Hunter WRCTX Wireless Rain-Clik Rain Sensors User Manual LC Trans Manual

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Document Description	linx tx
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Date Submitted	2002-04-09 00:00:00
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Creation Date	2001-12-21 11:32:03
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Document Title	LC Trans Manual
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Document Author:	Chris Gesner

TXM-315-LC
TXM-418-LC
TXM-433-LC
LC SERIES TRANSMITTER MODULE DATA GUIDE
PHYSICAL DIMENSIONS
DESCRIPTION:
The LC Series is ideally suited for volume use
in OEM applications such as remote control,
security, identification, and periodic data
transfer. Packaged in a compact SMD package,
the LC transmitter utilizes a highly optimized
SAW architecture to achieve an unmatched
blend of performance, size, efficiency and cost.
When paired with a matching LC series
receiver, a highly reliable wireless link is
formed, capable of transferring serial data at
distances in excess of 300 Feet. No external RF
components, except an antenna, are required,
making design integration straightforward, even
for engineers lacking previous RF experience.
.360
.500
TOP VIEW
FEATURES:
■
■
■
■
■
Low Cost
No External RF Components
Required
Ultra-low Power Consumption
Compact Surface-Mount Package
Stable SAW-based Architecture
PINOUTS
■
Supports Data Rates to 5,000 bps
■
Wide Supply Range (2.7-5.2 VDC)
■
Direct Serial Interface
■
Low Harmonics
■
No Production Tuning
APPLICATIONS INCLUDE:
ORDERING INFORMATION
■
■
■
■
■
■
■
■
■
■
■
■
PART #
DESCRIPTION
EVAL-***-LC
MDEV-***-LC
TXM-315-LC
TXM-418-LC
TXM-433-LC
RXM-315-LC
RXM-418-LC
RXM-433-LC
Basic Evaluation Kit
Master Development Kit
Transmitter 315 MHZ
Transmitter 418 MHZ
Transmitter 433 MHZ
Receiver 315 MHZ
Receiver 418 MHZ
Receiver 433 MHZ
Remote control
Keyless entry
Garage / Gate openers
Lighting control
Medical monitoring / Call systems
Remote industrial monitoring
Periodic data transfer
Home / Industrial automation
Fire / Security alarms
Remote status / Position sensing
Long-range RFID
Wire Elimination
*** Insert Frequency
Not covered in this manual
LC Transmitters are supplied in tube
packaging - 50 pcs. per tube.
Revised 12/21/01
PERFORMANCE DATA– TXM-***-LC
+8
+7
+6
+5
CC
+4
+3
+2
+1
-1
-2
-3
-4
-5
-6
-7*NOTE* Exceeding any of the
2.5
5.0 (V)
4.0
4.5
3.0
3.5
Absolute Maximum Ratings:
Supply voltage V , using pin 7 -0.3
Operating temperature
-30°C
Storage temperature
-45°C
Soldering temperature
+225°C
Any input or output pin
-0.3
ABOUT THESE MEASUREMENTS
The performance parameters listed
below are based on module
operation at 25°C from a 3.3Vdc
supply unless otherwise noted.
Figure 1 at the right illustrates the
connections necessary for testing
and operation. It is recommended
that all ground pins be connected
to the groundplane.
to
+6 VDC
to
+70°C
to
+85°C
for 10 sec.
to
VCC
limits of this section may lead to
permanent damage of the device. Furthermore, extended operation at
SUPPLY VOLTAGE
these maximum ratings may reduce the life of this device.
figure 1: Test/Basic application circuit
TYPICAL PERFORMANCE GRAPHS
Parameters
LCTX 433, 418, 315MHz
Designation
Min.
Typical
Max.
Units
Operating Voltage Range
VCC
2.7
–
5.2
Volts
–
Current Continuous
ICC
–
3.0
6.0
mA
1, 5
Current Average
ICA
–
1.5
–
mA
2, 5
Current In Sleep
ISLP
–
–
1.5
µA
Data Input Low
VIL
–
0.4
Volts
–
Data Input High
VIH
2.5
–
VCC
Volts
–
Oscillator Start-up Time
TOSU
–
–
80
µS
Oscillator Ring-down Time
TORD
–
–
100
nSec
PO
-4
+4
dBm
Typical
315.0
Max.
