Gilbarco MRIR8 Drive-Thru Reader Radio Identification Device User Manual Manual

Gilbarco Inc. Drive-Thru Reader Radio Identification Device Manual

Manual

1Series 2000 Reader SystemHigh Performance RFM RI-RFM-007BReference Guide11-06-21-042 April 1999
High Performance RFM RI-RFM-007B April 19992Second Edition - April 1999This manual describes the TIRIS High Performance RFM RI-RFM-007B,hereafter referred to as the RFM.Important NoticeTexas Instruments reserves the right to change its products or services or todiscontinue any product or service at any time without notice. TI provides customerassistance in various technical areas, but does not have full access to dataconcerning the use and applications of customer's products.Therefore, TI assumes no liability and is not responsible for customer applicationsor product or software design or performance relating to systems or applicationsincorporating TI products. In addition, TI assumes no liability and is not responsiblefor infringement of patents and/or any other intellectual or industrial property rightsof third parties, which may result from assistance provided by TI.TI products are not designed, intended, authorized or warranted to be suitable forlife support applications or any other life critical applications which could involvepotential risk of death, personal injury or severe property or environmental damage.The TIRIS logo and the word TIRIS are registered trademarks of TexasInstruments Incorporated.Copyright  1998 Texas Instruments Incorporated. All rights reserved.
April 1999 Contents3Table of ContentsPreface.................................................................................................................5Chapter 1: Product Description ........................................................................71.1 General.......................................................................................................81.2 Transmitter ...............................................................................................101.3 Receiver ...................................................................................................111.4 RFM Connectors and Jumpers ................................................................11Chapter 2: Specifications ................................................................................172.1 Recommended Operating Conditions ......................................................182.2 Dimensions...............................................................................................22Chapter 3: Installation......................................................................................233.1 Power Supply Requirements....................................................................243.2 Power Supply Connection ........................................................................25Chapter 4: Associated Antenna Systems ......................................................274.1 Antenna Requirements.............................................................................284.2 Antenna Resonance Tuning.....................................................................294.3 Tuning Procedure.....................................................................................30AppendicesAppendix 1: Expanding Antenna Tuning Inductance Range..........................33Appendix 2: Field Strength Adjustment..........................................................37Appendix 3: Adjustment of Oscillator Signal Pulse Width..............................39Appendix 4: Threshold Level Adjustment.......................................................41Appendix 5: Transmitter Carrier Phase Synchronization (CPS) ....................43Appendix 6: Noise Considerations .................................................................47Appendix 7: Over Voltage Protection .............................................................49
High Performance RFM RI-RFM-007B April 19994Table LocationsTable 1: J1 Pin Functions ................................................................................................................................ 13Table 2: J2 Pin Functions ................................................................................................................................ 14Table 3: J4 Pin Functions ................................................................................................................................ 14Table 4: J3 Pin Functions ................................................................................................................................ 15Table 5: Antenna Connectors.......................................................................................................................... 15Table 6: Operating Conditions......................................................................................................................... 18Table 7: Electrical Characteristics ................................................................................................................... 20Table 8: Timing Characteristics ....................................................................................................................... 21Table 9: Mechanical Parameters..................................................................................................................... 21Table 10: Power Supply Ripple Specifications................................................................................................ 24Table 11: Antenna Requirements.................................................................................................................... 28Table 12: Capacitor Values for Expanding Antenna Tuning Range to Lower Values..................................... 34Table 13: Capacitor Values Expanding Antenna Tuning Range to Higher Values ......................................... 35Table 14: Oscillator Signal Pulse Width versus Resistor Value (estimated values)........................................ 40Table 15: Maximum Distances between Antennas ......................................................................................... 44Table 16: Characteristics of Radiated and Conducted Noise.......................................................................... 47Figure LocationsFigure 1: RFM Block Schematic........................................................................................................................ 8Figure 2: Pulse Width Examples ..................................................................................................................... 10Figure 3: RFM Top View.................................................................................................................................. 12Figure 4: RFM Bottom View............................................................................................................................. 13Figure 5: Mechanical Dimensions ................................................................................................................... 22Figure 6: External Ground Connection (GND to GNDP)................................................................................. 26Figure 7: Tuning Example showing Increase of Total Tuning Capacity.......................................................... 31Figure 8: Flow-chart for Tuning the Antenna to Resonance............................................................................ 32Figure 9: Circuit for Expanding Antenna Tuning Range to Lower Values....................................................... 34Figure 10: Circuit for Expanding Antenna Tuning Range to Higher Values.................................................... 35Figure 11: Distance between Antennas (top view).......................................................................................... 44Figure 12: Noise Testing Configuration........................................................................................................... 48Figure 13: Circuit for Overvoltage Protection .................................................................................................. 50
5FCC/PTT RegulationsThe TIRIS RFM generates RF emissions at 134.2 kHz. The radiation of thefundamental and harmonics will vary with the type of antenna and other devices orfunctions connected to the RFM.Prior to operating the RFM together with antenna(s), power supply and a controlmodule or other devices, the required FCC, PTT or relevant government agencyapprovals must be obtained.Sale, lease or operation in some countries may be subject to prior approval bygovernmental and other organizations or agencies.CE ConformityA CE Declaration of Conformity is available for this module in a typicalconfiguration. Any device or system incorporating this module in any other than theoriginal CE configuration needs to be verified against the European EMC directive.A separate Declaration of Conformity must be issued by the system integrator oruser of such a system prior to marketing it and operating it in the EuropeanCommunity. Preface
High Performance RFM RI-RFM-007B April 19996ConventionsCertain conventions are used in order to display important information in thismanual, these conventions are:WARNING: A warning is used where care must betaken, or a certain procedure must be followed, inorder to prevent injury or harm to your health.CAUTION: This indicates information on conditions whichmust be met, or a procedure which must be followed,which if not heeded could cause permanent damage to theRFM.Note: Indicates conditions which must be met, or procedures whichmust be followed, to ensure proper functioning of the RFM.
7Product DescriptionThis chapter introduces the RFM component assemblies, showing the transmitterand receiver sections and placement of key user-accessible components. Topic Page1.1 General.......................................................................................................81.2 Transmitter ...............................................................................................101.3 Receiver ...................................................................................................111.4 RFM Connections and Jumpers...............................................................11 Chapter 1
High Performance RFM RI-RFM-007B April 199981.1 GeneralWARNING: Care must be taken when handling theRFM. High voltage across the antenna terminals, allantenna components and some parts of the printedcircuit board (PCB) could be harmful to your health. Ifthe antenna insulation is damaged, the antennashould not be connected to the RFM.CAUTION: This product may be subject to damage byelectrostatic discharge (ESD). It should be handled by ESDprotected personnel at ESD secured workplaces only. Thetransmitter power output stage can only operate with alimited duty cycle. Please pay attention to this whilstperforming antenna tuning procedures. Ground pins GNDand GNDP must be connected externally to avoid damageto the unit.The RFM is an integral part of the TIRIS system. Coupled with a Control Moduleand an antenna, it is used for wireless identification of TIRIS transponders. A blockschematic is shown in Figure 1.Figure 1: RFM Block SchematicPWMTXOscillatorRX demodulatorRXSS-InterfaceAntennaCircuit TX/RXAntennaRXAmplif ierRXSSthresholdATIInt.TX PowerStageCPSTXCT-RXDTRXCKATI 6ThresholdDemodulatorPWM Control Input Overvoltage Protection
April 1999 Product Description9The RFM contains all the analogue functions of a TIRIS reading unit needed tosend an energizing signal via the antenna to initialize a TIRIS transponder, todemodulate the received identification signal and to send the received datatogether with clock signals to a Control Module.The RFM also sends the necessary programming and addressing signals toRead/Write and Multipage transponders.The data input and output lines, which are connected to a data processing unit, arelow-power Schottky TTL and HCMOS logic compatible.The functions of the RFM are described in the following section.
