Texas Instruments 2000 series, Reference Manual

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High Performance RA-RFM RI-RFM-008B February 2002
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If several antennas are used close to each other, a check should be made to
determine if the charge-up field strength changes regularly (i.e. beat effect ). This
may be checked by verifying the antenna resonance voltage with an oscilloscope.
If the antenna resonator voltage changes periodically by more than approximately
5% of the full amplitude it is appropriate to use wired transmitter carrier phase
synchronization.
In addition, the distances given in Table 17 can be used as a guideline to
determine when it is necessary to cross-check for beat effect. If these distances
are less than the value given in Table 17, a check for beat effect should be made.
The values given refer to the distances shown in Figure 11 and are valid for
maximum charge-up field strength.
Figure 11: Distance between Antennas (top view)
Table 17: Maximum Distances between Antennas
Antenna type Distance D1 [m] Distance D2 [m]
RI_ANT_S02 <=> RI_ANT_S02 0.8 1.0
RI_ANT_G01 <=> RI_ANT_G01 1.7 1.5
RI_ANT_G02 <=> RI_ANT_G02 1.3 1.0
RI_ANT_G04 <=> RI_ANT_G04 2.0 1.7
This effect will not occur if the transmitters of different RA-RFMs are operated from
the same oscillator signal. This is the reason why the pulse width modulated
oscillator signal is accessible at the connector J1.
Configuration
Master or Slave setting of a RA-RFM is determined by switch 1 position 1 (SW1/1).
If this is in the ON position, the RFM is a MASTER, if in the OFF position, it is a
SLAVE. When a RA-RFM has been configured as a master, then J1 pin 12 of this
unit should be connected to J1 pin 16 of the slave units to allow the master
oscillator output (CPS_OUT) to drive the slave oscillator inputs (CPS_IN). The logic
ground (e.g. J1 pin 1) of both master and slave units should be connected
together.
CAUTION:
Use overvoltage protection components at the CPS
connector for CPS lines between 0.5m and 5m.
Distance D1
Antenna 1 Antenna 2
Distance D2
Antenna 1 Antenna 2