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4 - 8
A portion of the signal from the buffer amplifier (IC2) is
amplified at the buffer amplifier (Q8) and is then fed back to
the PLL IC (IC3, pin 11) as the comparison signal.
• B-BAND CIRCUIT (1STBVCO BOARD)
The oscillated signal at 1st B-VCO circuits is applied to the
buffer amplifiers (IC2) via one of the LO switches (D7–D10).
The amplified signal is applied to the 1st mixer circuit (RF
unit; IC15, pin 3) via the LO amplifier (Q9). Components and
osillating frequences of each circuits are as follow list.
A portion of the signal from the buffer amplifier (IC2) is
amplified at the buffer amplifier (Q8) and is then fed back to
the PLL IC (IC3, pin 11) as the comparison signal.
4-2-4 2ND VCO CIRCUITS
(2NDCVCO AND 2NDDVCO BOARDS)
The 2nd VCO circuit generates the 2nd LO frequencies, and
the signals are applied to the 2nd mixer circuit.
• A-BAND CIRCUIT (2NDCVCO BOARD)
The 2nd C-VCO circuit (Q1 and D1) generates 409.4500
MHz and 448.7500 MHz. The oscillated signal is applied to
the 2nd mixer (RF unit; IC10, pin 3), and is then mixed with
the 1st IF signal.
A part of oscillated signal from the 2nd C-VCO circuit is
applied to the PLL IC (IC1, pin 8) as the comparison signal,
and is then output from pin 5. The signal passes through the
loop filter (R14, R15 and R22), and is then applied to the 2nd
C-VCO circuit again as PLL lock voltage.
Shift register
Prescaler
Phase
detector
Loop
filter
REF.
OSC.
REF.
CONT.
Programmable
counter
Programmable
divider
X1
19.2 MHz
to the FM IF IC
RF UNIT
1BVCO
Buffer
Buffer
Buffer
LO
switch
Q9
Q8
IC2
16
17
18
PLLBSTB
IC3 (PLL IC)
PLLDATA
PLLCK
to the 1st mixer circuit
19
5
11
Q1, D1, D2
D7
D8
D9
D10
2BVCO
Q2, D3
3BVCO
Q3, D4
4BVCO
Q4, Q5, D5
Q6,
Q7
• B-BAND PLL CIRCUIT
Q1, D1
VCO
2ND
VCO
Loop
filter
Q4
A_R3V
OSC
(19.2 MHz)
Ripple
filter
to the 2nd mixer (IC10, pin 3)
5
8
1
PLL IC
IC1
Buffer
Q3
• 2ND C VCO CIRCUIT
1st B-VCO
Components
Oscillating freq. (MHz)
1BVCO
Q1, D1 and D2
863.3–1099.6999
2BVCO
Q2 and D3
683.3–866.6999
3BVCO
Q3 and D4
566.3–686.6999
4BVCO
Q4, Q5 and D5
384.7–441.6999