Motorola CDM1550 LS+ Detailed Service Manual page 4

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2.3.4.3 Dual Tone Multiple Frequency (DTMF) Data ........................ ... 2-12
2.3.5 Receive Audio Circuits ......................................................................... 2-13
2.3.5.1 Squelch Detect ......................................................................... 2-13
2.3.5.2 Audio Processing and Digital Volume Control ......................... 2-13
2.3.5.3 Audio Amplification Speaker(+) Speaker(-) ........................... 2-14
2.3.5.4 Handset Audio ......................................................................... 2-14
2.3.5.5 Filtered Audio and Flat Audio ................................................... 2-15
2.3.5.6 RX Secure Audio Option .......................................................... 2-15
2.3.5.7 Option Board Receive Audio .................................................... 2-15
2.3.6 Receive Signalling Circuits ................................................................... 2-16
2.3.6.1 Sub-Audible Data (PLIDPL) and High Speed Data Decoder ... 2-16
2.3.6.2 Alert Tone Circuits ................................................................... 2-16
2.3.6.3 Voice Storage Option ............................................................... 2-17
2.4 200 MHz Receiver Front-End ............................................................................. 2-18
2.4.1 Receiver Front End .............................................................................. 2-18
2.4.2 Receiver Back End ............................................................................... 2-19
2.5 Transmitter Power Amplifier (PA) 25 W ..... .......................................... .............. 2-19
2.5.1 Power Controlled Stage .......... .............. ......... ..... .. ...... .. ...... ................. 2-20
2.5.2 Pre-Driver Stage .... ...... ......................................................................... 2-20
2.5.3 Final Stage .......... ........ ................................................ ..... .. ... ............... 2-20
2.5.4 Directional Coupler .. ................. ........................... .... .... ... ........ .............. 2-20
2.5.5 Antenna Switch ...... .............................. ..... ............................. .............. 2-20
2.5.6 Harmonic Filter ...... ..................... ................................. ........... .............. 2-21
2.5.7 Power Control ............ ..................... ..... ........................ ........... .............. 2-21
2.6 Frequency Synthesis ........... .................................... ............... ......... ..... .............. 2-21
2.6.1 Reference Oscillator ......................... ........................ ... ........................ . 2-21
2.6.2 Fractionai-N Synthesizer .................... .......... , ....................................... 2-22
2.6.3 Voltage Controlled Oscillator (VC0) ..................................................... 2-23
2.6.4 Synthesizer Operation ........................ ...................... ............................ 2-24
2.7 700 MHz Receiver Front-End ......................... ..... ............................................... 2-25
2.7.1 Receiver Front-End ......................... .. ............... ............... ..................... 2-25
2.7.2 Receiver Back-End ........................... ..... .............. ...... .................... ... .... 2-25
2.8 Transmitter Power Amplifier (PA) 15 W ........ ..................................................... 2-26
2.8.1 Power Controlled Stage ........ ....................... ..... .............. .... ..... ............ 2-26
2.8.2 Driver Stage ................... .................................. ................ ........ ............ 2-27
2.8.3 Final Stage ...... ....... ..................... .. ......... ..... ... ........................ .......... ... . 2-27
2.8.4 Antenna Switch .................................................................................... 2-27
2.8.5 Harmonic Filter ... ........ ... ..... ......... ... .................... ............... .. ..... ............ 2-27
2.8.6 Bi-Directional Coupler .......................................................................... 2-27
2.8.7 Power Control ....................................................................................... 2-27
2.9 Frequency Synthesis .......................................................................................... 2-28
2.9.1 Reference Oscillator ............................................................................. 2-28
2.9.2 Fractionai-N Synthesizer ...................................................................... 2-28
2.9.3 Voltage Controlled Oscillator (VC0) ..................................................... 2-29
2.9.4 Synthesizer Operation .......................................................................... 2-31 . )