The transmit section of the BiM2A 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.
User Interface
Figure 2: BiM2A pin-out and dimension
BiM1pin
Name
Function
1, 3
RF GND
RF ground
pin; internally connected to the module screen and pin
5, 9, 10, 18 (0 Volt).
2
RF IN/OUT
50W
RF input/output from the antenna
17
Vcc
2.9V -
16V DC power supply
16
RX
select
Pull
low to enable Receiver
15
TX select
Pull low to enable Transmitter
14
TXD
DC coupled
input for 3V CMOS logic. Rin = 100kW
13
AF
200-400mV
pk-pk audio. DC coupled, approx 1V bias
12
RXD
Digital
output from internal data slicer. Output is "open-collector"
format with internal 10kW
pullup to Vcc (pin 17)
11
RSSI
0.17-0.33Vdc
(no signal), 1.25Vdc (maximum).. 60dB dynamic
range
9, 10,
18
0V
Supply
ground connection
NOTES:
1. RX select and TX
select have (10kW
approx.) pullups to Vcc
2. Pinout is as stanadrd BiM3A and BiM3B. On RF connector
end only pins 1, 2, 3, 9 are present.
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 The Office of Communications
(Ofcom) web site: Licensing
policy manual
