TK-3178
(
L
)
16
The RX pin of IC4 goes “low” in receive mode causing
Q503 and Q504 (2/2) turn on. The TX pin goes “low” in
transmit mode causing Q502 and Q504 (1/2) turn on.
The outputs from Q502 and Q503 are amplifi ed by buffer
amplifi er (Q506) and doubled by Q501 and then sent to PLL
IC.
The PLL IC consists of a prescaler, reference divider,
phase comparator, charge pump (The frequency step of the
PLL circuit is 5 or 6.25kHz). The input signal from the pins 8
and 5 of the PLL IC is divided down to the 5 or 6.25kHz and
compared at phase comparator. The pulsed output signal
of the phase comparator is applied to the charge pump and
transformed into DC signal in the loop fi lter (LPF). The DC
signal is applied to the CV of the VCO and locked to keep
the VCO frequency constant.
PLL data is output from PLLDAT (pin 18), PCK (pin 17) and
PLE (pin 10) of the microprocessor (IC7). The data are input
to the PLL IC when the channel is changed or when trans-
mission is changed to reception and vice versa. A PLL lock
condition is always monitored by the pin 7 (UL) of the micro-
processor. When the PLL is unlocked, the UL goes low.
I C4 的 R X 针 脚 在 接 收 模 式 时 为“ 低 ” 电 位， 使 Q503 和
Q504(2/2) 打 开。T X 针 脚 在 发 射 模 式 时 为“ 低 ” 电 位， 使
Q502 和 Q504(1/2) 导通。
Q502 和 Q503 的输出由缓冲放大器 ( Q506) 放大，并由 Q501
倍频，然后发送到 PLL IC。
PLL IC 由预计数器、基准除法器、相位比较器、电荷泵组
成 (PLL 电路的频率步长为 5kHz 或 6.25kHz)。PLL IC 的针脚
8 和 5 的输入信号下分成 5k H z 或 6.25k H z，并在相位比较器
处进行比较。相位比较器的脉冲输出信号加在电荷泵上，并
转换成环路滤波器 (LPF) 的 DC 信号。DC 信号加在 VCO 的 CV
上并锁定，使 VCO 的频率恒定。
PLL 数据从微处理器 (IC7) 的 PLLDAT( 针脚 18)，PCK( 针
脚 17) 和 PLE( 针脚 10) 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 P L L I C。P L L 的锁定
条件总是由微处理器的针脚 7( U L ) 监控。当 P L L 失锁时，U L
为低电位。
5. Control Circuit
The control circuit consists of microprocessor (IC7) and
its peripheral circuits. It controls the TX-RX unit. IC7 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.
6) Transmitting tone and encode data.
5. 控制电路
控制电路是由微处理器 ( I C7) 和外部电路构成。它控制
TX-RX 单元。IC7 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) 从存储电路读出系统、区域、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。
LPF
BUFF
VCO
PLL
MCU
20
15
5
Doubler
x2
CV
Q507
TCXO
X501
SW
D516
SW D515
To
drive
amp
Q501
To mixer
8
FC
BAL
IC17
VC
TX
RX
IC501
UL
IC7
PLLDT,PCK,PLE
Fig. 7 PLL block diagram /
图 7 PLL 方块图
CIRCUIT DESCRIPTION /
电路说明
