TXM-418-LR [ETC]
LR SERIES TRANSMITTER MODULE; LR系列变送器模块
| 型号： | TXM-418-LR |
| 厂家： | 
ETC |
| 描述： | LR SERIES TRANSMITTER MODULE |
| 文件： | 总11页 (文件大小：374K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
TXM-315-LR
TXM-418-LR
TXM-433-LR
WIRELESS MADE SIMPLE ®
LR SERIES TRANSMITTER MODULE DATA GUIDE
DESCRIPTION
The LR Series transmitter is ideal for the cost-
effective wireless transfer of serial data, control, or
command information in the favorable 260-470MHz
RF MODULE
TXM-418-LR
LOT 2000
band. When paired with a compatible Linx receiver, a
reliable wireless link is formed, capable of
transferring data at rates of up to 10,000bps at
distances of up to 3,000 feet. Applications operating
over shorter distances or at lower data rates will also
benefit from increased link reliability and superior
noise immunity. The transmitter’s synthesized
architecture delivers outstanding stability and
frequency accuracy and minimizes the affects of
antenna pulling. Housed in a tiny reflow-compatible
SMD package, the transmitter requires no external
components (except an antenna), which greatly
simplifies integration and lowers assembly costs.
0.360"
0.500"
0.130"
Typ.
Figure 1: Package Dimensions
FEATURES
Low power consumption
Low voltage (2.1 to 3.6VDC)
Long range
Low cost
Compact surface mount package
Wide temperature range
Power-down function
PLL-synthesized architecture
Direct serial interface
Data rates to 10,000bps
No external RF components needed
No production tuning
APPLICATIONS INCLUDE
Remote Control
Keyless Entry
ORDERING INFORMATION
PART #
DESCRIPTION
Garage / Gate Openers
Lighting Control
TXM-315-LR
TXM-418-LR
TXM-433-LR
RXM-315-LR
RXM-418-LR
RXM-433-LR
EVAL-***-LR
*** = Frequency
Transmitter 315MHz
Transmitter 418MHz
Transmitter 433MHz
Receiver 315MHz
Receiver 418MHz
Receiver 433MHz
Basic Evaluation Kit
Medical Monitoring / Call Systems
Remote Industrial Monitoring
Periodic Data Transfer
Home / Industrial Automation
Fire / Security Alarms
Remote Status / Position Sensing
Long-Range RFID
Transmitters are supplied in tubes of 50 pcs.
Wire Elimination
Revised 1/28/08
ELECTRICAL SPECIFICATIONS
PERFORMANCE DATA
These performance parameters
are based on module operation at
25°C from a 3.0VDC supply unless
VCC
Parameter
Designation
Min.
Typical
Max.
Units
Notes
POWER SUPPLY
Operating Voltage
PDN
VCC
GND
GND
DATA
GND
VCC
ICC
2.1
–
3.0
3.4
3.6
–
VDC
mA
–
otherwise
illustrates
necessary
noted.
the
for
Figure
connections
testing and
2
Supply Current:
1,2
Logic High
–
–
–
5.1
1.8
5.0
–
–
–
mA
mA
nA
2
–
–
VCC
Logic Low
operation. It is recommended all
ground pins be connected to the
ground plane.
750
LADJ/VCC ANT
Power-Down Current
IPDN
TRANSMITTER SECTION
Transmit Frequency Range:
Figure 2: Test / Basic Application Circuit
FC
TXM-315-LR
–
–
315
418
433.92
–
–
–
MHz
MHz
MHz
kHz
dBm
dB
–
–
–
–
2
3
–
TYPICAL PERFORMANCE GRAPHS
TXM-418-LR
1. 500mV/div
2. 2.00V/div
TXM-433-LR
–
–
Center Frequency Accuracy
Output Power
–
PO
–
-50
-4
+50
+4
+10
–
0.0
–
Output Power Control Range
Harmonic Emissions
-80
-36
ASK RF Output
TX Data
PH
–
dBc
1
2
Data Rate
Data Input:
Logic Low
–
DC
–
10,000
bps
–
VIL
VIH
–
–
–
0.25
–
VDC
VDC
–
–
Logic High
VCC-0.25
Power Down Input:
Logic Low
100nS/div
VIL
VIH
–
–
–
0.25
–
VDC
VDC
–
–
Figure 3: Modulation Delay
Logic High
VCC-0.25
12
ANTENNA PORT
RF Output Impedance
ROUT
–
50
–
Ω
4
10
8
TIMING
Transmitter Turn-On Time:
Via VCC or PDN
–
–
–
–
1.0
–
–
mSec
nS
4
4
6
Modulation Delay
30.0
4
ENVIRONMENTAL
Operating Temperature Range
–
-40
–
+85
°C
4
2
Table 1: LR Series Transmitter Electrical Specifications
0
9.00
6.00
3.00
0.00
-3.00
-6.00
-9.00
-12.00
-15.00
-18.00
-21.00
Output Power (dBm)
