ABSTRACT
This chapter describes the design of a short-range underwater acoustic modem starting with the most critical component from a cost perspective—the transducer. The transducer is a device that converts electrical energy to/from acoustic energy, which is equivalent to the antenna in radios. The chapter also describes the modem’s transducer design, followed by its analog transceiver design and digital transceiver design. It discusses the selection of the transducer’s piezoceramic material based on its type and geometry. For underwater communication, ceramics are usually omnidirectional in the horizontal plane to reduce reflection off the surface and bottom. Although the piezoelectric element is a key component of the transducer, there are other aspects to manufacturing a transducer that are important to its performance. The chapter concludes by describing real-world tests performed on the complete low-cost modem design which illustrate the modem provides bit rates of up to 200 bps for ranges up to 400 m at a components cost of U. S. $350.
