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Radiometrix
Issue 4, 13 July 2001
Hartcran House, Gibbs Couch, Watford, WD19 5EZ, England
Tel: +44 (0) 20 8428 1220, Fax: +44 (0) 20 8428 1221
RXM-UHF
UHF Radio Telemetry Receiver Module
UK Version - RXM-418-10 Euro Version- RXM-433-10 The RXM-UHF radio receiver and the matching DTI approved transmitter (TXM-UHF) are self contained, PCB mounting modules capable of transferring analogue or digital data up to a distance of 200m.
Features: * PCB Mounting * 418 MHz SAW controlled wide band FM reception * Selective double conversion superhet * Sensitive typ. 0.35V for 10dB S/N * High data rates, 10 kbps * Analogue and Digital data outputs * Receive signal strength output * Carrier detect output * Jamming signal detector * Fast enable time. < 5ms for duty cycle power save use * Logic compatible supply (5.0V @ 20 mA) * Antenna Tamper sensing * 433.92MHz version available
left: TXM Transmitter
right: RXM Receiver
These modules are most commonly employed in Wireless Security systems. The transmitter is approved to DTI (RA) specification MPT 1340 thus avoiding the need to submit the finished product for approval. The receiver provides all the outputs necessary to satisfy the requirements of a class 5, BS6799 wireless alarm system. The modules are also suitable for general purpose telemetry/telecommand where their small size and high data rates may be used to advantage. Typical applications include:* Domestic and commercial security * Guard patrol/lone worker protection * Medical Alert/Nurse Call system * Mobile panic attack * Computer networking * Remote industrial process monitoring * Data transfer through hazardous environments * Lighting control, Garage door openers * Fire alarms * Picture/antique protection alarms * Remote control, Access control
Radiometrix Ltd, RXM-UHF Data Sheet
page 1
Absolute Maximum Rating Supply voltage Vcc, pin 13 RF input, pin 1 Any input or out put pin Operating temperature Storage temperature Performance Data ambient temperature supply voltage test circuit Parameter Operating supply range (Vcc) pin 13 Supply current pin 13 Receive frequency Overall frequency accuracy Sensitivity for 10dB S/N pin 1 Sensitivity for 20dB S/N pin 1 Jam det, threshold pin 1 Carrier det, threshold pin 1 RF input impedance pin 1 IF bandwidth AF output level pin 4 AF bandwidth, -3dB pin 4 Logic low, pin 6,8,10,11 Logic high, pin 6,8,10,11 Antenna tamper detector pin 1 Sig. strength dynamic range pin 9 Sig. strength FSD pin 9 Sig. strength O/P resistance pin 9 enable time pin 11 signal detect time pin 11 20C +5.0V unless noted otherwise Fig 3 Min 4.5 17 -80 DC 0 4.5 0 20 3.0 6.6 Typical 5.0 21 418 0 0.35 0.7 10 3 50 250 400 0.2 5 30 3.3 6.8 2 1 Max 5.5 27 +80 1.0 2.0 10 0.5 5 5 3.6 7.0 5 3 Units V mA MHz kHz V V V V kHz mVpp mV/kHz V V k dB V k ms ms Notes -0.3V to +8.0V 0dBm -0.3V to Vcc V, 10mA 0C to +40C -40C to 100C
1 2 2
3 2,3 4 5 6 9
3,7 3,8
notes - 1. Temperature 0C to 40C 2. 25 kHz deviation, 2 kHz tone 3. 3 V input 4. The conversion slope is -ve on the 418 MHz version 5. 10mA sink 6. No load, (from 22k internal pullup) 7. From application of supply to carrier detect low 8. From application of signal to carrier detect low 9. For logic high on pin 8
Radiometrix Ltd, RXM-UHF Data Sheet
page 2
51 mm
15 16 14 13 12 11 10
31 mm
9 8 7 6 5 1 2 4 3
9 mm square 9 mm
3 mm 2.5 mm
Fig 1 Mechanical detail
Holes 1mm diameter on 2.54 mm pitch
1.1 INCH
1.8 INCH
Fig 2 PCB mounting detail (top view)
Radiometrix Ltd, RXM-UHF Data Sheet
page 3