315.075
Units
MHz
Notes
–
–
-40
dBc
Output Power
Parameter
LCTX 315MHz
Frequency of Carrier
Harmonic Emissions
Parameter
LCTX 418MHz
Frequency of Carrier
Harmonic Emissions
Parameter
LCTX 433MHz
Frequency of Carrier
Harmonic Emissions
Designation Min.
FC
314.925
PH
–
Designation Min.
FC
417.925
PH
–
Designation Min.
FC
433.845
PH
–
Current draw with data pin held continuously high.
Current draw with 50% mark/space ratio.
Current draw with data pin low.
RF out connected to 50Ω load.
Ladj (pin 4) through 430Ω resistor.
Page 2
2.5
3.0
3.5
4.0
Typical
418
Max.
418.075
Units
MHz
Notes
–
–
-40
dBc
Typical
433.92
Max.
433.995
Units
MHz
Notes
–
–
-45
dBc
4.5
5.0
(V)
+8
+7
+6
+5
+4
+3
+2
+1
-1
-2
-3
-4
-5
-6
-7
2.5
SUPPLY VOLTAGE
With Iadj tied to ground
With 430Ω resistor at Iadj (pin)
dBm
Output Power
Supply Current (mA)
12
11
10
3.0
3.5
4.0
4.5
5.0
(V)
SUPPLY VOLTAGE
With Iadj tied to ground
With 430Ω resistor at Iadj (pin)
figure 2: Consumption vs. Supply Voltage
figure 4: Typical Oscillator
Turn-On Time
Notes:
1.
2.
3.
4.
5,
Notes
figure 3: Typical RF power into 50Ω
Data
Carrier
2.5
3.0
12
11
10
3.5
4.0
4.5
5.0
(V)
SUPPLY VOLTAGE
Data
figure 5: Typical Oscillator
Turn-Off Time
Carrier
Page 3
TRANSMITTER AUTOMATED ASSEMBLY
PRODUCTION GUIDELINES
For high-volume assembly most users will want to auto-place the modules. The
modules have been designed to maintain compatibility with most pick-and-place
equipment; however, due to the module's hybrid nature certain aspects of the
automated assembly process are far more critical than for other component
types.
Following are brief discussions of the three primary areas where caution must be
observed.
Reflow Temperature Profile
The single most critical stage in the automated assembly process is the reflow
process. The reflow profile below should be closely followed since excessive
temperatures or transport times during reflow will irreparably damage the
modules. Assembly personnel will need to pay careful attention to the oven's
profile to insure that it meets the requirements necessary to successfully reflow
all components while still meeting the limits mandated by the modules
themselves.
Since some internal module components may reflow along with the components
placed on the board being assembled, it is imperative that the module not be
subjected to shock or vibration during the time solder is liquidus.
250
220°C
210°C
200
180°C
Temperature
150
Reflow Zone
125°C
20-40 Sec.
Soak Zone
2 Minutes Max.
Preheat Zone
2-2.3 Minutes
50
Ramp-up
Cooling
1-1.5 Minutes
30
60
90
120
150
180
210
240
270
300
330
360
Time (Seconds)
figure 6: Required reflow profile
Washability
The modules are wash resistant, but are not hermetically sealed. They may be
subject to a standard wash cycle; however, a twenty-four-hour drying time should
be allowed before applying electrical power to the modules. This will allow any
moisture that has migrated into the module to evaporate, thus eliminating the
potential for shorting during power-up or testing.
Page 4
The following pad layout diagrams are designed to facilitate both hand and
automated assembly.
TX Layout Pattern Rev. 2
(Not to Scale)
LC-P RX Layout Pattern Rev. 3
Pinned SMD Version
LC-S RX Layout Rev. 1
Compact SMD Version
(Not to Scale)
(Not to Scale)
0.100"
0.150
0.065"
.100
0.310"
0.610"
.070
0.070"
0.775
0.070"
0.100"
figure 7: Suggested Pad Layout
TRANSMITTER HAND ASSEMBLY
Forced Air Reflow Profile
Ideal Curve
Limit Curve
100
PAD LAYOUT
0.100"
Shock During Reflow Transport
300
°C
The LC modules are packaged in a hybrid SMD package which has been
designed to support hand- or automated-assembly techniques. Since LC devices
contain discrete components internally, the assembly procedures are critical to
insuring the reliable function of the LC product. The following procedures should
be reviewed with and practiced by all assembly personnel.
