BIM3A

Radiometrix Hartcran House, 231 Kenton Lane, Harrow, HA3 8RP, England Issue: 2, 25 October 2005 Tel: +44 (0) 20 8909 9595, Fax: +44 (0) 20 8909 2233 BiM3A 869/914MHz high speed FM radio transceiver module The BiM3A radio transceiver module is similar in size and pinout to the BiM2, offering all the advantages of the latter but with reduced power consumption and antenna size. The BiM3A replaces the obsolete BiM3. The BiM3A suited to battery-powered portable and handheld equipment requiring a high degree of miniaturisation. Two frequency variants are available as standard to suit applications in Europe or North America. Fig. 1: BiM3A-869-64 Features CE certified by independent Notified Body EU version to harmonised standards EN 300 220 and EN 301 489 North American version to FCC Part 15.249 and RSS-210 Usable range up to 200 metres external, 50 metres in building Data rates up to 64kbps Crystal controlled PLL FM circuitry for both Tx and Rx SAW front end filter and full screening Low profile with small footprint Low power requirements: 2.7V - 6V @ typically 8mA Tx, 11mA Rx The BiM3A is a half duplex radio transceiver module for use in bidirectional data transfer applications at ranges up to 200 metres. Two frequency variants are available for licence-exempt operation in either the European 868-870MHz or North American 902-928MHz bands. Internal voltage regulation is incorporated allowing operation from DC supplies of 2.7V to 6V. The small footprint of 33 x 23mm and low profile of 5mm facilitate convenient integration onto a motherboard. The raw data rate capability of 64kbps supports high data throughput in ‘streaming’ applications, or alternatively allows efficient airtime utilisation in multi-node scanning networks. Applications PDAs, organisers and laptops Handheld terminals EPOS equipment, barcode scanners, belt clip printers Data loggers Audience response systems In-building environmental monitoring and control Security and fire alarms Restaurant ordering systems Vehicle data up/download Radiometrix Ltd, BiM3A Data Sheet page 1 Functional overview The transmit section of the BiM3A consists of a frequency modulated crystal locked PLL feeding a buffer amplifier and RF filter. Operation is controlled by a Tx select line, the transmitter achieving full RF output typically within 1ms of this line being pulled low. Modulation is applied at the TXD input and may be either a serial digital stream toggling between 0V and 3V (digital drive) or a high level analogue waveform with the same peak limits (linear drive). Modulation shaping is performed internally by a 2nd order lowpass filter which minimises spectral spreading. The RF output is filtered to ensure compliance with the appropriate regulations and fed via a Tx/Rx changeover switch to the antenna pin. The receive section is a single conversion FM superhet with an IF of 10.7MHz. A SAW bandpass filter in the receiver front-end provides image rejection and suppression of other unwanted out-of-band signals. Like the transmitter, the receiver is controlled by its own active low select line. A post-detection lowpass filter establishes the signal bandwidth and ensures clean operation of the subsequent adaptive data slicer. The slicer is optimised for balanced data such as bi-phase code. A received signal strength (RSSI) output with 60dB of range is provided. matching & lpf buffer VCO ÷ 64 Loop Filter φ ref osc 35kHz LPF TXD Antenna Tx/Rx switch ÷ 32 φ Loop Filter Vcc ref osc Regulator & Tx/Rx logic Tx select Rx select VCO RSSI 869/914MHz bpf LPF data slicer preamp IF Amp Demod RXD Mixer 10.7MHz AF Fig. 2: Block diagram Pin description RF GND pins 1 & 3 RF ground pins, internally connected to the module screen and to pins 5, 9, 10 & 18 (0V). These pins should be connected directly to the RF return path (e.g. coax braid, main PCB ground plane etc). Antenna pin 2 50 RF connection to the antenna, DC-isolated. See pages 7 & 8 for details of suitable antennas and feeds. 0V (GND) pins 5, 9, 10 & 18 Supply ground connection and screen. RSSI pin 11 Received Signal Strength Indicator with 60dB range, operational when Rx is enabled. Output voltage nominally 0.17-0.33Vdc (no signal), 1.25Vdc (maximum). See page.6 for typical characteristics. Radiometrix Ltd, BiM3A Data Sheet page 2 RXD pin 12 Digital output from internal data slicer. The output is a squared version of the signal on pin 13 (AF) and may be used to drive a decoder directly. The data is true data, i.e. as fed to the transmitter. Output is “open-collector” format with internal 10kΩ pullup to Vcc (pin 17). AF pin 13 Buffered & filtered analogue output from FM demodulator. Standing DC bias of 1V approx. Useful for test purposes or for driving external decoders. External load should be >10kΩ // 50kΩ. TX select pin 15 Active-low Transmit select. 47kΩ internal pull-up to Vcc. RX select pin 16 Active-low Receive select. 47kΩ internal pull-up to Vcc. Pin 15 TX 1 1 0 0 Pin 16 RX 1 0 1 0 Function Power down (