Motorola HT Series Service Manual page 9

Table of Contents
6.3.3 Automatic Gain Control Circuit......................................................................... 6-7
6.4 Frequency Generation Circuitry .................................................................................... 6-8
6.5 Synthesizer ................................................................................................................... 6-9
6.6 Voltage-Controlled Oscillator (VCO) ........................................................................... 6-10
Chapter 7 Low Band, 800 MHz, PassPort & 900 MHz
Theory of Operation...........................................................7-1
7.1 Introduction ................................................................................................................... 7-1
7.2 Low Band Transmitter................................................................................................... 7-1
7.2.1 Power Amplifier (PA)........................................................................................ 7-1
7.2.2 Antenna Switch ................................................................................................ 7-2
7.2.3 Harmonic Filter................................................................................................. 7-2
7.2.4 Antenna Matching Transformer ....................................................................... 7-2
7.2.5 Power Control Integrated Circuit (PCIC).......................................................... 7-2
7.2.6 Temperature Cut Back Circuit.......................................................................... 7-2
7.2.7 Electrostatic Discharge (ESD) Protection Circuit ............................................. 7-2
7.3 Low Band Receiver....................................................................................................... 7-3
7.3.1 Receiver Front-End.......................................................................................... 7-3
7.3.2 Receiver Back-End .......................................................................................... 7-4
7.3.3 Automatic Gain Control (AGC)......................................................................... 7-4
7.3.4 Frequency Generation Circuit .......................................................................... 7-4
7.4 Synthesizer ................................................................................................................... 7-5
7.5 Voltage Control Oscillators (VCO) ................................................................................ 7-6
7.5.1 Receive VCO ................................................................................................... 7-6
7.5.2 Transmit VCO .................................................................................................. 7-6
7.5.3 Buffer ............................................................................................................... 7-6
7.5.4 Diplexer/Output Filters ..................................................................................... 7-7
7.5.5 Prescalar Feedback ......................................................................................... 7-7
7.6 800 MHz Transmitter .................................................................................................... 7-7
7.6.1 Power Amplifier................................................................................................ 7-7
7.6.2 Antenna Switch ................................................................................................ 7-8
7.6.3 Harmonic Filter................................................................................................. 7-8
7.6.4 Power Control Integrated Circuit (PCIC).......................................................... 7-8
7.7 800 MHz Receiver ........................................................................................................ 7-9
7.7.1 Receiver Front-End.......................................................................................... 7-9
7.7.2 Receiver Back-End ........................................................................................ 7-10
7.7.3 Automatic Gain Control Circuit....................................................................... 7-10
7.7.4 Frequency Generation Circuit ........................................................................ 7-11
7.8 Synthesizer ................................................................................................................. 7-12
7.8.1 Voltage Control Oscillator (VCO) ................................................................... 7-13
7.9 Trunked Radio Systems.............................................................................................. 7-14
7.9.1 Privacy Plus Trunked Systems ...................................................................... 7-14
7.9.2 LTR™ Trunked Systems................................................................................ 7-14
7.9.3 MPT Trunked Systems .................................................................................. 7-14
7.9.4 PassPort™ Trunked Systems........................................................................ 7-15
7.9.4.1 Power Supplies..................................................................................... 7-15
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