Kenwood NXR-800H Service Manual page 20

NXR-800H
Fig. 10 Forward/Refl ect power detector circuit / 图 10 前向 / 反射功率检测器电路
3-4. Harmonic fi lter circuit
The harmonic filter circuit uses a three-stage "pi" type
Chebyshev type LPF.
This circuit removes harmonics from the transmitter out-
put and sends the fi ltered signal to the antenna connector
(CN22).
3-5. APC circuit
The APC circuit stabilizes the transmitter power so that
the output power specifi ed by the Control Voltage from the
MPU is obtained. It consists of a Forward/Refl ect power
detector circuit and Differential amplifi ers (IC2 and IC5).
It compares the voltage detected by the Forward/Refl ect
power detector circuit (voltage detected by the Forward
Power) and the Control Voltage (PWR_CONT) from the
MPU (IC802: X56-312 A/3). It stabilizes the output power
by changing pin 2 (Vgg).
The voltage detected (that detected Reflect Power) by
the Forward/Refl ect power detector circuit is compared to
the Control Voltage (PWR_PRT) from the MPU (IC802: X56-
312 A/3). When a load V.S.W.R. is connected to the An-
tenna Connector and is more than 1.5, it functions so that
the output power gets smaller as the detection voltage (that
detected Refl ect Power) gets larger.
20
CIRCUIT DESCRIPTION /
Directional coupler
Foward
ATT
D9
DET
IC10
Power module
VGG VDD
Pin Pout
HPF
IC2
Diff. AMP
Fig. 11 APC circuit / 图 11 APC 电路
电路说明
Reflect
ATT
IC4
D10
Diff. AMP
DET
3-4. 谐波滤波器电路
谐波滤波器电路采用三阶"pi"式切比雪夫 LPF。
该电路从发射机输出中消除谐波，并将滤波的信号发送到
天线连接器 (CN22)。
3-5. APC 电路
A P C 电路可稳定发射机功率，从而获得由 M P U 的控制电压
指定的输出功率。它由前向 / 反射功率检测器电路和差分放
大器 (IC2 和 IC5) 组成。
它将前向 / 反射功率检测器电路所检测的电压 ( 由向前
功率检测的电压 ) 和 MPU(IC802: X56-312 A/3) 的控制电压
(PWR_CONT) 进行比较。 它通过改变针脚 2(Vgg) 稳定输出功率。
前向 / 反射功率检测器电路所检测的电压 ( 反射功率检测
的电压 ) 与 MPU(IC802: X56-312 A/3) 的控制电压 (PWR_PRT)
进行比较。负载 V.S.W.R. 被连接到天线连接器并且大于 1.5
时，它就会发挥作用，使得输出功率随着检测电压 ( 反射功
率检测的电压 ) 的变大而变小。
Directional coupler
Reflect
Foward
ATT ATT
D9 D10
DET DET
IC4
Diff. AMP
+
IC5
Add. AMP
Diff. AMP
PWR_PRT
PWR_CONT