Pin Description pin 1 RF IN The receiver antenna connects to this 50 input. A 22 k pull up resistor, internal to the module is used for `tamper' sensing on this pin. This pin should be connected to any ground plane against which the antenna works. It is internally connected to pin 3,14,15 & 16 Ground for supply This is the FM demodulator output. It has an output impedance of 330 and a standing DC bias V of approximately CC 2 The voltage on this pin is the peak -ve at pin 4 (AF). A resistor between this in and pin 7 (Max) controls the data slicer's transient response. This CMOS compatible output from the data slicer is a squared version of the signal on pin 4 (AF). This signal is used to drive external digital decoders, it is true data (ie as fed to the transmitters data input). The voltage on this pin is the peak +ve at pin 4 (AF). This CMOS compatible output goes low if the DC resistance of the antenna exceeds 5k to 0V. Received Signal Strength Indicator. 0V to 3.3V. This CMOS compatible output goes low when a strong greater than a period of time determined by a capacitor on pin 12 (JAM TC) This CMOS compatible output goes low when an incoming signal has sufficient strength to provide a clean decodable signal at pin 6 (DATA). A capacitor between this pin and ground controls the jamming detectors delay time. Positive supply of 5V 10%. The supply must be clean, stable (<10mV ac) and free of high frequency digital noise. A 10F supply decoupling capacitor is recommended. Ground to earth plane
pin 2
RF GND
pin 3 pin 4
0V AF
pin 5
Min
pin 6
Data out
pin 7 pin 8 pin 9 pin 10
Max Tamper RSSI JAM
pin 11
DET
pin 12 pin 13
JAM TC Vcc
pin 14,15,16
0V
Radiometrix Ltd, RXM-UHF Data Sheet
page 4
Typical Performance Data ambient temperature 20C supply voltage +5.0V test circuit Figure 3
signal, noise, dB PIN 4 (AF) 0
AF O/P, Volts (PIN 4)
signal 5
-20 -40 noise
4 3 2
-60
1 0 -150 -100 -50 0 50 100 150
0.1
RSSI O/P Volts (PIN 9)
0.3 1 3 10 30 100 RF Input Level V (PIN 1)
Frequency Shift , kHz
4 3 2 1 0 0.1
0.3
1 3 10 30 100 RF Input level, V (PIN1)
0v 14
15
0v Vcc 13 10R
+ 5v
10 F
16 0v JAM TC 12
10 F
+ 5v
DETECT 11 330R
RXM 418-10 / RXM 433-10
+ 5v
JAM 10 330R
RSSI
9
TAMPER
8
330R
+ 5v
MAX 7
MIN DATA 1 RF IN RF 2 RF GND 0V
5 6 4 3
DATA OUT
AF TEST POINT
0v
Fig 3 TEST CIRCUIT
Radiometrix Ltd, RXM-UHF Data Sheet page 5
Application Notes
+5V 13 +5V DC BIAS + 22K JAM 10 JAM TC 12 DET 11 22K RSSI +5V 0 - 3.3 v 9 6K8 MAX +5V + 1M
- Ve peak detector
DC BIAS +
SAW 1st Local Oscilltaor 433.92 MHz 2nd Local Oscillator 16 MHz
BUFFER
+ Ve peak detector
RF IN 1
418 MHz BPF PRE-AMP 1st MIXER
2nd MIXER IF AMPLIFIER DEMODULATER
STRENGTH AF
7 DATA 6 MIN
5 AF
22K
BUFFER
DE -EMPHASIS
330R +5V +5V RFC 0.9 V 22K +
4
22K TAMPER
RF GROUND 2 0V 3
Internal block. Fig 4 The simplest applications of the module requires only 3 connections, +5V supply, ground and the data output. A simple quarter wave antenna (17cm of wire or track on pin 1) will give good results. A 10F supply decoupling capacitor is recommended directly on pin 13. ANTENNA The positioning of the antenna is of the utmost importance and is the main determining factor of system range, the following notes should assist in obtaining optimum performance:Keep it clear of other metal in the system, particularly the `hot' end. The best position by far, is sticking out the top of the product. This is often not desirable for practical/ergonomic reasons thus a compromise may need to be reached. If an internal antenna must be used try to keep it away from other metal components, particularly large ones like transformers, batteries and PCB tracks/earth plane. The space around the antenna is as important as the antenna itself. Keep it away from interference sources, bad interference can easily reduce system range by a factor of 5. High speed logic is one of the worst in this respect, fast logic edges have harmonics which extend into the UHF band and the PCB tracks radiate these harmonics most efficiently. Single chip microprocessors and ground planed logic boards reduce this problem significantly. A simple test for interference is to monitor the RSSI output of the receiver, there should be no change in the reading when the logic circuits are run or held reset. Interference can also be easily identified by listening to the AF output of the receiver, smooth white noise should be heard.
