RXM-869-ES
RXM-916-ES
WIRELESS MADE SIMPLE
®
ES SERIES RF RECEIVER MODULE DATA GUIDE
DESCRIPTION
Housed in a tiny SMD package, the ES Series
0.812"
offers an impressive combination of features,
performance and cost-effectiveness. The ES
utilizes an advanced synthesized FM / FSK
architecture to provide superior performance
and noise immunity when compared to AM /
0.630"
RF MODULE
RXM-916-ES
OOK solutions. An outstanding 56kbps
LOT 10000
maximum data rate and wide-range analog
capability make the ES Series equally at home
with digital data or analog sources such as
audio. A host of useful features including RSSI,
0.125"
PDN, and an audio reference are provided. ES
Series components will be available in a wide
range of frequencies to take full advantage of
Figure 1: Package Dimensions
worldwide applications. The ES Series requires no tuning or external RF components
(except an antenna).
FEATURES
Ultra-compact SMD package
FM / FSK modulation for
outstanding performance
High noise immunity
Precision synthesized
architecture
Excellent sensitivity
Low current consumption
High 56,000bps data rate
Direct interface to analog and
digital sources
Wide-range analog capability
No tuning or external RF
components required
RSSI and power-down lines
APPLICATIONS INCLUDE
Wireless Data Transfer
Wireless Analog / Audio
Home / Industrial Automation
Keyless Entry
Remote Control
Fire / Security Alarms
Telemetry
Remote Status Sensing
RS-232 / 485 Data Links
MIDI Links
Long-Range RFID
ORDERING INFORMATION
PART #
DESCRIPTION
TXM-869-ES
ES Series Transmitter 869MHz
TXM-916-ES
ES Series Transmitter 916MHz
RXM-869-ES
ES Series Receiver 869MHz
RXM-916-ES
ES Series Receiver 916MHz
EVAL-***-ES
Basic Evaluation Kit
MDEV-***-ES
Master Development System
*** = Frequency
Receivers are supplied in tubes of 25 pcs.
Revised 1/28/08
ELECTRICAL SPECIFICATIONS
Parameter
POWER SUPPLY
Operating Voltage
Supply Current
Power-Down Current
RECEIVER SECTION
Receive Frequency:
RXM-869-ES
RXM-916-ES
Center Frequency Accuracy
LO Frequency:
RXM-869-ES
RXM-916-ES
IF Frequency
Spurious Emissions
Receiver Sensitivity
Noise Bandwidth
Audio Bandwidth
Audio Output Level
Data Rate
Data Output:
Logic Low
Logic High
Power Down Input:
Logic Low
Logic High
RSSI:
Dynamic Range
Gain
Voltage with No Carrier
Voltage with Max Carrier
ANTENNA PORT
RF Input Impedance
TIMING
Receiver Turn-On Time:
Via V
CC
Via PDN
Max Time Between Transitions
ENVIRONMENTAL
Operating Temperature Range
Designation
V
CC
I
CC
I
PDN
F
C
–
–
-60
–
–
–
–
-92
–
20
–
200
–
V
CC
- 1.1
0.0
2.8
–
–
–
–
–
869.85
916.48
–
859.15
905.78
10.7
-75
-97
280
–
360
–
0.0
V
CC
- 1
–
–
60
30
1.1
2.9
50
–
–
+60
–
–
–
-50
-102
–
28,000
–
56,000
0.1
V
CC
- 0.9
0.8
V
CC
–
–
–
–
–
MHz
MHz
kHz
MHz
MHz
MHz
dBm
dBm
kHz
Hz
mV
P-P
bps
VDC
VDC
VDC
VDC
dB
mV/dB
V
V
Ω
–
–
–
–
–
–
1
2
–
3,4
4,5
4
–
–
–
–
4
4
4
4
4
Min.
4.5
5.5
Typical
5.0
6.0
50.0
Max.
5.5
6.5
Units
VDC
mA
µA
Notes
–
–
4
ABSOLUTE MAXIMUM RATINGS
Supply Voltage V
CC
Any Input or Output Pin
Operating temperature
Storage temperature
Soldering temperature
-0.3
-0.3
0
-40
+260°C
to
+5.5
to V
CC
+ 0.3
to
+70
to
+125
for 15 seconds
VDC
VDC
°C
°C
*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.