Notes
1. With a 50% duty cycle.
2. With a 750Ω resistor on LADJ.
3. See graph on Page 3.
Figure 4: Output Power vs. LADJ Resistance
4.5
4. Characterized, but not tested.
4
3.5
3
ABSOLUTE MAXIMUM RATINGS
Supply Voltage VCC
-0.3
-0.3
-40
-40
to
+3.6
VDC
Any Input or Output Pin
Operating Temperature
Storage Temperature
Soldering Temperature
to VCC + 0.3 VDC
to
to
+85
+90
°C
°C
2.5
+225°C for 10 seconds
2
3.00
-9.00
Output Power (dBm)
-12.00
-15.00
6.00
0.00
-3.00
-6.00
-18.00
-21.00
*NOTE* Exceeding any of the limits of this section may lead to permanent
damage to the device. Furthermore, extended operation at these maximum
ratings may reduce the life of this device.
Figure 5: Current Consumption vs. Output Power (50% Duty Cycle)
Page 3
Page 2
PIN ASSIGNMENTS
MODULE DESCRIPTION
The LR transmitter is a low-cost, high-performance synthesized ASK / OOK
transmitter, capable of sending serial data at up to 10,000bps. Because the
transmitter is completely self-contained, requiring an antenna as the only
additional RF component, application is extremely straightforward and assembly
and testing costs are reduced. When combined with an LR Series receiver, a
reliable serial link is formed capable of transferring data over line-of-site
distances of up to 3,000 feet. The LR is housed in a compact surface-mount
package that integrates easily into existing designs and is equally friendly to
prototyping and volume production. The module’s low power consumption
makes it ideal for battery-powered products. The transmitter is compatible with
many other Linx receiver products, including the LC, LR, KH, and OEM product
families. For applications where range is critical, the LR receiver is the best
choice due to its outstanding sensitivity. LR Series modules are capable of
meeting the regulatory requirements of domestic and international applications.
1
2
3
4
GND
DATA
GND
PDN
VCC
GND
8
7
6
5
LADJ/VCC ANT
Figure 5: LR Series Transmitter Pinout (Top View)
PIN DESCRIPTIONS
Pin # Name
THEORY OF OPERATION
Description
DATA
PDN
1
2
3
GND
DATA
GND
Analog Ground
Digital Data Input
Analog Ground
RF OUT
PA
PLL
VCO
Level Adjust. This line can be used to adjust the output
power level of the transmitter. Connecting to VCC will give
LADJ/VCC
4
the highest output, while placing a resistor to VCC will lower
the output level (see Figure 4 on Page 3).
XTAL
5
6
7
ANT
GND
VCC
50-ohm RF Output
Analog Ground
Supply Voltage
Figure 6: LR Series Transmitter Block Diagram
The LR Series transmitter is designed to generate 1mW of output power into a
50-ohm single-ended antenna while suppressing harmonics and spurious
emissions to within legal limits. The transmitter is comprised of a VCO locked by
a frequency synthesizer that is referenced to a high precision crystal. The output
of the VCO is amplified and buffered by an internal power amplifier. The amplifier
is switched by the incoming data to produce a modulated carrier. The carrier is
filtered to attenuate harmonics and then output to free space via the 50-ohm
antenna port.
Power Down. Pulling this line low will place the transmitter
into a low-current state. The module will not be able to
transmit a signal in this state.
8
PDN
The synthesized topology makes the module highly immune to the effects of
antenna port loading and mismatch. This reduces or eliminates frequency
pulling, bit contraction, and other negative effects common to low-cost
transmitter architectures. It also allows for reliable performance over a wide
operating temperature range. Like its companion LR Series receiver, the LR
Series transmitter delivers a significantly higher level of performance and
reliability than the LC Series or other SAW-based devices, yet remains very
small and cost-effective.
*CAUTION*
This product incorporates numerous static-sensitive components.
Always wear an ESD wrist strap and observe proper ESD handling
procedures when working with this device. Failure to observe this
precaution may result in module damage or failure.
Page 4
Page 5
THE DATA INPUT
POWER SUPPLY REQUIREMENTS
The CMOS-compatible data input on Pin 2 is normally supplied with a serial bit
stream from a microprocessor or encoder, but it can also be used with standard
UARTs.
The module does not have an internal voltage regulator; therefore it requires a
clean, well-regulated power source. While it is preferable to power the unit from
a battery, it can also be operated from a power supply as long as noise is less
than 20mV. Power supply noise can affect the
When a logic ‘1’ is present on the DATA line and the PDN line is high, then the
Power Amplifier (PA) will be activated and the carrier frequency will be sent to
the antenna port. When a logic ‘0’ is present on the DATA line or the PDN line is
low, the PA is deactivated and the carrier is fully suppressed.
transmitter modulation; therefore, providing a clean
power supply for the module should be a high priority
during design.
