3 - 2
• 1ST RX IF AND 2ND RX IF CIRCUITS
• DEMODULATOR CIRCUITS
1ST RX IF CIRCUITS (RF-A UNIT)
The RX signal from the BPF UNIT is passed through the
LPF, which removes unwanted signals (60 MHz and higher),
and then applied to the 1st RX IF mixer (Q721–Q724) to
be mixed with the 1st RX LO signal (64.485–124.455 MHz)
from the PLL UNIT, resulting in the 64.455 MHz 1st RX IF
signal.
The 1st RX IF signal is amplified by the 1st RX IF AMP
(Q741) and passed through one of the 1st IF fi lters (FI911;
FL-434, or optional FL-430 or FL-431), which has different
passband widths, according to the IF fi lter setting.
The fi ltered 1st RX IF signal is amplifi ed by the RX IF AMPs
(Q1051 and Q1071, Q1072), and then applied to the 2nd RX
IF circuits.
2ND RX IF CIRCUITS (RF-A UNIT)
The 1st RX IF signal from the 1st RX IF circuits is divided
into two paths, and then each signal is applied to the 2nd RX
IF mixers (the image reduction mixers; D1102/D1101) to be
mixed with the 2nd RX LO signal (64.491 MHz) from the PLL
UNIT, resulting in the 36 kHz 2nd RX IF signal.
The image reduction mixer removes image frequency
components by using two LO signals which are 90 degrees
phase-shifted from each other.
The 2nd RX IF signals are independently amplified by the
buffers (Q1201/Q1251) and IF AMPs (IC1221).
These amplifi ed 2nd RX IF signals are 90 degrees phase-
shifted and combined by the combiner (IC1222), and then
applied to the MAIN UNIT.
IF
AMP
IC1221
BUFF
Q1251
IF
AMP
IC1221
Σ
IC1222
To the demodulator circuits
IF
AMP
Q1051
BUFF
Q1201
D1101
IF
AMP
Q1071/Q1072
D1102
90deg
IC1222
Q721/Q722/
Q723/Q724
IF
AMP
Q741
BPF
XTAL
64.455MHz(BW=3kHz)
BPF
XTAL
64.455MHz(BW=15kHz)
FI911
ATT
BPF
XTAL
64.455MHz(BW=6kHz)
FL-430(Optional)
FL-431(Optional)
LPF
fc=60MHz
LO
AMP
Q811
LPF
BUFF
IC1121
BUFF
IC1121
LO
AMP
Q1141
2nd RX LO
1st RX/TX LO
BUFF
IC1121
From the preamplifier circuits
90deg
ATT
LPF
LPF
RF-A UNIT
64.485~
124.455 MHz
DEMODULATOR CIRCUITS (MAIN UNIT)
The 2nd RX IF signal from the 2nd RX IF circuits is passed
through the RX mute SW (IC4604) and the balance-
unbalance converter (Balun; IC4602/IC4603), and then
applied to the CODEC (IC4651) to be converted into digital
audio signal.
The converted digital audio signal is applied to the DSP
(IC4001), and demodulated and processed.
AMP
IC4483
BUFF
IC4602
MUTE
IC4604
LPF
IC4603
LPF
IC4603
IC1201
IC1261
MAIN
CPU
CPLD
MAIN UNIT
CODEC
IC4461
IC4001
DSP
From the 2nd RX circuits
To the RX AF circuits
CODEC
IC4651
The demodulated signal is applied to another CODEC
(IC4461) to be converted into analog AF signal, and then
applied to the buffer amplifi er (IC4483).
The buffer amplifi ed AF signal is applied to the CONNECT
UNIT.