Radiometrix Ltd, RXM-UHF Data Sheet
page 6
ANTENNA TYPES Any of the integral antenna shown in the data sheet for the transmitter module (TXM-418-5) is suitable for use on the receiver. Additionally a coax fed external dipole or 1/4 wave ground plane antenna may be considered if system range is paramount. A 2.2k resistor wired across the coax at the antenna end will allow tamper detection (cutting) of the coax using at the tamper sense facility in the receive module; pin 8 will go low if the coax is cut. DATA SLICER A CMOS compatible data output is available on pin 6, this output is normally used to drive a digital decoder IC or a microprocessor which is performing the data decoding. The signal detect output on pin 11 may be used to gate the data output before it is supplied to a decoder, however this should only be done on systems with `weak' digital coding i.e where there is a danger of the decoder giving false outputs on the `noise data' which is present on pin 6 when no valid signals are being received. Systems with good CRC, checksum or repeat code verification will not require the `noise data' to be gated off and as a result will be able to decode weaker signals (ie greater range). The data detect output on pin 11 is normally used for duty cycle power saving for portable equipment where battery life is a problem. By pulsing the receiver on/off the average supply current may often be reduced by a factor of 20 or more depending upon the system requirements, the data detect output is valid 5ms after application of the supply and is used to inhibit the power saving while data decoding is done. The data slicer in the receiver module is designed to accept data with a wide range of pulse widths and mark: space ratio's. The voltage waveform on pin 4 (AF) is fed to 2 peak detectors, one +ve, one -ve and a comparator threshold is set half way between the max and min voltage, a small amount of hysterisis is applied. The data on pin 6 is the output of this comparator. The date slicer has a transient response time, this is the settling time/hold time of the peak detectors. It is programmable by an external resistor between pin 5 & 7 (min & max). With no resistor fitted (normal use) the data slicer settles in approx 300ms from reception of a coded signal (ie the first 300ms of signal may be corrupt at the data output) and will pass pulse widths up to 50 ms of continuous 1 or 0. A resistor between pin's 5 & 7 shortens these time ie Resistor Value (pin 5 to 7) Open Circuit 1 M 220 k 47 k Code Preamble (minimum length) 300ms 150ms 30ms 7.5ms Longest 1 or 0 allowed
50ms 25ms 5ms 1.3ms
Radiometrix Ltd, RXM-UHF Data Sheet
page 7
JAMMING DETECTOR provides a logic 0 on pin 10 when a strong signal of greater than 10V is being received. The detector may be set to give a delayed output by connecting an electrolytic capacitor between pin 12 (JAM TC) and 0V. The delay is approxiamtely0.7s/F ie a 10F capacitor will need the jamming signal to be present for 7s before pin 10 goes low. The delay time will be subject to the electrolytic's tolerance so may vary widely. For accurate/long delays it is recommended that a delay of 7s (10F) to be used and the jam signal be fed to a digital timer to determine the required delay. AF OUTPUT This output is the FM demodulator's output after buffering and de-emphasis. Since it is taken before the data slicer in the module, it may be used to drive external data slicers/demodulators in cases where the internal data slicer is not suitable. This is the case where an analogue subcarrier is being employed eg 2 tone AFSK or DTMF tones. In these cases the AF Output is used to drive the FSK/DTMF decoder directly. The AF Output is also a very useful test point for listening for signals or interference. The output will drive low impedance headphones via a 10F DC blocking capacitor for monitoring purposes. The phones