Vcc TO
MODULE
10Ω
Vcc IN
+
A 10Ω resistor in series with the supply followed by a
The DATA line should always be driven with a voltage that is common to the
supply voltage present on Pin 7 (VCC). The DATA line should never be allowed
10μF
10µF tantalum capacitor from VCC to ground will help
in cases where the quality of the supply is poor. Note
that the values may need to be adjusted depending
on the noise present on the supply line.
to exceed the supply voltage, as permanent damage to the module could occur.
Figure 7: Supply Filter
USING THE PDN PIN
The transmitter’s Power Down (PDN) line can be used to power down the
transmitter without the need for an external switch. It allows easy control of the
transmitter’s state from external components, such as a microcontroller. By
periodically activating the transmitter, sending data, then powering down, the
transmitter’s average current consumption can be greatly reduced, saving power
in battery operated applications.
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 LR Series modules do not
incorporate internal encoding or decoding, a user has tremendous flexibility in
how data is handled.
The PDN line does not have an internal pull-up, so it will need to be pulled high
or tied directly to VCC to turn on the transmitter. The pull-up should be a minimum
If you want to transfer simple control or status signals, such as button presses or
switch closures, and your product does not have a microprocessor on board, or
you wish to avoid protocol development, consider using an encoder and decoder
IC set. These chips are available from a range of manufacturers, including Linx.
They take care of all encoding and decoding functions and generally provide a
number of data pins to which switches can be directly connected. In addition,
address bits are usually provided for security and to allow the addressing of
multiple units independently. These ICs are an excellent way to bring basic
remote control / status products to market quickly and inexpensively.
Additionally, it is a simple task to interface with inexpensive microprocessors,
such as the Microchip PIC, or one of many IR, remote control, or modem ICs.
of 30μA (10kΩ or less). When the PDN line is pulled to ground, the transmitter
will enter into a low-current (<5nA) power-down mode. When in this mode, the
transmitter will be completely off and cannot perform any function.
Note: The voltage on the PDN line should not exceed VCC. When used with a higher
voltage source, such as a 5V microcontroller, an open collector line should be used or a
diode placed in series with the control line (anode toward the module). Either method
avoids damage to the module by preventing 5V from being placed on the PDN line while
allowing the line to be pulled low.
USING LADJ
It is always important to separate what types of transmissions are technically
possible from those that are legally allowable in the country of intended
operation. While the LR Series is ideally suited to the long range transfer of
control and command information, it can also be used with great success for the
transfer of true variable data such as temperature, pressure, or sensor data.
However, the 260 - 470MHz band in which the module operates is regulated by
Part 15, Section 231 of the FCC regulations. Many types of transmissions,
especially those involving automatic transmissions or variable data, may need to
be periodic. You may wish to review Application Notes AN-00125 and AN-00140
along with Part 15, Section 231 of the FCC regulations for further details on
acceptable transmission content in the Unites States.
The Level Adjust (LADJ) line allows the transmitter’s output power to be easily
adjusted for range control, lower power consumption, or to meet legal
requirements. This is done by placing a resistor between VCC and LADJ. The
value of the resistor determines the output power level. When LADJ is connected
to VCC, the output power and current consumption will be at its maximum. Figure
4 on Page 3 shows a graph of the output power vs. LADJ resistance.
This line is very useful during FCC testing to compensate for antenna gain or
other product-specific issues that may cause the output power to exceed legal
limits. A variable resistor can be temporarily used so that the test lab can
precisely adjust the output power to the maximum level allowed by law. The
variable resistor’s value can be noted and a fixed resistor substituted for final
testing. Even in designs where attenuation is not anticipated, it is a good idea to
place a resistor pad connected to LADJ and VCC so that it can be used if needed.
Another area of consideration is that of data structure or protocol. The data
should be formatted in a predictable way and should be able to deal with errors
due to interference. This will ensure that the data is received and interpreted
correctly. If you are not familiar with the considerations for sending serial data in
a wireless environment, you will want to review Application Note AN-00160.
For more sophisticated designs, LADJ can be also controlled by a DAC or digital
potentiometer to allow precise and digitally variable output power control.
Page 6
Page 7
PROTOCOL GUIDELINES
TYPICAL APPLICATIONS
While many RF solutions impose data formatting and balancing requirements,
Linx RF modules do not encode or packetize the signal content in any manner.
The received signal will be affected by such factors as noise, edge jitter, and
interference, but it is not purposefully manipulated or altered by the modules.
This gives the designer tremendous flexibility for protocol design and interface.
Figure 8 shows a circuit using a Linx MS Series encoder. This chip works with
the Linx LICAL-DEC-MS001 decoder to provide simple remote control
capabilities. The decoder detects the transmission from the encoder, checks for
errors, and if everything is correct, replicates the encoder’s inputs on its outputs.
