Short-range ultrasonic digital communications in air

The use of ultrasound in air as a means of communicating digital signals is demonstrated. The work uses capacitive transducers with a useful bandwidth to transmit digitally coded signals across an air gap in the laboratory, using three of the common methods used in digital communications. These are on-off keying (OOK), binary frequency-shift keying (BFSK), and binary phase shift keying (BPSK). All three methods are simulated numerically using the available bandwidth of the transducer systems and are compared to results obtained experimentally. It is demonstrated that BPSK can be used to transmit signals with a low bit error rate.