Low-rate ultrasonic communication axially along a cylindrical pipe

Single layered acoustic-electric channels have been used in the recent past to send power and data through metallic barriers. Multi-layered acoustic-electric channels, as well as those formed along a structure, which are highly attenuative and non-reverberant, could have potential applications in aerospace, nuclear, and oil industries, among others. This work considers data transmission along the length of a cylindrical pipe both when in air and when filled and immersed in water. To combat the effects of frequency selectivity and address the available power constraints, a simple modulation scheme using non-coherent demodulation is employed for data transmission-Chirp-On-Off Keying (Chirp-OOK). The wideband nature of the chirp waveform provides resilience against nulls in the channel response while making it possible to implement a simple non-coherent detector. A test data link is assembled using an arbitrary waveform signal generator to generate the chirp signal which is then applied to the transmit transducer, a demodulator circuit followed by a computer controlled digitizer is used to capture the signal from the receive transducer, and final processing and bit-decoding are done via the computer. Successful data transmission is achieved across the 4.8 m length of pipe (in air and water) for a data rate of 100 bps using less than 10 mW of transmit power. Monte-Carlo simulation results suggest that the bit error rate performance of the scheme matches quite closely with the theoretical results.