High Performance RFM RI-RFM-007B April 1999101.2 TransmitterThe transmitter power stage is supplied with power via two separate supply linesVSP and GNDP. Because of the high current requirements for the transmitterpower stage, these supply lines are separated from the logic section supply linesand have two pins per line.The ground pins for the logic section and the transmitter are not connectedinternally in order to avoid possible problems with a high resistivity of GNDP pinsand in order to increase flexibility when using long supply lines. Pins GND andGNDP must be connected to each other externally. For more details, refer toSection 3.1, Power Supply Connection.The regulated transmitter power stage supply may vary between +7V and +24V.The supply lines VSP and VSL should be connected together when the supplyvoltage is +7 V or more. For details refer to Section 2, Specifications.Note: The RFM has an in-built temperature protection circuit whichsharply limits the transmitter power stage output if an over-currentsituation or an over-temperature environment causes the temperatureto exceed the allowed limits. After the device is switched off and hastime to recover (when the temperature drops again or the over-currentsituation is otherwise rectified) the unit reverts to normal operationwhen it is switched on again. Such an occurrence is an indication thatthe RFM is not being operated within specification.The transmit frequency (134.2 kHz) from the oscillator is fed to the pulse widthmodulator (PWM). By changing the value of a resistor, the PWM can set the pulsewidth ratio between 0% and 50%. For an example of two different oscillator signalpulse widths see Figure 2. Decreasing the 134.2 kHz frequency pulse width ratiodecreases the generated transmit (charge-up) field strength.It is therefore possible to adjust the generated field strength by selecting differentpulse width ratios. For more information about setting the field strength, refer toAppendix 2, Field Strength Adjustment.Figure 2: Pulse Width ExamplesPulse width of 50% Pulse width of 12.5%
April 1999 Product Description11CAUTION: The RFM must not be operated in continuoustransmit mode when operated at full power output. Fordetails please refer to Section 2, Specifications. Whenusing pulse widths smaller than 50%, the RFM transmitterpower stage works in a less efficient way. This leads to anincreased power dissipation and thus to highertemperature increase of the transmitter power stage, soensure that more cooling is provided.Note: If the RFM is going to be physically located within the antennafield, it may be necessary to shield the module.1.3 ReceiverThe signal received from the transponder is a frequency shift keying (FSK) signalwith typical low and high bit frequencies of 134.2 kHz and 123.2 kHz respectively.The signal is received from the antenna resonator, which is capacitively coupled tothe receiver.The signal RXCK is the reference clock signal to decode the RXDT data stream.The RXCK signal changes from low to high level during each data bit and theRXDT signal is valid before and after this positive slope for a certain time window.For more details refer to Table 8, Timing Characteristics.The receiver also has a built-in RF receive signal strength detector. The receivesignal strength is indicated by the digital output RXSS-.RXSS- becomes active ( logic low level) when the received RF signal strengthexceeds a defined level. This threshold level can be adjusted with a potentiometer(R409) on the RFM. The potentiometer is located near SW1 on the board. SeeFigure 3, RFM Top View.The RXSS- output is used for detection of other transmitting reading units and thuscan be used for wireless read cycle synchronization of several reading units.1.4 RFM Connectors and JumpersThere are a number of connectors, jumpers and other components on the RFMavailable for use.These are:J1 Connector for supply voltages and interface signal lines to and from theRFMJ2 Connector for the (optional) Antenna Tuning Indicator (ATI), which can beused for easy antenna tuning during installation.
High Performance RFM RI-RFM-007B April 199912J3 Connector for antenna resonance tuning, used to connect the requiredtuning capacitors.J4 Connector for field strength adjustment resistor and also direct access toreceiver input.JP3 Additional antenna damping connector.JP4 Common-mode noise choke bypass.R409 RXSS noise level adjustment potentiometer.SW1 Default all on. (Pos. 1 CPS setting see Appendix 5.)ANT1/ANT2 (two M3 screw connectors) connect the transmit/receive (TX/RX)antenna to the RFM.The RFM is normally mounted from the underside utilizing appropriate spacers andM3 mounting bolts.The top view of the RFM (without the normally fitted heatsink) is shown in Figure 3.Connectors J2, J3, J4, JP3, JP4, R409, switch SW1 and the antenna terminals areaccessible from the top.Figure 3: RFM Top View
April 1999 Product Description13The bottom view of the RFM is shown in Figure 4. The connectors J1, J2, J3 andJ4 are accessible from the underside. J1 is the 16-pin module connector, thiscarries the supply voltage lines, the data, and the control lines.Figure 4: RFM Bottom ViewTable 1 lists the pin functions for connector J1. The connector type is 16 pin, 2 rowwith 2.54 mm pin spacing.Table 1: J1 Pin FunctionsPin# Signal Direction Description1 GND IN Logic ground2 TXCT- IN Transmitter control input for activation of transmitter (active low, internalpull-up resistor)3 VSL IN Supply voltage for logic and receiver4 RXDT OUT Logic level compatible receiver data signal output5 RXSA IN/OUT Receiver signal strength adjust for RXSS- threshold level6 RXCK OUT Logic level compatible receiver clock output7 GNDP IN Transmitter power stage ground8 No connection9 GNDP IN Transmitter power stage ground10 RSTP OUT Analog receiver signal strength test pin11 VSP IN Supply voltage for transmitter power stage12 CPS_OUT OUT Carrier Phase Synchronization oscillator signal output13 VSP IN Supply voltage for transmitter power stage14 RXSS- OUT Receiver signal strength output (active low)15 No connection16 CPS_IN IN Carrier Phase Synchronization oscillator signal inputANT 1ANT 25313113579111315• •• •• •• •• •• •• •• •• •• •• •• •• •64242246810121416• •• •• •• •• •• •• •J1J2J4J31412108642131197531
High Performance RFM RI-RFM-007B April 199914CAUTION: The transmitter ground pins GNDP and logicground pin GND must be connected together externally.The RFM may be otherwise permanently damaged.Table 2 lists the pin functions for the ATI connector J2: The connector type is a6 pin, 2 row connector with 2.54 mm pin spacing.Table 2: J2 Pin FunctionsPin# Signal Direction Description1 TXCT-R IN Transmitter control signal via resistor (active low)2 GND OUT Logic ground3 VD OUT Internal regulated logic supply voltage output4 F_OSC-R IN/OUT Pulse width modulated transmitter oscillator signal via resistor5 RXSS- OUT Receiver signal strength output (active low)6 F_ANT OUT Antenna resonance frequency output signal (open collector)Table 3 lists the pin functions for the J4 pulse width adjustment connector. Theconnector type is 4 pin, 2 row with 2.54 mm pin spacing.Table 3: J4 Pin FunctionsPin# Signal Description1 RX Analog transponder signal2 GNDA Ground antenna circuit3 Pulse width adjusting resistorconnecting pin4 GND Logic ground
April 1999 Product Description15Table 4 lists the functions for connector J3. This is a 14 pin, 2 row connector with2.54 mm pin spacing.Table 4: J3 Pin FunctionsPin# Signal Description1 ATC1 Antenna tuning capacitor 1 (weighted value 1)2 GNDA Ground antenna circuit3 ATC2 Antenna tuning capacitor 2 (weighted value 2)4 GNDA Ground antenna circuit5 ATC3 Antenna tuning capacitor 3 (weighted value 4)6 GNDA Ground antenna circuit7 ATC4 Antenna tuning capacitor 4 (weighted value 8)8 GNDA Ground antenna circuit9 ATC5 Antenna tuning capacitor 5 (weighted value 16)10 GNDA Ground antenna circuit11 ATC6 Antenna tuning capacitor 6 (weighted value 32)12 GNDA Ground antenna circuit13 AMTP Antenna circuit test point14 No connectionTable 5 lists the pin functions for the antenna terminal connectors: Metric screwssize M3 are used for connection.Table 5: Antenna ConnectorsSignal DescriptionANT1 Antenna resonator (capacitor side)ANT2 Antenna resonator (transformer side)Jumper JP4 allows enabling and disabling of common noise filtering for EMIpurposes. The default setting, with common noise filtering active, jumpers pins 2and 3. A jumper between pins 1 and 2 bypasses common noise filtering.
