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AIS

Applied Technology has been working on the Marine AIS system since the company was founded in 2002. Involvement includes active participation in the committees writing the international standards for AIS as well as product development for AIS Class A, Class B and ‘receive-only’ products. Applied Technology can offer a range of product design services including:

• Design of RF solutions compatible with the CMX910 /CMX7032 /CMX7042 for AIS
• AIS Antenna Splitter design for license
• Design solutions for DSC channel receivers
• Product design consultancy
• Consultancy on Base-stations and Aids-to-Navigation

A fast track solution for AIS Class B and AIS receive-only products is now available through our parent company CML Microcircuits. The DE70321 is a complete radio and baseband demonstrator for AIS processing. For Class B operation all that is needed is a simple host microcontroller (e.g. 80C51 class). For dual channel receive-only operation the DE70321 is a complete solution offering a NMEA 0183-HS interface to a PC serial port. An external GPS unit may also be connected for own position display. We believe that this CMX7032 based design offers comfortably the lowest cost solution in the world for AIS products.

The DE70321 design must be accessed through CML Microcircuits however Applied Technology offers design and development services for organisations looking to customise the DE70321 to specific product requirements.

For a real-time display of received data from a DE70321 located at our office near Shepton Mallet, UK click here . The display is updated every minute. Please note that Applied Technology is not ideally located for receiving AIS data but we usually receive some data from both the Bristol Channel area and south coast of Weymouth. The image is generated using Ship Plotter.

To complement the AIS receiver and transponder solutions Applied Technology offers the ATB011 antenna splitter design, which is available for license to OEM manufacturers. The design is field proven and provides safe operation with power removed form the unit.

The ATB011 design is licensed on a royalty basis giving access to the full design and PCB information. For further details on the ATB011 contact enquiries@app-tech.co.uk .

 For some general background on AIS read our briefing document.

DE70321 Solution 

The DE70321 is a third generation AIS design optimised for minimum cost while maintaining optimum performance. The BoM has been optimised for production with minimum number of component types and low-cost design solutions. All components are available off-the-shelf, no-specials and no custom programmed devices. All the intelligence in the design is provided by the CMX7032.

Low cost radio

The radio design use a truly minimum cost architecture. Low cost FM demodulator chips are used along with standard off-the-shelf filters meeting AIS Class B performance requirements. Excellent performance is achieved as the CMX7032 implements an advanced demodulator achieving the best possible co-channel performance for this type of architecture.

The transmitter is a classic two-point PLL design and thus comprises just a VCO, divider and power amplifier. This simple design avoids mixing spurious  and the cost of complex modulators such as fractional-n or I/Q techniques. The power amplifier is a low cost integrated type.

Low Power

The receiver circuits are optimised for a low power class B compliant performance. For a receive-only solution further power reduction is possible.

The design operates from a single +5V supply. In Rx only operation is may be configured to operate from a USB port on a PC.

Typical Results

Sensitivity at 162.025MHz: ‑112dBm (<20% PER)

Adjacent Channel Rejection (162.025MHz): 73dB (typical)

Tx Output power: +33dBm (2W)

Tx Mask: Compliant with IEC 61993-2 - AIS Class A (see plot).  

Glossary

AIS                           Automatic Identification System. Radio based system for tracking vessel position and other key information such as speed and heading

AIS Class A            Type of AIS Transponder used on large vessels

AIS Class B            Variant of AIS system designed to be lower cost and targeted at smaller vessels including leisure craft

AIS Transponder    Radio Transmitter/Receiver unit that performs the AIS functions.

A-to-N                      Aids to Navigation (e.g. Buoys)

COG                        Course over ground

CS-TDMA               Carrier Sense Time Division Multiple Access – system used in class B units instead of SoTDMA

DSC                        Digital Selective-Calling – Data signalling system used as the primary emergency channel for Marine applications

ECDIS                    Electronic chart display and information system

EPFS                      Electronic position fixing system

FATDMA                Fixed Access Time Division Multiple Access

IEC 61993              IEC Standard for AIS Class A

IEC 62287              IEC Standard for AIS Class B

IEC 62320              IEC Standard for Base-stations (AIS shore stations - Minimum operational and performance requirements - methods of test and required test results)

IMO                          International Maritime Organisation

ITU-R M1371          ITU-R Standard outlining the system parameters for AIS.

ITU-R M.493           ITU Standard for DSC

MMSI                       Maritime Mobile Service Identity

RATDMA                Random Access Time Division Multiple Access

SoTDMA                 Self-organising Time Division Multiple Access – is the signalling scheme used in all AIS class A transponders

VDL                        VHF Data Link