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Keywords = Kasami codes

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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 1698
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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Figure 1

Figure 1
<p>Structure diagram of an SPUT in longitudinal vibration.</p> Full article ">Figure 2
<p>PSpice model of an SPUT in longitudinal vibration.</p> Full article ">Figure 3
<p>Kasami sequence analysis of ACF and CCF, (<b>a</b>) one 63−bit Kasami sequence, (<b>b</b>) the other 63−bit Kasami sequence, (<b>c</b>,<b>d</b>) the corresponding ACF and CCF.</p> Full article ">Figure 4
<p>Comparison analysis of single pulse and Kasami sequence encoding excitation, (<b>a</b>) vibration signal under single pulse, (<b>b</b>) vibration signal under Kasami sequence encoding, (<b>c</b>,<b>d</b>) normalized waveform and envelope.</p> Full article ">Figure 4 Cont.
<p>Comparison analysis of single pulse and Kasami sequence encoding excitation, (<b>a</b>) vibration signal under single pulse, (<b>b</b>) vibration signal under Kasami sequence encoding, (<b>c</b>,<b>d</b>) normalized waveform and envelope.</p> Full article ">Figure 5
<p>ACF envelopes analysis of Kasami sequences, (<b>a</b>,<b>b</b>) comparing the effect of different bits on ACF envelopes, (<b>c</b>,<b>d</b>) comparing the effect of different cycles on ACF envelopes, (<b>e</b>,<b>f</b>) comparing the effect of different carrier waveform.</p> Full article ">Figure 5 Cont.
<p>ACF envelopes analysis of Kasami sequences, (<b>a</b>,<b>b</b>) comparing the effect of different bits on ACF envelopes, (<b>c</b>,<b>d</b>) comparing the effect of different cycles on ACF envelopes, (<b>e</b>,<b>f</b>) comparing the effect of different carrier waveform.</p> Full article ">Figure 6
<p>Field test diagram of encoding excitation.</p> Full article ">Figure 7
<p>Results analysis of encoding excitation by 15−bit Kasami sequence under different carrier cycles, (<b>a</b>–<b>d</b>) the corresponding received signals, (<b>e</b>–<b>h</b>) the decoding results.</p> Full article ">Figure 8
<p>Results analysis of encoding excitation by 63−bit Kasami sequence under different carrier cycles, (<b>a</b>–<b>d</b>) the corresponding received signals, (<b>e</b>–<b>h</b>) the corresponding decoding results.</p> Full article ">Figure 8 Cont.
<p>Results analysis of encoding excitation by 63−bit Kasami sequence under different carrier cycles, (<b>a</b>–<b>d</b>) the corresponding received signals, (<b>e</b>–<b>h</b>) the corresponding decoding results.</p> Full article ">Figure 9
<p>The effect analysis of carrier cycles on the amplitude of received signals and MLW, (<b>a</b>) 15-bit amplitude, (<b>b</b>) 15−bit MLW, (<b>c</b>) 63−bit amplitude, (<b>d</b>) 63−bit MLW, (<b>e</b>) 15−bit PSL, (<b>f</b>) 63−bit PSL.</p> Full article ">Figure 9 Cont.
<p>The effect analysis of carrier cycles on the amplitude of received signals and MLW, (<b>a</b>) 15-bit amplitude, (<b>b</b>) 15−bit MLW, (<b>c</b>) 63−bit amplitude, (<b>d</b>) 63−bit MLW, (<b>e</b>) 15−bit PSL, (<b>f</b>) 63−bit PSL.</p> Full article ">Figure 10
<p>The received signals under encoding excitation by 63−bit Kasami sequence, (<b>a</b>) the received signal under test distance equaling 100 m, (<b>b</b>,<b>c</b>) the corresponding time frequency analysis results, (<b>d</b>) the received signal under test distance equaling 200 m, (<b>e</b>,<b>f</b>) the corresponding time frequency analysis results.</p> Full article ">Figure 11
<p>Peaks detection logic.</p> Full article ">Figure 12
<p>Peak detection algorithm flow.</p> Full article ">Figure 13
<p>Peak detection of the received signals under different test distances, (<b>a</b>) bandpass filtered signal under test distance equaling 100 m, (<b>b</b>) the corresponding square transformed signal, (<b>c</b>) the corresponding envelope, (<b>d</b>) peaks detection results, (<b>e</b>) bandpass filtered signal under test distance equaling 200 m, (<b>f</b>) the corresponding square transformed signal, (<b>g</b>) the corresponding envelope, (<b>h</b>) peaks detection results.</p> Full article ">Figure 13 Cont.
<p>Peak detection of the received signals under different test distances, (<b>a</b>) bandpass filtered signal under test distance equaling 100 m, (<b>b</b>) the corresponding square transformed signal, (<b>c</b>) the corresponding envelope, (<b>d</b>) peaks detection results, (<b>e</b>) bandpass filtered signal under test distance equaling 200 m, (<b>f</b>) the corresponding square transformed signal, (<b>g</b>) the corresponding envelope, (<b>h</b>) peaks detection results.</p> Full article ">Figure 14
<p>The analysis of peak detection under Gaussian noise, (<b>a</b>) SNR = −20 dB, (<b>b</b>) peaks detection.</p> Full article ">Figure 15
<p>The analysis of peak detection time under test distance equaling to 100 m, (<b>a</b>) encoded excitation decoding, (<b>b</b>) peak detection.</p> Full article ">Figure 15 Cont.
<p>The analysis of peak detection time under test distance equaling to 100 m, (<b>a</b>) encoded excitation decoding, (<b>b</b>) peak detection.</p> Full article ">
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 2510
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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Figure 1

