Service Manual

PAGE 6 TABLE OF CONTENTS
3.5.7 USB Connector.................................................................................................21
3.5.8 Line 1 & 2 (RJ45)..............................................................................................22
3.5.9 Facilities............................................................................................................22
3.5.10 PSTN Port (RJ11) .............................................................................................23
4 TECHNICAL DESCRIPTION ................................................................................25
4.1 MMI Board..........................................................................................................25
4.1.1 Description........................................................................................................26
4.2 Control Board ....................................................................................................27
4.2.1 Circuit Board Layout .........................................................................................27
4.2.2 Circuit Description.............................................................................................29
4.2.2.1 LEDs .......................................................................................................29
4.2.2.2 Test Points..............................................................................................29
4.2.2.3 DSP ........................................................................................................33
4.2.2.4 Power......................................................................................................34
4.2.2.5 IXP ..........................................................................................................34
4.2.2.6 CoDec.....................................................................................................35
4.2.2.7 Audio Interface........................................................................................35
4.2.2.8 PSTN Interface .......................................................................................36
4.2.3 Links .................................................................................................................37
4.3 Receiver and Transmitter Modules..................................................................39
4.3.1 Frequency Bands..............................................................................................39
4.3.2 Receiver............................................................................................................39
4.3.2.1 Front-end Filters and Rx Front-end Amplifier .........................................39
4.3.2.2 First Mixer and IF Section.......................................................................41
4.3.2.3 Quadrature Demodulator........................................................................41
4.3.2.4 Receiver Audio Processing.....................................................................41
4.3.3 Transmitter........................................................................................................41
4.3.3.1 Drivers and PA Stages ...........................................................................42
4.3.3.2 Tx Power Control ....................................................................................44
4.3.3.3 Antenna Changeover and Harmonic Filter .............................................44
4.3.3.4 Transmitter Audio Processing.................................................................44
4.3.4 Frequency Synthesis ........................................................................................45
4.3.4.1 General...................................................................................................45
4.3.4.2 PLL .........................................................................................................45
4.3.4.3 VCO ........................................................................................................45
4.3.4.4 Negative Bias Generator and Loop Filter ...............................................45
4.3.4.5 Phase Modulator.....................................................................................46
4.3.4.6 Reference Oscillator...............................................................................46
4.3.5 RF Sub-Assembly Internal Control Logic..........................................................48
4.3.5.1 DSP and FPGA.......................................................................................49
4.3.5.2 DSP Clock Oscillator ..............................................................................49
4.3.6 RF Sub-Assembly Internal Memory ..................................................................49
4.3.6.1 Multiplexer ..............................................................................................49
4.3.7 RF Sub-Assembly Internal Power Supplies ......................................................50