Ultrasonic wireless communication using capacitive micromachined ultrasonic transducers in liquid with OOK digital modulation

The modulation scheme of ultrasonic communication using capacitive micromachined ultrasonic transducers, acting as the transmitted port and received port, was simulated and experimented with four parallel channels in silicone oil. Four channel signals were coded by a steady and reliable binary amplitude shift keying method such as on-off keying modulation. The modulation scheme was simulated with additive Gaussian noise and attenuated for every channel in silicone oil, and the sound attenuation influence was evaluated with different distances. The capacitive micromachined ultrasonic transducers were measured to achieve a -6 dB bandwidth of 305 kHz when operating in silicone oil. The channels were operated at different frequencies ranging from 300 kHz to 600 kHz with a channel spacing of 100 kHz. The bit rate of 50 kbps for one channel was achieved with a data rate of 200 kbps over a short-range distance of 0.1 m. The proposed correction coefficient could be used to adjust the threshold. The high overall signal-to-noise ratio of 29.41 dB ensured the system to have a low-level bit error rate.