This makes registering key presses very simple.
Despite this transparency and ease of use, it must be recognized that there are
distinct differences between a wired and a wireless environment. Issues such as
interference and contention must be understood and allowed for in the design
process. To learn more about protocol considerations, we suggest you read Linx
Application Note AN-00160.
100k
100k
100k
100k
100k
100k
1
2
20
19
18
17
16
15
14
13
12
11
3
4
5
6
Errors from interference or changing signal conditions can cause corruption of
the data packet, so it is generally wise to structure the data being sent into small
packets. This allows errors to be managed without affecting large amounts of
data. A simple checksum or CRC could be used for basic error detection. Once
an error is detected, the protocol designer may wish to simply discard the corrupt
data or implement a more sophisticated scheme to correct it.
100k
100k
7
8
1
2
3
4
8
7
6
5
GND
PDN
VCC
GND
9
VCC
DATA
220
100k
DATA
DATA IN
GND
10
LICAL-ENC-MS001
VCC
IADJ/VCC RF OUT
TXM-xxx-LR
2.7k
INTERFERENCE CONSIDERATIONS
The RF spectrum is crowded and the potential for conflict with other unwanted
sources of RF is very real. While all RF products are at risk from interference, its
effects can be minimized by better understanding its characteristics.
Figure 8: LR Transmitter and MS Encoder
Figure 9 shows a typical RS-232 circuit using the LR transmitter and a Maxim
MAX232 chip. The MAX232 converts RS-232 compliant signals from a PC to a
serial data stream, which is then transmitted by the LR module.
Interference may come from internal or external sources. The first step is to
eliminate interference from noise sources on the board. This means paying
careful attention to layout, grounding, filtering, and bypassing in order to
eliminate all radiated and conducted interference paths. For many products, this
is straightforward; however, products containing components such as switching
power supplies, motors, crystals, and other potential sources of noise must be
approached with care. Comparing your own design with a Linx evaluation board
can help to determine if and at what level design-specific interference is present.
VCC
VCC
+
C2
C1
4.7uF
4.7uF
DB-9
MAX232
1
6
2
7
3
8
4
9
5
+
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
TXM-xxx-LR
GND
C3
4.7uF
C1+
V+
VCC
1
2
3
4
8
7
6
5
GND
T1OUT
R1IN
GND
PDN
GND
DATA
GND
C1-
VCC
GND
C2+
C2-
V-
VCC
GND
R1OUT
T1IN
+
C4
4.7uF
GND
750
T2OUT
R2IN
T2IN
External interference can manifest itself in a variety of ways. Low-level
interference will produce noise and hashing on the output and reduce the link’s
overall range.
R2OUT
GND
VCC
LADJ/VCC ANT
C5
4.7uF
GND
GND
High-level interference is caused by nearby products sharing the same
frequency or from near-band high-power devices. It can even come from your
own products if more than one transmitter is active in the same area. It is
important to remember that only one transmitter at a time can occupy a
frequency, regardless of the coding of the transmitted signal. This type of
interference is less common than those mentioned previously, but in severe
cases it can prevent all useful function of the affected device.
Figure 9: LR Transmitter and MAX232 IC
Figure 10 shows an example of using the LR transmitter with a Linx QS Series
USB module. The USB module converts low-speed USB compliant signals from
a PC into a serial data stream, which is then transmitted by the LR module.
USB-B
4
3
2
1
SDM-USB-QS-S
USBDP
USBDM
GND
GND
DAT+
DAT -
5V
GND
GND
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
RI
DCD
DSR
Although technically it is not interference, multipath is also a factor to be
understood. Multipath is a term used to refer to the signal cancellation effects
that occur when RF waves arrive at the receiver in different phase relationships.
This effect is a particularly significant factor in interior environments where
objects provide many different signal reflection paths. Multipath cancellation
results in lowered signal levels at the receiver and, thus, shorter useful distances
for the link.
TXM-xxx-LR
1
2
3
4
8
7
6
5
GND
PDN
GND
DATA
GND
VCC
DATA_IN
DATA_OUT
RTS
VCC
GND
SUSP_IND
RX_IND
TX_IND
485_TX
GND GND
VCC
GND
GND
750
VCC
CTS
DTR
LADJ/VCC ANT
Figure 10: LR Transmitter and Linx QS Series USB Module
Page 8
Page 9
BOARD LAYOUT GUIDELINES
MICROSTRIP DETAILS
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 modules, integrating them is very straightforward. Despite
this ease of application, it is still necessary to maintain respect for the RF stage
and exercise appropriate care in layout and application in order to maximize
performance and ensure reliable operation. The antenna can also be influenced
by layout choices. Please review this data guide in its entirety prior to beginning
your design. By adhering to good layout principles and observing some basic
design rules, you will be on the path to RF success.
