Frequency Synthesizer Circuits; Voltage Block Diagram - Icom IC-M35 Service Manual

4-3 FREQUENCY SYNTHESIZER CIRCUITS

VCO
While transmitting, the VCO (Q21, 22, D20–23) oscillating
frequency is determined by the value of D22, D23, L22, C26
and C27, and the frequency modulation is carried out by
adding modulation signals to D20.
While receiving, D21 is turned ON and C28 is connected to
the GND to shift the oscillation frequency lower.
The oscillated signals are output via the buffers (Q23, 24).
• FREQUENCY SYNTHESIZER CIRCUITS
IC1
PLL IC
PLLO
X1
21.25MHz
2ND LO
CPU
IC360

4-4 VOLTAGE BLOCK DIAGRAM

Voltage from the power supply is routed to the whole of the transceiver via regulators and switches.
CHASSIS
HV
Battery
Q 21,Q22
Q23
D22,D23
LOOP
BUFF
FIL
Q25
BUFF
I C170
IF IC
IC220
regulator
Q224 Q225
Q353
POWER
VCC
regulator
CTRL
PLL
IC1 is a PLL IC which contains prescaler, programmable
counter, phase comparator and charge pump in its package.
The 21.25 MHz reference frequency signal is fed from X1.
The loop fi lter for the VCO is composed by R8, R10, R22,
C11, C13 and C24.
D 50,D51
Q24
LO
BUFF
SW
BPF
VCO
Q150
1st mixer
5V
: To CPU and EEPROM
CPU5V
5V
Q221
R5V
SW
Q220
V5V
SW
Q222
T5V
SW
4 - 3
TX AMPs
MAIN UNIT
S5V : To TX/RX common circuits
: To RX circuits
R5V
V5V : To VCO
T5V : To TX circuits