–
F
LO
PERFORMANCE DATA
These performance parameters
are based on module operation at
25°C from a 5.0VDC supply unless
otherwise
noted.
Figure
2
illustrates
the
connections
necessary
for
testing
and
operation. It is recommended all
ground pins be connected to the
ground plane. The pins marked NC
have no electrical connection.
1
2
3
4
5
6
7
8
ANT
GND
NC
GND
VCC
NC
NC
NC
NC
NC
PDN
RSSI
DATA
AUDIO
A REF
NC
16
15
14
13
12
11
10
9
F
IF
–
–
N
3dB
–
–
–
V
OL
V
OH
V
OL
V
OH
–
–
–
–
R
IN
5VDC
Figure 2: Test / Basic Application Circuit
TYPICAL PERFORMANCE GRAPHS
3.0
2.5
RSSI Voltage (V)
2.0
1.5
–
–
–
–
3.8
–
0
4.7
5.0
–
5.4
–
+70
mSec
mSec
mSec
°C
4,6
4,6
4,7
4
1.0
-110
-100
-90
-80
-70
-60
-50
-40
1
CH1 500mV
1mS
RF Input (dBm)
Figure 3: RSSI Characteristics Chart
Figure 4: Worst Case RSSI Response Time
Table 1: ES Series Receiver Specifications
DATA IN
Supply
Notes
1. Into a 50-ohm load.
2. For 10
-5
BER at 9,600 baud.
3. The audio bandwidth is wide to accommodate the needs of the data slicer. In audio applications, audio
quality may be improved by using a low-pass filter rolling off at the maximum frequency of interest.
4. Characterized, but not tested.
5. Input frequency deviation-dependent.
6. Time to receiver readiness from the application of power to V
CC
or PDN going high.
7. Maximum time without a data transition.
1
1
RX Data
AUDIO OUT
2
CH1 2.00V
CH2 2.00mV
1mS
2
CH1 396mV
CH2 100mV
250uS
Figure 5: RX V
cc
to Valid Data
Page 2
Figure 6: Sine-Wave Modulation Linearity
Page 3
RX On >-35dBm
RX Off
PIN ASSIGNMENTS
1
2
3
4
5
6
7
8
ANT
GND
NC
GND
VCC
NC
NC
NC
NC
NC
PDN
RSSI
DATA
AUDIO
A REF
NC
16
15
14
13
12
11
10
9
MODULE DESCRIPTION
The RXM-***-ES module is a single-channel receiver designed for the wireless
reception of digital or analog information over distances of up to 1,000 feet
outdoors and up to 500 feet indoors. It is based on a high-performance,
synthesized, single conversion, superhet architecture. FM / FSK modulation and
SAW filtering are utilized to provide performance and noise immunity that are
superior to AM-based solutions. The ES series is incredibly compact and cost-
effective when compared with other FM / FSK devices. Best of all, it is packed
with many useful features, offering a great deal of design flexibility.
RF In
SAW BPF
LNA
10.7MHz
IF Filter
Limiter
PLL
Demodulator
Precision
Crystal
PLL Frequency
Synthesizer
Data
Slicer
Data
Output
Figure 7: ES Series Receiver Pinout (Top View)
PIN DESCRIPTIONS
Pin #
1
2
3
4
5
6-9
10
11
12
Audio
Output
Name
ANT
GND
NC
GND
V
CC
NC
A REF
AUDIO
DATA
Description
50-ohm RF Input
Analog Ground
No Electrical Connection. Soldered for physical support
only.
Analog Ground
Supply Voltage
No Electrical Connection. Soldered for physical support
only.
Audio RMS (Average) Voltage Reference
Recovered Analog Output
Digital Data Output. This line will output the demodulated
digital data.
Received Signal Strength Indicator. This line will supply an
analog voltage that is proportional to the strength of the
received signal.
Power Down. Pulling this line low will place the receiver
into a low-current state. The module will not be able to
receive a signal in this state.
No Electrical Connection. Soldered for physical support
only.
