TK-3230
8
CIRCUIT DESCRIPTION /
电路说明
Frequency Confi guration
ANT
SW
BPF
MIX, IF
DET
AF
AMP
TCXO
RF
AMP
RF
AMP
MIC
AMP
PLL VCO
1st MIX
CF
450kHz
38.85MHz
MCF
38.4MHz
SP
MIC
ANT
460~470MHz
460~470MHz
421.15~
431.15MHz
RF
AMP
Tripler
X3
12.8MHz
Reception method
Double super heterodyne
1st IF frequency
38.85MHz
2nd IF frequency
450kHz
Transmission method
VCO direct oscillation amplifi cation
Modulation
Variable reactance phase modulation
Table 1 Basic confi guration
Receiver System
■
Front End
The high-frequency signal from the antenna passes
through a low-pass fi lter and a high-frequency switch (D101,
D200, D201 and L220) which switches between transmis-
sion and reception, and goes to the BPF (L218) to remove
unwanted signals. The resulting signal is amplifi ed by high-
frequency amplifi er (Q204) and goes to the fi rst mixer (Q203).
■
First Mixer
The signal that reaches Q203 is mixed with the fi rst local
signal from the VCO to produce a fi rst IF signal (38.85MHz).
(Receive frequency – First local frequency
=
First
IF
frequency
=
38.85MHz)
The fi rst IF signal passes through MCF: XF200 (monolithic
crystal fi lter) to remove unwanted signals.
The fi rst IF signal is amplifi ed by IF amplifi er (Q201) and
goes to IF IC (IC200).
Fig. 1 Frequency confi guration /
图 1 频率构成
频率构成
接收方式
双超外差
第一中频
38.85MHz
第二中频
450kHz
发射方式
VCO 直接振荡放大
调制
可变电抗相位调制
表 1 基本构成
接收系统
■前端
天线的高频信号通过低通滤波器和高频开关 ( D101、D200、
D201 和 L220)( 用于切换发射和接收 )，然后进入 BPF (L218)
消除不需要的信号。最终的信号由高频放大器 ( Q204) 进行放
大，然后进入第一混频器 (Q203)。
■第一混频器
到达 Q203 的信号与来自 VCO 的第一本振信号混频，进而产
生第一中频信号 (38.85MHz)。
( 接收信号 – 第一本振信号 = 第一中频 = 38.85MHz)
第一中频信号通过 MCF:XF200( 单片晶体滤波器 ) 消除不需
要的信号。
第一中频信号由中频放大器 ( Q201) 进行放大，然后进入中
频 IC (IC200)。
BPF
L218
RF AMP
Q204
1st MIXER
Q203
MCF
XF200
IF AMP
Q201
IF AMP, DET
IC200
AF AMP
IC303
SP
1st local OSC (PLL)
2nd local OSC
ANT
38.85MHz
465.0MHz
D101
D200
D201
L220
LPF
ANT
SW
Fig. 2 Receiver section confi guration /
图 2 接收部分构成
