scholarly journals Code Optimisation Framework for Multicode Sonar Systems

2021 ◽  
Author(s):  
◽  
Muhammad Rashed
Keyword(s):  
Transmission Loss ◽  
Matched Filter ◽  
Signal To Noise Ratio ◽  
Welch Bound ◽  
Optimisation Algorithm ◽  
Sonar System ◽  
Channel Effects ◽  
Sonar Systems ◽  
Mismatched Filters ◽  
Quadratically Constrained

<p>The ocean is a temporally and spatially varying environment, the characteristics of which pose significant challenges to the development of effective underwater wireless communications and sensing systems.  An underwater sensing system such as a sonar detects the presence of a known signal through correlation. It is advantageous to use multiple transducers to increase surveying area with reduced surveying costs and time. Each transducers is assigned a dedicated code. When using multiple codes, the sidelobes of auto- and crosscorrelations are restricted to theoretical limits known as bounds. Sets of codes must be optimised in order to achieve optimal correlation properties, and, achieve Sidelobe Level (SLL)s as low as possible.  In this thesis, we present a novel code-optimisation method to optimise code-sets with any number of codes and up to any length of each code. We optimise code-sets for a matched filter for application in a multi-code sonar system. We first present our gradient-descent based algorithm to optimise sets of codes for flat and low crosscorrelations and autocorrelation sidelobes, including conformance of the magnitude of the samples of the codes to a target power profile. We incorporate the transducer frequency response and the channel effects into the optimisation algorithm. We compare the correlations of our optimised codes with the well-known Welch bound. We then present a method to widen the autocorrelation mainlobe and impose monotonicity. In many cases, we are able to achieve SLLs beyond the Welch bound.  We study the Signal to Noise Ratio (SNR) improvement of the optimised codes for an Underwater Acoustic (UWA) channel. During its propagation, the acoustic wave suffers non-constant transmission loss which is compensated by the application of an appropriate Time Variable Gain (TVG). The effect of the TVG modifies the noise received with the signal. We show that in most cases, the matched filter is still the optimum filter. We also show that the accuracy in timing is very important in the application of the TVG to the received signal.  We then incorporate Doppler tolerance into the existing optimisation algorithm. Our proposed method is able to optimise sets of codes for multiple Doppler scaling factors and non-integer delays in the arrival of the reflection, while still conforming to other constraints.  We suggest designing mismatched filters to further reduce the SLLs, firstly using an existing Quadratically Constrained Qaudratic Program (QCQP) formulation and secondly, as a local optimisation problem, modifying our basic optimisation algorithm.</p>

scholarly journals Code Optimisation Framework for Multicode Sonar Systems

2021 ◽  
Author(s):  
◽  
Muhammad Rashed
Keyword(s):  
Transmission Loss ◽  
Matched Filter ◽  
Signal To Noise Ratio ◽  
Welch Bound ◽  
Optimisation Algorithm ◽  
Sonar System ◽  
Channel Effects ◽  
Sonar Systems ◽  
Mismatched Filters ◽  
Quadratically Constrained

<p>The ocean is a temporally and spatially varying environment, the characteristics of which pose significant challenges to the development of effective underwater wireless communications and sensing systems.  An underwater sensing system such as a sonar detects the presence of a known signal through correlation. It is advantageous to use multiple transducers to increase surveying area with reduced surveying costs and time. Each transducers is assigned a dedicated code. When using multiple codes, the sidelobes of auto- and crosscorrelations are restricted to theoretical limits known as bounds. Sets of codes must be optimised in order to achieve optimal correlation properties, and, achieve Sidelobe Level (SLL)s as low as possible.  In this thesis, we present a novel code-optimisation method to optimise code-sets with any number of codes and up to any length of each code. We optimise code-sets for a matched filter for application in a multi-code sonar system. We first present our gradient-descent based algorithm to optimise sets of codes for flat and low crosscorrelations and autocorrelation sidelobes, including conformance of the magnitude of the samples of the codes to a target power profile. We incorporate the transducer frequency response and the channel effects into the optimisation algorithm. We compare the correlations of our optimised codes with the well-known Welch bound. We then present a method to widen the autocorrelation mainlobe and impose monotonicity. In many cases, we are able to achieve SLLs beyond the Welch bound.  We study the Signal to Noise Ratio (SNR) improvement of the optimised codes for an Underwater Acoustic (UWA) channel. During its propagation, the acoustic wave suffers non-constant transmission loss which is compensated by the application of an appropriate Time Variable Gain (TVG). The effect of the TVG modifies the noise received with the signal. We show that in most cases, the matched filter is still the optimum filter. We also show that the accuracy in timing is very important in the application of the TVG to the received signal.  We then incorporate Doppler tolerance into the existing optimisation algorithm. Our proposed method is able to optimise sets of codes for multiple Doppler scaling factors and non-integer delays in the arrival of the reflection, while still conforming to other constraints.  We suggest designing mismatched filters to further reduce the SLLs, firstly using an existing Quadratically Constrained Qaudratic Program (QCQP) formulation and secondly, as a local optimisation problem, modifying our basic optimisation algorithm.</p>

