Kenwood TK-3230 Service Manual page 14

TK-3230
The transmission power 3T is supplied to the transmis-
sion output circuit when the MCU turns Q404 on only in
transmit mode.
The reception power 3R is provided to the receive and IF
circuits when the MCU turns Q406 on only in receive mode.
The transmission/reception power 3C is supplied to the
VCO and PLL circuits when the MCU turns Q405 on in
transmit and receive modes.
If no signal is received for 10 seconds, the MCU enters
the power save mode, and turns common power 3C and
reception power 3R on for one cycle and off for three cycles
according to the signals from the MCU to save the battery
power.
■ QT/DQT
• Encode (Transmit)
QT/DQT signal is generated by MCU (IC403). Output sig-
nal (IC403 pin 18 (TO)) goes to TCXO modulation and VCO
modulation (Through the VR300).
• Decode (Receive)
Detected AF signal go to IC300 and then IC301. Function
of IC301 is LPF for sub-audible frequency. This signal goes
to IC403 pin 77 (TI). IC403 is detected the QT or DQT.
B
Power
SW
BATT
IC403
MCU
Fig. 9 Reset, Battery voltage detection and
Power supply circuits
图 9 复位 , 电池电压检测 , 电源电路
14
CIRCUIT DESCRIPTION /
SB
3M
IC404 Q405
AVR SW 3C
Q406
3R
SW
Q404
3T
SW
电路说明
仅在发射模式下 M C U 打开 Q404 时，发射电源 3T 才为发射
输出电路供电。
仅在接收模式下 M C U 打开 Q406 时，接收电源 3R 才为接收
及中频电路供电。
在发射和接收模式下 M C U 打开 Q405 时，发射 / 接收电源
3C 为 VCO 及 PLL 电路供电。
如果 10 秒钟内没有接收到任何信号，M C U 进入省电模式，
然后根据 M C U 的信号循环打开公共电源 3C 和接收电源 3R 一
段时间长度而后关闭三段时间长度，从而达到节省电池电量
的目的。
■ QT/DQT
●编码 ( 发射 )
Q T / D Q T 信号由 M C U ( I C403) 产生。输出信号 ( I C403 针脚
18) 进入 TCXO 调制和 VCO 调制 ( 通过 VR300)。
●解码 ( 接收 )
检测到的 A F 信号进入 I C300 并随后进入 I C301。I C301 的
功能为用于亚音频的 L P F。该信号进入 I C403 针脚 77 ( T I )。
IC403 检测 QT 或 DQT。
18
TO LPF
IC403
MCU
IC301
77
TI LPF
Fig. 10 QT/DQT circuit / 图 10 QT/DQT 电路
TCXO
VR300
VCO
TX AF
IC300 IC200
Baseband
IF IC
IC