should not be left connected during normal system operation as their low impedance will cause a certain amount of audio distortion which may upset the on board data slicer, if permanent audio monitoring is required a Hi-Z (>1k) buffer should be used to drive the headphones. The AF Output is DC coupled to the FM demodulator thus the DC level varies with the frequency of the incoming signal and may be used to check frequency shifts / drifts between the transmitter and receiver. Note - the polarity of this signal is different on different frequency versions of the module, check the specific data sheet for polarity. RSSI (Signal Strength) OUTPUT This is also very useful for monitoring the performance of the radio link. It is a 0V to 3.3V signal which increases logarithmically with increasing incoming signal strength. There is an internal 6.8k resistor is series with this output so that a 0.5mA fsd meter may be connected directly to this output for monitoring purposes. In more sophisticated systems this signal may be fed to an A-D converter to automatically monitor the integrity of the radio link.
Additional Reading BS 6799 BS 4737 - British Standard for Wire-free intruder alarm systems - British Standard for Intruder alarm systems in buildings from British Standards Institution 0171 629 9000 - DTI type approval specification for 418MHz Telemetry from Department of Trade and Industry 0171 211 0502 or 0171 211 0505 e-mail: library@ra.gtnet.gov.uk - Excellent radio engineering text - Practical antenna design book from Radio Society of Great Britain - 01707 659 015 or 01707 663 279
MPT1340
ARRL HANDBOOK ARRL ANTENNA BOOK
Radiometrix Ltd, RXM-UHF Data Sheet
page 8
Radiometrix Ltd
Hartcran House Gibbs Couch Watford WD19 5EZ ENGLAND Tel: +44 (0)20 8428 1220 Fax: +44 (0)20 8428 1221 info@radiometrix.co.uk www.radiometrix.co.uk Copyright notice
This product data sheet is the original work and copyrighted property of Radiometrix Ltd. Reproduction in whole or in part must give clear acknowledgement to the copyright owner.
Limitation of liability
The information furnished by Radiometrix Ltd is believed to be accurate and reliable. Radiometrix Ltd reserves the right to make changes or improvements in the design, specification or manufacture of its subassembly products without notice. Radiometrix Ltd does not assume any liability arising from the application or use of any product or circuit described herein, nor for any infringements of patents or other rights of third parties which may result from the use of its products. This data sheet neither states nor implies warranty of any kind, including fitness for any particular application. These radio devices may be subject to radio interference and may not function as intended if interference is present. We do NOT recommend their use for life critical applications. The Intrastat commodity code for all our modules is: 8542 6000.
R&TTE Directive
After 7 April 2001 the manufacturer can only place finished product on the market under the provisions of the R&TTE Directive. Equipment within the scope of the R&TTE Directive may demonstrate compliance to the essential requirements specified in Article 3 of the Directive, as appropriate to the particular equipment. Further details are available on Radiocommunications Agency (RA) web site: http://www.radio.gov.uk/topics/conformity/conform-index.htm The Library and Information Service The Radiocommunications Agency Wyndham House 189 Marsh Wall London E14 9SX United Kingdom Tel: +44 (0)20 7211 0502/0505 Fax: +44 (0)20 7211 0507 library@ra.gsi.gov.uk For further information on radio matters contact the Agency's 24 Hour Telephone Enquiry Point: +44 (0)20 7211 0211 European Radiocommunications Office (ERO) Midtermolen 1 DK 2100 Copenhagen Denmark Tel. +45 35250300 Fax +45 35250330 ero@ero.dk www.ero.dk

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