17SpecificationsThis chapter lists the recommended operating conditions, electrical and mechanicalcharacteristics and dimensions. Topic Page2.1 Recommended Operating Conditions ......................................................182.2 Dimensions...............................................................................................22 Chapter 2
High Performance RFM RI-RFM-007B April 199918CAUTION: Exceeding recommended maximum ratings maylead to permanent damage of the RFM. The RFM must notbe operated in continuous transmit mode when operated atfull power output. Install suitable heatsinks when operatingthe RFM at pulse widths smaller than 50%.2.1 Recommended Operating ConditionsTable 6 shows the recommended operating conditions.Table 6: Operating ConditionsSymbol Parameter min. typ. max. UnitV_VSP Supply voltage of transmitter power stage 7.0 12.0 24.0 V DCI_VSP Current consumption of transmitter power stage - refer to the formulabelow 1.0 1.7 ApeakP_VSP Peak pulse power input to transmitter power stage (I_VSP * V_VSP *Duty Cycle) 20 WV_ANT Antenna resonance voltage 250 380 VpeakV_ANT-25 Antenna resonance voltage (Pulse width setting ≤ 25%) 200 VpeakV_ANT-D1 Antenna resonance voltage for damping option using jumper JP3 50 60 VpeakV_ANT-ATI Minimum antenna resonance voltage for correct operation of ATI 25 VpeakV_VSL Supply voltage input for logic part 7.0 24.0 V DCI_VD External current load on internal regulated logic supply voltage output 1.0 mAT_oper Operating free-air temperature range -25 +70 ° CT_store Storage temperature range -40 +85 ° CNote: Free-air temperature is the air temperature immediatelysurrounding the RFM module. If the module is incorporated into ahousing, it must be guaranteed by proper design or cooling that theinternal temperature does not exceed the recommended operatingconditions.
April 1999 Specifications19In order to keep power consumption (P_VSP) below 20 W it is advisable to limitI_VSP. The maximum allowed value, dependent on the configuration, can bedetermined as follows (in the following examples a supply voltage of 24 V_VSP isused):I_VSP =where Duty Cycle =Example 1: Using Standard/Default Settings (≈10 read cycles/second):I_VSP = = 1.66 A Duty Cycle = = 0.5Example 2: Configured to No Sync (≈12 read cycles/second):I_VSP = = 1.33 A Duty Cycle = = 0.625The following methods can be used to measure the actual I_VSP value:1. Use a battery powered oscilloscope to measure the voltage drop across a0.1 Ohm resistor placed in the DCIN+ line, and then calculate the actualcurrent using the formula I = V/R.2. If a battery powered oscilloscope is not available, measure the potential at bothsides of the 0.1 Ohm resistor (signal probe) with the GND probe at DCIN- anddetermine the potential difference.Ensure that the measured I_VSP value does not exceed the calculated value. 20 W24V x 0.5 50 ms100 ms 20 W24V x 0.625 50 ms 80 ms P_VSPV_VSP x Duty Cycle Power on timeTotal Read Cycle Time
High Performance RFM RI-RFM-007B April 199920Table 7: Electrical CharacteristicsSymbol Parameter min. typ. max. UnitI_VSL Supply current for logic and receiver part in transmit and receivemode 14 18 22 mAViL Low level input voltage of TXCT- 0 0.4 0.8 VViH High level input voltage of TXCT- 2.4 5.0 VVoL Low level output voltage of RXDT and RXCK 0 0.4 0.8 VVoH High level output voltage of RXDT and RXCK 4.0 5.25 VVoL_R Low level output voltage of RXSS- 0.8 VVoH_R High level output voltage of RXSS-(see note below) 5.25 VFan-In Low power Schottky compatible fan-in of signals TXCT- (Iin = -400µA) 1-I_IN-TXCT- Input current for TXCT- signal, when the Accessory Module RI-ACC-ATI2 is connected 2.0 2.5 3.0 mAFan-Out Low power Schottky compatible fan-out of signals RXDT and RXCK 3 -FanOut_Rl Low power Schottky compatible fan-out of signal RXSS- (low levelonly) 1-FanOut_Rh Low power Schottky compatible fan-out of signal RXSS- (high levelonly)(see note below)l_J1 Cable length for connecting J1 of RFM to a Control Module using flatcable 00.52.0ml_CPS Cable length for connecting the Carrier Phase Synchronization signalbetween two RFMs 01.05.0mn_CPS Number of oscillator SLAVE RFMs, which can be driven from oneoscillator MASTER RFM 15-Com_Mode Common Mode Noise reduction ratio for noise coupled to bothantenna terminals ANT1 and ANT2 20 dBR_GND Decoupling resistor between GND and GNDP (+/- 5%) 64.6 68 71.4 OhmNote: RXSS- has an internal pull-up resistor of 10 kOhm. Theparameter VoH_R therefore depends on application specific externalcomponents.
