2.1.2.1
Digital Section
The digital section is based on a Dual Core System On a Chip (SoC) processor. It consists of a low-power
Advanced RISC Machine (ARM) application core and Digital Signal Processor (DSP) core with floating point.
This section also has a coprocessor that does keypad scanning and several input or output (IO) interfaces.
The dual-core architecture of the Dual Core Processor SoC provides benefits of both DSP and Reduced
Instruction Set Computing (RISC) technologies.
The 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 Algebraic Code Excited Linear
Prediction (ACELP) speech coding. The DSP carries the following function:
● linear 16-bit analog to digital conversions
● audio filtering
● level amplification for the microphone audio input and the received audio output
2.1.2.2
Transmitter Path
The transmitter circuitry includes a linear class AB Power Amplifier (PA) for the TETRA linear modulation of
the terminal. It includes a Cartesian Loop to enhance its transmitter linearity and reduce splattering power
into adjacent channels.
The transmitter path consists of a Cartesian Loop that contains forward and feedback paths. The forward
path includes the following items.
● Tx Power Control Integrated Circuit
● Balanced-Unbalanced Converter (BALUN)
● Forward Attenuator
● Power Amplifier
● Directional Coupler
The loop feedback path includes the following items.
● Directional Coupler
● Feedback Attenuator
● BALUN
● Tx Power Control Integrated Circuit
The Cartesian Loop output power passes to the antenna through the Antenna Switch, Harmonic Filter, and
Diplexer.
2.1.2.3
Receiver Path
The receiver section in the radio is based on the DCR (Direct Conversion) technology. The main concept of
this technology is down converting of the RF signal directly into a base band signal, skipping the intermediate
stage of IF signal.
The receiver path includes the following items.
● Diplexer
● Antenna Switch
68015000841-EL
Chapter 2: Overview
35
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