BIM3A Radiometrix, BIM3A Datasheet - Page 5

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

Receiver (cont’d)
Distortion on recovered AF
Ultimate (S+N)/N
Load capacitance, AF & RXD
Dynamic Timing
Rx power up with signal present
Power up to valid RSSI, t
Power up to stable data, t
Power up to stable data, t
Signal applied with Rx on
RSSI response time (rise/fall)
Signal to stable data, t
Signal to stable data, t
Allowable time between data
transitions
Allowable time between data
transitions
Averaged code mark:space
Note:
Modulation formats and range extension
The module will produce the specified FM deviation with a 2-level digital input to TXD which toggles
between 0V and 3V. Reducing the amplitude of the data input from this value (usually as a result of
reducing the supply voltage) reduces the transmitted FM deviation, typically to 20-22kHz minimum at
2.7V. The receiver will cope with this quite happily and no significant degradation of link performance
should be observed.
TXD is normally driven directly by logic levels but will also accept analogue drive, e.g. 2-tone signalling.
In this case it is recommended that TXD (pin 14) should be DC-biased to 1.5V with the modulation AC-
coupled and limited to a maximum of 3V peak-to-peak. The instantaneous modulation voltage must not
swing below 0V or above 3V at any time if waveform distortion and excessive FM deviation is to be
avoided – use a resistive potential divider and/or level shifter to accomplish this if necessary. The
varactor modulator in the transmitter introduces some 2nd harmonic distortion which may be reduced if
necessary by predistortion of the analogue waveform.
At the other end of the link the AF output (pin 13) can be used to drive an external decoder directly.
Although the module baseband response extends down to DC, data formats containing a DC component
are unsuitable and should not be used. This is because frequency errors and drifts between the
transmitter and receiver occur in normal operation resulting in DC offset errors on the AF output.
The time constant of the adaptive data slicer in the BiM3A is set at a reasonable compromise to allow
the use of low code speeds where necessary whilst keeping settling times acceptably fast for battery-
economised operation. RXD output on pin 12 is “true” sense, i.e. as originally fed to the transmitter.
Radiometrix Ltd, BiM3A Data Sheet
1. Increases at high RF input level (>-20dBm)
2. See page 6 for further details
3. For specified FM deviation
4. Tx select low > full RF output
5. ±30kHz FM deviation
6. Min/max at ±50kHz offset
7. Max at ±50kHz offset
8. Average, at max. data rate
sig-data
sig-data
PU-RSSI
PU-data
PU-data
Application Information
12, 13
11
12
12
11
12
12
14
14
14
13
13
15.6
0.1
20
-
-
-
-
-
-
-
-
-
100
40
10
50
1
-
1
5
5
5
-
-
1500
100
10
10
30
10
30
15
80
-
-
-
dB
pF
ms
ms
ms
ms
ms
ms
%
%
s
s
-50dBm RF input
-64 version
-10 version
-64 version
-10 version
-64 version
-10 version
Note 7
Note 8
page 5