Figure 8: ES Series Receiver Block Diagram
Peak
Detector
RSSI
Output
THEORY OF OPERATION
The receiver operates in a single conversion superhet configuration, with an IF
of 10.7MHz and a baseband analog bandwidth of 28kHz. It is capable of
receiving a signal as low as -97dBm (typical). The signal is filtered at the front
end by a SAW band-pass filter. The filtered signal is then amplified and down-
converted to the 10.7MHz IF by mixing it with a LO frequency generated by a
PLL-locked VCO. The 10.7MHz IF is then amplified and filtered. Finally, a PLL
demodulator is used to recover the baseband analog signal from the carrier. This
analog signal is low-pass filtered and then output on the AUDIO line.
The analog output can be individual frequencies or complex waveforms, such as
voice or music. The AUDIO line can also be used to recover unsquared data in
instances where a designer wishes to use an external data slicer.
The ES receiver also features a high-performance on-board data slicer for
recovery of data transmission. Its output is internally derived from the filtered
analog baseband, which is squared and made externally available on the DATA
line. The data slicer is capable of recreating squared waveforms from 100Hz to
28kHz, giving a data rate bandwidth of 200bps to 56kbps.
It is important to note that this receiver does not provide hysteresis or squelching
of the DATA line. This means that in the absence of a valid transmission or
transitional data, the DATA line will switch randomly. The effects of this noise
must be considered and will be discussed in further detail later in this guide.
The receiver features a Received Signal Strength Indicator (RSSI) output. The
RSSI pin outputs a linear voltage relative to the incoming signal level. This output
has many valuable uses, including interference assessment, signal strength
indication, external data squelching and qualification, and transmitter presence
indication. Since RSSI values vary from part to part and correspond to signal
strength and not necessarily distance, it is not recommended for range-finding
applications.
Page 5
13
RSSI
14
PDN
15 - 16
Page 4
NC
USING THE PDN PIN
The Power Down (PDN) line can be used to power down the receiver without the
need for an external switch. This line has an internal pull-up, so when it is held
high or simply left floating, the module will be active.
When the PDN line is pulled to ground, the receiver will enter into a low-current
(<50µA) power-down mode. During this time the receiver is off and cannot
perform any function. It may be useful to note that the startup time coming out of
power-down will be slightly less than when applying V
CC
.
The PDN line allows easy control of the receiver state from external components,
like a microcontroller. By periodically activating the receiver, checking for data,
then powering down, the receiver’s average current consumption can be greatly
reduced, saving power in battery-operated applications.
PROTOCOL GUIDELINES
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.
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.
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.
USING THE RSSI PIN
The receiver’s Received Signal Strength Indicator (RSSI) line serves a variety of
uses. The RSSI line has a dynamic range of 60dB (typical) and outputs a voltage
proportional to the incoming signal strength. A graph of the RSSI line’s
characteristics appears in the Typical Performance Graphs section. It should be
realized that the RSSI levels and dynamic range will vary slightly from part to
part. It is also important to remember that the RSSI output indicates the strength
of any in-band RF energy and not necessarily just that from the intended
transmitter; therefore, it should only be used to qualify the level and presence of
a signal.
The RSSI output can be used to create external squelch circuits. It can be
utilized during testing or even as a product feature to assess interference and
channel quality by looking at the voltage level with all intended transmitters off.
The RSSI output can also be used in direction-finding applications although
there are many potential perils to consider in such systems. Finally, it can be
used to save system power by “waking up” external circuitry when a transmission
is received or crosses a certain threshold. The RSSI output feature adds
tremendous versatility for the creative designer.
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.
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.
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.
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.
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.
Page 7
POWER SUPPLY REQUIREMENTS
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 significantly affect the receiver
sensitivity, therefore; providing clean power to the
module should be a high priority during design.
Vcc TO
MODULE
10Ω
Vcc IN
+
10μF
A 10Ω resistor in series with the supply followed by a
Figure 9: Supply Filter
10µF tantalum capacitor from V
CC
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.
Page 6
USING THE RXM-***-ES FOR ANALOG APPLICATIONS
The ES Series is an excellent choice for sending a wide range of analog
information, including audio. The ability of the ES to receive combinations of
analog and digital signals also opens new areas of opportunity for creative
product design.
The transmission may contain simple or complex analog signals within the
specified audio bandwidth. Signal sources ranging from a single frequency to
complex content, such as audio, are handled with ease.
