NX-200
37
5-4. Doubler (Q4)
The doubler (Q4) extracts the twice harmonic component
from the signal from the VCO. This twice harmonic compo-
nents is then fed into PLL (IC3) through band pass fi lter.
Band pass fi lter is consists of two fi lter. One is for TX
(L3,L5,L7) and pass band is 272.0 to 348.0MHz. The other
is for RX 1st local (L2,L6,L30) and pass band is 388.1 to
464.1MHz.
5-5. Local Switch (D100, D201)
The connection destination of the signal output from the
buffer amplifier (Q100) is changed with the diode switch
(D100) that is controlled by the transmission power supply,
50T, and the diode switch (D201) that is controlled by the
receive power supply, 50R. If the 50T logic is high, it is con-
nected to a send-side pre-drive (Q102). If the 50T logic is
low, it is connected to a receive-side mixer (Q203).
Loop
Filter
BUFF
AMP
Ripple
Filter
VCO
150C
VC
TCXO
PLL
IC
IC3
Q11
Q8,Q10
D8,D9,D12~D17
BUFF
AMP
Q100
Q4
SDO1
SCK1
/PCS_RF
X1
19.2MHz
T/R
SW
D100,D201
50C
50C
to TX stage
50T 50R
to 1st Mixer
IC4 (1/2)
Q12
Q3
IC2
CV
VCO_MOD
ASSIST
BPF(RX)
L2,L6,L30
BPF(TX)
L3,L5,L7
RF
SW
D5,D6
RF
SW
D2,D3
Doubler
6. Control Circuit
The control circuit consists of the ASIC (IC108) and its
peripheral circuits. IC108 mainly performs the following;
1) Switching between transmission and reception by PTT
signal input.
2) Reading system, zone, frequency, and program data
from the memory circuit.
3) Sending frequency program data to the PLL.
4) Controlling squelch on/off by the DC voltage from the
squelch circuit.
5) Controlling the audio mute circuit by decode data input.
Fig. 7 PLL block diagram /
图 7 PLL 结构图
CIRCUIT DESCRIPTION /
电路说明
5-4. 倍频器 (Q4)
倍频器 (Q4) 从 VCO 的信号当中选取两倍的谐波成分。然后，
这两倍的谐波成份通过带通滤波器送入 PLL(IC3)。
带通滤波器由两个滤波器组成。一个用于 TX(L3，L5，L7)，
通频带为 272.0 到 348.0M H z。另一个用于 R X 第 1 本地 ( L2，
L6，L30)，通频带为 388.1 到 464.1MHz。
5-5. 本地开关 (D100，D201)
缓 冲 放 大 器 ( Q100) 输 出 信 号 的 连 接 目 标 由 二 极 管 开 关
(D100)( 由发射电源 50T 控制 ) 和二极管开关 (D201)( 由接收
电源 50R 控制 ) 进行改变。如果 50T 逻辑高，则它被连接到
发送侧预驱动 ( Q102)。如果 50T 逻辑低，则它被连接到接收
侧混频器 (Q203)。
6. 控制电路
控制电路由 A S I C ( I C108) 和外围电路组成。I C108 主要有
以下功能 :
1) 由输入的 PTT 信号切换发射和接收。
2) 从存储电路读取系统，区域，频率和编程数据。
3) 将频率数据发送到 PLL。
4) 由静噪电路的 DC 电压控制静噪的开 / 关。
5) 由输入的解码数据控制音频静音电路。