April 1999 Specifications21Table 8: Timing CharacteristicsSymbol Parameter min. typ. max Unitt_TX Transmit burst length for correct operation(see note below) 15 50 100 mst_dtck Delay time from beginning of data bit at RXDT being valid to positiveslope of RXCK signal 20 µst_dtvd Time for data bit of RXDT signal being valid after positive slope ofRXCK 90 µst_ckhi Time for clock signal RXCK being high 55 µst_rit_fi Necessary rise and fall times for input signal TXCT- and TXCT-R 11µsµst_rot_fo Rise and fall time of output signals RXDT and RXCK 11µsµst_ro_R Rise time of output signal RXSS-(no external connection) 1µst_fo Fall time of output signal RXSS- 1 µstss_01Tl Propagation delay time from positive slope of TXCT- to positive slopeof RXSS- signal (maximum sensitivity) 500 1000 1500 µstss_10Tr Propagation delay time from negative slope of TXCT- to negative slopeof RXSS- signal (minimum sensitivity) 50 100 200 µst_short Maximum time of short circuit between antenna terminals ANT1 andANT2 and short circuit of ANT1 or ANT2 to GNDA 10 sNote: Due to transponder parameters a minimum charge-up time of 15ms is necessary. Decreasing charge-up time decreases read range bysending less energy to the transponder.CAUTION: The parameter t_short refers to a static shortcircuit of the antenna terminals. Shorting the antennaterminals during operation may cause permanent damageto the RFM.Table 9: Mechanical ParametersParameter Typical UnitHeight including mounting bolts 44.0 +/- 1.5 mmWeight 260 gNote: The heatsink is connected to the antenna resonator groundGNDA. When connecting the heatsink to a housing, the heatsink mustbe insulated from the housing.
High Performance RFM RI-RFM-007B April 1999222.2 DimensionsAll measurements are in millimeters with a tolerance of +/- 0.5 mm unlessotherwise noted.Figure 5: Mechanical Dimensions8.8 mm+/- 1.0 mm9.9 mm+/- 1.0 mm70.36 mm 83 mm +/- 1.0 mm57.6 mm +/- 1.0 mm16.0 mm+/- 1.0 mm93 mm +/- 1.0 mm71.1mm4.83 mm+/- 1.0 mmM3 Pressnuts
23InstallationThis chapter shows how to install the RFM and specifies power supplyrequirements and connections. Topic Page3.1 Power Supply Requirements....................................................................243.2 Power Supply Connection ........................................................................25 Chapter 3
High Performance RFM RI-RFM-007B April 1999243.1 Power Supply RequirementsThe logic and receiver sections of the RFM must be supplied via the VSL and GNDpins with unregulated voltage.The transmitter power stage is separately supplied via VSP and GNDP. As there isno stabilization circuitry on the RFM and as the transmitter power stage needs aregulated supply voltage in order to meet FCC/PTT regulations, the supply voltagefor the transmitter power stage must be regulated externally.For the voltage supply range please refer to Section 2, Specifications.Note: The RFM should not be supplied by switched mode powersupplies (SMPS) as most SMPS operate at frequencies of around 50kHz. The harmonics of the generated field may interfere with theTIRIS receiver and therefore only linear power supplies, or SMPS witha fundamental operating frequency of 200 kHz or higher arerecommended.Noise from power supplies or from interface lines may interfere with receiveroperation. It is recommended to add additional filters in series to the supply andinterface lines if required by the application. For more details refer to Appendix 6,Noise Considerations and Appendix 7, Over Voltage Protection.In order to guarantee full RFM performance, the power supplies should fulfill thespecifications for ripple voltage given in Table 10.Table 10: Power Supply Ripple SpecificationsSupply Type Maximum Ripple Voltage Allowable Ripple FrequencyUnregulated VSL supply 30 mVrms 0 to 100 kHz maximum(sinusoidal)Regulated VSP supply 50 mVrms 0 to 50 kHz maximum(sinusoidal)
April 1999 Installation253.2 Power Supply ConnectionGround pins for the logic/receiver part and the transmitter power stage are notdirectly connected internally, the two different grounds having to be connected toeach other externally.The only internal connection is via resistor R_GND, in order to avoid floatinggrounds if these grounds are accidentally not connected to each other externally.This is necessary for two reasons:1. A high resistivity of the GNDP pins could cause a voltage drop across thesepins, due to high transmitter power stage current (this does not apply to thesupply pins of the logic section). If the grounds were connected to each otherinternally, this would also lift the internal logic ground and cause logic levelcompatibility problems with the Control Module (see Figure 6).2. In order to provide greater flexibility when using long supply lines.Long VSP supply lines between the RFM and the Control Module cause avoltage drop across this supply line (again due to high transmitter power stagesupply current). This voltage drop would also lift the logic ground and causelogic level compatibility problems with the Control Module. This can be avoidedby connecting the grounds externally in any of three different ways (see alsoFigure 6) as described below:• For cable lengths of up to 0.5 m between RFM and Control Module, the RFMground pins GND and GNDP must be connected at the Control Module, asshown in Figure 6. The grounds for the VSP, VSL and the Control Modulesupply are connected together at a common ground. Alternatively, if thevoltage drop across the VSP supply line is less than 0.5 V (likely in this case),the ground pins GND and GNDP may be connected together at the RFM. If thesystem has a TIRIS Control Module, the RFM ground pins GND and GNDP arealready connected together correctly on the Control Module. When using acustomer-specific controller, care must be taken to connect the RFM groundpins GND and GNDP to an appropriate ground on the controller.• For cable lengths of between 0.5 m and 2 m, the RFM ground pins GND andGNDP must be connected together at the Control Module in order to avoidlogic level compatibility problems caused by the voltage drop across the VSPsupply lines. Connecting the ground pins at the RFM is not permitted since thiswould lift the logic ground level.
High Performance RFM RI-RFM-007B April 199926• Cable lengths longer than 2 m are not recommended. If the applicationdemands cabling longer than 2 m, the logic signal connections between theRFM and the Control Module should be done via a differential interface (forexample RS422). Due to different ground potentials at different locations it mayalso be necessary to provide galvanic separation of the interface signals by, forexample, opto-couplers. In this case, to avoid problems with differencevoltages between GND and GNDP, these pins must always be connecteddirectly at the RFM. As shown in Figure 6, a shorting bridge is necessary forthis purpose, situated as close as possible to the RFM.CAUTION: The voltage between GND and GNDP must notexceed ±0.5 V, otherwise the RFM will suffer damage.Figure 6: External Ground Connection (GND to GNDP)TIRIS RF ModuleCustomer Specific Controller+ VsupplyGroundCommon GroundVSP 13VSP 11VSL 3GND 1GNDP 9GNDP 7Bridge+ VSL+ VSP Connector ST1to TX power stageto Logic partGround LogicGround TX power stageR_GND
27Associated Antenna SystemsThis chapter discusses antenna requirements and antenna tuning procedures andflowcharts.Topic Page4.1 Antenna Requirements.............................................................................284.2 Antenna Resonance Tuning.....................................................................294.3 Tuning Procedure.....................................................................................30Chapter 4
High Performance RFM RI-RFM-007B April 1999284.1 Antenna RequirementsIn order to achieve high voltages at the antenna resonance circuit and thus highfield strength at the antenna for the charge-up (transmit) function, the antenna coilmust be high Q. The recommended Q factor for proper operation is listed in Table11, Antenna requirements. The Q factor of the antenna may vary depending on thetype, the construction and the size of the antenna. Furthermore, this factordepends on the wire type and wire cross-sectional area used for winding of theantenna.RF braided wire, consisting of a number of small single insulated wires isrecommended for winding of an antenna since it gives the highest Q factor andthus the highest charge-up field strength, for example single wire diameter of 0.1mm (4 mil) and 120 single insulated wires.Note: If a high Q is not required (for example for large in-groundantennas), standard braided wire can be used.In order to ensure that the transmitter and receiver function correctly, the antennamust be tuned to the resonance frequency of 134.2 kHz. For a detailed descriptionof the antenna resonance tuning procedure, refer to Chapter 4.2, AntennaResonance Tuning.To ensure that the antenna can be tuned to resonance with the RFM, the antennainductance can only vary within the limits given in Table 11.Table 11: Antenna RequirementsParameter Conditions min. typ. max. UnitL_ANT Antenna inductance range within which the antenna canbe tuned to resonance 26 27 27,9 µHQ_ANT Recommended Q factor of antenna coil for correctoperation 40 450 -Note: Although a ferrite core antenna may have a high Q factor undertest conditions with low magnetic field strengths, the Q factordecreases when a high magnetic field strength is applied to the ferritecore.WARNING: Care must be taken when handling theRFM. HIGH VOLTAGE across the antenna terminalsand all antenna resonator parts could be harmful toyour health. If the antenna insulation is damaged theantenna should not be connected to the RFM.
