Service Manual
144
Information
10.1 TX Circuit
A) circuit, power control circuit, diagnosis and detection
power control circuit is used for keeping the RF power of antenna at a fixed
n circuit, it detects the current TX power, antenna VSWR and
result to the repeater’s control unit for monitoring the
10. UHF2 (450-520MHz)
The TX circuit consists of power amplifier (P
circuit and protection circuit. It is to amplify the RF signal from exciter module to 50W, which then will be
output via the antenna. The
level. For the diagnosis and detectio
transmitter temperature, and sends the detection
transmitter status. The role of protection circuit is to protect the power amplifier from being damaged due
to high temperature or VSWR.
MOSFET
RD01
Pre-driver
MOSFET
RD07
Driver
LDMOS
PD85035S-2
Power sensor
Harmonics Filters
RF Out
LDMOS
PD85035S-1
Matching/
Attenuation
5dB
Wideband
Matching
Network
50ohm
Matching
Network
13.6V,12A˄B+˅
28.5dBm
48.5dBm
Temp Sensor
ADC
0
0
0
0
0
DAC
Vset
APC
35.5dBm
V_Contr
Pr_DET
uP/DSP(BB)
RTH1,RTH2
Pad
Attenuator/20dB
Pad Attenuator
Log Amp
Po=47.5dBm
RFC RFC
RFC
ADC
Matching
13dBm
IL:<1.0dB
V_APC
Pf_DET
Sample FWD
Final_Bias(5V)
RFIN
5V LDO
XC6209F502P
R
5V
9.3V,1A
RF In
Bias_Setting
DAC
9V
Voltage
Regulator
9.3V,3A
7809
13.6V (B+)
PA_Enable
Diff. Amp
Diff. Amp
Temp_Protect_Volt
VSWR_Protect_Volt
Figure 10-1 Block Diagram of PA Board
A Module
A module of transmitter consists of a 3-stage PA unit: pre-driver stage (Q401), driver stage (Q402) and
age (Q403 and Q404). Q401 and Q402 form the driver circuit, whose gain can be adjusted via the
PC circuit, ensuring a constant RF power output of 50W.
P
P
final-st
A
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