scholarly journals Low Correlation Codes for Sonar Systems

2021 ◽  
Author(s):  
◽  
Rajiv Pratap
Keyword(s):  
Matched Filter ◽  
Optimization Method ◽  
Detection Methods ◽  
Water Tank ◽  
Matched Filters ◽  
Welch Bound ◽  
Sonar Systems ◽  
Gradient Based ◽  
Digital Transmitter ◽  
New Codes

<p>Sonar is a vital technology for the detection of objects in the water. Sonarsystems have been redefined over many decades, but research is still beingconducted into optimal detection methods. Codes, and the filters thatprocess the codes, have been at the forefront of this research. An importantobjective has been the minimization of interference caused by reflections.Matched filters are commonly used in sonar systems. They are equivalent tocorrelation filters, which are bound by the Welch bound. The Welch boundgoverns the minimum peak correlation for points outside of detection.This thesis investigated matched filters and their bounds, and it wasfound that by relaxing the condition for detection, properties beyond theWelch bound could be achieved. By relaxing these conditions, the Welchbound no longer applies, and so a modified Welch bound was developedto accurately investigate the nature of these codes. In this thesis, methodsto generate codes for these new codes were investigated. Generating codesfor a matched filter is a non-convex problem, so gradient based methodswere utilised. Methods to improve correlation and power characteristicswere developed, along with methods for mapping a sequence for use witha digital transmitter having particular limitations. Mis-matched filters wereused to improve signal characteristics that may be lost due to this mapping.The performance of the generated codes was evaluated, and the rela-tionships between input parameters and output properties of the resultingsignal were observed. These performance assessments demonstrate thattradeoffs are required between various properties, and a balance is neededto obtain codes useful for sonar. The optimization was parametrized by anexample set of requirements for sonar. The signals were found to meet the given requirements, and when compared to codes typically used in sonar,the optimized signals were shown to have significantly better correlationproperties. Furthermore, compared to the general bounds for the propertiesof codes, it was found that the new codes had nearly optimal properties,and performed better than equivalent codes bounded by the Welch bound.The performance of codes were also investigated in a water tank toverify their feasibility. There were several additional considerations whichlimit codes that can be tested, and once these are taken into account thetest provided a robust method to verify the design process. Initial testsshowed results that differed from simulations, but after the inclusion ofzero padding before upscaling, the results from empirical testing agreewith simulation.Summarizing the research in this thesis, a new set of codes were devel-oped using a gradient based optimization method. The codes were mappedto a digital transmitter, and the filter adjusted using a mis-matched filter. The optimization was shown to generate near optimal codes which met allthe given sonar system requirements</p>

scholarly journals Low Correlation Codes for Sonar Systems

2021 ◽  
Author(s):  
◽  
Rajiv Pratap
Keyword(s):  
Matched Filter ◽  
Optimization Method ◽  
Detection Methods ◽  
Water Tank ◽  
Matched Filters ◽  
Welch Bound ◽  
Sonar Systems ◽  
Gradient Based ◽  
Digital Transmitter ◽  
New Codes

