CONEL CDA 70 [5/43] Cda70 modem description

CDA70 MODEM DESCRIPTION

2. Description of the CDA70 radio modem

2.1. General

The CDA70 radio modem is a device for wireless data transmission. Communication

between two radio modems is a simplex one and is carried out on a single frequency. Modems

work in frequency band of 143 to 174 MHz (CDA70V) and 403 to 470 MHz (CDA70U).

Transmission rate is 21.7 kbit/sec when using the FFSK modulation and channel spacing 20

and 25 kHz or 10.8 kbit/sec when using channel spacing 12.5 kHz. Transmission rate is 10.8

kbit/sec when using the GMSK modulation and channel spacing 20 and 25 kHz or 5.4 kbit/sec

when using channel spacing 12.5 kHz. Transmission power output of the radio modem is

adjustable from 10 mW to 3 W for CDA70V and from 10 mW to 5 W for CDA70U.

The CDA70 radio data modem is controlled by a 32-bit communication processor

providing communication on the radio channel and individual interfaces. The CDA70 modem

has four serial data interfaces (communication ports) and one with direct attachment

of input/output peripherals for data collection and CIO technological process control. It is

possible to set transfer parameters and communication protocol separately for each port.

As a result, you may use the radio modem to communicate with various user interfaces using

different communication protocols on the serial interface.

The communication protocol used for communication between modems on the radio

channel provides for access of the modem to the radio channel, collision solving,

retranslations and other functions necessary for cooperation of modems within a radio data

network. It allows creating of a large network on a single radio channel and independent

operation of multiple radio networks on a single frequency. The radio data modem CDA-70 is

possible to use in combination with other modems of the system AGNES. Description

of the system AGNES is in reference [2].

2.2. Examples of possible applications

• Security systems

• Telematics

• Telemetry

• Vending and dispenser machines

2.3. Description of individual components

2.3.1. Radio component

Working frequency of the radio component is synthetizer-controlled separately for

reception and transmission. It is tuneable within a broad frequency band (see Technical

parameters table). Several levels of the radio module transmitter power output can be set

(from 10 mW to 5 W). The controlling microcomputer program controls setting of the working

frequency and transmitting power output. The radio module supplies the microcomputer

with information on the radio signal level being received (RSSI – Received Signal Strength

Indicator). This information is used for measuring of the signal strength between individual

nodes of the radio network.