A transmission line is a medium whereby RF energy is transferred from one
place to another with minimal loss. This is a critical factor, especially in high-
frequency products like Linx RF modules, because the trace leading to the
module’s antenna can effectively contribute to the length of the antenna,
changing its resonant bandwidth. In order to minimize loss and detuning, some
form of transmission line between the antenna and the module should be used,
unless the antenna can be placed very close (<1/8in.) to the module. One
common form of transmission line is a coax cable, another is the microstrip. This
term refers to a PCB trace running over a ground plane that is designed to serve
as a transmission line between the module and the antenna. The width is based
on the desired characteristic impedance of the line, the thickness of the PCB,
and the dielectric constant of the board material. For standard 0.062in thick FR-
4 board material, the trace width would be 111 mils. The correct trace width can
be calculated for other widths and materials using the information below. Handy
software for calculating microstrip lines is also available on the Linx website,
www.linxtechnologies.com.
The adjacent figure shows the suggested
PCB footprint for the module. The actual pad
dimensions are shown in the Pad Layout
section of this manual. A ground plane (as
large as possible) should be placed on a
lower layer of your PC board opposite the
module. This ground plane can also be critical
to the performance of your antenna, which will
be discussed later. There should not be any
ground or traces under the module on the
same layer as the module, just bare PCB.
GRROOUUNNDD PPLLAANNEE
ONN LLOOWER LAYER
Trace
Figure 11: Suggested PCB Layout
Board
During prototyping, the module should be soldered to a properly laid-out circuit
board. The use of prototyping or “perf” boards will result in horrible performance
and is strongly discouraged.
Ground plane
No conductive items should be placed within 0.15in of the module’s top or sides.
Do not route PCB traces directly under the module. The underside of the module
has numerous signal-bearing traces and vias that could short or couple to traces
on the product’s circuit board.
The module’s ground lines should each have their own via to the ground plane
and be as short as possible.
AM / OOK receivers are particularly subject to noise. The module should, as
much as reasonably possible, be isolated from other components on your PCB,
especially high-frequency circuitry such as crystal oscillators, switching power
supplies, and high-speed bus lines. Make sure internal wiring is routed away
from the module and antenna, and is secured to prevent displacement.
The power supply filter should be placed close to the module’s VCC line.
In some instances, a designer may wish to encapsulate or “pot” the product.
Many Linx customers have done this successfully; however, there are a wide
variety of potting compounds with varying dielectric properties. Since such
compounds can considerably impact RF performance, it is the responsibility of
the designer to carefully evaluate and qualify the impact and suitability of such
materials.
Figure 12: Microstrip Formulas
Effective Dielectric
Constant
Characteristic
Impedance
Dielectric Constant Width/Height (W/d)
The trace from the module to the antenna should be kept as short as possible.
A simple trace is suitable for runs up to 1/8-inch for antennas with wide
bandwidth characteristics. For longer runs or to avoid detuning narrow bandwidth
antennas, such as a helical, use a 50-ohm coax or 50-ohm microstrip
transmission line as described in the following section.
4.80
4.00
2.55
1.8
2.0
3.0
3.59
3.07
2.12
50.0
51.0
48.0
Page 10
Page 11
PAD LAYOUT
AUTOMATED ASSEMBLY
The following pad layout diagram is designed to facilitate both hand and
automated assembly.
For high-volume assembly, most users will want to auto-place the modules. The
modules have been designed to maintain compatibility with reflow processing
techniques; however, due to the their hybrid nature, certain aspects of the
assembly process are far more critical than for other component types.
0.065"
Following are brief discussions of the three primary areas where caution must be
observed.
Reflow Temperature Profile
0.340"
0.070"
The single most critical stage in the automated assembly process is the reflow
stage. The reflow profile below should not be exceeded, 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 ensure that it meets the requirements necessary to successfully reflow
all components while still remaining within the limits mandated by the modules.
The figure below shows the recommended reflow oven profile for the modules.
0.100"
Figure 13: Recommended PCB Layout
PRODUCTION GUIDELINES
300
Recommended RoHS Profile
Max RoHS Profile
Recommended Non-RoHS Profile
The modules are housed in a hybrid SMD package that supports hand or
automated assembly techniques. Since the modules contain discrete
components internally, the assembly procedures are critical to ensuring the
reliable function of the modules. The following procedures should be reviewed
with and practiced by all assembly personnel.
255°C
250
200
150
100
50
235°C
217°C
185°C
180°C
HAND ASSEMBLY
Pads located on the bottom of the
module are the primary mounting
surface. Since these pads are
inaccessible during mounting,
Soldering Iron
Tip
125°C
castellations that run up the side of
the module have been provided to
facilitate solder wicking to the
module’s underside. This allows for
very quick hand soldering for
Solder
PCB Pads
0
30
60
90
120
150
180
210
240
270
300
330
360
Castellations
Time (Seconds)
prototyping and small volume
Figure 15: Maximum Reflow Profile
Figure 14: Soldering Technique
production.
