Voice Compression Technology; Description; Transceiver Description; Digital Section Description - Motorola MTH500 Service Manual

Overview

Voice Compression Technology

Description

Transceiver Description

1 - 2
Voice is converted into a digital bit stream by sampling the voice at high rate and
converting the samples into numbers, which are represented by bits.
Voice compression reduces the number of bits per second while maintaining the
voice at an acceptable quality level. The
ACELP (Algebraic Code Excited Linear Prediction). The compressed voice-data
bits modulate the RF signal.
All the radio circuitry is contained in the Digital/RF Board and the keypad board.
The Digital/RF board is divided into the following sections: digital, frequency
generating, transmitter, and receiver.

Digital Section Description

The digital section includes the Redcap 2 that consists of the Mcore risk machine
and the Digital Signal Processor (DSP).
The Mcore is the controller of the Digital/RF Board. It controls the operation of
the transmitter, receiver, audio, and synthesizer integrated circuits located in the
RF section. It communicates with the keypad and display.
The Digital Signal Processor (DSP) which performs modulation and de-modula-
tion functions for the radio. It also performs Forward Error Correction and other
correction algorithms for overcoming channel errors and ACELP speech coding.
It carries out linear 16-bit analog to digital conversions, audio filtering, and level
amplification for the microphone audio input and the received audio output.
The power and audio section is based on the GCAP III and includes power sup-
plies, 13-bit CODEC, audio routing, microphone and ear piece amplifiers. A audio
power amplifier is used for the loud speaker.

Transmitter Path Description

The transmitter circuitry includes a linear class AB Power Amplifier (PA) for the
linear modulation of the
loop to enhance its transmitter linearity and reduced splattering power into adja-
cent channels.
MTH500
MTH500
. It also includes a novel cartesian feedback
uses a coding technique called
68P02963C70-O