Binary Coded Pulse Compression and its Application to Ultrasonics

D. M. J. Cowell and S. Freear

Institute of Integrated Information Systems (I3S), School of Electronic and Electrical Engineering, Faculty of Engineering, University of Leeds, Leeds, LS2 9JT, United Kingdom

Email: d.m.j.cowell@leeds.ac.uk

ABSTRACT

Industrial applications of ultrasound require large excitation energies as often the materials encountered are highly attenuating and the path lengths large. Simple pulsed excitation is often unable to provide power levels sufficient to enable successful measurements to be made, but inherently provides good positional information. Continuous wave (CW) excitation has a high power spectrum but contains no positional information. We have previously reported the use of low voltage analogue linear frequency modulated (LFM) excitation as a method of increasing the power spectrum without sacrificing positional information when combined with a pulse compression filter. In this paper we present a method for further increasing the excitation energy through the use of high voltage binary coded excitation sequences whilst retaining positional accuracy through the use of complementary Golay codes combined with compression filters. An explanation of the coding theory is presented along with simulated results.

Keywords Non-invasive, ultrasound, binary coded, pulse compression, spread spectrum