If the recommended pad guidelines have been followed, the pads will protrude
slightly past the edge of the module. Use a fine soldering tip to heat the board
pad and the castellation, then introduce solder to the pad at the module’s edge.
The solder will wick underneath the module, providing reliable attachment. Tack
one module corner first and then work around the device, taking care not to
exceed the times listed below.
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 modules not be
subjected to shock or vibration during the time solder is liquid. Should a shock
be applied, some internal components could be lifted from their pads, causing
the module to not function properly.
Washability
Absolute Maximum Solder Times
The modules are wash resistant, but are not hermetically sealed. Linx
recommends wash-free manufacturing; however, the modules can be subjected
to a wash cycle provided that a drying time is allowed prior to applying electrical
power to the modules. The drying time should be sufficient to allow any moisture
that may have migrated into the module to evaporate, thus eliminating the
potential for shorting damage during power-up or testing. If the wash contains
contaminants, the performance may be adversely affected, even after drying.
Hand-Solder Temp. TX +225°C for 10 Seconds
Hand-Solder Temp. RX +225°C for 10 Seconds
Recommended Solder Melting Point +180°C
Reflow Oven: +220°C Max. (See adjoining diagram)
Page 12
Page 13
ANTENNA CONSIDERATIONS
GENERAL ANTENNA RULES
The choice of antennas is a critical
The following general rules should help in maximizing antenna performance.
and
consideration.
often
overlooked
The
design
range,
1. Proximity to objects such as a user’s hand, 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.
performance, and legality of an RF link
are critically dependent upon the
antenna. While adequate antenna
performance can often be obtained by
trial and error methods, antenna
design and matching is a complex
2. Optimum performance will be obtained
from a 1/4- or 1/2-wave straight whip
mounted at a right angle to the ground
plane. In many cases, this isn’t desirable
OPTIMUM
for practical or ergonomic reasons, thus,
NOT RECOMMENDED
task.
A
professionally designed
Figure 16: Linx Antennas
USEABLE
an alternative antenna style such as a
helical, loop, or patch may be utilized
antenna, such as those from Linx, will
help ensure maximum performance and FCC compliance.
Figure 18: Ground Plane Orientation
and the corresponding sacrifice in performance accepted.
Linx transmitter modules typically have an output power that is slightly higher
than the legal limits. This allows the designer to use an inefficient antenna, such
as a loop trace or helical, to meet size, cost, or cosmetic requirements and still
achieve full legal output power for maximum range. If an efficient antenna is
used, then some attenuation of the output power will likely be needed. This can
easily be accomplished by using the LADJ line or a T-pad attenuator. For more
details on T-pad attenuator design, please see Application Note AN-00150.
3. If an internal antenna is to be used, keep it away from other metal components,
particularly large items like transformers, batteries, PCB tracks, and ground
planes. In many cases, the space around the antenna is as important as the
antenna itself. Objects in close proximity to the antenna can cause direct
detuning, while those farther away will alter the antenna’s symmetry.
4. In many antenna designs, particularly 1/4-wave
VERTICAL λ/4 GROUNDED
ANTENNA (MARCONI)
whips, the ground plane acts as a counterpoise,
forming, in essence, a 1/2-wave dipole. For this
reason, adequate ground plane area is essential.
A receiver antenna should be optimized for the frequency or band in which the
receiver operates and to minimize the reception of off-frequency signals. The
efficiency of the receiver’s antenna is critical to maximizing range performance.
Unlike the transmitter antenna, where legal operation may mandate attenuation
or a reduction in antenna efficiency, the receiver’s antenna should be optimized
as much as is practical.
E
DIPOLE
ELEMENT
λ/4
The ground plane can be a metal case or ground-fill
I
areas on a circuit board. Ideally, it should have a
surface area > the overall length of the 1/4-wave
radiating element. This 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 ground plane as
GROUND
PLANE
VIRTUAL λ/4
DIPOLE
λ/4
It is usually best to utilize a basic quarter-wave whip until your prototype product
is operating satisfactorily. Other antennas can then be evaluated based on the
cost, size, and cosmetic requirements of the product. You may wish to review
Application Note AN-00500 “Antennas: Design, Application, Performance”
Figure 19: Dipole Antenna
possible in proximity to the base of the antenna. In cases where the antenna is
remotely located or the antenna is not in close proximity to a circuit board,
ground plane, or grounded metal case, a metal plate may be used to maximize
the antenna’s performance.