April 1999 Associated Antenna Systems29When low field strength for larger antennas is necessary (Vpeak <60 V), theantenna resonator can additionally be damped by connecting an onboard dampingresistor, which may be done by closing jumper JP3 (see Figure 3). This jumper isopen by default.CAUTION: Only a certain maximum antenna resonancevoltage is allowed for this option. Please refer to Chapter2.1, Recommended Operating Conditions, for details.Note: The transformer of the transmitter power stage is operated at ahigh magnetic flux. Due to the high level of magnetic flux change, thetransformer may emit an audible tone. This may also occur withantennas that have ferrite cores (e.g. TIRIS Standard Stick AntennaRI-ANT-S02). This tone does not indicate a malfunction.4.2 Antenna Resonance TuningIn order to achieve a high charge-up field strength, the antenna resonatorfrequency must be tuned to the transmitter frequency of 134.2 kHz. This is done bychanging the capacitance of the antenna resonator.To compensate for the tolerances of the antenna coil and the capacitors, six binaryweighted tuning capacitors (C_ATC1 to C_ATC6) have been included. Their valuesare weighted in steps of 1, 2, 4, 8, 16 and 32, where C_ATC1 has the smallestvalue corresponding to the factor 1, C_ATC2 has double the capacity of C_ATC1,so that C_ATC2 corresponds to the factor 2 and so on. Each of the 6 tuning pinshas an adjacent ground pin for antenna tuning, using shorting bridges (jumpers).Monitoring of the correct antenna resonance tuning can be performed using theAntenna Tuning Indicator (ATI) tool RI-ACC-ATI2.This device allows the transmitter to be operated in pulsed mode, independently ofthe Control Module. It indicates by LEDs whether the tuning capacity should beincreased or decreased (marked on the ATI as IN for increase and OUT fordecrease) and when the antenna is tuned to resonance, in which case the greenLED is on or flashing together with the IN or OUT LED. The device is plugged intothe RFM connector J2 during the tuning procedure, power being supplied from thismodule.
High Performance RFM RI-RFM-007B April 199930The following notes refer to antenna resonance tuning in general:Note: If an antenna has to be installed in an environment where metalis present, the tuning of the antenna must be done in thisenvironment, since the presence of metal changes the inductance ofthe antenna. In addition, the Q factor of the antenna decreases,thereby decreasing the field strength. The extent of the inductanceand quality factor reduction depends on the kind of metal, the distanceof the antenna from it and its size.When the oscillator signal pulse width, or the supply voltage VSP of aRFM with a pre-tuned ferrite core antenna (for example: RI-ANT-S02)is changed by a factor of more than 50%, the ferrite core antenna hasto be re-tuned to the new conditions due to the inductance changingslightly at different field strengths.Each antenna is tuned individually to the RFM and this results in aunique tuning jumper arrangement for this combination of antennaand RFM.If a different antenna or RFM is connected, the new combination mustbe tuned to resonance again.4.3 Tuning Procedure1. Switch RFM power supply off.2. Connect the antenna to the RFM by means of the two M3 screw connectors.3. Install antenna tuning monitoring unit.4. Switch RFM power supply on.5. Tune antenna to resonance by changing the tuning capacity.6. Switch RFM power supply off.7. Disconnect monitoring unit.8. Switch RFM power supply on again.The antenna resonance tuning is now complete.The tuning of a new antenna to the RFM is started with no jumpers (shortingbridges) connected. While monitoring the resonance condition as described above,the jumpers are plugged in or out, thus connecting and disconnecting the tuningcapacitors in such a way that the total tuning capacity will increase in steps of thesmallest capacitance C_ATC1.
April 1999 Associated Antenna Systems31Counting-up of the binary weighted tuning capacitors is in principle done in thefollowing way:1. No jumpers connected.2. connect C_ATC1 (J3 pins 1 and 2).3. disconnect C_ATC1 and connect C_ATC2.4. Connect both C_ATC1 and C_ATC2 (and so on).However, the tuning steps do not offer an absolutely continuously increasingfunction, due to component tolerances. It is therefore possible that when the tuningvalue is increased by one binary step the total tuning capacity actually decreases(especially from tuning step 31 to 32), which can result in the generated fieldstrength not steadily increasing (as shown in Figure 7). This is not the case whenusing the Antenna Tuning Indicator tool (ATI) since the indicated resonancecondition is always correct.It is therefore recommended to perform resonance tuning according to the flow-chart shown in Figure 8.051015202530354045501 4 7 101316192225283134374043464952555861Decimal value of tuning stepT uning capacityField strength'false' resonancepointcorrect resonance pointFigure 7: Tuning Example showing Increase of Total Tuning Capacityand Generated Field Strength (typical values)
High Performance RFM RI-RFM-007B April 199932Figure 8: Flow-chart for Tuning the Antenna to ResonanceNoNoYesYesCONNECT ANTENNA TO THE RF MODULESTARTDISCONNECT ALL JUMPERSCONTROL CURRENT INTO VSP PININCREASE TUNING CAPACITY BY ONE BINARY STEPCONTROL CURRENT INTO VSP PINMEASUREDVALUE HAS DECREASED INCOMPARISON TO THEPREVIOUS TUNING VALUEINCREASE TUNING CAPACITY BY ONE BINARY STEPCONTROL CURRENT INTO VSP PINMEASUREDVALUE HAS DECREASED INCOMPARISON TO THEPREVIOUS TUNING VALUEDECREASE TUNING VALUE BY TWO BINARY STEPSPLUG IN JUMPERS FOR TUNING THIS ANTENNA TOTHIS RF MODULESTOP
33Expanding Antenna TuningInductance RangeIt is possible to expand the tuning range of the antenna inductance. This may benecessary when TIRIS standard antennas are used close to metal, when antennaextension cables are used or when customer specific antennas which might not bewithin the necessary antenna tuning inductance range are used.Note: Please remember that the capacitors of external modules haveto be able to withstand higher voltages when used together with aRFM.Expanding the antenna tuning inductance range to lower or higher values can bedone by connecting additional capacitors in parallel and in series to the antennaresonator.The capacitors have to be connected in parallel and in series in order to withstandhigh voltages and currents occurring at the antenna resonance circuit.WARNING: There is HIGH VOLTAGE present at allantenna resonator components, which may beharmful to health. The RFM must be switched OFFwhile working on it. External components must bemounted such that they cannot be accidentallytouched.To ensure that the RFM functions correctly when the antenna tuning inductancerange is expanded, special capacitors, as listed below, must be used:Capacitor type: - Polypropylene film capacitor- Minimum 1250V DC operating voltage- Capacitance tolerance: max. ±5%- Type: SIEMENS "KP" or WIMA "FKP1" Appendix 1
