An Improved Design of Automatic-Identification-System-Based Man Overboard Device: A Multidisciplinary Product
In this paper, the improved design of a small automatic-identification-system (AIS) based man overboard (MOB) device is described. The device is one of the state-of-the-art maritime vehicular technologies and has been widely used in marine vehicles for search and rescue (SAR) purposes. Similar devices have been available in the market for years; however, the design methodology and hardware circuitries have never been exposed in literature. This paper first reviews the basic principles of Gaussian minimum-shift keying modulation and the direct digital frequency synthesis technique. Second, the design methodology and hardware implementation of subsystems of the device with design objectives in effective SAR are presented. Finally, a prototype of the AIS MOB was fabricated and fully tested. The experimental results demonstrate that the emitted signal spectrum meets the AIS standards. The fabricated prototype has a minimum effective range of five nautical miles with a battery life of 36 h under continuous operation. This AIS MOB device is a multidisciplinary design product. The described work comprises of active antenna design, the microcontroller-based AIS control circuit design, the global positioning system circuit design, and the implementation of Gaussian minimum-shift keying modulation.