Figure 1
<p>Modulator (<b>a</b>) and demodulator (<b>b</b>) block schemes of the DSSS UAC system.</p> Full article ">Figure 2
<p>Real parts of exemplary signals at the output of a filter matched to m-sequence of rank 8 (<b>a</b>) and Kasami code of rank 8 (<b>b</b>); B = 1 kHz.</p> Full article ">Figure 3
<p>Impulse responses used during the simulation tests.</p> Full article ">Figure 4
<p>BER as a function of SNR for transmission in an UAC channel simulated using impulse response generated by 1 virtual source.</p> Full article ">Figure 5
<p>BER as a function of SNR for transmission in an UAC channel simulated using impulse response generated by 3 virtual sources.</p> Full article ">Figure 6
<p>BER as a function of SNR for transmission in an UAC channel simulated using impulse response generated by 5 virtual sources.</p> Full article ">Figure 7
<p>BER as a function of SNR for transmission in an UAC channel simulated using impulse response generated by 8 virtual sources.</p> Full article ">Figure 8
<p>BER as a function of SNR for transmission in an UAC channel simulated using impulse response generated by 13 virtual sources.</p> Full article ">Figure 9
<p>BER as a function of SNR for transmission in an UAC channel simulated using impulse response generated by 21 virtual sources.</p> Full article ">Figure 10
<p>The dimensions of the model pool and the location of the transmitting (projector) and receiving transducers.</p> Full article ">Figure 11
<p>The module of time-varying impulse response, measured using PRBS of a bandwidth equal to 1 kHz, and estimated power delay profile and space-frequency correlation function.</p> Full article ">Figure 12
<p>The module of time-varying impulse response, measured using PRBS of a bandwidth equal to 2 kHz, and estimated power delay profile and space-frequency correlation function.</p> Full article ">Figure 13
<p>The module of time-varying impulse response, measured using PRBS of a bandwidth equal to 4 kHz, and estimated power delay profile and space-frequency correlation function.</p> Full article ">Figure 14
<p>The module of time-varying impulse response, measured using PRBS of a bandwidth equal to 5 kHz, and estimated power delay profile and space-frequency correlation function.</p> Full article ">Figure 15
<p>The module of time-varying impulse response, measured using PRBS of a bandwidth equal to 8 kHz, and estimated power delay profile and space-frequency correlation function.</p> Full article ">
529 KiB  
Article
Ultrasonic Array for Obstacle Detection Based on CDMA with Kasami Codes
by Cristina Diego, Álvaro Hernández, Ana Jiménez, Fernando J. Álvarez, Rebeca Sanz and Joaqúın Aparicio
Sensors 2011, 11(12), 11464-11475; https://doi.org/10.3390/s111211464 - 2 Dec 2011
Cited by 16 | Viewed by 8708
Abstract
This paper raises the design of an ultrasonic array for obstacle detection based on Phased Array (PA) techniques, which steers the acoustic beam through the environment by electronics rather than mechanical means. The transmission of every element in the array has been encoded, [...] Read more.
This paper raises the design of an ultrasonic array for obstacle detection based on Phased Array (PA) techniques, which steers the acoustic beam through the environment by electronics rather than mechanical means. The transmission of every element in the array has been encoded, according to Code Division for Multiple Access (CDMA), which allows multiple beams to be transmitted simultaneously. All these features together enable a parallel scanning system which does not only improve the image rate but also achieves longer inspection distances in comparison with conventional PA techniques. Full article
(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)
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Graphical abstract

