Diagram For Rx Audio & Signalling Process - HYT TC-610 Service Manual

2. Diagram for Rx Audio & Signalling Process
2ndIF BPF
CF300
450KHz+/4.5K
OUT
To MCU
RSSI
IFAMP2
DET
SQ
PE
De
Emphasis
U200 outputs the initial audio signal (including noise, signalling, audio, etc) after performing
frequency-discrimination and demodulation on the received signal. Therefore, the audio process is
divided into three parts:
Rx Audio Process: One part of the audio signal output by U200 is fed to the RC low-pass filter and
de-emphasis circuit and then amplified at U200. The audio signal is recovered after frequencies below
300Hz are removed at U200. The recovered audio signal is adjusted by the potentiometer and then goes
to audio power amplifier U201, which amplifies power for the input audio signal to drive the speaker
directly. To obtain higher power, the BTL bridge dual-end output is utilized.
Rx Signalling Process: One part of the audio signal output by U200 is fed to the 300Hz low-pass filter
circuit (U640). After audio signals above 300Hz are removed, CTCSS/CDCSS goes to the QTIN pin of
CPU, which decodes the input signals.
Nuisance Signal Process: One part of the audio signal output by U200 goes to U200 again. After the
signal is filtered, amplified and rectified inside U200, a DC voltage signal (SQ) corresponding to the
noise component is derived. The DC signal is fed to the BUSY pin of MCU via the ND pin of U200. Then
MCU processes the input signal.
IN
IFAmp1
U200
AN29160AA
PROCESSER
mix2
VREF
Mic amp
tone-LPF
5th-LPF
信令输出
To MCU
CDC/CTC
VCC
VCO TX RX MCU
POWERREG
IC
AF
mute
LIM
5th-HPF
(TX)
AF
HPF
mic mute
Figure 8
16
TC-610/620 Service Manual
SPVCC
EN DATA
LATCH
volume
sp Amp
SF
AMP(TX)
AUDIO OUT
U201
AF
SW
AMP
0
16Ω IW