Motorola Professional GP640 Service-informatie - Pagina 11

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1.0

This Chapter provides a detailed theory of operation for the UHF circuits in the radio. For details of

the theory of operation and trouble shooting for the the associated Controller circuits refer to the

Controller Section of this manual.

2.0

(Refer to Figure 2-1 and the UHF Transmitter schematic diagram)

The UHF transmitter consists of the following basic circuits:

Power amplifier (PA).

Antenna switch/harmonic filter.

Antenna matching network.

Power Control Integrated Circuit (PCIC).

From

VCO

2.1

The power amplifier (PA) consists of two principle devices:

LDMOS PA driver IC, U101.

LDMOS PA final stage, Q110.

The LDMOS driver IC provides 2-stage amplification using a supply voltage of 7.3V. The amplifier is

capable of supplying an output power of 0.3W (pins 6 and 7) with an input signal of 2mW at 3dBm

(pin16). The current drain is typically 160mA while operating in the frequency range of 403-470MHz.

P CI C

Vcontrol

Power

Amplifier

Driver

Figure 2-1 UHF Transmitter Block Diagram.

THEORY OF OPERATION

Vcontrol

Antenna Switch/

P A Final

S t a g e

Harmonic Filter

Chapter 2

Antenna

Matching

Network