The LC transmitter's primary mounting
surface is eight pads located on the bottom
of the module. Since these pads are Soldering Iron
inaccessible during mounting, castellations Tip
that run up the side of the module have
been provided to facilitate solder wicking to
the module's underside. If the recommended pad placement (Rev.2) has been Solder
followed, the pad on the board will extend
slightly past the edge of the module. Touch PCB Pads
Castellations
both the PCB pad and the module
castellation with a fine soldering tip. Tack Figure 8: LC-TX Soldering Technique
one module corner first, then work around
the remaining attachment points using
care not to exceed the solder times listed
below.
Absolute Maximum Solder Times
Hand-Solder Temp. TX +225°C for 10 Sec.
Hand-Solder Temp. RX +225°C for 10 Sec.
Recommended Solder Melting Point +180°C
Reflow Oven: +220° Max. (See adjoining diagram)
Page 5
PHYSICAL PACKAGING
MODULE DESCRIPTION
The transmitter is packaged as a hybrid SMD module with eight pads spaced
0.100" apart on center. The SMD package is equipped with castellations which
allow for side introduction of solder. This simplifies prototyping or hand assembly
while maintaining compatibility with automated pick-and-place equipment.
Modules are available in tube or tape-and-reel packaging (see page 1 for
ordering information).
The LC-TXM is a low-cost, high-performance SAW-(Surface Acoustic Wave) based
CPCA (Carrier-Present Carrier-Absent) transmitter capable of sending serial data at
up to 5,000 bits/second. The LC’s compact surface-mount package integrates easily
into existing designs and is equally friendly to prototype and volume production. The
LC’s ultralow power consumption makes it ideally suited for battery powered
products. When combined with a Linx LC series receiver a reliable RF link capable
of transferring data over line-of-sight distances in excess of 300 feet (90M) is formed.
PIN DESCRIPTIONS:
Pin 1 GROUND
TOP VIEW
Connect to quiet ground or groundplane.
Serial data input pin. TTL and CMOS compatible.
.505
Pin 3 GROUND
Output Isolation
& Filter
SIDE VIEW
Connect to quiet ground or groundplane.
.150 Max.
Pin 4 LADJ/GND
Output power level adjustment. Connect to ground
for 3V operation. Connect to ground through 430
Ohm resistor for 5V operation. (see graph on
page 3 and page 10)
.042
.060 x .060
Typ.
THEORY OF OPERATION
.290
The LC-TXM transmits data using CPCA (Carrier-Present Carrier-Absent)
modulation. This type of AM modulation is often referred to by other designations
including CW and OOK. This type of modulation represents a logic low ‘0’ by the
absence of a carrier and a logic high ‘1’ by the presence of a carrier. This modulation
method affords numerous benefits. Three of the most important are: 1) Costeffectiveness due to design simplicity. 2) No minimum data rate or mark/space ratio
requirement. 3) Higher output power and thus greater range in countries (such as the
US) where output power measurements are averaged over time. (Please refer to
Linx application note #00130).
8 7 6 5
.103
.100 (Typ.)
Connect to 50Ω matched antenna.
figure 9: LC -TXM Physical
Package
Connect to quiet ground or groundplane.
Pin 7 POSITIVE SUPPLY (Vcc 2.7-6 VDC)
The supply must be clean (<20 mV pp), stable and
free of high-frequency noise. A supply filter is
recommended unless the module is operated from its own regulated supply or
battery.
The LC-TXM is based on a simple but highly optimized architecture which achieves
a high fundamental output power with low harmonic content. This insures that most
approval standards can be met without external filter components. The LC transmitter
is exceptionally stable over time, temperature, and physical shock as a result of the
precision SAW (Surface Acoustic Wave) frequency reference. Due to the of the SAW
device most of the output power is concentrated in a narrow bandwidth. This allows
the receiver’s pass opening can be quite narrow, thus increasing sensitivity and
reducing susceptibility to near-band interference. The quality of components and
overall architecture utilized in the LC series is unusual in a low-cost RF device and is
one reason the LC transmitter is able to outperform far more expensive products.
