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@article{Syms:2022:1361-665X/ac8385,
author = {Syms, R and Noorwali, A},
doi = {1361-665X/ac8385},
journal = {Smart Materials and Structures},
title = {Polyphase codes for multiplexed acoustic signalling and sensing on pipes},
url = {http://dx.doi.org/10.1088/1361-665X/ac8385},
volume = {31},
year = {2022}
}

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TY - JOUR
AB - Transmission of acoustic signals between distributed sensor nodes may be useful for status monitoring of elongated structures such as pipelines. In principle, coded signals can be used in an asynchronous multiplexed system, provided the signals are distinguishable. However, multimode effects complicate signal propagation, so any such codes should be short. A search for polyphase code families with properties suitable for acoustic code division multiple access is presented. Algorithms for reduction of search space to allow use of a laptop for code discovery are described. Short codes of base 6 are shown to outperform codes of bases 2, 3, 4 and sets suitable for systems with 2 and 3 users are identified. The codes have similar properties to Barker codes but larger sidelobes. Their use is demonstrated by simulation and experiment at kHz frequencies using an air-filled copper pipe, an electromagnetic acoustic transducer (EMAT) and a microphone designed to excite and detect the $L\left( {0,1} \right)$ mode. Low loss propagation over 25 m is achieved with a 20 kHz carrier. Excellent agreement between experiment and theory is demonstrated, with performance limited by transducer bandwidth.
AU - Syms,R
AU - Noorwali,A
DO - 1361-665X/ac8385
PY - 2022///
SN - 0964-1726
TI - Polyphase codes for multiplexed acoustic signalling and sensing on pipes
T2 - Smart Materials and Structures
UR - http://dx.doi.org/10.1088/1361-665X/ac8385
UR - http://hdl.handle.net/10044/1/98456
VL - 31
ER -

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