Icom IC-F7000 User Manual download pdf (Page 14)

4 - 3

4-2 TRANSMITTER CIRCUITS

4-2-1 MICROPHONE AMPLIFIER CIRCUIT

(RC-26, MAIN AND DSP UNITS)

The microphone amplifier circuit amplifies microphone audio

signal to a level needed for the DSP circuit.

Audio signals from the [MIC] connector (J8701, pin 6) are

amplified at the AF amplifier (IC8280, pin 3), and then

applied to the gate modulator IC (MAIN unit; IC2001, pin 3)

via the J2051, pin 1 as “FMOD” signal. The signal is applied

to the DSP unit after being passed through the AF amplifier

and low-pass filter IC (MAIN unit; IC1051, pins 3, 7) as

“DSPI1” signal.

4-2-2 DSP TRANSMITTER CIRCUIT (DSP UNIT)

The DSP (Digital Signal Processor) circuit enables PSN

(Phase Shift Network)/Low Power/Phase modulator, trans-

mitter monitor, side tone, and etc.

The microphone audio signals from the MAIN unit via the

“DSPI1” line are amplified at the differential amplifiers

(IC9651a/b), and are then applied to the A/D converter sec-

tion in the CODEC IC (IC9501). at the same time, the con-

verted signals are level-shifted 5 V to 3.3 V in the IC

(IC9501).

The level shifted signals are applied to the DSP IC (IC9301)

and modulated at the DSP IC to produce the 12 kHz trans-

mitter IF signal.

The modulated IF signal from the DSP IC is applied to the

D/A convertor section in the CODEC IC (IC9501) to convert

into the analog IF signal. Also the signal is level-shifted

3.3 V to 5 V at the level converter section in the IC (IC9501).

The level-shifted IF signal is passed through the active filter

(IC9701a), and then applied to the MAIN unit via J9901 (pin

17) as the “DSPO1” signal.

4-2-3 SPEECH COMPRESSOR CIRCUIT

(DSP UNIT)

The DSP (Digital Signal Processor) circuit enables PSN.

The speech compressor compresses the transmitter audio

input signals to increase the average output level (average

talk power).

When the speech compressor function is ON, the level-shift-

ed signal from the CODEC IC (IC9501) is applied to the DSP

IC (IC9301) and compressed at the DSP IC to obtain an

average audio level.

At the same time, the compressed signals are modulated at

the DSP IC and applied to the D/A converter section in the

CODEC IC (IC9501).

4-2-4 IF AMPLIFIER AND MIXER CIRCUITS

(MAIN UNIT)

The modulated 3rd IF signal from the DSP unit (“DSPO1”

signal: 12 kHz) passes through the transmit/receive switch

(IC1703, pins 1, 6), and then applied to the 3rd mixer circuit

(IC901, pin 3). The applied 3rd IF signal is mixed with the

3rd LO signal from the DDS circuit (PLL unit; IC5701) to pro-

duce a 455 kHz 2nd IF signal.

The 2nd IF signal is output from IC901, pin 5 and passes

through the ceramic bandpass filter (FL402) to suppress the

unwanted signals via the D132. The filtered 2nd IF signal is

amplified at the 2nd IF amplifier (Q801), and then applied to

the 2nd mixer circuit after being passed through the D305

and low-pass filter (L305, L306, C307, C308, C310, C311,

C315).

The 2nd IFsignal is mixed with 64 MHz 2nd LO signal, com-

ing from the PLL circuit, at the 2nd mixer circuit (D303) to

obtain 64.455 MHz 1st IF signal. The 1st IF signal is passed

through the bandpass filter (FI1201) to cut off the unwanted

signals. The signal is applied to the transmitter mixer circuit

(Q702, Q703) to obtain the desired signal via the

transmit/receive switch (D205) and attenuator (R712, R715,

R716).

The operating (transmitting) frequency is produced at the 1st

IF mixer circuit (Q702, Q703) by mixing the 1st IF and 1st

LO signals. The mixed signal is then applied to the RF cir-

cuit.

FI402

Q801

MIC

BPF

Ceramic

LPF

IC1001

DSPI1 DSPO1

(12 kHz)

455 kHz

3rd LO

(443 kHz)

DSP

UNIT

IC1051IC2001

Controller

AMP. AMP.VCA

AMP.

2nd mixer

D303

2nd LO (64.00 MHz)

FI201

64.455 kHz

Bandwidth:

15 kHz

Q401

BPF

Crystal

amp.

1st mixer

Q702, Q703

1st LO

(64 94 MHz)

LPF

BPFs

2 30 MHz

0.5 1.9999 MHz

IC1

YGR

LPFs

PA UNIT FILTER UNIT

Antenna

D7271,

D7272

PWR

DET

Q6106, Q6401,

Q6402, Q6801,

Q6851

AMPs

• TRANSMIT CONSTRUCTION

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Icom IC-F7000 User Manual Page 14

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