<p>Sonar is a vital technology for the detection of objects in the water. Sonarsystems have been redefined over many decades, but research is still beingconducted into optimal detection methods. Codes, and the filters thatprocess the codes, have been at the forefront of this research. An importantobjective has been the minimization of interference caused by reflections.Matched filters are commonly used in sonar systems. They are equivalent tocorrelation filters, which are bound by the Welch bound. The Welch boundgoverns the minimum peak correlation for points outside of detection.This thesis investigated matched filters and their bounds, and it wasfound that by relaxing the condition for detection, properties beyond theWelch bound could be achieved. By relaxing these conditions, the Welchbound no longer applies, and so a modified Welch bound was developedto accurately investigate the nature of these codes. In this thesis, methodsto generate codes for these new codes were investigated. Generating codesfor a matched filter is a non-convex problem, so gradient based methodswere utilised. Methods to improve correlation and power characteristicswere developed, along with methods for mapping a sequence for use witha digital transmitter having particular limitations. Mis-matched filters wereused to improve signal characteristics that may be lost due to this mapping.The performance of the generated codes was evaluated, and the rela-tionships between input parameters and output properties of the resultingsignal were observed. These performance assessments demonstrate thattradeoffs are required between various properties, and a balance is neededto obtain codes useful for sonar. The optimization was parametrized by anexample set of requirements for sonar. The signals were found to meet the given requirements, and when compared to codes typically used in sonar,the optimized signals were shown to have significantly better correlationproperties. Furthermore, compared to the general bounds for the propertiesof codes, it was found that the new codes had nearly optimal properties,and performed better than equivalent codes bounded by the Welch bound.The performance of codes were also investigated in a water tank toverify their feasibility. There were several additional considerations whichlimit codes that can be tested, and once these are taken into account thetest provided a robust method to verify the design process. Initial testsshowed results that differed from simulations, but after the inclusion ofzero padding before upscaling, the results from empirical testing agreewith simulation.Summarizing the research in this thesis, a new set of codes were devel-oped using a gradient based optimization method. The codes were mappedto a digital transmitter, and the filter adjusted using a mis-matched filter. The optimization was shown to generate near optimal codes which met allthe given sonar system requirements</p>

scholarly journals An Improved Velocity Estimation Method for Wideband Multi-Highlight Target Echoes in Active Sonar Systems

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 2794 ◽  
Author(s):  
Shuxia Huang ◽  
Shiliang Fang ◽  
Ning Han
Keyword(s):  
Matched Filter ◽  
Estimation Method ◽  
Velocity Estimation ◽  
Filter Method ◽  
Improved Method ◽  
Matching Algorithm ◽  
Active Sonar ◽  
Estimation Performance ◽  
Effective Performance ◽  
Sonar Systems

In active sonar systems, the target echoes are usually equivalent to a superposition of the Doppler-scaled reflections from multiple highlights. The reflections overlap with each other both in the time and frequency domain, which results in a decreased velocity estimation performance. Recently, the hyperbolic-frequency modulated signal has been widely employed in sonar systems for moving targets due to its Doppler tolerance, while the precise velocity estimation becomes a great challenge under such conditions. In this paper, the echo c is modeled onsidering a target with a constant velocity and multi-highlights. The velocity estimation performance is analyzed though the signal’s matched filter and the wideband ambiguity function. An improved method based on the sliding window matching algorithm is proposed to improve the performance. The method controls the energy of environmental noise and interference by focusing on the dominant target highlight, and applying a designed window which utilizes the Doppler characteristics of hyperbolic-frequency modulated signals. Simulations and lake experiment allow us to compare between the improved method and the conventional matched filter method. The results verify the influence of the multi-highlights in velocity estimation and indicate that the improved method has more effective performance.

scholarly journals Performance of the matched filter in sonar systems having time variable gain

2020 ◽  
Vol 14 (3) ◽  
pp. 425-430
Author(s):  
Muhammad Salman Rashed ◽  
Marco Meijer ◽  
Paul D. Teal
Keyword(s):  
Matched Filter ◽  
Time Variable ◽  
Variable Gain ◽  
Sonar Systems

On the Feasibility of Using Underwater Acoustic Data Transmission for Subsea Equipment Monitoring

2017 ◽  
Author(s):  
Bessie A. Ribeiro ◽  
Viviane Rodrigues ◽  
Viviane Ferreira ◽  
Fabio C. Xavier ◽  
Theodoro A. Netto
Keyword(s):  
Data Transmission ◽  
Oil And Gas ◽  
Transmission Loss ◽  
Signal To Noise Ratio ◽  
Water Environment ◽  
Acoustic Propagation ◽  
Gas Production ◽  
Brazilian Coast ◽  
Propagation Channel ◽  
Oil And Gas Production

