Chapter 2 General Overview
2.1 Introduction
The ASTRO Digital Spectra radio is a dual-mode (trunked/conventional), microcontroller-based
transceiver incorporating a Digital Signal Processor (DSP). The microcontroller handles the general
radio control, monitors status, and processes commands input from the keypad or other user
controls. The DSP processes the typical analog signals and generates the standard signaling
digitally to provide compatibility with existing analog systems. In addition it provides for digital
modulation techniques utilizing voice encoding techniques with error correction schemes to provide
the user with enhanced range and audio quality all in a reduced bandwidth channel requirement. It
allows embedded signaling which can mix system information and data with digital voice to add the
capability of supporting a multitude of system features.
The ASTRO Digital Spectra radio comes in five models and are available in the following bands:
VHF (136–174 MHz), UHF (403–470 MHz or 450–512 MHz), and 800 MHz (806–870 MHz).
The ASTRO Digital Spectra radio comprises seven major assemblies, six of which are in the main
radio housing. They are:
• Control-Head Assembly (Dash- or Remote-Mount) – is connected, directly or remotely, to the
front of the transceiver by the interconnect board or remote interconnect board and control
cable. This assembly contains a vacuum fluorescent (VF) display, VF driver, microprocessor
and serial bus interface.
• Power Amplifier (PA) – contains antenna switch, directional coupler/detector, and amplifier(s).
• Front-End Receiver Assembly – contains pre-amplifier, preselector, mixer, and injection filter.
• RF Board – contains receiver I-F amplifier, demodulator, synthesizer logic and filtering circuitry,
and digital receiver back-end integrated circuit (IC).
• VCO/Buffer/Divider Board – contains voltage controlled oscillator (VCO), divider, receive and
transmit buffers.
• Command Board – contains power control/regulator, digital-to-analog (D/A) IC, serial bus
interface, and audio power amplifier (PA).
• VOCON (Vocoder/Controller) Board – contains the microcomputer unit (MCU), its associated
memory and memory management integrated circuit, and the digital signal processor (DSP)
and its associated memories and support IC.
• VOCON Plus (Vocoder/Controller) Board – the architecture is based on a Dual-Core processor,
which contains a DSP Core, an MCORE 210 Microcontroller Core, and custom peripherals.
The board also contains memory ICs and DSP support ICs.
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General