Frequency Synthesizer Circuits; Voltage Diagram; Pll - Icom ic-f5021 Service Manual

5-3 FREQUENCY SYNTHSIZER CIRCUITS
VCOs
The TX VCO which generates TX signal is composed
by Q13, D16, D31, L25, L38, etc., and the frequency
modulation is carried out by applying modulation signals to
D18.
The RX VCO which generates 1st LO signals is composed
by Q14, D33, D34, L26, L39, etc.
These two VCOs are switched by the VCO SW (Q15, 16)
using "RXC" signal.
The output signals from each VCO are amplified by the
buffer AMP (Q11) and LO AMP (Q10), then applied to the
TX or RX circuits.
A portion of oscllated signals is applied to the PLL IC (IC4)
via buffer AMP (Q12).

• FREQUENCY SYNTHESIZER CIRCUITS

X2
IC19 CR-794
15.3MHz
REF
REF
AMP
Q34
Clock,Data,Strobe
X3
45.9MHz
BPF

5-4 VOLTAGE DIAGRAM

Voltage from the power supply is routed to the whole of the transceiver via regulators and switches.
IF IC (IC1), PLL IC(IC4), etc.
Driver(Q9), APC AMP(IC2), etc.
RF AMP(Q2), 1st IF AMP(Q4), 1st mixer(Q3), etc.
External output(from J6)
VCOs, FRONT UNIT
HPA module(IC3)
RLVA
IC4
MB15A02

PLL

LOOP
LV
IC FIL
TLVA
T8V
LPF BPF
D54,55
IF IC
IC1:TA31136FN
Q27 Q28
CPU5
5V +5
REG
8V
D23 Q25 Q29
TMUT
T8
T8V VCC
REG
8V
Q26 Q30
RXC
R8
R8V
REG
8V
VCC
8V
HV
PLL
The applied VCO output is divided according to the serial
data including divide ratio from the CPU, at the prescaler
and programmable divider. In the same way, the reference
frequency signal from the reference frequency signal
oscillator is applied to the PLL IC and divide so that these
are the same frequency.
The frequency-matched signals are applied to the phase
comparator and phase-compared. The resulted phase
difference is detected as a phase-type signal, and level-
adjusted at the charge pump then output. The output pulse
type signal is passed through the loop filter to be converted
into the DC voltage (=Lock Voltage).
Applying the lock voltage to the variable capacitors
(VD) which composes a part of the resonator of VCO,
the capacitance of VDs changes corresponding to the
applied lock voltage. This causes the change of resonation
frequency that determines the VCO oscillating frequency to
keep the VCO frequency constant.
When the oscillation frequency drifts, its phase changes
from that of the reference frequency, causing a lock voltage
change to compensate for the drift in the VCO oscillating
frequency.
8V
Q17
Q15,16
RIPPLE
FIL
D52
Q14,D33,34
RLV
AD J
RX VCO
LV
D53
Q13,D16,31
TLV
AD J
TX VCO
D18
FM
MOD
CPU5
IC9
IC10
+8
CPU5
REG
REG
Q23 Q24
HV
POWER Power supply cable
SW
W2
PWON
5 - 4
VCO
RXC
SW
TXC
D14,D15
Q11 Q10
TX/RX
BUFF BUFF
SW
LPF
Q12
X2
136/146 MHz-1740 MHz
182.35 MHz-220.35 MHz