Graphical abstract
Full article ">
<p>Proposed array design.</p> Full article ">
<p>Azimuthal pattern depending in deflection angle <span class="html-italic">θ</span>: <b>(a)</b> <span class="html-italic">θ</span> = 0° and <b>(b)</b> <span class="html-italic">θ</span> = 40°.</p> Full article ">
<p>Variation of the azimuth pattern according to the number <span class="html-italic">N</span> of elements.</p> Full article ">
<p>Array azimuth pattern as the steered angle increases <span class="html-italic">θ</span> for <span class="html-italic">N</span> = 32 elements.</p> Full article ">
<p>Encoded PA proposal scheme.</p> Full article ">
<p>Detail of the emission stage: Each element is driven by the sum of the <span class="html-italic">K</span> delayed codes.</p> Full article ">
<p>Full system scheme when a reflector is placed in angular sector Δ<span class="html-italic">θ</span><sub>2</sub>.</p> Full article ">
<p><b>(a)</b> Reflector location estimation with Encoded PA after a single simulation. <b>(b)</b> Zoom of the reflector location.</p> Full article ">
<p><b>(a)</b> Reflector location estimation with Conventional PA after a single simulation. <b>(b)</b> Zoom of the reflector location.</p> Full article ">
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 7884
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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Graphical abstract

Graphical abstract
Full article ">
<p>Spectral features of the longest BPSK modulated codes.</p> Full article ">
<p>Simulated auto-correlation bound for the sequences with lengths close to <b>(a)</b> 64 bits <b>(b)</b> 256 bits <b>(c)</b> 1,024 bits.</p> Full article ">
<p>Simulated auto-correlation bound for the sequences with lengths close to <b>(a)</b> 64 bits <b>(b)</b> 256 bits <b>(c)</b> 1,024 bits.</p> Full article ">
<p>Simulated cross-correlation bound for the sequences with lengths close to <b>(a)</b> 64 bits <b>(b)</b> 256 bits <b>(c)</b> 1,024 bits.</p> Full article ">
<p>Simulated cross-correlation bound for the sequences with lengths close to <b>(a)</b> 64 bits <b>(b)</b> 256 bits <b>(c)</b> 1,024 bits.</p> Full article ">
<p>Emitter frequency response: experimental values (blue dotted) and IIR filter model (red solid).</p> Full article ">
<p>Simulated auto-correlation bound for the sequences with lengths close to <b>(a)</b> 64 bits <b>(b)</b> 256 bits <b>(c)</b> 1,024 bits (transducer response and atmospheric absorption are considered).</p> Full article ">
<p>Simulated cross-correlation bound for the sequences with lengths close to <b>(a)</b> 64 bits <b>(b)</b> 256 bits <b>(c)</b> 1,024 bits (transducer response and atmospheric absorption are considered)</p> Full article ">
<p>Experimental setup.</p> Full article ">
<p>Features of the proof 40 kHz carrier signal. <b>(a)</b> Received Signal; <b>(b)</b> Spectrogram.</p> Full article ">
<p>Simulated and experimental auto-correlation bounds for the sequences with lengths close to <b>(a)</b> 64 bits <b>(b)</b> 256 bits <b>(c)</b> 1,024 bits.</p> Full article ">
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 10067
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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Graphical abstract

Graphical abstract
Full article ">
<p>Block diagram of the ultrasonic LPS.</p> Full article ">
<p>Block diagram of the receiver.</p> Full article ">
<p>Block diagram of the proposed positioning system model.</p> Full article ">
<p>Block diagram of the estimation process of the arrival instant for a sequence <span class="html-italic">j</span> based on GCC.</p> Full article ">
<p>Position of the beacons and the receiver for the analysis of the detection process.</p> Full article ">
<p>Beacon detection in the absence of noise by applying the cross-correlation (CC) method in the time domain.</p> Full article ">
<p>Beacon detection in the absence of noise, by applying generalised cross-correlation (GCC) with PHAT filtering.</p> Full article ">
<p>Beacon detection with a signal-noise ratio of 0 dB, by applying generalised cross-correlation (GCC) with PHAT filtering.</p> Full article ">
<p>Beacon detection by applying CC, for a modulation symbol formed by four carrier cycles (<span class="html-italic">m</span> = 4).</p> Full article ">
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