Control Circuit; Pll Block Diagram; Frequency Shift Circuit - Kenwood TK-2317 Service Manual

CIRCUIT DESCRIPTION / 电路说明
phase comparator, and charge pump. The input signal from
pin 10 and 17 of the PLL-IC is divided down and compared
at the phase comparator. The pulsed output signal of the
phase comparator is applied to the charge pump and trans-
formed into a DC signal in the loop fi lter (LPF). The DC sig-
nal is applied to the CV of the VCO and locked to keep the
VCO frequency constant.
PLL data is output from PL_STB (pin 20), PL_CLK (pin 8),
and PL_DAT (pin 21) of the MCU (IC820). The data is input
to the PLL-IC when the channel is changed or transmission
is changed to reception and vice versa. PLL lock condition is
always monitored by pin 18 (PL_UL) of the MCU. When the
PLL is unlocked, PL_UL goes low.

5. Control Circuit

The control consists of the MCU (IC820) and its peripher-
al circuits. It controls the TX-RX unit. IC820 mainly performs
the following;
1) Switching between transmission and reception by PTT
signal input.
2) Reading channel information, frequency, and program
data from the memory circuit.
3) Sending frequency program data to the PLL.
4) Controlling squelch on/off via the DC voltage from the
squelch circuit.
5) Controlling the audio mute circuit via the decode data in-
put.
6) Transmitting tone and encode data.

5-1. Frequency Shift Circuit

The MCU (IC820) and baseband IC (IC812) operates at
a clock frequency of 19.2MHz. The oscillator circuit has the
baseband IC. This oscillator has a circuit that shifts the fre-
quency via Beat shift switch (Q806).
A beat sound may be able to be evaded form generation
if "Beat Shift" is set to ON when it is generated in the internal
spurious transmission modulated sound of the transceiver.
Q8
TX/RX VCO BUFF
(TX: High)
CV
LPF
IC1
21
PLL
7
PL_UL
MCU
PL_STB,PL_CLK,PL_DAT
IC820
Fig. 6 PLL block diagram / 图 6 PLL 方块图
P L L 数据从微处理器 ( IC820) 的 PL _D AT ( 针脚 21)，P L_
CLK( 针脚 8) 和 PL_STB( 针脚 20) 输出。当信道改变时，或当
由发射变为接收或由接收变为发射时，数据输入 PLL IC。PLL
的锁定条件总是由微处理器的针脚 18(P L_ UL ) 监控。当 PL L
失锁时，UL 为低电位。
Q9 D18
BUFF SW
Q2 D17
RF
SW
AMP
To mixer
17
VC
Baseband
TCXO
IC
10
X1 IC812
5. 控制电路
控制电路是由微处理器 ( IC820) 和外部电路构成。它控制
收发单元。IC820 的主要功能如下 :
1) 根据 PTT 的输入信号来转换发射和接收状态。
2) 从存储电路读出信道信息、频率以及编程数据。
3) 发送频率数据给 PLL。
4) 根据静噪电路输出的 DC 电压来控制静噪的开启和关闭。
5) 根据解码数据控制音频静音。
6) 发射 Tone 及编码数据。
5-1. 频率偏移电路
微处理器 (IC820) 和基带 IC(IC812) 在 19.2MHz 时钟下工
作。此振荡器有可以被拍频偏移开关 (Q806) 变换频率的电路。
如果"拍频偏移"被设定为 ON，可以避免产生拍频声音。
TK-2317
To
RF AMP
25