High Performance RFM RI-RFM-007B April 199934The antenna tuning inductance range can be decreased to 13.7 µH in six ranges,as shown in Figure 9 and Table 12.Figure 9: Circuit for Expanding Antenna Tuning Range to Lower ValuesTable 12: Capacitor Values for Expanding Antenna Tuning Range to LowerValuesAntenna inductance range Capacitor value24.1 µH to 25.9 µHC1, C2, C3, C4 = 3.3 nF22.3 µH to 24.0 µHC1, C2, C3, C4 = 6.8 nF20.4 µH to 22.2 µHC1, C2, C3, C4 = 11 nF(10 nF and 1 nF in parallel)18.4 µH to 20.3 µHC1, C2, C3, C4 = 16 nF16.5 µH to 18.3 µHC1, C2, C3, C4 = 22 nF13.7 µH to 16.4 µHC1, C2, C3, C4 = 32 nFThe antenna tuning inductance range can be increased to 37.6 µH in 7 ranges, asshown in Figure 10 and Table 13.As shown, three capacitors (C1, C2, C3) are connected in series with the antennacoil. The specification for these capacitors is listed below:Capacitor type: - Polypropylene film capacitor- Minimum 1250 VDC operating voltage- Capacitance: 47 nF ±2.5%- Type: SIEMENS "KP" or WIMA "FKP1"In addition to C1, C2 and C3, the capacitor C4 must be connected in parallel to theRFM antenna terminals. Different capacitor values are used for each range, thevalues being given in Table 13.ANT 2ANT 1••••••C1 C3C4C2
April 1999 Appendix 135Figure 10: Circuit for Expanding Antenna Tuning Range to Higher ValuesTable 13: Capacitor Values Expanding Antenna Tuning Range to HigherValues(C1, C2 & C3 = 47 nF)Antenna inductance range Capacitor value28.0 µH to 29.3 µHC4 = 18.3 nF(parallel 6.8 nF, 6.8 nF, 4.7 nF)29.4 µH to 31.0 µHC4 = 13.6 nF(parallel 6.8 nF, 6.8 nF)31.1 µH to 32.4 µHC4 = 10 nF32.5 µH to 33.8 µHC4 = 6.8 nF33.9 µH to 35.0 µHC4 = 3.98 nF(parallel 3.3 nF, 0.68 nF)35.1 µH to 36.2 µHC4 = 2.2 nF36.3 µH to 37.6 µHC4 not neededTwo serial connected TIRIS standard antennas C4 = 3.3 nFC2 and C3 not neededNote: It is not recommended to use antennas with Q factors lowerthan 50. Antennas with inductances lower than 13.7 µH or more than37.8 µH should not be used except when connecting two antennas inseries since the additional capacitor values become very large.Antennas with fewer turns (i.e. smaller inductance) generate lesscharge-up field strength under the same operating conditions and inaddition also have less receive sensitivity. Using capacitors parallel tothe antenna resonator changes the coupling of the RFM's transmitterpower stage thus reducing the generated field strength.In order to avoid adaptation problems, it is strongly recommended touse standard TIRIS antennas.ANT 2ANT 1•••••••••C4 C1C2C3•
37Field Strength AdjustmentThe magnetic field strength generated determines the charge-up distance of thetransponder. The higher the magnetic field strength, the further the transpondercharge-up distance. The charge-up distance does not, however, increase linearlywith the field strength.The reading distance of a transponder is determined, amongst other factors, by thecharge-up distance and the local noise level. Increasing the charge-up fieldstrength does not necessarily increase the reading distance.The field strength generated by the RFM depends on the four factors listed below:1. Q factor of the antenna.The Q factor is a measure of the efficiency of the antenna and therefore the higherthe Q factor of the antenna coil, the higher the field strength generated by theRFM, assuming that all other parameters remain unchanged. The Q factor of theantenna itself depends on the cross-sectional area of the wire, the wire type, thesize of the antenna and the type of antenna (gate or ferrite). The larger the cross-sectional area of the RF braided wire, the higher the Q factor of the antenna. RFbraided wire gives a higher Q factor than solid wire assuming that all otherparameters remain unchanged.2. Size of the antenna.The larger the antenna, the higher the field strength which is generated by theRFM, since the antenna covers a larger area and thus generates a higher fluxassuming that all other parameters remain unchanged. Large antennas have lessimmunity to noise for receive functions than small antennas. Appendix 2
High Performance RFM RI-RFM-007B April 1999383. Supply voltage of the RFM power stage.The higher the supply voltage of the RFM transmitter power stage (VSP voltage),the higher the field strength which is generated by the RFM assuming that all otherparameters remain unchanged. However, the generated field strength does notincrease linearly with VSP supply voltage. In addition, ferrite core antennas showsaturation effects (saturation means here that the ferrite core cannot generatemore magnetic field strength, even with a higher input current).4. The oscillator signal pulse width.The bigger the selected transmitter oscillator signal pulse width, the higher themagnetic field strength which is generated by the RFM, since more power is fedinto the antenna resonator by the transmitter power stage assuming that all otherparameters remain unchanged.The generated field strength can be measured in several ways. It may bemeasured using a calibrated field strength meter or by measuring the antennaresonance voltage using an oscilloscope and then calculating the field strength.In summary: the generated field strength of an antenna can be adjusted with thesupply voltage VSP of the RFM transmitter power stage and by selecting thecorresponding oscillator signal pulse width.In cases where low field strengths should be generated with large antennas (RI-ANT-G01 and RI-ANT-G03), the antenna resonator can be additionally damped byclosing jumper JP3.Using this optional damping function allows the field strength to be again fine-tunedto meet FCC/PTT regulations with selection of the oscillator signal pulse width in awide range of both larger and smaller values.CAUTION: This damping option can only be used togetherwith the TIRIS standard antennas RI-ANT-G01 and RI-ANT-G03. Only a certain maximum antenna resonance voltage isallowed for this option. Please refer to Section 2.1,Recommended Operating Conditions, for details.Note: For correct adjustment of field strength according to FCC/PTTvalues, especially for customized antennas, a calibrated field strengthmeter must be used. Field strength measurements must be taken on afree field test site according to VDE 0871 or equivalent regulation.