The AUDIO line of the receiver should be buffered and filtered to obtain
maximum signal quality. This is particularly important because the audio output
is AC-coupled, which means any DC loading will cause errors in the data slicer
since data is derived from the audio voltage. For voice, a 3-4kHz low-pass filter
is often employed. For broader-range sources, such as music, a 12-20kHz cutoff
may be more appropriate. When only sending audio, the DATA line should be
pulled to V
CC
to reduce noise resulting from the data slicer switching.
The Signal-to-Noise Ratio (SNR) of the audio will depend on the bandwidth you
select. The higher the SNR, the less hiss you will hear in the background. For
the best SNR, choose the lowest filter cutoff appropriate for the intended signal.
For applications that require true high fidelity, audio RF links designed expressly
for this purpose may prove to be a more appropriate solution; however, a
compandor may also be used with the ES Series transmitter to provide further
SNR improvements.
The 360mV
P-P
output level of the AUDIO line is not sufficient to drive a speaker,
so an amplifier will be required. This amplifier can also be used to provide the
buffering and filtering described above. Some manufacturers make amplifiers
specifically for audio applications, but standard filter designs, such as
Butterworth or Sallen-Key, can also be used with success.
To avoid audible white noise or hiss when no transmission is present, a squelch
circuit can be implemented to provide muting. This is easily accomplished with a
circuit like the one shown below.
VCC
39k
USING THE ES FOR DIGITAL APPLICATIONS
As previously discussed, it is important to note that this receiver does not provide
hysteresis or squelching of the DATA line. This means that in the absence of a
valid transmission or transitional data, the DATA line will switch randomly. In
many applications this hash will be ignored by the decoder or system software,
but, depending on your application, it may be useful to add an external circuit to
provide data squelching and hysteresis.
A squelch circuit will disable the DATA output when the RSSI voltage falls below
a reference level. Hysteresis will make the RSSI voltage have to fall lower than
the reference voltage before switching off, and to have to rise higher than the
reference voltage before switching on. This will prevent low amplitude noise from
causing the data line to switch, reducing hash during times that the transmitter is
off or during transmitter steady-state times exceeding 5mS. Strong signals can
still get through, so it is a good idea to have a noise tolerant protocol.
Creating a circuit that has additional hysteresis characteristics is very basic and
requires very few parts thanks to the A REF line. All you need is a couple of
resistors to provide some isolation for the AUDIO and A REF lines, a large
feedback resistor, a pull-up resistor, and an open collector comparator.
The RSSI and A REF lines allow a wide variety of squelch circuits to be
implemented. One such possibility is the circuit below, which is used on the ES
Series Master Development System, and may be employed for audio or data
squelching. It is ultimately the responsibility of the designer to determine what, if
any, circuit would be most appropriate for the needs of the product.
VCC
VCC
VCC
Qualified Data
39k
390k
1
RSSI
39k
10k
0.01uF
3
4
8
10k
5k
OUTA
INA-
INA+
GND
LM393
VCC
2M
AUDIO REF
10k
AUDIO
10k
2M
GND
GND
GND
GND
5k
POT
RSSI
LM393
–
+
39k
10k
2M
GND
GND
0.01uF
AUDIO REF
Figure 11: ES Series Receiver Squelch / Hysteresis Circuit
10-20k
GND
Figure 10: ES Series Receiver Squelch Circuit
Data squelching in the circuit above is accomplished by comparing the RSSI
voltage to a voltage reference (typically a voltage divider) with an open collector
style comparator. When the voltage from the RSSI becomes lower than the
voltage reference, the comparator output is pulled to GND. This is useful
because this output can be used to disable the data-slicer circuit either when the
receiver is out of range or the transmitter is turned off.
The squelch threshold will normally be set as low as possible to ensure
maximum sensitivity and range. It is important to recognize that in many actual
use environments, ambient noise and interference may enter the receiver at
levels well above the squelch threshold. For this reason, it is always
recommended that the product’s protocol be structured to allow for the possibility
of hashing even when an external squelch circuit is employed.
Page 9
Analog squelching is implemented by comparing the RSSI voltage to a voltage
reference (typically a voltage divider) with an open collector-style comparator.
When the RSSI voltage becomes lower than the voltage reference, the
comparator output is pulled to ground, disabling the AUDIO output. This is useful
because the analog circuit can be disabled either when the receiver is out of
range or the transmitter is turned off. Of course it is the designer’s responsibility
to choose a squelch topology that best fits the specific needs of the product.
Page 8
Talking
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