Pin 8 GROUND
Connect to quiet ground or groundplane.
POWER SUPPLY REQUIREMENTS
The transmitter module requires a clean, wellregulated power source. While it is preferable to power
the unit from a battery, the unit can also be operated
from a power supply as long as noise and ‘hash’ are
kept to less than 20 mV. A 10Ω resistor in series with
the supply followed by a 10µF tantalum capacitor from
Vcc to ground as shown at the right will help in cases
where the quality of supply power is poor.
Page 6
RF Amplifier
figure 11: LC Series Transmitter Block Diagram
BOTTOM VIEW
1 2 3 4
Pin 5 RF OUT
Pin 6 GROUND
Vcc
Data In
300-5000 BPS
Keyed Output
.365
Pin 2 DATA IN
SAW
Oscillator
50 Ω RF OUT
(Ant.)
THE DATA INPUT
10R
figure 10: Supply Filter
A CMOS/TTL level data input is provided on pin 2. This pin is normally supplied with
a serial bitstream input directly from a microprocessor, encoder, or UART. During
standby or the input of a logic low, the carrier is fully suppressed and the transmitter
consumes less than 2µA of current. During a logic high the transmitter generates a
carrier to indicate to the receiver the presence of a logic 1. The applied data should
not exceed a rate of 5,000 bits/sec. The data input pin should always be driven with
a voltage common to the supply voltage present at pin 7 (Vcc). The data pin should
never be allowed to exceed the supply voltage (Vcc).
Page 7
TRANSMITTING DATA
Once a reliable RF link has been established, the challenge becomes how to
effectively transfer data across it. While a properly designed RF link provides reliable
data transfer under most conditions, there are still distinct differences from a wired
link that must be addressed. Since the LC modules do not incorporate internal
coding/decoding, a user has tremendous flexibility in how data is formatted and sent.
It is always important to separate what type of transmissions are technically possible
from those that are legally allowable in the country of intended operation. You may
wish to review application notes #00125 and #00140 along with Part 15 Sec. 231 for
further details on acceptable transmission content.
Another consideration is that of data structure or protocol. If you are not familiar with
the sending serial data in a wireless environment read Linx application note #00232
(Considerations for sending data with the LC series). This application note details
important issues such as the effect of start-up times, pulse stretching and shortening
and the relationship between data and output power in a CPCA-based transmitter.
These issues should be understood prior to commencing a design effort.
If you want to send simple control or status signals such as button presses or switch
closures, consider using an encoder and decoder IC set available from a wide range
of manufacturers including: Microchip (Keeloq), Holtek, and Motorola. These IC’s take
care of all encoding, error checking, and decoding functions and generally provide a
number of data pins to which switches can be directly connected. Address bits are
usually provided for security and to allow the addressing of multiple receivers
independently. Additionally, it is a simple task to interface with inexpensive
microprocessors such as the Microchip PIC or one of many IR, remote control,
DTMF, and modem IC’s.
Shown below is an example of a basic remote control transmitter utilizing a encoder
chip from Holtek. When a key is pressed at the transmitter, a corresponding pin at the
receiver goes high. A schematic for the receiver/decoder circuit may be found in the
LC receiver guide.
BOARD LAYOUT CONSIDERATIONS
If you are at all familiar with RF devices you
may be concerned about specialized board
layout requirements. Fortunately, because
of the care taken by Linx in designing the
LC series,
integration
is
very
straightforward. This ease of application
results from the advanced multi-layer
construction of the module. By adhering to
the following layout principles and
observing a few basic design rules, you can
enjoy a straightforward path to RF success.
GROUNDPLANE
ON BOTTOM LAYER
1. A groundplane should be placed under
the module as shown. It will generally be figure 13: Example of proper
placed on the bottom layer. The amount
groundplane
of overall plane is also critical for the
correct function of many antenna styles and is covered in the next section.
2. Observe appropriate layout practice between the module and its antenna. A
simple trace may suffice for runs of less than .25" but longer distances should be
covered using 50Ω coax or a 50Ω microstrip transmission line. In order to
minimize loss and detuning, a microstrip transmission line is commonly utilized.