ANTENNA SHARING
In cases where a transmitter and receiver
module are combined to form a transceiver,
0.1μF
it is often advantageous to share a single
Module
V
DD
Transmitter
0.1μF
Antenna
5. Remove the antenna as far as possible from potential interference sources. Any
frequency of sufficient amplitude to enter the receiver’s front end will reduce
system range and can even prevent reception entirely. Switching power
supplies, oscillators, or even relays can also be significant sources of potential
interference. 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 ground plane under potential sources of noise
to shunt noise to ground and prevent it from coupling to the RF stage. Shield
noisy board areas whenever practical.
antenna. To accomplish this, an antenna
switch must be used to provide isolation
between the modules so that the full
0.1μF
GND
0.1μF
GND
Receiver
Module
transmitter output power is not put on the
0.1μF
sensitive front end of the receiver. There
Select
are a wide variety of antenna switches that
are cost-effective and easy to use. Among
Figure 17: Typical Antenna Switch
the most popular are switches from Macom and NEC. Look for an antenna
switch that has high isolation and low loss at the desired frequency of operation.
Generally, the Tx or Rx status of a switch will be controlled by a product’s
microprocessor, but the user may also make the selection manually. In some
cases, where the characteristics of the Tx and Rx antennas need to be different
or antenna switch losses are unacceptable, it may be more appropriate to utilize
two discrete antennas.
6. In some applications, it is advantageous to
place the module and antenna away from the
CASE
main equipment. This can avoid interference
problems and allows the antenna to be
oriented for optimum performance. Always use
GROUND PLANE
NUT
(MAY BE NEEDED)
50Ω coax, like RG-174, for the remote feed.
Figure 20: Remote Ground Plane
Page 15
Page 14
COMMON ANTENNA STYLES
ONLINE RESOURCES
There are literally hundreds of antenna styles and variations that can be
employed with Linx RF modules. Following is a brief discussion of the styles
most commonly utilized. Additional antenna information can be found in Linx
Application Notes AN-00100, AN-00140, and AN-00500. Linx antennas and
connectors offer outstanding performance at a low price.
®
www.linxtechnologies.com
• Latest News
A whip-style antenna provides outstanding overall performance
Whip Style
and stability. A low-cost whip is can be easily fabricated from a
wire or rod, but most designers opt for the consistent
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.
• Data Guides
• Application Notes
• Knowledgebase
• Software Updates
The wavelength of the operational frequency determines an
antenna’s overall length. Since a full wavelength is often quite
If you have questions regarding any Linx product and have Internet access,
make www.linxtechnologies.com your first stop. Our website is organized in an
intuitive format to immediately give you the answers you need. Day or night, the
Linx website gives you instant access to the latest information regarding the
products and services of Linx. It’s all here: manual and software updates,
application notes, a comprehensive knowledgebase, FCC information, and much
more. Be sure to visit often!
long, a partial 1/2- or 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 straight 1/4-wave can be
easily determined using the adjacent formula. It is also possible
to reduce the overall height of the antenna by using a helical
winding. This reduces the antenna’s bandwidth, but is a great
way to minimize the antenna’s physical size for compact
applications. This also means that the physical appearance is
not always an indicator of the antenna’s frequency.
234
L =
F
MHz
Where:
L
= length in feet of
quarter-wave length
F = operating frequency
in megahertz
Specialty Styles
Linx offers a wide variety of specialized antenna styles.
Many of these styles utilize helical elements to reduce the
overall antenna size while maintaining reasonable
performance. A helical antenna’s bandwidth is often quite
narrow and the antenna can detune in proximity to other
objects, so care must be exercised in layout and placement.
www.antennafactor.com
The Antenna Factor division of Linx offers
a diverse array of antenna styles, many of
which are optimized for use with our RF
modules. From innovative embeddable
antennas to low-cost whips, domes to
Yagis, and even GPS, Antenna Factor
likely has an antenna for you, or can
design one to meet your requirements.
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. The element can be made self-resonant or externally
resonated with discrete components, but its actual layout is
usually product specific. Despite the cost advantages, loop-style
antennas are generally inefficient and useful only for short-range
applications. They are also very sensitive to changes in layout and
PCB dielectric, which can cause consistency issues during
production. In addition, printed styles 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 cause instability in the RF stage.
Loop Style
www.connectorcity.com
Through its Connector City division, Linx offers a wide
selection of high-quality RF connectors, including FCC-
compliant types such as RP-SMAs that are an ideal
match for our modules and antennas. Connector City
focuses on high-volume OEM requirements, which
allows standard and custom RF connectors to be offered
at a remarkably low cost.
Linx offers low-cost planar and chip antennas that mount directly
to a product’s PCB. These tiny antennas do not require testing and
provide excellent performance in light of their small size. They
offer a preferable alternative to the often-problematic “printed”
antenna.
Page 16
Page 17
LEGAL CONSIDERATIONS
ACHIEVING A SUCCESSFUL RF IMPLEMENTATION
Adding an RF stage brings an exciting new
DECIDE TO UTILIZE RF
NOTE: Linx RF modules are designed as component devices that 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 use in the country of operation.
