4 - 1
• RF CIRCUITS
4-1 RECEIVE CIRCUITS
RF CIRCUIT (RF UNIT AND MAIN UNIT)
The RX signal from the antenna is passed through the LPF
(RF UNIT: L612–L614, C653–C656, C658, C659), the ANT
SW (RF UNIT: D607, D609, L611, C649, C652), and then
applied to the MAIN UNIT.
The RX signal from the RF UNIT is passed through the
2-staged tuned BPF (MAIN UNIT: D21, D24, L27, L29,
C308, C309, C312, C320, C323), and then applied to the
RF AMP (MAIN UNIT: Q39). The amplifi ed signal is passed
through another 2-staged tuned BPF (MAIN UNIT: D17,
D18, L23, L25, C273, C278, C287, C291) to remove un-
wanted signals, and then applied to the 1st IF circuit.
• 1ST IF CIRCUITS
SECTION 4. CIRCUIT
DESCRIPTION
• 2ND IF CIRCUITS
ANT
SW
LPF
BPF
RF
AMP
BPF
ANT
SW
MAIN-A/B/C UNIT
Q39
RF-A/B/C UNIT
D17,D18
D605-D607,
D609
From the TX AMP circuit
To the 1st IF circuit
D21,D22,
D24,D25
D26
BPF
XTAL
1st IF
AMP
BPF
XTAL
MAIN-A/B/C UNIT
FI4
SW
FI3
D16
Q33
SW
N/W
From RF AMP
1st IF MIXER
1st LO signal
from the RX VCO-A/B
D8
Q23
N/W
46.35MHz
To the IF IC
X4
PLL
IC
BPF
BPF
CERAMIC
BPF
CERAMIC
MAIN-A/B/C UNIT
DET
Q21
FM IC
X3
IC15
To the RX AF circuit
IC14
From the 1st IF circuit
FI1
FI2
SW
N/W
SW
N/W
450KHz
D3,D4
D3,D4
1ST IF CIRCUIT (MAIN UNIT)
The RF signal is applied to the 1st IF mixer (Q33) to be
mixed with the 1st LO signal from the RX VCO; RX VCO-A
(Q30, D10, D14) or RX VCO-B (Q31, D11, D15), resulting
in a 46.35 MHz 1st IF signal. The signal is passed through
the Narrow/Wide SW (D16) and 1st IF fi lter (FI3; for FM wide
mode, or FI4; for FM narrow and digital modes) to remove
unwanted signals.
The filtered IF signal is passed through another Narrow/
Wide SW (D8), and amplifi ed by the 1st IF AMP (Q23), and
then applied to the 2nd IF circuit.
2ND IF CIRCUIT (MAIN UNIT)
The 1st IF signal is applied to the IF IC (IC15, pin 16), which
contains the 2nd IF mixer, 2nd IF AMP, demodulator and
other circuits.
The 1st IF signal is mixed with the 45.9 MHz 2nd LO signal
from the tripler (Q21), resulting in a 450 kHz 2nd IF signal.
The signal is passed through the Narrow/Wide SW (D3) and
2nd IF filter/s (FI2 and FI1; for FM narrow or digital mode,
only FI2; for the FM wide mode) to remove unwanted sig-
nals.
The filtered IF signal is passed through another Narrow/
Wide SW (D4), and then applied to next circuitry.
• WHILE OPERATING IN THE ANALOG MODE
The filtered signal is amplified by the internal 2nd IF AMP,
and applied to the demodulator circuit.
The demodulated AF signal is output from pin 9, and then
applied to the RX AF circuit, through the AF SW (IC8, pins
2 and 15).
• WHILE OPERATING IN THE DIGITAL MODE
The filtered signal is applied to the IF AMP (IC13, pin 3),
through the buffer (Q19).
The amplified signal is filtered by the IF filter (FI5) to elimi-
nate unwanted signals, and then applied to the A/D con-
verter (IC22, pin 3).
The applied signal is converted into a digital signal, and then
applied to the DSP (IC24) and processed.
The processed signal is applied to the linear codec (IC23)
to be decoded into an analog audio signal. The decoded AF
signal is applied to the RX AF circuit, through the AF SW
(IC8, pins 1 and 15).