39Adjustment of Oscillator SignalPulse WidthThe RFM has an built-in feature to allow setting of the pulse width of the transmittersignal coming from the oscillator. This enables the generated field strength to bereduced from 50% down to 0%.For this purpose a pulse width setting resistor may be inserted between J4 pins 3and 4 on the RFM. Inserting a smaller resistance value decreases the pulse widthand thus also the field strength. As default, no resistor is connected, thus selectingthe maximum pulse width of 50% and the maximum field strength. By connecting ashorting bridge, the smallest pulse width of approximately 0% is selected.Table 14 provides an overview of oscillator signal pulse width and correspondingfield strength reduction when different oscillator signal pulse widths are selected byconnecting different resistor values. Appendix 3
High Performance RFM RI-RFM-007B April 199940Table 14: Oscillator Signal Pulse Width versus Resistor Value (estimatedvalues)Resistor value[kΩΩΩΩ]Oscillator signalpulse width [%] Field strengthreduction [dB]open 50 0151 37 -359 25 -617 12 -1210 6 -18shorted 0 ∞CAUTION: When using pulse widths smaller than 50%, theRFM transmitter power stage works less efficiently. Thisleads to an increased power dissipation and thus to ahigher temperature of the transmitter power stage. Ensurethat the antenna resonance voltage does not exceed 200Vp when the selected oscillator signal pulse width settingis smaller than 25%.Note: The pulse width for an oscillator signal pulse width setting of 5%and smaller is extremely short. The pulse response of the RFMtransmitter power stage to this short pulse is different for each unit. Inorder to have reproducible field strength values for different RFMs, it isnot recommended to use the smallest pulse width setting.
41Threshold Level AdjustmentThe RFM has a built-in receive signal field strength detector with the output signalRXSS- and an on-board potentiometer (R409) to adjust the threshold level of fieldstrength detection. The digital output RXSS- is used for wireless synchronization oftwo or more reading units. This is necessary to ensure that if more than onereading unit is in an area, they do not interfere with each other. The Control Modulesoftware monitors the RXSS- signal to detect whether other reading units aretransmitting. The Control Module can operate the transmitter of the RFM such thatthe reading units either transmit simultaneously or alternately. In this way the readcycles of each of the reading units occur at the same time or at secure differenttimes. Depending on the antenna type used and the local noise level, the RXSS-threshold level has to be adjusted. This needs to be done after the antenna hasbeen tuned to resonance. It is recommended to use a small screwdriver to adjustthe RXSS- threshold level. The R409 potentiometer is located on the upper side ofthe RFM board near connector switch SW1. Turning the potentiometer all the wayclockwise (right-hand stop), results in minimum threshold sensitivity, i.e. the RXSS-signal will be activated at high receive field strength. This is the default position andcan be used for standard gate antennas. It may be necessary to increase thesensitivity when using ferrite core antennas. If there is high noise level in the area,it is necessary to adjust the RXSS- threshold level.Adjust the RXSS- threshold level as follows:1. Turn the RXSS- threshold level potentiometer fully counter-clockwise (left-handstop).2. Deactivate the transmitter by jumpering pin 1 to pin 3 of connector J2.3. Ensure that no other reading units are transmitting, by connecting pin 1 to pin 3of connector J2 (jumper) of all other RFMs in the area.4. Monitor the voltage at RXSS- output pin with a voltmeter or an oscilloscope. Appendix 4
High Performance RFM RI-RFM-007B April 1999425. Turn the RXSS- threshold level adjustment potentiometer on the RFMclockwise, until the RXSS- output is just statically inactive. "Statically" meansno voltage spikes present on the RXSS- signal. 'Inactive' means that thereceive signal strength is below the RXSS- threshold level and not triggeringRXSS- (the RXSS- output voltage remains > 4 V).6. Remove all jumpers connected to J2Note: Reducing the RXSS- threshold level sensitivity (turning thepotentiometer clockwise), reduces the sensitivity of the built-in receivesignal strength detector. This has the effect that the distance forwireless detection of other transmitting reading units is decreased,leading to reduction of wireless synchronization distance. The wirelesssynchronization distance between two reading units is normally about15 meters for two aligned stick antennas (RI-ANT-S02) with maximumreceive field strength detection sensitivity.When the RXSS- threshold level is adjusted such that it is toosensitive, then the RXSS- output is constantly active (i.e. low RXSS-output level). Therefore a Control Module assumes that anotherreading unit is transmitting and continually tries to synchronise to thisother reading unit. As a result, the reading repetition rate decreasesfrom approximately 10 down to 5 readings per second. This readingunit can additionally no longer synchronise to other reading units,causing interference with other reading units and reading at allreading units becomes impossible.The RXSS- threshold level must be adjusted individually for everyRFM and reading system antenna. In addition, the RXSS- thresholdlevel must be individually adjusted to the local noise level in theapplication area where the antenna is used.As high noise levels mean that the RXSS- threshold level must beadjusted to a less sensitive value, it is recommended to reduce thelocal noise level in order to have high synchronization sensitivity and along reading distance.The RXSS- threshold level must be adjusted so that no spikes occuron the RXSS- signal output since these lead to an incorrectsynchronization function. An oscilloscope should therefore be usedwhen adjusting the threshold level.The Antenna Tuning Indicator (RI-ACC-ATI2) accessory can be usedto adjust the RXSS- threshold level, since this device automaticallyswitches the transmitter off and has an internal spike extension circuit,causing the RXSS- threshold level to be adjusted such that no spikesoccur on the RXSS- output.
