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

Hunter Industries Inc Wireless Rain-Clik Rain Sensors LC Trans Manual

Contents

linx tx

TOP VIEW
.360
.500
PINOUTS
LC SERIES TRANSMITTER MODULE DATA GUIDE
■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
APPLICATIONS INCLUDE:
■Low Cost
■No External RF Components
Required
■Ultra-low Power Consumption
■Compact Surface-Mount Package
■Stable SAW-based Architecture
■Supports Data Rates to 5,000 bps
■Wide Supply Range (2.7-5.2 VDC)
■Direct Serial Interface
■Low Harmonics
■No Production Tuning
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.
TXM-315-LC
TXM-418-LC
TXM-433-LC
PHYSICAL DIMENSIONS
DESCRIPTION:
FEATURES:
Revised 12/21/01
PART # DESCRIPTION
EVAL-***-LC Basic Evaluation Kit
MDEV-***-LC Master Development Kit
TXM-315-LC Transmitter 315 MHZ
TXM-418-LC Transmitter 418 MHZ
TXM-433-LC Transmitter 433 MHZ
RXM-315-LC Receiver 315 MHZ
RXM-418-LC Receiver 418 MHZ
RXM-433-LC Receiver 433 MHZ
*** Insert Frequency
Not covered in this manual
LC Transmitters are supplied in tube
packaging - 50 pcs. per tube.
ORDERING INFORMATION
Page 3
PERFORMANCE DATA– TXM-***-LC
Page 2
Parameter
LCTX 418MHz Designation Min. Typical Max. Units Notes
Frequency of Carrier FC417.925 418 418.075 MHz –
Harmonic Emissions PH– – -40 dBc 4
Parameter
LCTX 315MHz Designation Min. Typical Max. Units Notes
Frequency of Carrier FC314.925 315.0 315.075 MHz –
Harmonic Emissions PH––-40 dBc 4
Parameter
LCTX 433MHz Designation Min. Typical Max. Units Notes
Frequency of Carrier FC433.845 433.92 433.995 MHz –
Harmonic Emissions PH––-45 dBc 4
figure 1: Test/Basic application circuit
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.
Absolute Maximum Ratings:
Supply voltage VCC, using pin 7 -0.3 to +6 VDC
Operating temperature -30°C to +70°C
Storage temperature -45°C to +85°C
Soldering temperature +225°C for 10 sec.
Any input or output pin -0.3 to VCC
*NOTE* Exceeding any of the limits of this section may lead to
permanent damage of the device. Furthermore, extended operation at
these maximum ratings may reduce the life of this device.
1. Current draw with data pin held continuously high.
2. Current draw with 50% mark/space ratio.
3. Current draw with data pin low.
4. RF out connected to 50Ωload.
5, Ladj (pin 4) through 430Ωresistor.
Notes:
Parameters
LCTX 433, 418, 315MHz Designation Min. Typical Max. Units Notes
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 3
Data Input Low VIL 0–0.4 Volts –
Data Input High VIH 2.5 –VCC Volts –
Oscillator Start-up Time TOSU –– 80 µS 4
Oscillator Ring-down Time TORD ––100 nSec 4
Output Power PO-4 0 +4 dBm 4
0
-1
-4
-5
-6
-7 2.5 3.0 3.5 4.0 4.5
-2
-3
SUPPLY VOLTAGE
+1
+3
+2
+4
+5
+6
+7
+8
5.0 (V)
2.5 3.0 3.5 4.04.0 4.54.5 5.0 (V)(V)
SUPPLY VOLTAGESUPPLY VOLTAGE
1
3
2
4
5
6
7
8
9
10
11
12
0
With 430Ω resistor at Iadj (pin)
With Iadj tied to ground
Supply Current (mA)
0
-1
-4
-5
-6
-7 2.5 3.0 3.5 4.0 4.54.5
-2
-3
SUPPLY VOLTAGESUPPLY VOLTAGE
+1+1
+3+3
+2
+4+4
+5+5
+6+6
+7+7
+8+8
5.0 (V)
2.5 3.0 3.5 4.0 4.5 5.0 (V)
SUPPLY VOLTAGE
1
3
2
4
5
6
7
8
9
10
11
12
0
dBm
With 430Ω resistor at Iadj (pin)
With Iadj tied to ground
pg
Output Power
figure 4: Typical Oscillator
Turn-On Time
figure 2: Consumption vs. Supply Voltage
TYPICAL PERFORMANCE GRAPHS
figure 5: Typical Oscillator
Turn-Off Time
figure 3: Typical RF power into 50Ω
Data
Carrier
Data
Carrier
Page 5
PRODUCTION GUIDELINES
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.
PAD LAYOUT
The following pad layout diagrams are designed to facilitate both hand and
automated assembly.
TRANSMITTER HAND ASSEMBLY
The LC transmitter's primary mounting
surface is eight pads located on the bottom
of the module. Since these pads are
inaccessible during mounting, castellations
that run up the side of the module have
been provided to facilitate solder wicking to
the module's underside. If the recom-
mended pad placement (Rev.2) has been
followed, the pad on the board will extend
slightly past the edge of the module. Touch
both the PCB pad and the module
castellation with a fine soldering tip. Tack
one module corner first, then work around
the remaining attachment points using
care not to exceed the solder times listed
below.
Castellations
PCB Pads
Soldering Iron
Tip
Solder
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)
figure 7: Suggested Pad Layout
Figure 8: LC-TX Soldering Technique
0.100"
0.310"
0.100"
0.070"
.100
0.150
.070
0.775
TX Layout Pattern Rev. 2
(Not to Scale) LC-P RX Layout Pattern Rev. 3
Pinned SMD Version
(Not to Scale)
0.100"
0.070"
0.065"
0.610"
LC-S RX Layout Rev. 1
Compact SMD Version
(Not to Scale)
Page 4
TRANSMITTER AUTOMATED ASSEMBLY
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.
Shock During Reflow Transport
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.
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.
125°C
600
0
50
100
150
200
250
300
°C
120 180 240 300
30 90 150 210 270 330 360
180°C
210°C
220°C
Temperature
Time (Seconds)
Ideal Curve
Limit Curve
Forced Air Reflow Profile
1-1.5 Minutes
2-2.3 Minutes
Ramp-up
Preheat Zone
Cooling
Soak Zone
Reflow Zone
20-40 Sec.
2 Minutes Max.
figure 6: Required reflow profile
Page 7
