Mini-sonar---A Miniaturized Sector Scanning Sonar

Use of small submersibles has increased in recent years. A vehicle that is simply a swimming TV camera can be made quite small, but its utility is limited because of its limited view of its surroundings. The mini-sonar program was started at NOSC to develop a small sector scanning sonar for use on small vehicles without affecting their bulk. A scan-within-a-pulse type sonar was selected. Design range is 100 yards, operating frequency 300kHz, sector 80 , beamwidth 4 , and size 9 × 5 × 4 inches. An added constraint is use of pressure tolerant electronics. The largest contributing factor to meeting all these design requirements was a unique beamformer. This beamformer uses sine and cosine weighted resistors rather than a delay and sum technique. Also, by electrically switching the receiving array end for end, the required number of beam- formers is halved. This paper discusses the design of this sonar, concentrating on the beamformer.