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 LR Series, the
design and approval process is greatly simplified. It
is still important, however, to have an objective view
of the steps necessary to ensure 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.
RESEARCH RF OPTIONS
ORDER EVALUATION KIT(S)
TEST MODULE(S) WITH
BASIC HOOKUP
CHOOSE LINX MODULE
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 legally market your
completed product.
INTERFACE TO CHOSEN
CIRCUIT AND DEBUG
CONSULT LINX REGARDING
ANTENNA OPTIONS AND DESIGN
LAY OUT BOARD
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
SEND PRODUCTION-READY
PROTOTYPE TO LINX
FOR EMC PRESCREENING
OPTIMIZE USING RF SUMMARY
GENERATED BY LINX
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 (FCC). The regulations are contained in Title
47 of the Code of Federal Regulations (CFR). 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 bookstore. Excerpts of applicable sections are
included with Linx evaluation kits or may be obtained from the Linx Technologies website,
www.linxtechnologies.com. In brief, these rules require that any device that 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 that 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 that is to be clearly placed on each product manufactured.
SEND TO PART 15
TEST FACILITY
RECEIVE FCC ID #
COMMENCE SELLING PRODUCT
Typical Steps For
Implementing RF
will not only survive implementing RF, you may even find the process enjoyable.
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. These
applications notes are available online at www.linxtechnologies.com or by
contacting the Linx literature department.
Questions regarding interpretations of the Part 2 and Part 15 rules or measurement
procedures used to test intentional radiators, such as Linx RF modules, for compliance
with the technical standards of Part 15, should be addressed to:
Federal Communications Commission
Equipment Authorization Division
Customer Service Branch, MS 1300F2
7435 Oakland Mills Road
NOTE
AN-00100
APPLICATION NOTE TITLE
RF 101: Information for the RF Challenged
Columbia, MD 21046
Phone: (301) 725-1585 Fax: (301) 344-2050 E-Mail: labinfo@fcc.gov
AN-00125
AN-00130
AN-00140
AN-00150
AN-00160
AN-00232
AN-00500
Considerations For Operation Within The 260-470MHz Band
Modulation Techniques For Low-Cost RF Data Links
The FCC Road: Part 15 From Concept To Approval
Use and Design of T-Attenuation Pads
International approvals are slightly more complex, although Linx 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.
Considerations For Sending Data Over a Wireless Link
General Considerations For Sending Data With The LC Series
Antennas: Design, Application, Performance
Page 18
Page 19
WIRELESS MADE SIMPLE ®
U.S. CORPORATE HEADQUARTERS
LINX TECHNOLOGIES, INC.
159 ORT LANE
MERLIN, OR 97532
PHONE: (541) 471-6256
FAX: (541) 471-6251
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 to our products without notice. The information contained in this
Overview Guide 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. "Typical" parameters can
and do vary over lots and application. Linx Technologies makes no guarantee, warranty, or representation
regarding the suitability of any product for use in any specific application. It is the customer's responsibility
to verify the suitability of the part for the intended application. NO LINX PRODUCT IS INTENDED FOR USE
IN ANY APPLICATION WHERE THE SAFETY OF LIFE OR PROPERTY IS AT RISK.
Linx Technologies DISCLAIMS ALL WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE. IN NO EVENT SHALL LINX TECHNOLOGIES BE LIABLE FOR ANY OF
CUSTOMER'S INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING IN ANY WAY FROM ANY DEFECTIVE
OR NON-CONFORMING PRODUCTS OR FOR ANY OTHER BREACH OF CONTRACT BY LINX
TECHNOLOGIES. The limitations on Linx Technologies' liability are applicable to any and all claims or
theories of recovery asserted by Customer, including, without limitation, breach of contract, breach of
warranty, strict liability, or negligence. Customer assumes all liability (including, without limitation, liability
for injury to person or property, economic loss, or business interruption) for all claims, including claims
from third parties, arising from the use of the Products. The Customer will indemnify, defend, protect, and
hold harmless Linx Technologies and its officers, employees, subsidiaries, affiliates, distributors, and
representatives from and against all claims, damages, actions, suits, proceedings, demands, assessments,
adjustments, costs, and expenses incurred by Linx Technologies as a result of or arising from any Products
sold by Linx Technologies to Customer. 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. Devices described in this publication may contain
proprietary, patented, or copyrighted techniques, components, or materials. Under no circumstances shall
any user be conveyed any license or right to the use or ownership of such items.
© 2008 by Linx Technologies, Inc. The stylized Linx logo,
Linx, “Wireless Made Simple”, CipherLinx, and the stylized
CL logo are the trademarks of Linx Technologies, Inc.
Printed in U.S.A.
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