4
4857C–AUTO–07/06
ATAK5276-83
Figure 4-2.
Antenna Module
The transmitter board (see
) is patched onto a microcontroller base board
communicating with a host PC. Operation software must be installed on the host via the
enclosed CD-ROM. A power source of typically 12V/2A is used to supply the microcontroller
base board and the transmitter board in parallel with separate connectors as seen in
. The antenna driver frequency is tracked according to the resonant condition of the
antenna in use. An external antenna module (see
) is used, with the high
voltage capacitor and resistor matching the resonant frequency and Q-factor. The capacitor
CANT (C1) is used to match the resonant frequency to fres = 125 kHz ±3 kHz, and the resistor
RANT (R1) sets the Q-factor to about 25. With the default module adjustment, a current flow of
around 0.6 Ap at VBATT = 12V can be achieved. Therefore, jumper J3 has to be closed
(R
CR
= R
CR1
//R
CR2
= 25 k
Ω
). If Jumper J3 is open (R
CR
= R
CR1
= 100 k
Ω
) the current set point is
decreased leading to a regulation level of typically 0.37 Ap.
To reach the maximum antenna current (1.5 Ap), the series resistor RANT (R1) on the antenna
module has to be shorted and the current regulation set point has to be set to maximum
R
CR
= R
CR1
//R
CR2
= 25 (J3 closed).
Optionally, RANT and CANT can be placed on the board if a customized pure antenna coil will
be used. Then, Jumpers J1 and J2 have to be opened.
Note:
The power dissipation of shunt resistor RSEN and module resistor RANT must be considered if a
high antenna current in continuous operation mode will be programmed.
4.2
Typical Parameters of Antenna Module
Coil Inductance:
L
125
= 345 [µH] ±5%
Coil Resistance:
R
125
= 2.5 [
Ω
]
Impedance: Z
125
= 271 [
Ω
]
Module Series Resistor:
RANT (R1) = 10 [
Ω
]
Series Capacitor:
4.7 nF/1400V
Total Q-Factor:
Q
125
= 22
