dB to 0dBSimulate output rays: NOAnswering ”YES” to this question causes the RVP8 to output bands of simulateddata. The bands can occupy a selectable range interval, and span a selectable intervalof data values.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–33 Start bin:0, Width:10 bins, Bands:16This question is only asked if we are simulating output rays. The Start Bin choosesthe bin number (origin zero) where the simulated bands will begin. The width ofeach band (in bins), and the total number of bands are also selected. The upper limitfor all parameters is the maximum bin count for the RVP8.Limits: Start: 0-Max, Width: 1-Max, Bands: 1-Max Start data value:0, Increment:16This question is only asked if we are simulating output rays. The data value that willbe assigned to the first simulated band, and the data increment from one band to thenext, are selected. The permissible values are from 0 to 65535, i.e., the full unsigned16-bit integer range. This full range is useful when simulating 16-bit output data; forthe more typical 8-bit output formats, only the low byte of the start and increment aresignificant.Limits: 0 to 65535Real Time TTY Monitor: NOThe Real Time TTY Monitor is a stream of characters that are continuously sent to aserial output of the RVP8, and which monitors selectable internal variables. Whenthis live monitor is enabled, status lines will be printed continuously. You maychoose the update rate, and which parameters are to be printed, using the questionsthat optionally follow. Pathname of TTY/FIFO: ’/dev/ttyS0’ Serial data rate: Update rate: 2.00 lines/sec Show burst frequency: NO Show burst pulse power: NO Show AFC information: NO Show pulse width: NO Show PRF: NO Show LOG noise: NO Show Polarization: NO Show IFD and link info: NO Show burst timing slew: NOMost of the data fields are printed in self-explanatory scientific units. The PRF is inHertz, but is printed without an “Hz” suffix. For historical reasons, the LOG Noise isprinted in old fashioned 8-bit A/D units, taken as the upper eight bits of the 12-bitlong LOG format described in Section 6.7. An 8-bit NSE value may be converted toan absolute dBm level using:dBm +PMax )16 s(NSE *224 )Where s is the LOG Slope (nominally equal to 0.03), and PMax is +4.5dBm for the12-bit IFD and +6.0dBm for the 14-bit IFD.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–343.2.8 Mz — Transmissions and ModulationsThese questions are used to configure the 8-Bit phase modulation codes that may be used tocontrol the phase of a coherent transmitter. The RVP8/Tx will output a pseudo-random sequenceof phase codes that are chosen from a specified set of available codes, i.e., all 8-bit patterns thatare valid for the phase modulation hardware. The random sequence is output only when theRVP8 is in one of its random phase processing modes (time series or parameter). At all othertimes, a fixed “idle” phase code pattern is output. See also Sections 3.2.1 and 3.2.5 whererelated phase control questions are found.8–Bit code to output when idle: 0x00This is the bit pattern to be output whenever the RVP8 is not in a random phaseprocessing mode. Note that this “idle” code does not have to be one of the“active”codes that are enabled below.Selection of Valid 8-Bit States–––––––––––––––––––––––––––––––00–0F: Y – – – – – – – – – – – – – – – 10–1F: – – – – – – – – – – – – – – – – 20–2F: – – – – – – – – – – – – – – – – 30–3F: – – – – – – – – – – – – – – – – 40–4F: – – – – – – – – – – – – – – – – 50–5F: – – – – – – – – – – – – – – – – 60–6F: – – – – – – – – – – – – – – – – 70–7F: – – – – – – – – – – – – – – – – 80–8F: – – – – – – – – – – – – – – – – 90–9F: – – – – – – – – – – – – – – – – A0–AF: – – – – – – – – – – – – – – – – B0–BF: – – – – – – – – – – – – – – – – C0–CF: – – – – – – – – – – – – – – – – D0–DF: – – – – – – – – – – – – – – – – E0–EF: – – – – – – – – – – – – – – – – F0–FF: – – – – – – – – – – – – – – – –This set of questions defines the subset of active 8-bit codes that are valid states forthe transmit phase modulator. Answer each line with a sequence of Y’s or N’s toindicate whether the corresponding 8-bit code is enabled. Only the codes that appearwith a “Y” will be used by the RVP8; the “–” indicates an unused code. The “–’character was used instead of “N” so that the visual contrast of the printed tablewould be improved.As an example, if your klystron transmitter has an octant phase modulator that iscontrolled by three digital lines, you might enable phase codes zero through seven,and then cable the modulator to the low three bits of the 8-bit code. The upper fivebits would not need to be used in this case.
RVP8 User’s ManualOctober 2005 TTY Nonvolatile Setups3–353.3 Advanced Options3.3.1 * — Sample current noise levelsThe “*” samples current noise levels from the receiver and then subtracts that noise fromsubsequent measurements. More information is provided in the Sample Noise Level (SNOISE)section 6–6.3.3.2 @ — Display/Change current Major ModeThis command provides developers with a simple way of switching modes enabling on–the–flytesting of code. The top level RVP8 operating modes are described in the documentation of theSOPRM command word #9. This question allows you to use the mode that has been selected bythat command, or to force the use of a particular mode.3.3.3 ~ — Burst-In / IF-In Swap Command (Rev.D IFD)The “~” command swaps the Burst and IF inputs at the IFD. Requests to toggle the state aremade from the top level as follows:RVP8> ~IFD Burst/IF Inputs are: SWAPPEDRVP8> ~IFD Burst/IF Inputs are: NORMALThe selection remains in effect for the duration of the setup session, but then returns toNORMAL upon exiting the TTY monitor. The “~” command is very handy because it allowsthe Pb,Pr, and Ps plotting commands to easily run with one input or the other. Here are twoexamples of how this might be useful.SWhen checking the range alignment on a Klystron system, the Pb plot can not be used inthe usual way to center the Tx burst because a continuous-wave COHO (rather than aburst pulse) is typically used as the phase reference in these systems. However, if youswap the Burst and IF inputs, you can then use the Pb command to view and center thereceived leakage of the Tx pulse, and thus locate range zero.SWhen setting up the AFC loop, you can use your RF signal generator to simulate thetransmitter’s frequency, and then run the loop with swapped RVP8/IFD inputs. The AFCservo will then hunt and follow the siggen frequency supplied via the receiver. You canthen make step changes in that frequency to verify that the loop responds properly.Note that the same input swapping function is also available via the RVP8/IFD toggle switches.However, those switches may be located far away from the operator’s terminal; hence, thecommand interface is still a valuable addition. The “~” command can only be used with a Rev.Dor later IFD; the command is unimplemented, and will not show up in the “Help” list, whenearlier receivers are connected.

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