Motorola GM1200E

Table of Contents
3.1-ii Introduction/Theory of Operation
Paragraph Page
5.0 Transmit Signalling Circuits ................................................................... 12
5.1 Sub-audible Data (PL/DPL)....................................................................... 12
5.2 High Speed Data ....................................................................................... 13
5.3 Dual Tone Multiple Frequency (DTMF) Data............................................. 13
6.0 Receive Audio Circuits ............................................................................ 14
6.1 Squelch Detect .......................................................................................... 14
6.2 Audio Processing and Digital Volume Control........................................... 15
6.3 Audio Amplification Speaker (+) Speaker (-) ............................................. 15
6.4 Handset Audio........................................................................................... 16
6.5 Filtered Audio ............................................................................................ 16
6.6 RX Secure Audio (optional)....................................................................... 16
7.0 Receive Signalling Circuits ..................................................................... 17
7.1 Sub-audible Data (PL/DPL) and High Speed Data Decoder..................... 17
7.2 Alert Tone Circuits..................................................................................... 17
UHF (403-470MHz) SPECIFIC CIRCUIT DESCRIPTION
8.0 Receiver Front-End .................................................................................. 18
8.1 Front-End Band-Pass Filter & Pre-Amplifier.............................................. 18
8.2 Mixer and Intermediate Frequency (IF) Section ........................................ 19
8.3 IF IC (U5201)............................................................................................. 19
9.0 Transmitter Power Amplifier (PA) 5-25W ............................................... 19
9.1 Power Controlled Stage............................................................................. 19
9.2 PA Stages.................................................................................................. 20
9.3 Directional Coupler.................................................................................... 20
9.4 Antenna Switch.......................................................................................... 21
9.5 Harmonic Filter .......................................................................................... 21
9.6 Power Control............................................................................................ 21
10.0 Frequency Synthesis ............................................................................... 23
10.1 Reference Oscillator.................................................................................. 23
10.2 Fractional-N Synthesizer (U5701) ............................................................. 23
10.3 Voltage Controlled Oscillator (VCO).......................................................... 24
10.4 Synthesizer Operation............................................................................... 24