Kenwood NX-3400 Service Manual page 12

2.3.3 Receiver System
2.3.3.1 RF Circuit
The receive signal from ANT SW (D201, D202, D203 and D207) passes through the high-pass filter (L302, L307, L308, L312, L314
and L315) to remove unwanted signals and amplified by a RF amplifier (incorporated in Transceiver IC (IC303)). The signal is then
fed to the mixer (incorporated in Transceiver IC (IC303)) and converted to the baseband signal.
2.3.3.2 Baseband Circuit
The baseband signal is then be fed into an ADC (incorporated in Transceiver IC (IC303)), generates the I and Q data. This data is in
the form of Serial Interface, and sent to the MPU/DSP (IC401).
D201
ANT
D202
D203
D207
ANT ANT
LPF SW
2.3.3.3 Audio Amplifier Circuit
Audio processing (high-pass filter, low-pass filter, de-emphasized and so on) at Analog FM mode and decoding at Digital mode are
processed by DSP. I2S signal from DSP is converted to audio signal at CODEC (IC601). The signal goes to internal speaker or
universal connector for external speaker through the internal Class D amplifier.
Audio path inside the Codec is controlled by I2C.
Transceiver IC
IC303
1-12 (No.RA070<Rev.001>)
L302
L307
L308
HPF
IC303
RFAMP
Fig.2 RF and Baseband circuit
Serial
I/F
DSP
MPU/DSP
IC401
Fig.3 Audio amplifier circuit
L312,
L314, L315
HPF
MIXER
PLL
VCO
Class D
I2S
DA
Class D
I2C
CODEC
IC601
Serial
I/F
ADC MPU/DSP
LC
Internal Speaker
Filter
LC
External Speaker
Filter
IC401