figure 11: LC Series Transmitter Block Diagram
MODULE DESCRIPTION
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.
THEORY OF OPERATION
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) Cost-
effectiveness 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).
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.
THE DATA INPUT
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 6
PIN DESCRIPTIONS:
Pin 1 GROUND
Connect to quiet ground or groundplane.
Pin 2 DATA IN
Serial data input pin. TTL and CMOS compatible.
Pin 3 GROUND
Connect to quiet ground or groundplane.
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)
Pin 5 RF OUT
Connect to 50Ωmatched antenna.
Pin 6 GROUND
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.
Pin 8 GROUND
Connect to quiet ground or groundplane.
POWER SUPPLY REQUIREMENTS
The transmitter module requires a clean, well-
regulated 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 10Ωresistor 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. figure 10: Supply Filter
PHYSICAL PACKAGING
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).
TOP VIEW
.150 Max.
.505
.365
.100 (Typ.)
.103.103
.060 x .060
Typ.
SIDE VIEW
BOTTOM VIEW
.042
.290
1 2 3 4
8 7 6 5
figure 9: LC -TXM Physical
Package
10R
Page 9
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.
1. A groundplane should be placed under
the module as shown. It will generally be
placed on the bottom layer. The amount
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 50Ωcoax or a 50Ωmicrostrip 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 50Ωtransmission 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.
GROUNDPLANE
ON BOTTOM LAYER
figure 13: Example of proper
groundplane
Effective
Dielectric Width/Height Dielectric Characteristic
Constant (W/d) Constant Impedance
4.8 1.8 3.59 50.0
4 2 3.07 51.0
2.55 3 2.12 48.0
figure 14: Microstrip formulas (Er = Dielectric constant of pc board material)
Page 8
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.
figure 12: Basic Remote Control Transmitter Circuit
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.
Page 11
ANTENNA CONSIDERATIONS
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 low-
cost 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.
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.
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
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%.
AB C
DESIRED FREQUENCY
Page 10
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.
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.
CIRCUIT TYPICAL LAYOUT
WITH PROVISION FOR ATTENUATION
GND
ANT. OUT
PADS FOR SMT
RESISTORS
PADS FOR SMT
RESISTORS ANT.
ANT.
R1
R1 R2
GR
GR
OUNDPLANE
OUNDPLANE
ON LO
ON LO
WER LA
WER LA
YER
YER
GROUNDPLANE
ON LOWER LAYER
GR
GR
OUND
OUND
GROUNDGR
GR
OUND
OUND
GROUND
figure 16: Attenuation pad layout
+8
+7
+6
+5
+4
+3
+2
+1
0
-1
-2
-3
-4
LADJ Pin Resistor Value
51 100 150 200 240 300 360 430 510 560 620 680 750 820 910 1.1K
Output Power dBm
3V
5V
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.
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
desirable for practical or ergonomic
reasons; thus, an alternative antenna
style such as a helical, loop, patch, or
base-loaded whip may be utilized.
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,
a 1/2-wave dipole. For this reason
adequate groundplane area is
essential. The groundplane can be a
metal case or ground-fill areas on a
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
50Ωcoax such as RG-174 for the remote feed.
Page 13
Helical Style
Whip Style
Loop Style
1/4-wave wire lengths
for LC frequencies:
315Mhz=8.9"
418Mhz=6.7"
433Mhz=6.5"
Where:
L=length in feet of quarter-wave length
F=operating frequency in megahertz
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.
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 1/4-
wave 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.
A helical antenna is precisely formed from wire or rod. A helical antenna
is a good choice for low-cost products requiring average range-
performance 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.
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. Loop-
style 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.
L =
234
F
MHz
Page 12
NUT GROUNDPLANE
(MAY BE NEEDED)
CASE
OPTIMUM
USEABLE NOT RECOMMENDED
figure 17: Groundplane orientation
figure 18: External antenna mounting
Page 15Page 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
LINX MODULE IS CHOSEN
ORDER EVALUATION KIT(S)
TEST MODULE(S) WITH
BASIC HOOKUP
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.
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
NOTE # LINX APPLICATION NOTE TITLE
LEGAL CONSIDERATIONS
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.
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.
Page 16
U.S. CORPORATE HEADQUARTERS:
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.
Disclaimer
© 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.
LINX TECHNOLOGIES, INC.
575 S.E. ASHLEY PLACE
GRANTS PASS, OR 97526
Phone: (541) 471-6256
FAX: (541) 471-6251
http://www.linxtechnologies.com

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