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Keywords = kasami sequences

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17 pages, 11116 KiB  
Article
Research on Coded Excitation Using Kasami Sequence in the Long Rail Detection Based on UGW
by Wenqing Yao, Yuan Yang and Xiaoyuan Wei
Electronics 2022, 11(9), 1465; https://doi.org/10.3390/electronics11091465 - 3 May 2022
Cited by 2 | Viewed by 1662
Abstract
For a broken rail detection system based on ultrasonic guided waves (UGW), the multimodal and dispersion characteristics of UGW degrade signal-to-noise ratio (SNR) and range resolution. To improve the SNR of the received signals and range resolution, the coded excitation based on Kasami [...] Read more.
For a broken rail detection system based on ultrasonic guided waves (UGW), the multimodal and dispersion characteristics of UGW degrade signal-to-noise ratio (SNR) and range resolution. To improve the SNR of the received signals and range resolution, the coded excitation based on Kasami sequences is presented in this work. Utilizing a PSpice model of piezoelectric ultrasonic transducers, as well as conducting field tests based on the pitch–catch mechanism, it is shown that encoded UGW signals can increase the SNRG (the gain of SNR) by 6.29 dB. The main lobe width of the coded excitation is mainly determined by the number of carrier cycles and the carrier waveform, and the size of the side lobes is mainly determined by the number of coding bits. To quickly identify the corresponding transmissions at the receivers, a peak detection algorithm is shown. It is based on bandpass filter, triangle filter and Hilbert transform. Its accuracy and effectiveness are validated by using some field tests under different distances. It can be concluded that the shown adaptive peak algorithm has strong robustness and immunity to noise. Full article
(This article belongs to the Section Circuit and Signal Processing)
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21 pages, 1066 KiB  
Communication
Study of the Performance of DSSS UAC System Depending on the System Bandwidth and the Spreading Sequence
by Iwona Kochanska, Roman Salamon, Jan H. Schmidt and Aleksander M. Schmidt
Sensors 2021, 21(7), 2484; https://doi.org/10.3390/s21072484 - 2 Apr 2021
Cited by 11 | Viewed by 2443
Abstract
A signal transmitted in an Underwater Acoustic Communication (UAC) system operating in a shallow-water channel suffers from strong time dispersion due to multipath propagation. This causes the Inter-Symbol Interference (ISI) observed in the received signal, which significantly limits the communication system’s reliability and [...] Read more.
A signal transmitted in an Underwater Acoustic Communication (UAC) system operating in a shallow-water channel suffers from strong time dispersion due to multipath propagation. This causes the Inter-Symbol Interference (ISI) observed in the received signal, which significantly limits the communication system’s reliability and transmission rate. In such propagation conditions, the Direct-Sequence Spread Spectrum (DSSS) method is one of the solutions that make reliable data transmission possible. In systems with one-to-one communication, it ensures communication with a satisfactory Bit Error Rate (BER). Additionally, it makes it possible to implement the Code-Division Multiple Access (CDMA) protocol in underwater acoustic networks. This paper presents the results of simulation and experimental communication tests on a DSSS-based UAC system using three types of spreading sequence, namely m-sequences, Kasami codes and Gold codes, and occupying different bandwidths from 1 kHz to 8 kHz around a carrier frequency equal to 30 kHz. The UAC channel was simulated by impulse responses calculated by the virtual sources method and the UAC chanel models available in the Watermark simulator. The experimental tests were conducted in a model pool. Based on the obtained results, a transmission rate was estimated, which is possible to achieve in strong multipath propagation conditions, assuming reliability expressed as BER less than 0.001. Full article
(This article belongs to the Special Issue Underwater Wireless Sensor Networks)
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5238 KiB  
Article
Analysis of Doppler Effect on the Pulse Compression of Different Codes Emitted by an Ultrasonic LPS
by José A. Paredes, Teodoro Aguilera, Fernando J. Álvarez, Jesús Lozano and Jorge Morera
Sensors 2011, 11(11), 10765-10784; https://doi.org/10.3390/s111110765 - 15 Nov 2011
Cited by 27 | Viewed by 7853
Abstract
This work analyses the effect of the receiver movement on the detection by pulse compression of different families of codes characterizing the emissions of an Ultrasonic Local Positioning System. Three families of codes have been compared: Kasami, Complementary Sets of Sequences and Loosely [...] Read more.
This work analyses the effect of the receiver movement on the detection by pulse compression of different families of codes characterizing the emissions of an Ultrasonic Local Positioning System. Three families of codes have been compared: Kasami, Complementary Sets of Sequences and Loosely Synchronous, considering in all cases three different lengths close to 64, 256 and 1,024 bits. This comparison is first carried out by using a system model in order to obtain a set of results that are then experimentally validated with the help of an electric slider that provides radial speeds up to 2 m/s. The performance of the codes under analysis has been characterized by means of the auto-correlation and cross-correlation bounds. The results derived from this study should be of interest to anyone performing matched filtering of ultrasonic signals with a moving emitter/receiver. Full article
(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)
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661 KiB  
Article
Measuring Time-of-Flight in an Ultrasonic LPS System Using Generalized Cross-Correlation
by José Manuel Villladangos, Jesús Ureña, Juan Jesús García, Manuel Mazo, Álvaro Hernández, Ana Jiménez, Daniel Ruíz and Carlos De Marziani
Sensors 2011, 11(11), 10326-10342; https://doi.org/10.3390/s111110326 - 31 Oct 2011
Cited by 28 | Viewed by 10020
Abstract
In this article, a time-of-flight detection technique in the frequency domain is described for an ultrasonic Local Positioning System (LPS) based on encoded beacons. Beacon transmissions have been synchronized and become simultaneous by means of the DS-CDMA (Direct-Sequence Code Division Multiple Access) technique. [...] Read more.
In this article, a time-of-flight detection technique in the frequency domain is described for an ultrasonic Local Positioning System (LPS) based on encoded beacons. Beacon transmissions have been synchronized and become simultaneous by means of the DS-CDMA (Direct-Sequence Code Division Multiple Access) technique. Every beacon has been associated to a 255-bit Kasami code. The detection of signal arrival instant at the receiver, from which the distance to each beacon can be obtained, is based on the application of the Generalized Cross-Correlation (GCC), by using the cross-spectral density between the received signal and the sequence to be detected. Prior filtering to enhance the frequency components around the carrier frequency (40 kHz) has improved estimations when obtaining the correlation function maximum, which implies an improvement in distance measurement precision. Positioning has been achieved by using hyperbolic trilateration, based on the Time Differences of Arrival (TDOA) between a reference beacon and the others. Full article
(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)
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