4 - 3
4-3 FREQUENCY SYNTHESIZER CIRCUITS
VCO
While transmitting, the oscillatinon frequency of VCO (Q21,
Q22, D22) is determined by the value of D22, L22, C26 and
C27, and the frequency modulation is carried out by adding
modulation signal to D20.
The generated signal is passed through the buffers (Q23
and Q24), and then applied to the pre-drive AMP (Q53),
through the LO SW (D50) and buffer (Q50).
While receiving, D21 is turned ON and C28 is connected to
the GND to shift the oscillation frequency lower.
The generated signal is passed through the buffers (Q23
and Q24), and then applied to the 1st mixer (Q150), through
the LO SW (D51).
PLL
IC1 is a PLL IC which contains the 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.
4-4 VOLTAGE BLOCK DIAGRAM
LO
SW
BPF
BUFFBUFF
BUFF
FIL
LOOP
X1
21.25MHz
1st mixer
D 50,D51
Q24Q23
Q25
Q 21,Q22
IC1
PLL IC
IF IC
CPU
VCO
Q150
TX AMPs
IC170
IC360
PLLO
2ND LO
D22
PLL control signal
POWER
CTRL
Q353
VCCHV
R3V
SW
Q221
R3V
T3V
SW
Q222
T3V
3V
regulator
Q224, Q225
M3V
: To the TX/RX common circuits
: To the RX circuits
: To CPU and EEPROM
: To the TX circuits
3V
regulator
IC220
CPU3V
CHASSIS
Battery
pack
MAIN UNIT
• FREQUENCY SYNTHESIZER CIRCUITS
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