Specifications

Table Of Contents
INSTALLATION
Page 21 MRC-565 Packet Data Radio Operations and Maintenance
3.2.1 Communications Management Unit (CMU)
The CMU contains a Host Processor and a Software Defined Radio that contains a Digital Signal
Processor (DSP) . The Host processor is used to control the wire side protocols and interfaces as
well as the Over the Air protocols. The main microprocessor is a Motorola-based, embedded
processor located on a single PCB that contains:
8M x 16 of non-volatile flash memory for program storage
8M x 16 of non-volatile flash memory for parameter storage
32M x 16 of low power dynamic RAM for data storage
3 External RS-232 I/O ports
Ethernet Adaptor
USB-B Device Port for connecting MNT port Laptop
Internal TTL GNSS Daughter board mounted onto CMU .
Transmitter communication port
12-bit 16 channel A/D converter (6 channels are available for external sensors)
Real-time clock (w or w/o an internal battery)
Power fail detection circuitry
Digital Signal Processor with D/A converters
4 Optically isolated digital inputs
2 Solid State SPST Relay Outputs with a current rating of .5 amps
All I/O ports are RS 232 compatible (+/- 5V) and can be programmed to adapt to various
customer protocols. The DATA port contains full flow control hardware lines. The A/D
converter measures TX forward and reverse power, battery voltage, antenna noise voltage,
transmitter board temperature, and 6 channels of 0-5V external sensor inputs.
A Digital Signal Processor (DSP), a Field Programmable Gate Array (FPGA), a D/A converter,
and a A/D converter form the Software Designed Radio. The DSP is composed of a receiver
portion and a transmitter portion. The receiver RF signal is amplified and routed to the A/D
converter used to digitize the RF signal at the RF frequency. The FPGA provides a digital down
conversion (DDC) of the digital RF signal. The converted signals are fed to the DSP for
demodulation of the BPSK or GMSK signal.
The transmitter portion is implemented with an AD 9957 Quadrature Digital Upconverter
(QDUC). The AD9957 functions as a universal I/Q modulator and agile Upconverter. The
AD9957 integrates a high speed, direct digital synthesizer (DDS), a high performance, high
speed, 14-bit digital-to-analog converter (DAC), clock multiplier circuitry, digital filters, and
other DSP functions onto a single chip. It provides baseband up-conversion for data transmission
in the Low Band VHF band. The RF output ( 0 DBM) is routed to the Power Amplifier (PA), via
a short coax cable.