FPGA Based Acoustic Modem for Underwater Communication

Abstract

The underwater communication modem is based on ultrasound a sensor which gives efficient result underwater applications. System performs Amplitude shift Key (ASK) also known as On-Off Shift Key (OOK) at the transmitter part and this signal is demodulated at receiver point with audio amplifier and diode detector. ASK modulation is the simplest type of digital modulation technique. In this carrier signal is getting modulated with baseband signal so for positive signal it gives level ‘1’ and at negative signal it gives level 0. This design uses commercial ultrasound transducer of 200 kHz bandwidth. The underwater channel is highly variable; each point can have changes in signal, which change according to environmental factors as well as the locations of the communicating nodes. So distance vs. voltage of the received signal is measured. It is observed that voltage decreases with increasing distance.