Fgu; Diagram Of Fgu; Finrf; Finif - Hytera PT580 Service Manual

demodulator. The AGC voltage varies within 0.2V~1.2V. When the AGC control voltage is 0.2V, the gain
gets to its maximum value.
(6) Rx I+/ - and Rx Q+/-
These interface are used to transfer the differential I/Q signals output by the I/Q demodulator.

1.3 FGU

FinIF

12MHz _REF
1
a1
SYNTH _LOCK
2
a2
SYN_CS
3
a3
SYN_ ON
4
a4

FinRF

The working principle of the FGU is described below:
The reference frequency output by the baseband enters the PLL for frequency division. Meanwhile, the
frequency generated by the VCO goes to the divider for frequency division. Then the signals resulted
from both frequency divisions are sent to the phase detector for phase detection. If the signals have
different frequencies or phases, the phase detector will output a signal corresponding to the phase
difference. The signal goes to the low-pass filter to remove high-order harmonics, so as to control the
oscillation frequency of the VCO.
The interfaces between the FGU and the baseband are described below:
(1) FinRF
This interface is used to transfer the feedback signal from the TX/RX VCO to the PLL.
(2) FinIF
This interface is used to transfer the feedback signal from the RX IF VCO to the PLL.
(3) CPout RF
This interface is used to transfer the charging voltage signal from the PLL to the TX/RX VCO.
(4) CPout IF
5V_ SYN
0
Vcc 1
CPout IF
5
b1
6
b2
FLout IF
PLL IC
7
b3
CPout RF
8
b4
GND
FLout RF
0
Figure 4 Diagram of FGU
Loop Filter
LOOP Filter
8
Service Manual
RxVCO 2
TXVCO & RXVCO1