BIM3A Radiometrix, BIM3A Datasheet - Page 2

• Manufacturer Part Number: BIM3A
• Description: 869/914mhz high Speed FM Radio Transceiver Module
• Manufacturer: Radiometrix

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.
Pin description
RF GND
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
50
feeds.
0V (GND)
Supply ground connection and screen.
RSSI
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
Antenna
RF connection to the antenna, DC-isolated. See pages 7 & 8 for details of suitable antennas and
matching
& lpf
pins 1 & 3
pin 2
pins 5, 9, 10 & 18
pin 11
preamp
Tx/Rx switch
buffer
869/914MHz
bpf
V C O
Fig. 2: Block diagram
V C O
Mixer
32
Loop
Filter
IF Amp
Demod
10.7MHz
Loop
Filter
64
osc
ref
LPF
osc
ref
35kHz
LPF
Regulator
& Tx/Rx
slicer
data
logic
TXD
Tx select
Rx select
RSSI
RXD
Vcc
AF
page 2