The term microstrip refers to a PCB trace running over a groundplane, the width
of which has been calculated to serve as a 50Ω transmission line. This effectively
removes the trace as a source of detuning. The correct trace width can be easily
calculated using the information below.The width is based on the desired
characteristic impedance, the thickness of the PCB, and its dielectric constant.
figure 14: Microstrip formulas (Er = Dielectric constant of pc board material)
figure 12: Basic Remote Control Transmitter Circuit
Notes:
1) DIP Switch used to set ID code. A 3-position switch was chosen for this example but all or none of the
address bits may be used. Settings of the Receiver and Transmitter must match for signal to be recognized.
Page 8
Dielectric
Constant
4.8
2.55
Width/Height
(W/d)
1.8
Effective
Dielectric
Constant
3.59
3.07
2.12
Characteristic
Impedance
50.0
51.0
48.0
Page 9
3. Depending on the type of antenna being used and duty cycle of incoming data,
the output power of the LC module may be higher than FCC regulations allow.
The output power of the module is intentionally set high since many designers
pair the module with an inefficient antenna in order to realize cost or space
savings. Since attenuation is often required it is generally wise to provide for its
implementation.
Output Power dBm
Two methods of attenuation are available using the LC module. First, a resistor
may be placed in series with Pad 4 (LVL. ADJ.) to achieve up to a 7 dB reduction
in output power. The resistor value is easily determined from the diagram below.
Do not exceed the resistance values shown as transmitter instability may result.
This method can also be used to reduce transmission range and power
consumption.
+8
+7
+6
+5
+4
+3
+2
+1
-1
-2
-3
-4
It is usually best to utilize a basic 1/4-wave whip for your initial concept evaluation.
Once the prototype product is operating satisfactorily, a production antenna should
be selected to meet the cost, size and cosmetic requirements of the product.
3V
51 100 150 200 240 300 360 430 510 560 620 680 750 820 910 1.1K
LADJ Pin Resistor Value
figure 15: Power Output vs. LADJ Pad Resistor Value
Another method commonly used to achieve attenuation, particularly at higher
levels, is the use of a T-pad. A T-pad is a 3-resistor network that allows for variable
attenuation while maintaining the quality of match to the antenna. It is usually
prudent to allow space for the addition of a T-pad. For further details on T-pads
please refer to Linx application note #00150.
TYPICAL LAYOUT
CIRCUIT
WITH PROVISION FOR ATTENUATION
PADS FOR SMT
RESISTORS
R1
R1
R2
ANT.
GROUNDPLANE
GR
OUNDPLANE
OUNDPLANE
ON GR
LOWER
LAYER
LOWER
LAYER
ON LOWER LAYER
GROUND
GROUND
GROUND
GND
ANT. OUT
figure 16: Attenuation pad layout
Page 10
The choice of antennas is one of the most critical and often overlooked design
considerations. The range, performance, and legality of an RF link is critically
dependent upon the type of antenna employed. Proper design and matching of an
antenna is a complex task requiring sophisticated test equipment and a strong
background in principles of RF propagation. While adequate antenna performance
can often be obtained by trial and error methods, you may also want to consider
utilizing a professionally designed antenna such as those offered by Linx. Our lowcost antenna line is designed to ensure maximum performance and compliance with
Part 15-attachment requirements. The purpose of the following sections is to give
you a basic idea of some of the considerations involved in the design and selection
of antennas. For a more comprehensive discussion please review Linx applications
note #00500 “Antennas: Design, Application, Performance”.
THE TRANSMITTER ANTENNA
The transmitter antenna allows RF energy to be efficiently radiated from the output
stage into free space. In modular designs such as the LC, a transmitter’s output
power is often slightly higher than the legal limit. This allows a designer to utilize an
inefficient antenna in order to achieve full legal power while meeting size, cost, or
cosmetic objectives. For this reason a transmitter's antenna can generally be less
efficient than the antenna used on the receiver.
5V
ANT.
ANTENNA CONSIDERATIONS
Maximum antenna efficiency is always obtained when the antenna is at resonance.
