TK-2217
26
CIRCUIT DESCRIPTION /
电路说明
2) Drive and Final Amplifier
The signal from the T/R switch (D101 is on) is amplified by
the pre-drive (Q102) and the drive amplifier (Q103) to 50mW.
The output of the drive amplifier is amplified by the RF
power amplifier (Q106) to 5.0W (1W when the power is
low). The RF power amplifier consists of two MOS FET
stages. The output of the RF power amplifier is then passed
through the harmonic filter (LPF) and antenna switch (D103
and D104) and applied to the antenna terminal.
3) APC Circuit
The APC circuit always monitors the current flowing through
the RF power amplifier (Q106) and keeps a constant current.
The voltage drop at R127, R128 and R129 is caused by the
current flowing through the RF power amplifier and this
voltage is applied to the differential amplifier IC101(1/2).
IC101(2/2) compares the output voltage of IC101(1/2) with
the reference voltage from IC405. The output of IC101(2/2)
controls the VG of the RF power amplifier and drive amplifier
to make both voltages the same.
The change of power high/low is carried out by the change
of the reference voltage.
4) Encode Signaling
(1) QT/DQT
QT,DQT data of the QTTCXO Line is output from pin 28 of
the CPU. The signal passes through a low-pass CR filter
and goes to the TCXO(X1).
The QT,DQT data of the QTVCO Line is output from pin 24
of the CPU. The signal passes through a low pass CR filter,
mixes with the audio signal, and goes to the VCO modulation
input. TX deviation is adjusted by the CPU.
IC301
IC405
LPF
DTMF
QTTCXO
QTVCO
CPU
AGC
VCO
MIC
X1
TCXO
LPF
LPF
AQUA-L
From
T/R SW
(D101)
DRIVE
AMP
RF
POWER AMP
LPF
ANT
SW
D103
D104
ANT
VG
VG
VD
Q103
Q106
Pre-DRIVE
AMP
Q102
VDD
5T
R127
R128
R129
+B
IC101
(2/2)
IC101
(1/2)
PCTV
(IC405)
Fig. 7 Drive and final amplifier and APC circuit /
图 7 驱动、终端放大器以及 APC 电路
Fig. 6 Microphone amplifier /
图 6 话筒放大器
2) 驱动器和终端放大器
来自于 T/R 开关 (D101 ON) 的信号被前置驱动放大器 (Q102)
和驱动放大器 (Q103) 放大到 50mW。
驱动放大器的输出被 RF 功率放大器 (Q106) 放大到 5.0W (当
低功率时为 1W)。RF 功率放大器由 2 个 MOS FET 构成。RF
功率放大器的输出通过谐波滤波器 (LPF) 和天线开关 (D103
和 D104) 并且送到天线终端。
3) 自动功率控制 (APC) 电路
APC 电路一直监视通过射频功率放大器 (Q106) 的电流并保
持电流稳定。经过射频功率放大器的电流的变化会引起
R127，R128和R129的电压降低，此电压送到差分放大器IC101
(1/2) 。
IC101 (2/2) 将 IC101 (1/2) 的输出电压与来自 IC405 的参考电
压进行比较。
IC101 (2/2) 的输出电压控制射频功率放大器和驱动放大器的
VG，使电压保持一致。
功率高 / 低的变化是通过变更参考电压来实现的。
4) 编码信令
(1) QT/DQT
QTTCXO 线的 QT,DQT 数据从 CPU 的 28 管脚输出。信号通过
低通 CR 滤波器，并且送到 TCXO (X1)。
QTVCO 线的 QT, DQT 数据从 CPU 的 24 管脚输出。信号通过
低通 CR 滤波器，与音频信号混合，然后输入到 VCO。TX 频
偏被 CPU 调整。
