Ultrasonic Communications Through a Reinforced Concrete Column

Measurements were obtained by sending high frequency acoustic waves through a reinforced concrete column. Past work involved through-wall digital communications and power delivery through metallic barriers; this paper extends that work to a reinforced concrete column. A pair of 35 mm diameter circular transducers with a thickness of 10 mm (corresponding to a resonance of 200 kHz) were epoxied to opposite sides of a 0.7 m thick reinforced concrete column. A vector network analyzer (VNA) obtained the characteristics of the acoustic channel formed between the two sensors. A voltage transfer function for this channel was found in the range of 30 kHz – 150 kHz. Although this transfer function shows a significant amount of frequency selectivity, i.e. variation with frequency, resulting from the multipath created by the acoustic energy interacting with the complex structure of column (rebar, aggregate, voids) and its surfaces, the channel is seen to be capable of supporting data transmission. The magnitude of the transfer function is seen to be highest in the region 40 kHz – 70 kHz with its theoretical capacity to be approximately 400 kbits/s for a received signal-to-noise ratio (SNR) of 60 dB. Lower SNR’s would still be able to provide data rates well in excess of 50 kbits/s, permitting the passing of low frequency data across the concrete column.Copyright © 2016 by ASME