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General Overview of an
ASTRO Digital SABER Radio 3
The ASTRO Digital SABER 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 SABER radio is available in three models, which are
available in the following bands; VHF (136-174MHz), UHF (403-
470MHz or 450-512MHz), and 800MHz (806-870MHz).
The ASTRO Digital SABER radio consists of:
• Vocoder/Controller (VOCON) Board
• Band-Dependent Transceiver Board
• Display/Keypad Assembly
• In secure models, a hardware, encryption module is also included.
It is advantageous to think of the vocoder/controller (VOCON) board
as two separate functional units; a vocoder and a controller. The
vocoder section consists of a Digital Signal Processor (DSP), Static-RAM
(SRAM), FLASH program memory, audio power amplifier (audio PA),
and a custom ABACUS/DSP support integrated circuit (ADSIC). This
section handles all the analog and signaling functions previously
accomplished with analog integrated circuits (ICs) by processing the
signals digitally. In addition, it provides advanced digital signal
processing functions which include digital modulation and voice
encoding techniques while still maintaining compatibility with
today’s analog radio systems. The controller section consists of a
microcontroller with FLASH program memory, EEPROM, SRAM, and a
custom IC; the SLIC. This section handles general radio control and
ergonomics through the various user buttons, and rotary knobs.
The transceiver is frequency dependent, and one transceiver exists for
each of the bands; VHF, UHF (range 1 and 2), and 800MHz. The
distinction with these transceivers is the incorporation of the ABACUS
IC. The ABACUS is a digital IF/Discriminator which provides a true
digital interface to the digital circuitry of the vocoder.
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