Texas Instruments 2000 series, Reference Manual

Page: 17 / 52

February 2002 Product Description
17
1.5 Antenna Tuning Board - General
In order to achieve high resonance voltage and thus high charge-up field strength,
the antenna circuit must be tuned to resonance. This is the purpose of the tuning
coil and capacitor array on this board, shown in Figure 6.
Figure 6: Antenna Tuning Board Schematic
The total resonance capacitance is as follows:
Antenna Tuning Board capac cable capacitance (Antenna Tuning
Board to RA-RFM)
The main resonance capacitance consists of capacitors C1, C2, C3, C4, C5, C6,
C7 and C8 on the Antenna Tuning Board. The high resonance voltage and current
flow through the resonator necessitate connecting these capacitors both in serial
and parallel. Each resonance capacitor can be switched in and out of circuit by a
single jumper in order to tune the RFM to resonance, i.e. match the RFM to
different antenna inductances.
CAUTION:
If only one capacitor is switched parallel to the resonance
circuit, the maximum allowed resonance voltage is 280 Vp
(560 Vpp).
WARNING:
CARE MUST BE TAKEN WHEN HANDLING THE RA-RFM
SYSTEM. HIGH VOLTAGE ACROSS THE ANTENNA
TERMINALS
AND ALL ANTENNA RESONATOR
COMPONENTS MAY BE HARMFUL TO YOUR HEALTH. IF
THE ANTENNA INSULATION IS DAMAGED, THE ANTENNA
SHOULD NOT BE CONNECTED TO THE RA-RFM SYSTEM.