If the antenna is too short, capacitive reactance is present; if it is too long, inductive
reactance will be present. The indicator of resonance is the minimum point in the
VSWR curve. You will see from the following example that antenna (A) is resonant
at too low a frequency, indicating excessive length, while antenna (C) is resonant at
too high a frequency, indicating the antenna is too short. Antenna (B), however, is
“just right.”
Antenna resonance should not be confused with antenna impedance. The difference
between resonance and impedance is most easily understood by considering the
value of VSWR at its lowest point. The lowest point of VSWR indicates the antenna
is resonant, but the value of that low point is determined by the quality of the match
between the antenna, the
DESIRED FREQUENCY
transmission line, and the
device to which it is
attached.
To fully appreciate the
importance of an antenna
that is both resonant and
matched consider that an
antenna with a VSWR of
1.5 will effectively transmit
approximately 95% of its
power while an antenna
with a VSWR of 10 will only
transmit about 30%.
Page 11
GUIDELINES FOR ACHIEVING OPTIMUM ANTENNA PERFORMANCE
1. Proximity to objects such as a user’s hand or body, or metal objects will cause
an antenna to detune. For this reason the antenna shaft and tip should be
positioned as far away from such objects as possible.
2. Optimum performance will be obtained
from a 1/4- or 1/2-wave straight whip
mounted at a right angle to the
groundplane. In many cases this isn’t
OPTIMUM
desirable for practical or ergonomic
NOT RECOMMENDED
USEABLE
reasons; thus, an alternative antenna
style such as a helical, loop, patch, or figure 17: Groundplane orientation
base-loaded whip may be utilized.
COMMON ANTENNA STYLES
There are literally hundreds of antenna styles that can be successfully employed with the
LC Series. Following is a brief discussion of the three styles most commonly utilized in
compact RF designs. Additional antenna information can be found in Linx application notes
#00500, #00100, #00126 and #00140. Linx also offers a broad line of antennas and
connectors which offer outstanding performance and cost-effectiveness.
Whip Style
3. If an internal antenna is to be used, keep it away from other metal components,
particularly large items like transformers, batteries, and PCB tracks and
groundplanes. In many cases, the space around the antenna is as important
as the antenna itself.
4. In many antenna designs, particularly
1/4-wave whips, the groundplane acts
as a counterpoise, forming, in essence,
CASE
a 1/2-wave dipole. For this reason
adequate
groundplane
area
is
GROUNDPLANE
NUT
(MAY BE NEEDED)
essential. The groundplane can be a
metal case or ground-fill areas on a figure 18: External antenna mounting
circuit board. Ideally, the groundplane to
be used as counterpoise should have a surface area ≥ the overall length of the
1/4-wave radiating element; however, Linx recognizes that this is impossible for
most compact designs, so all Linx antennas are characterized using a 4.5” X
4.5” groundplane with the antenna centered and oriented at a 90° angle. Such
an orientation is often not practical due to size and configuration constraints.
In these instances a designer must make the best use of the area available to
create as much groundplane in proximity to the base of the antenna as
possible. In instances where the antenna is remotely located or the antenna is
not in close proximity to a circuit board plane or grounded metal case, a small
metal plate may be fabricated to maximize antenna performance.
5. Remove the antenna as far as possible from potential interference sources.
There are many possible sources of internally generated interference.
Switching power supplies, oscillators, even relays can also be significant
sources of potential interference. Remember, the single best weapon against
such problems is attention to placement and layout. Filter the module’s power
supply with a high-frequency bypass capacitor. Place adequate groundplane
under all potential sources of noise. Shield noisy board areas whenever
practical.
6. In some applications it is advantageous to place the transmitter and its
antenna away from the main equipment. This avoids interference problems and
allows the antenna to be oriented for optimum RF performance. Always use
50Ω coax such as RG-174 for the remote feed.
Page 12
1/4-wave wire lengths
for LC frequencies:
315Mhz=8.9"
418Mhz=6.7"
433Mhz=6.5"
A whip-style monopole antenna provides outstanding overall
performance and stability. A low-cost whip can be easily fabricated from
wire or rod, but most product designers opt for the improved
performance and cosmetic appeal of a professionally made model. To
meet this need, Linx offers a wide variety of straight and reduced-height
whip-style antennas in permanent and connectorized mounting styles.
