Icom IC-2100H

3-3
PLL
CIRCUITS
3-3-1
PLL CIRCUIT
A
PLL
circuit
provides
stable
oscillation
of
the
transmit
fre-
quency
and
the
receive
1st LO
frequency.
The
PLL
circuit
compares
the
phase
of
the
divided VCO
frequency
to
the
ref-
erence
frequency. The
PLL output
frequency
is
controlled
by
the
divided
ratio
(N-data)
of
a
programmable
divider.
An
oscillated
signal
from
the VCO
passes
thorough
the
buffer
amplifiers
(Q4,
Q6)
is
applied to
the
PLL IC
(IC1,
pin
2)
and
is
prescaled
In
the
PLL
IC based
on
the
divided
ratio
(N-
data).
The
reference
signal
is
generated
at
the
reference
oscillator
(XI) and
is also
applied to
the
PLL
IC.
The
PLL
IC
detects
the
out-of-step
phase
using the
reference
frequency
and
outputs
it
from pin
8. The
output
signal
is
passed
thor-
ough
the
loop
filter (R89,
R90,
Cl
05,
Cl
07)
and is
then
applied
to
the VCO
circuit
as
the
lock
voltage.
The
lock
voltage
is also
used
for the
receiver
tunable
band-
pass
filters
to
match
the filter's
center
frequency
to
the
desired
receive
frequency.
The
lock
voltage
is
applied to
the
bandpass
filters
(D13-D16)
via
the
tune
control
circuit
(IC4,
D4).
3-3-2
VCO
CIRCUIT
(MAIN
unit)
The VCO
circuit
contains a
separate
TX-VCO
(01,
Q2,
D1)
and
RX-VCO
(Q33,
D23),
The
oscillated
signal
is
amplified
at
the
buffer
(Q4)
and LO
(Q5)
amplifiers,
and is
then
applied to
the
T/R
switching
circuit (D5).
Then
the
Tx and
Rx
signals
are
applied
to
the
pre-driver
(013)
and
1st
mixer
(Q21)
respec-
tively.
A
portion
of the
signal
from Q4
is
amplified
at the
buffer
amplifier
(06)
and is
then
fed back to
the
PLL 1C
(IC1
pin
2)
as the
comparison
signal.
3-4
POWER
SUPPLY
CIRCUITS
VOLTAGE
LINES
Line
Description
HV
The
voltage
from
the
connected
DC
power
sup-
ply.
13.8V
The
same
voltage as
the
HV
line
which
Is
con-
trolled by
the
power
switching
circuit
(Q25,
Q26,
035).
When
the
[POWER]
switch is
pushed,
the
CPU
outputs
the
“PWRON”
control
signal
to
the
power
switching
circuit to
turn
the
circuit
ON.
CSV
Common 5
V
for the
CPU
converted
from
the
HV
line by
the CSV
regulator
circuit
(IC9).
The
circuit
outputs
the
voltage
regardless
of the
power
ON/OFF
condition.
-h8V
Common
8
V
converted
from
the
13.8V
line by
the
-I-8V
regulator
circuit
(ICS).
R8V
Receive
8
V
controlled
by
the
R8V
regulator
cir-
cuit
(029,
030)
using
the
“RX”
signal
from
the
I/O
expander
IC
(IC10).
T8V
Transmit 8
V
controlled
by
the
T8V
regulator
cir-
cuit
(Oil
,
012)
using
the
“TX”
signal
from
the
I/O
expander
IC
(IC10).
+5V
Common 5
V
converted
from the
+8V
line by
the
+5V
regulator
circuit
(031,
032).
•
PLL
circuit
3-3
for free by
RadioAmateur.eu