43Transmitter Carrier PhaseSynchronization (CPS)In some applications it is necessary to use several charge-up antennas close toeach other. Under these circumstances, the magnetic charge-up fields generatedby different antennas superimpose on each other and may cause a beat effect onthe magnetic charge-up field, due to the slightly different transmit frequencies ofdifferent RFMs.The impact of this effect depends on three factors:1. Antenna size:The larger the size of the antennas, the further the distance between theantennas must be, so that this effect does not occur.2. Magnetic field strength:The stronger the generated magnetic field strength, the further the distancebetween the antennas must be such that the effect does not occur.3. Orientation and distance between antennas:Increasing the distance between antennas decreases the impact of this effect.Note: Putting two antennas close together also changes antennainductance, so that the antennas may no longer be tuneable toresonance. Appendix 5
High Performance RFM RI-RFM-007B April 199944If several antennas are used close to each other, a check should be made todetermine if the charge-up field strength changes regularly (i.e. beat effect ). Thismay be checked by verifying the antenna resonance voltage with an oscilloscope.If the antenna resonator voltage changes periodically by more than approximately5% of the full amplitude it is appropriate to use wired transmitter carrier phasesynchronization.In addition, the distances given in Table 15 can be used as a guideline todetermine when it is necessary to cross-check for beat effect. If these distancesare less than the value given in Table 15, a check for beat effect should be made.The values given refer to the distances shown in Figure 11 and are valid formaximum charge-up field strength.Figure 11: Distance between Antennas (top view)Table 15: Maximum Distances between AntennasAntenna type Distance D1 [m] Distance D2 [m]RI_ANT_S02 <=> RI_ANT_S02 0,8 1,0RI_ANT_G01 <=> RI_ANT_G01 1.7 1.5RI_ANT_G02 <=> RI_ANT_G02 1.3 1.0RI_ANT_G04 <=> RI_ANT_G04 2.0 1.7This effect will not occur if the transmitters of different RFMs are operated from thesame oscillator signal. This is the reason why the pulse width modulated oscillatorsignal is accessible at the connector J1.ConfigurationMaster or Slave setting of a RFM is determined by switch 1 position 1 (SW1/1). Ifthis is in the ON position, the RFM is a MASTER, if in the OFF position, it is aSLAVE. When a RFM has been configured as a master, then J1 pin 12 of this unitshould be connected to J1 pin 16 of the slave units to allow the master oscillatoroutput (CPS_OUT) to drive the slave oscillator inputs (CPS_IN). The logic ground(e.g. J1 pin 1) of both master and slave units should be connected together.Caution: Use overvoltage protection components at theCPS connector for CPS lines between 0.5m and 5m.Distance D1Antenna 1 Antenna 2Distance D2Antenna 1 Antenna 2
April 1999 Transmitter Carrier Phase Synchronization45Note: When using the transmitter Carrier Phase Synchronizationfeature, it is absolutely necessary that the read cycles of each of thedifferent Control Modules are synchronized. When the transmitter ofthe oscillator MASTER RFM is not activated by its Control Module, theoscillator signal output of the oscillator MASTER RFM is disabled.This means that all the oscillator SLAVE RFMs have no transmitteroscillator input signal and thus none of the oscillator SLAVE RFMs areable to transmit.The read cycles of all RFMs connected to this CPS interface must be synchronizedand all read cycles must occur simultaneously. Refer to the Hardware andSoftware Manuals for the TIRIS Control Modules for more information about thenecessary wiring and settings for synchronization of the RFM when usingtransmitter Carrier Phase Synchronization (CPS). If an application requires morethan one RFM to be used, or a longer Carrier Phase Synchronization line than thatspecified in chapter 2, Specifications, must be used, it is necessary to drive thepulse width modulated oscillator signal via a differential interface such as anRS422 interface.
47Noise ConsiderationsNoise can have a negative effect on the receive performance of the RFM. Thereare two different kinds of noise: radiated and conducted. Their characteristics areshown in Table 16.Table 16: Characteristics of Radiated and Conducted NoiseRadiated Noise Conducted NoiseSource Inductive parts for example:deflection coils, motor coils. Power units, for example: motors, switchedmode power supplies. Can be seen as voltagespikes or ripple voltage.Path Via magnetic fields. Galvanically conducted via all cables (supplyand interface) connected to the RFM.Effect Disturbs receive function bymagnetic interference with signalfrom transponder at the antenna.Leads to malfunction and reduced sensitivity ofreceiver circuitry due to, for example, interferedsupply voltage.Conducted noise can also cause radiated noise.Method for detecting and distinguishing between noise types:The principle of this procedure is to eliminate any conducted noise from the supplyand all interface lines. In order to do this test the RFM must be powered from abattery (for example: 9 V, 20 mA) in order to eliminate any conducted noise from apower supply. Conducted noise via the interface lines is eliminated for this test bysimply disconnecting all interface lines to the RFM. The measurement criteria forlow noise is the amplitude of the receive signal strength detector of the RFM.The test pin RSTP at connector J1 pin 10 carries an analog output voltageindicating the receive signal strength. This voltage should be measured incombination with the antenna RI-ANT-G02. The necessary set-up for this test isshown in Figure 12. This configuration operates the RFM from a battery and has nointerface line connected. As the transmitter is switched off in this configuration, anormal battery may be used. A low noise level is indicated by an RSTP voltage ofless than 1.0 VDC when using antenna RI-ANT-G02. Appendix 6
High Performance RFM RI-RFM-007B April 199948Note: Both noise types can be either differential or common modenoise. Use common mode noise filters (for example: a BALUNtransformer) to reduce common mode noise and use selective filtersto reduce differential noise.The following procedure for testing for noise impact should be implemented whenthe normal set-up for the RFM and antenna gives bad reading distances, eventhough the antenna is correctly tuned for sufficient transponder charge-up.Try the configuration shown in Figure 12. If this configuration shows bad noiseconditions (RSTP voltage more than approximately 1.0 VDC) then the problem isradiated noise.Eliminate noise sources or try special antennas (e.g. noise-balanced antennas).1. When the configuration of Figure 12 shows good noise conditions (RSTPvoltage less than 1.0 VDC) then the problem is conducted noise.2. Change the configuration so that the interface lines are again connected to theRFM with the transmitter still switched off. If the RSTP voltage now indicatesbad noise conditions, the conducted noise is coming via the interface lines.3. Try to eliminate the noise on the interface lines. See Appendix 7, Over VoltageProtection.4. When the configuration above (interface lines connected) shows good noiseconditions (RSTP voltage less than 1.0 VDC), then the problem is conductednoise via the supply lines.5. Try to eliminate the noise on the supply lines. See Appendix 7, Over VoltageProtection.Figure 12: Noise Testing ConfigurationGND 1TIRIS standardantennaRI-ANT-G02J1RSTPVSP 13VSP 11GNDP 97VSL 310ANT 1ANT 2••••
49Over Voltage ProtectionFor applications where there is a risk that voltage spikes and noise are on the linesto the RFM, additional protection circuitry and filters must be added.A proposal on how this may be achieved is shown in Figure 13, and this circuit maybe used as a guideline for protection circuitry. This may not be sufficient for allapplications, however, and must be checked individually when necessary.1. The supply input has to be protected against voltage spikes. R1 and D1 fulfilthis purpose. Zener diode D1 clamps the voltage spikes to 18 volts so that themaximum allowed transmitter power stage supply voltage is not appreciablyexceeded. For diode D1, type ZY18 is recommended, this type having a 2 Wpower dissipation. If a higher current is needed, dump type ZX18 may be used,this diode having a 12.5 W power dissipation.2. The Common Mode Choke Coil and the capacitors C1 and C2 are used toreduce the conducted noise coming to the RFM via the supply lines.3. All input and output signals should be protected with 5.6 V zener diodes. Thespecified type can dump 1.3 W.4. The coils L1 to L6 are ferrite beads and should put in series to the line whenconducted noise is observed entering via the interface lines.5. The varistor V1 protects the antenna circuit against high voltage induced at theantenna coil, for example by lightning. The type of varistor given is commonlyavailable but may not be sufficient for protection in all cases.Note: The zener diodes types given in Figure 13 are commonly usedtypes, not special suppresser diodes for fast voltage spikesuppression. If the application requires it, special suppresser diodesshould be used. Appendix 7
High Performance RFM RI-RFM-007B April 199950Figure 13: Circuit for Overvoltage ProtectionAll components must be mounted close to the RFM with the shortest possiblewiringC1: 100 nF Ceramic R1: 1 Ohm / 2W V1: Varistor 420Ve.g Siemens S10V-520K420C2: 100 µF low ESR R2, R3, R4, R5, R6, R7:22 Ohm / 0.25WCHOKE: CommonMode Choke CoilL1, L2, L3, L4, L5, L6:Ferrite beadsD1: ZY18 resp. ZX18D2,D3, D4, D5, D6, D7:BZX85C5V6

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