Icom IC-7600 Service Manual page 14

TX AMPLIFIER CIRCUITS (RF AND PA UNITS)
The TX signal from the BPF circuits is applied to the YGR
AMP (RF UNIT; IC201) via the attenuator. The amplifi ed TX
signal is applied to the PA UNIT via the LPF.
The TX signal from the RF UNIT is applied to the pre-drive
AMP (Q1) via the attenuator, and the amplifi ed TX signal is
applied to the drive AMP (Q2, 3) via the LPF. The amplifi ed
TX signal is then power-amplifi ed by the power AMP (Q4, 5).
The power-amplified TX signal is applied to the TX filter
circuits.
TX FILTER CIRCUITS
The power-amplifi ed TX signal from the PA UNIT is passed
through one of LPFs according to the transmitting frequency,
to remove harmonic components contained in the TX signal.
The fi ltered TX signal is applied to the CTRL UNIT.
ANTENNA TUNING AND SWITCHING CIRCUITS
(CTRL UNIT)
The TX signal from the FILTER UNIT is passed through
4 detection circuits on the CTRL UNIT before being fed to
the antenna connector [ANT1] or [ANT2].
Based on the parameters from these 4 detection circuits,
the tuner CPU (IC201) controls matching networks on the
TUNER UNIT to match the transceiver and connected
antenna.
SWR DETECTION CIRCUIT
The forward wave is rectified by D2 at the current detect
transformer (L1). The rectifi ed voltage is DC amplifi ed by IC1
and applied to the A/D port of the tuner CPU (IC201).
The reflected wave is rectified by D1 at the current detect
transformer (L1). The rectifi ed voltage is DC amplifi ed by IC1
and applied to the A/D port of the tuner CPU (IC201).
• TX AMPLIFERS AND TX FILTER CIRCUITS
RF UNIT
IC201
From TX circuits
YGR
ATT
AMP
PA UNIT
Q1
PRE
ATT
DRIVE
Q2,Q3
LPF DRIVE
(PUSH-PULL)
LPF
Q4,Q5
PWR
AM P
PHASE DETECTION CIRCUIT
The TX signal which is picked up at the current detect
transformer (L21) and the TX signal which is divided by C21,
C22 and C24, are rectifi ed by D21 and D22, and amplifi ed
by C-MOS IC (IC21).
The amplified signal is applied to the IC23 via the buffer
(IC22) for phase comparison. The resulting signal of phase
comparison is rectifi ed by D23 and D24, and composed and
amplifi ed by IC51, then applied to the A/D port of the tuner
CPU (IC201).
This AMP, as the fi rst stage, employs a C-MOS type AMP to
detect the low TX signal. The inverter AMP requires input level
lower than others need, and provides high speed operation
for stable high frequency operation with low TX signal.
RESISTANCE DETECTION CIRCUIT
A portion of the TX signal is divided by C42 and C44, and
rectifi ed by D42 to be converted into DC signal.
Another portion of the TX signal is rectified at the current
detect transformer (L41) to be converted into DC signal too.
And the voltage of these signals are the same when the
connected load (=antenna) is 50 Ω. Thus the difference of
these voltages represents the resistance components.
By comparing the difference of these voltages, the
transceiver detects the resistance components.
The detected resistance components are amplifi ed by IC51
and applied to the A/D port of the tuner CPU (IC201).
CURRENT DETECTION CIRCUIT
A portion of the TX signal is rectifi ed by D81, L81 and R81,
and applied to IC81 to be level-compared with the voltage
from the SWR detection circuit.
When the connected load (=antenna) is less than 10 Ω,
the TX signal is bypassed the TUNER UNIT via the tuner
switches (RL104 and RL105) compulsorily, to protect the
circuit on the TUNER UNIT from refl ected waves.
FILTER UNIT
1.8MHz
RL402 RL401
LPF-1
3.5M/3.8M/4.63MHz
RL352 RL351
LPF-2
5M/7MHz
RL252 RL251
LPF-3
10M/14MHz
RL152 RL151
LPF-4
18M/21MHz
RL302 RL301
LPF-5
24M/28MHz
RL202 RL201
LPF-6
50MHz
RL102 RL101
LPF-7
3 - 5
CTRL UNIT
ANT1
RL101
D8
D301/D302
CURRENT
DETECT
TUNER
UNIT
TUNER_
NET
RX circuits
RL103
D41/D42
IC51
RESIST
AMP
DET
L21
IC201
D21,22
IC51
PHASE TUNER_
AMP
DET CPU
D 1/D2
IC1
SW R
AMP
DET
FORV (FORWARD WAVE)
REFV (REFLECT WAVE)
ANT2