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Coded excitation for pulse-echo systems

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Title: Coded excitation for pulse-echo systems
Authors: Isla, J
Cegla, FB
Item Type: Journal Article
Abstract: Pulse compression has been used for decades in radar, sonar, medical, and industrial ultrasound. It consists in transmitting a modulated or coded excitation, which is then cross-correlated with the received signal such that received echoes are time compressed, thereby increasing their intensity and hence the system resolution and signal-to-noise ratio (SNR). A central problem in pulse-echo systems is that while longer coded excitations yield higher SNRs, the length of the coded excitation or sequence is limited by the distance between the closest reflector and the transmitter/receiver. In this paper, a new approach to coded excitation is presented whereby receive intervals or pauses are introduced within the excitation itself; reception takes place in these intervals. As a result, the code length is no longer limited by the distance to the closest reflector and a higher SNR increase can be realized. Moreover, the excitation can be coded in such a way that continuous transmission becomes possible, which reduces the overall duration of the system response to changes in the medium. The optimal distribution of the receive intervals within the excitation is discussed, and an example of its application in industrial ultrasound is presented. The example consists of an electromagnetic-acoustic transducer driven with 4.5 V, where a clear signal can be obtained in quasi-real-time (e.g., ~9-Hz refresh rate), while commercially available systems require 1200 V for a similar performance.
Issue Date: 1-Apr-2017
Date of Acceptance: 24-Jan-2017
URI: http://hdl.handle.net/10044/1/44235
DOI: 10.1109/TUFFC.2017.2661383
ISSN: 0885-3010
Publisher: Institute of Electrical and Electronics Engineers
Start Page: 736
End Page: 748
Journal / Book Title: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Volume: 64
Issue: 4
Copyright Statement:  © 2017 The Authors. This work is licensed under a Creative Commons Attribution 3.0 License. For more information, see http://creativecommons.org/licenses/by/3.0/
Sponsor/Funder: Engineering & Physical Science Research Council (EPSRC)
Funder's Grant Number: EP/K033565/1
Keywords: Science & Technology
Technology
Acoustics
Engineering, Electrical & Electronic
Engineering
Binary codes
electromechanical sensors
signalto-noise ratio (SNR)
ultrasonic transducers
ULTRASONIC GUIDED-WAVES
BINARY SEQUENCES
MERIT FACTOR
ACOUSTIC TRANSDUCERS
EFFICIENT GENERATION
MEDICAL ULTRASOUND
COMPLEMENTARY SETS
CORRELATION BOUNDS
COMPRESSION
OPTIMIZATION
Acoustics
02 Physical Sciences
09 Engineering
Publication Status: Published
Online Publication Date: 2017-01-30
Appears in Collections:Mechanical Engineering
Faculty of Engineering