Transmitter Carrier Phase Synchronization (Cps); Distance Between Antennas (Top View); Maximum Distances Between Antennas - Texas Instruments 2000 Series Reference Manual

Transmitter Carrier Phase Synchronization (CPS)

In some applications it is necessary to use several charge-up antennas close to each other. Under these
circumstances, the magnetic charge-up fields generated by different antennas superimpose on each other
and may cause a beat effect on the magnetic charge-up field, due to the slightly different transmit
frequencies of different RFMs.
The impact of this effect depends on three factors:
1. Antenna size:
The larger the size of the antennas, the further the distance between the antennas must be, so that
this effect does not occur.
2. Magnetic field strength:
The stronger the generated magnetic field strength, the further the distance between the antennas
must be such that the effect does not occur.
3. Orientation and distance between antennas:
Increasing the distance between antennas decreases the impact of this effect.
Note: Putting two antennas close together also changes antenna inductance, so that the
antennas may no longer be tuneable to resonance.
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
to cross-check for beat effect. If these distances are less than the value given in
beat effect should be made. The values given refer to the distances shown in
maximum charge-up field strength.
Antenna 1
Antenna type
RI_ANT_S02 <=> RI_ANT_S02
RI_ANT_G01 <=> RI_ANT_G01
RI_ANT_G02 <=> RI_ANT_G02
RI_ANT_G04 <=> RI_ANT_G04
SCBU022 – November 2002
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Table E-1 can be used as a guideline to determine when it is necessary
Distance D1
Antenna 2
Figure E-1. Distance Between Antennas (Top View)
Table E-1. Maximum Distances Between Antennas
Distance D2
Antenna 1
Distance D1 [m] Distance D2 [m]
0.8
1.7
1.3
2.0
Transmitter Carrier Phase Synchronization (CPS)
Appendix E
SCBU022 – November 2002
Table E-1, a check for
Figure E-1 and are valid for
Antenna 2
1.0
1.5
1.0
1.7
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