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Improving safety at sea – New Advanced Man Overboard baseband modem solution

20 January 2021

CML Microcircuits Ltd, a global supplier of Marine Wireless Data solutions has recently released a new solution that increases the functionality of Maritime Survival Locating Systems (“Man overboard devices”) whilst enabling small form factor solutions to still be maintained.

Traditionally Man Overboard location solutions have operated using just a single AIS (Automatic Identification System) transmission or supplemented with an additional DSC (Digital Selective Calling) transmission, sending GPS location information to alert vessels nearby to an incident with a person in the water.

The CML solution supports both of these modes, integrating a 9600bps GMSK modulator for AIS signalling and 1200bps FFSK transmitter for DSC.  They share a common transmit path, using 2 point VCO modulation.  Signals are generated accurately by on chip digital to analogue converters and programmable gain stages are included that enable electronic trimming of the modulator during manufacturing to take in to account component variations in the VCO.  The transmit chain also incorporates a power amplifier ramping DAC to ensure spurious emissions are minimized.

Standardization bodies such as the IEC are currently revising regulations (IEC 63269) and so in addition to supporting both AIS and DSC transmission DSC reception will be required.  In response this new solution from CML Microcircuits also adds a high performance DSC receive channel to the CMX7341, integrating a 1200baud FFSK receiver supporting a direct conversion receiver architecture and employing digital signal processing for accurate and fast signal demodulation.

The receiver meet EN 301 025 DSC receiver requirements for sensitivity, blocking, co channel interference and intermodulation.

The CMX7341 interfaces to the system controller via CML’s SPI compatible C-BUS interface and an additional low power ADC is available for monitoring and testing battery voltage, etc.

The CML solutions utilises the company’s FirmASIC® approach by which its CMX7341 baseband processor is configured by downloading a small configuration file known as a Function Image™, downloadable free of charge from CML Microcircuits Technical Portal.  Function Image FI-6 provides the AIS/DSC MOB functionality (other Function Images allow the same device to be configured to support multiple analog and digital PMR radio standards).

When combined with other CML RF devices, the CMX994A Direct conversion receiver and CMX902 2W VHF/UHF power amplifier together with a low cost microcontroller, a compact palm sized Man Overboard device can be designed.

The CMX7341 baseband processor has been in the mass production for a number of years and the configuration Function Image™ supporting the DSC Man Overboard functionality will be available from January 2021.

Visit the CMX7241/7341 Marine Common Platform Processor product page for further information.

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