Kenwood NXR-700H Service Manual page 28

NXR-700H
voltage detected by the IF system IC (IC12 pin12), the
squelch voltage detected by the IF system IC (IC12 pin11),
and the control voltage of the 2nd-VCO (pin10), and outputs
each state in serial data (IC30 pin18), sends the signal from
CN42 (pin22) to the control unit (X53-413). The signal is pro-
cessed by the MPU.
5. Base-Band Signal Processing Part
The base-band circuit is located on unit X53-413. This
circuit enables the selection of the Analog Signal Processing
mode and the Digital Signal Processing mode, and adjusts
the level of the base-band signals in each mode. This circuit
consists of IC2, IC3, IC5, IC8, IC9, IC12, IC14, IC19, IC20
and IC21.
The type of input modulation signals are local microphone
terminal, low-speed data (LSD), high-speed data (HSD), ex-
ternal audio input (TA), and external data input (TD), and also
the type of output demodulation signals are receiving audio
output (RA), and receiving data output (RD).
The multiplexer (IC2, IC3, IC14) selects the signal path,
the electronic volume (IC8) adjusts the signal level, and the
operational amplifi ers (IC5, IC9, IC12, IC19, IC20, and IC21)
amplify and sum various signals.
5-1. Demodulation circuit
(Analog/NXDN signal processing)
In case of the Analog Signal Processing mode, the de-
tected audio signal obtained from the IF SYSTEM IC (X55-307
IC8) is amplifi ed by IC5 (A/2), input into the AINR terminal
of CODEC IC (IC4), and then processed as an audio signal
by the DSP (IC37). The processed audio signal from the
AOUTR terminal of IC4 is amplifi ed to a suffi cient level by
IC12 (A/2), and is then passed through the anti-aliasing fi lter
at IC12 (B/2).
In case of the NXDN Signal Processing mode, the detect-
ed audio/data signal obtained from the IF SYSTEM IC (X55-
28
CIRCUIT DESCRIPTION /
IC32
A/2
1st
VCO_A
1st
VCO_B
IC33
2nd CV
IC12
ASQL
IC12
RSSI
IC35
TEMP.
IC4
LNA
IC6
1st CV
Fig. 23 Other circuits / 图 23 其它电路
电路说明
IC (IC12 针脚 12) 检测的 RSSI 电压、IF 系统 IC (IC12 针脚
11) 检测的静噪电压以及第 2 VCO( 针脚 10) 的控制电压，并
在串行数据 ( I C30 针脚 18) 中输出各种状态，将 C N42( 针脚
22) 的信号发送到控制单元 (X53-413)。信号由 MPU 进行处理。
1
6
IC23
2
7
3 8
10 18
11
IC31
12
EEPROM
IC30
5
14
6
15
CN42
16
5. 基带信号处理部分
基带电路位于单元 X53-413 上。该电路可实现模拟信号处
理模式和数字信号处理模式的选择，并调整各模式基带信号
的电平。该电路由 IC2、IC3、IC5、IC8、IC9、IC12、IC14、
IC19、IC20 和 IC21 组成。
输入调制信号的类型包括本地麦克风端子、 低速数据 (LSD)、
高速数据 (HSD)、外部音频输入 (TA) 和外部数据输入 (TD)，
输出解调信号的类型包括接收音频输出 (RA) 和接收数据输出
(RD)。
多路器 (IC2、IC3、IC14) 选择信号路径，电子音量 (IC8)
调整信号电平，运算放大器 ( I C5、I C9、I C12、I C19、I C20
和 IC21) 放大并累加信号。
5-1. 解调电路
( 模拟 /NXDN 信号处理 )
在模拟信号处理模式中，从 IF SYSTEM IC(X55-307 IC8)
获得的经检测的音频信号由 I C5( A /2) 放大，输入到 C O D E C
IC(IC4) 的 AINR 端子，然后作为音频信号由 DSP(IC37) 进行
处理。IC4 的 AOUTR 端子的已处理音频信号由 IC12(A/2) 放大
到足够的电平，然后通过 IC12(B/2) 的抗混叠滤波器。
在 NXDN 信号处理模式中，从 IF SYSTEM IC(X55-307 IC7)
11
9
8
22
32
30