The present work uses the BELLHOP ray tracing model to simulate an acoustic propagation channel in a deep water environment in order to analyze its viability to provide data transmission for monitoring submarine equipment. The simulated scenario is located in the Campos Basin, Rio de Janeiro, on the Brazilian coast, responsible for more than 80% of Brazilian oil and gas production. Temperature and salinity data from five stations were used to calculate the sound speed profiles required to the transmission loss simulations of the acoustic propagation channel. In order to estimate the signal detection capacity according to the medium characteristics, a characterization of the parameters that influence the physical propagation channel was performed. The parameters of three modem models with different operation frequencies were selected and analyzed in order to obtain the Signal to Noise Ratio (SNR) of the transmission signal.

scholarly journals Seabed Identification and Characterization Using Sonar

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Henry M. Manik
Keyword(s):  
Single Frequency ◽  
Single Beam ◽  
Sonar System ◽  
Mean Diameter ◽  
Backscattering Strength ◽  
Sonar Systems ◽  
Simple Analog ◽  
Identification And Characterization

Application of sonar technologies to bottom acoustics study has made significant advances over recent decades. The sonar systems evolved from the simple analog single-beam and single-frequency systems to more sophisticated digital ones. In this paper, a quantified sonar system was applied to detect and quantify the bottom echoes. The increasing of mean diameter is accompanied by a higher backscattering strength. From this study, identification and characterization using sonar is possible.

scholarly journals Parameter estimation and signal detection algorithm based on adaptive capture in non-cooperative communication

2021 ◽  
Vol 336 ◽  
pp. 04002
Author(s):  
Zilong He ◽  
Peng Sun ◽  
Kexian Gong ◽  
Hua Jiang
Keyword(s):  
Parameter Estimation ◽  
Signal Detection ◽  
Cooperative Communication ◽  
Matched Filter ◽  
Signal To Noise Ratio ◽  
Frequency Offset ◽  
Detection Algorithm ◽  
Estimation Accuracy ◽  
Signal Frequency ◽  
Signal Spectrum

Aiming at the problem that the frequency offset in the non-cooperative communication system causes the received signal spectrum to shift, which exceeds the passband of the matched filter and affects the subsequent demodulation, a parameter estimation and signal detection algorithm based on adaptive capture is proposed by this paper, which is more convenient for hardware implementation and consumes less resources. The algorithm is divided into three parts. Firstly, use the correlation value between the signal and the preamble sequence as the basis for frequency capture. Secondly, the frequency is accurately estimated based on the interpolation algorithm. Finally, the phase-locked loop structure is used to track the frequency according to the characteristics of the frequency gradually changing and the signal frequency offset is eliminated in the Digital Down Converter stage. It provides necessary conditions for accurate signal detection and phase estimation. The simulation results show that the algorithm has high estimation accuracy, wide esti-mation range and low complexity. It can also achieve better estimation accuracy and detection performance under low signal-to-noise ratio.

Amplification of High Quality of Signal Strength Using Corner Reflector Antenna for Satellite Communications

2021 ◽  
Vol 7 (1) ◽  
pp. 01-09
Author(s):  
◽  
Ameer Hamza ◽  
Keyword(s):  
Satellite Communication ◽  
Matched Filter ◽  
Signal To Noise Ratio ◽  
Random Phase ◽  
Signal Strength ◽  
Satellite Communications ◽  
Reflector Antenna ◽  
Corner Reflector ◽  
High Quality ◽  
Corner Reflector Antenna

The strengths of the corner reflector antenna (CRA) which spans space's dynamic pseudo-random phase wave-front, which can be used in frequency modulation of the echo, replacing doppler's typical style. Radiometric assumes that Imaging discoveries can change lives a kind of special geosynchronous in geostationary orbit for the extremely low SNR in this geometry, just have a very low signal to noise ratio (SNR) posit the use of such a matched filter to strengthen the SNR and enable the existence of good specificity. In this paper, the signal is amplified to send a high-quality signal to the transmitter for satellite communication using a corner reflector antenna. Apart from other antennas, the corner reflector antenna plays an important role in increasing the signal strength in satellite communication. Using this corner reflector antenna the system will be good and fast so that the transmitter or the receiver can transmit or receive the signal very fast. While transmitting the signal the noise or interference in the system can be eliminated for that reason the corner reflector antenna is used. The corner reflector antenna can reduce the system noise or interference so that the system will be in proper condition to transmit or receive the signal.

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