Signal Processing In The If Stage; If-Agc - Kenwood TS-890S In-Depth Manual

07 DSP
SCP IF

Signal Processing in the IF Stage

The IF AGC for signal reception forms the core that determines the character of the TS-890S.
Following advancements of analog circuits and digital signal processing, the IF-AGC has undergone many innovative
developments while inheriting the tradition. New enhancements have also been made on the TS-890S.

IF-AGC

RX IF
AGC loops of the TS-890S are placed before and after the interference rejection, such as an IF filter or notch filter. The
AGC loop of the preceding stage functions to prevent signals whose level is higher than the reference from being input
to the A/D converter for the IF input and is called the out-band AGC loop. The AGC loop of the succeeding stage has the
same AGC performance as the predecessors and is called the in-band AGC. With the in-band AGC operated after the IF
filter and interference rejection, the desired signal can be highlighted.
The basic approach to AGC response characteristics is to control the AGC amplifier gain with an ultra-high-speed attack
in the same way as conventional transceivers to control the gain without causing unnecessary amplitude fluctuation, and
to reduce factors causing fatigue due to long hours of listening.
30
RX IF
ADC
PCM4202
MIC
ANI / USB-Audio
ADC
WM8782
Play back
ADC
FPGA
AD9649
Fig. 31 DSP Hardware Block Diagram
IF ADC NB Type A
AGCV
AGC
DAC
Fig. 32 IF Stage Block Diagram
TXMRX DSP
(ADSP-21363)
Clock: 331.776MHz
SCP DSP
(ADSP-21363)
Clock: 331.776MHz
NB Type B,
Soft Attack
Notch,
CONT
IF Filter
AGC,
AGCQR
TX IF
DAC
AK4387
AGCV
Recording
DAC
AK4387
BEEP
SP
DAC
AK4396
ANO
USB-Audio
DAC
AK4387
VoIP
Digital
Analog
DEMOD RX Audio
AGC