The wavelength of the operational frequency determines an antenna's
overall length. Since a full wavelength is often quite long, a partial 1/4wave antenna is normally employed. Its size and natural radiation
resistance make it well matched to Linx modules. The proper length for
a 1/4-wave antenna can be easily found using the formula below. It is
also possible to reduce the overall height of the antenna by using a
helical winding. This decreases the antenna's bandwidth but is an
excellent way to minimize the antenna's physical size for compact
applications.
L=
234
F MHz
Where:
L=length in feet of quarter-wave length
F=operating frequency in megahertz
Helical Style
A helical antenna is precisely formed from wire or rod. A helical antenna
is a good choice for low-cost products requiring average rangeperformance and internal concealment. A helical can detune badly in
proximity to other objects and its bandwidth is quite narrow so care must
be exercised in layout and placement.
Loop Style
A loop- or trace-style antenna is normally printed directly on a product's
PCB. This makes it the most cost-effective of antenna styles. There are
a variety of shapes and layout styles which can be utilized. The element
can be made self-resonant or externally resonated with discrete
components. Despite its cost advantages, PCB antenna styles are
generally inefficient and useful only for short-range applications. Loopstyle antennas are also very sensitive to changes in layout or substrate
dielectric which can introduce consistency issues into the production
process. In addition, printed styles initially are difficult to engineer,
requiring the use of expensive equipment including a network analyzer.
An improperly designed loop will have a high SWR at the desired
frequency which can introduce substantial instability in the RF stages.
Linx offers a low-cost planar antenna called the “SPLATCH” which is an
excellent alternative to the sometimes problematic PCB trace style. This
tiny antenna mounts directly to a product's PCB and requires no testing
or tuning. Its design is stable even in compact applications and it
provides excellent performance in light of its compact size.
Page 13
LEGAL CONSIDERATIONS
NOTE: LC Series Modules are designed as component devices which require
external components to function. The modules are intended to allow for full Part
15 compliance; however, they are not approved by the FCC or any other agency
worldwide. The purchaser understands that approvals may be required prior to
the sale or operation of the device, and agrees to utilize the component in keeping
with all laws governing its operation in the country of operation.
When working with RF, a clear distinction must be made between what is technically
possible and what is legally acceptable in the country where operation is intended.
Many manufacturers have avoided incorporating RF into their products as a result of
uncertainty and even fear of the approval and certification process. Here at Linx our
desire is not only to expedite the design process, but also to assist you in achieving
a clear idea of what is involved in obtaining the necessary approvals to market your
completed product legally.
In the United States the approval process is actually quite straightforward. The
regulations governing RF devices and the enforcement of them are the responsibility
of the Federal Communications Commission. The regulations are contained in the
Code of Federal Regulations (CFR), Title 47. Title 47 is made up of numerous
volumes; however, all regulations applicable to this module are contained in volume
0-19. It is strongly recommended that a copy be obtained from the Government
Printing Office in Washington, or from your local government book store. Excerpts of
applicable sections are included with Linx evaluation kits or may be obtained from the
Linx Technologies web site (www.linxtechnologies.com). In brief, these rules require
that any device which intentionally radiates RF energy be approved, that is, tested,
for compliance and issued a unique identification number. This is a relatively painless
process. Linx offers full EMC pre-compliance testing in our HP/Emco-equipped test
center. Final compliance testing is then performed by one of the many independent
testing laboratories across the country. Many labs can also provide other
certifications the product may require at the same time, such as UL, CLASS A/B, etc.
Once your completed product has passed, you will be issued an ID number which is
then clearly placed on each product manufactured.
Questions regarding interpretations of the Part 2 and Part 15 rules or measurement
procedures used to test intentional radiators, such as the LC modules, for
compliance with the Part 15 technical standards, should be addressed to:
Federal Communications Commission
Equipment Authorization Division
Customer Service Branch, MS 1300F2
7435 Oakland Mills Road
Columbia, MD 21046
Tel: (301) 725-1585 / Fax: (301) 344-2050 E-Mail: labinfo@fcc.gov
International approvals are slightly more complex, although many modules are
designed to allow all international standards to be met. If you are considering the
export of your product abroad, you should contact Linx Technologies to determine
the specific suitability of the module to your application.
