Description; Transceiver Description; Digital Section Description; Transmitter Path Description - Motorola MTP850 S Service Manual

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at an acceptable quality level. The terminal uses a coding technique called
ACELP (Algebraic Code Excited Linear Prediction). The compressed voice-data
bits modulate the RF signal.

Description

Transceiver Description

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 Patriot IC that consists of the MCORE RISC
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) performs modulation and de-modulation
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 PCAP and includes power supplies,
13-bit CODEC, audio routing, microphone and earpiece amplifiers. PCAP audio
power amplifier is used for the loudspeaker.

Transmitter Path Description

The transmitter circuitry includes a linear class AB Power Amplifier (PA) for the
linear modulation of the terminal. It includes a Cartesian Loop to enhance its
transmitter linearity and reduced splattering power into adjacent channels.
The transmitter path consists of a Cartesian Loop that contains the forward and
feedback paths. The forward path includes the JAVELIN IC, BALUN, Attenuator,
and Power Amplifier and Isolator (the Isolator is used in the 800 MHz band only).
The Loop feedback path includes the directional coupler, attenuator, BALUN, and
JAVELIN IC.
MTP850 TETRA Handportable Terminal / Basic Service Manual OVERVIEW