Texas Instruments 2000 series, Справочное руководство

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High Performance RA-RFM RI-RFM-008B February 2002
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As the transmitter is switched off in this configuration, a normal battery may be
used. A low noise level is indicated by an RSTP voltage of less than 1.0 VDC when
using antenna RI-ANT-G02.
Note:
Both noise types can be either differential or common mode noise.
Use common mode noise filters (for example: a BALUN transformer)
to reduce common mode noise and use selective filters to reduce
differential noise.
The following procedure for testing for noise impact should be implemented when
the normal set-up for the RA-RFM and antenna gives bad reading distances, even
though the antenna is correctly tuned for sufficient transponder charge-up.
Try the configuration shown in Figure 12. If this configuration shows bad noise
conditions (RSTP voltage more than approximately 1.0 VDC) then the problem is
radiated noise.
Eliminate noise sources or try special antennas (e.g. noise-balanced antennas).
1. When the configuration of Figure 12 shows good noise conditions (RSTP
voltage less than 1.0 VDC) then the problem is conducted noise.
2. Change the configuration so that the interface lines are again connected to the
RA-RFM with the transmitter still switched off. If the RSTP voltage now
indicates bad noise conditions, the conducted noise is coming via the interface
lines.
3. Try to eliminate the noise on the interface lines. See Appendix 5, Noise
Considerations.
4. When the configuration above (interface lines connected) shows good noise
conditions (RSTP voltage less than 1.0 VDC), then the problem is conducted
noise via the supply lines.
5. Try to eliminate the noise on the supply lines. See Appendix 6, Over Voltage
Protection.
Figure 12: Noise Testing Configuration
GND 1
J1
RSTP
VSP 13
VSP 11
GNDP 9
7
VSL 3
10
•
•
•
•
GND
ANT2
ANT1
Tuning Module
& antenna