All Linx modules are designed with the approval process in mind and thus much of
the frustration that is typically experienced with a discrete design is eliminated.
Approval is still dependent on many factors such as the choice of antennas, correct
use of the frequency selected, and physical packaging. While some extra cost and
design effort are required to address these issues, the additional usefulness and
profitability added to a product by RF makes the effort more than worthwhile.
Page 14
SURVIVING AN RF IMPLEMENTATION
Adding an RF stage brings an exciting new dimension
to any product. It also means that additional effort and
commitment will be needed to bring the product
successfully to market. By utilizing premade RF
modules, such as the LC series, the design and
approval process will be greatly simplified. It is still
important, however, to have an objective view of the
steps necessary to insure a successful RF
integration. Since the capabilities of each customer
vary widely it is difficult to recommend one particular
design path, but most projects follow steps similar to
those shown at the right.
In reviewing this sample design path you may notice
that Linx offers a variety of services, such as antenna
design, and FCC prequalification, that are unusual for
a high-volume component manufacturer. These
services, along with an exceptional level of technical
support, are offered because we recognize that RF is
a complex science requiring the highest caliber of
products and support. “Wireless Made Simple” is
more than just a motto, it’s our commitment. By
choosing Linx as your RF partner and taking
advantage of the resources we offer, you will not only
survive implementing RF, you may even find the
process enjoyable.
DECISION TO UTILIZE RF IS MADE
RESEARCH RF OPTIONS
ORDER EVALUATION KIT(S)
TEST MODULE(S) WITH
BASIC HOOKUP
LINX MODULE IS CHOSEN
INTERFACE TO CHOSEN
CIRCUIT AND DEBUG
CONSULT LINX REGARDING
ANTENNA OPTIONS AND DESIGN
LAY OUT BOARD
SEND PRODUCTION-READY
PROTOTYPE TO LINX
FOR EMC PRESCREENING
OPTIMIZE USING RF SUMMARY
GENERATED BY LINX
SEND TO PART 15
TEST FACILITY
RECEIVE FCC ID #
COMMENCE SELLING PRODUCT
TYPICAL STEPS FOR
IMPLEMENTING RF
HELPFUL APPLICATION NOTES FROM LINX
It is not the intention of this manual to address in depth many of the issues that
should be considered to ensure that the modules function correctly and deliver
the maximum possible performance. As you proceed with your design you may
wish to obtain one or more of the following application notes, which address in
depth key areas of RF design and application of Linx products.
NOTE #
LINX APPLICATION NOTE TITLE
00232
General considerations for sending data with the LC Series
00500
Antennas: Design, Application, Performance
00130
Modulation techniques for low-cost RF data links
00125
Considerations for operation in the 260 Mhz to 470 Mhz band
00100
RF 101: Information for the RF challenged
00110
Understanding the performance specifications of receivers
00140
The FCC Road: Part 15 from concept to approval
00150
Use and design of T-Attenuation Pads
Page 15
U.S. CORPORATE HEADQUARTERS:
LINX TECHNOLOGIES, INC.
575 S.E. ASHLEY PLACE
GRANTS PASS, OR 97526
Phone: (541) 471-6256
FAX: (541) 471-6251
http://www.linxtechnologies.com
Disclaimer
Linx Technologies is continually striving to improve the quality and function of its products; for
this reason, we reserve the right to make changes without notice. The information contained in
this Data Sheet is believed to be accurate as of the time of publication. Specifications are based
on representative lot samples. Values may vary from lot to lot and are not guaranteed. Linx
Technologies makes no guarantee, warranty, or representation regarding the suitability of any
product for use in a specific application. None of these devices is intended for use in
applications of a critical nature where the safety of life or property is at risk. The user assumes
full liability for the use of product in such applications. Under no conditions will Linx Technologies
be responsible for losses arising from the use or failure of the device in any application, other
than the repair, replacement, or refund limited to the original product purchase price. Some
devices described in this publication are patented. Under no circumstances shall any user be
conveyed any license or right to the use or ownership of these patents.
© 1999 by Linx Technologies, Inc. The stylized
Linx logo, Linx, and “Wireless Made Simple”
are the trademarks of Linx Technologies, Inc.
Printed in U.S.A.
Page 16

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