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1
Content available Theoretical analysis of a new approach to order determination for a modified Prony method in swath mapping application
Grall P., Marszal J.
Hydroacoustics
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2017
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Vol. 20
63--74
EN
This article presents a new approach to determine the model order (number of principal components) in the modified Prony method applied to swath acoustic mapping. Determination of the number of principal components is a crucial step in the modified Prony method. In the proposed approach the model order is chosen based on the underlying physical model of the underwater acoustic environment, and utilised signal processing operations. This data-driven approach, attempts to make use of all available information to assess the number of signals arriving at the receiver using pipeline processing in lieu of iterative processing.
2
Content available Analysis of distance measurement errors in CW FM sonar with MLS code modulation
Jedel A., Marszal J., Salamon R.
Hydroacoustics
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2017
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Vol. 20
75--84
EN
Although used in the classic silent sonar, the CW FM sounding signal has a major flaw which is its inaccuracy in determining the distance to a target. The authors of the article have developed a concept of silent sonar using frequency modulation signals switched by pseudorandom codes, already discussed in their previous work. This article presents a detailed analysis of errors in CW FM sonar with pseudo-random sequence code modulation confronted with errors which occur in similar sonar without code modulation.
3
Content available Signal conditioning for examination of shallow-water acoustic noise correlation properties
Rudnicki M., Marszal J.
Hydroacoustics
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2016
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Vol. 19
335--340
EN
The article describes the process of signal conditioning for examination of acoustic noise correlation properties in shallow water. Knowledge of these properties is very important for the design processes of passive and active hydroacoustic systems. This paper focuses on the above issue from the point of view of passive sonar. In sonar systems, signal processing algorithms operate on both useful acoustic signals, and accompanying noise. Quantitative estimation of the correlation properties of acoustic noise enables an accurate determination of detection conditions. This will verify the validity of certain commonly used simplified models in simulations of hydroacoustic systems. The article presents how the measurement system was constructed, and the structure of files for storing measurement data. It describes the processing algorithm developed for the measured signal conditioning. Research results are presented and discussed.
4
Content available Continuous wave sonar with hyperbolic frequency modulation keyed by pseudo-random sequence
Jedel A., Marszal J., Salamon R.
Hydroacoustics
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2016
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Vol. 19
185--196
EN
A CW FM type sounding signal is used in the classical solution of silent sonar. While the signal provides a relatively simple implementation of digital signal processing, and ensures good detection conditions, unfortunately, in the presence of the Doppler effect, distance measurement results tend to be wrong. This is due to the fact that the received signal’s instantaneous frequency value is dependent both on the distance to the object, and its speed. Sounding signal, as patented by the authors, is a combination of Pseudo-Random Sequences (PRS), and elementary signals of Hyperbolic Frequency Modulation (HFM) type. The structure of this signal is aimed at minimizing measurement error. The article presents the idea of a sounding signal of HFM+PRS type, and the results of computer simulations.
5
Content available Mutual Clutter Suppression Techniques for FM Sonars
Marszal J., Rudnicki M., Jedel A., Salamon R., Kochańska I.
Archives of Acoustics
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2016
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Vol. 41, No. 4
721--729
EN
The article presents methods that help in the elimination of mutual clutter as well as the consequences of two FM sounding signal sonars operating in the same body of water and frequency band. An in-depth analysis of mutual clutter was carried out. The effects of sounding signal differentiation were determined, as was the Doppler effect on mutual clutter suppression. One of the methods analysed is of particular interest in a situation in which collaborating sonars are operating in opposite frequency modulation directions. This method is effective for both linear and hyperbolic frequency modulations. A formula was derived, identifying exactly how much quantities of clutter may be lessened. The work included comprehensive computer simulations and measurements as well as tests in real-life conditions.
6
Content available Investigation into interferometric sonar system accuracy
Grall G., Marszal J.
Hydroacoustics
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2015
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Vol. 18
69-76
EN
The results of the accuracy measurements of phase differencing bathymetric sonar (PDBS) system in shallow waters are presented in the article. The measurement results were compared with the theoretical calculations for sonar system accuracy and international standards for hydrographic surveys. The proposed formulas enable to assess a priori sonar system performance using system quality factor (SQF), which takes into account influence of variable environmental conditions and auxiliary sensors on depth accuracy in a real-life scenario. The proposed SQF can be used in survey planning process to predict the swath width.
7
Content available Impact of Microphytobenthos Photosynthesis on the Characteristics of the Echo Signal from Baltic Sandy Sediments
Gorska N., Kowalska-Duda E., Marszal J., Schmidt J., Klusek Z.
Archives of Acoustics
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2015
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Vol. 40, No. 3
395--405
EN
The understanding the influence of biological processes on the characteristics of the signals backscattered by the sea floor is crucial in the development of the hydroacoustical benthic habitat classification techniques. The impact of the microphytobenthos photosynthesis on the acoustical backscattering properties of the Atlantic sandy sediments was previously demonstrated by Holliday et al. (2004) and Wildman and Huettel (2012). To account for the sensitivity of the hydroacoustical classification techniques to the backscattering properties of local marine sediments, it is important to understand the microphytobenthos photosynthesis impact for the Baltic Sea where the techniques are being actively developed now. This is the main motivation of the paper. In the paper the influence of the microphytobenthos photosynthesis on the characteristics of the echo signals reflected by sandy sediments in the typical Baltic temperature and the salinity conditions is discussed. The interdisciplinary multiday laboratory experiment was conducted to study the impact of benthic microalgal photosynthesis on the characteristics of the echo signal reflected by sandy sediments. Hydroacoustical data were collected under controlled constant light, temperature and salinity conditions. The oxygen content at different levels of the water column was simultaneously monitored.
8
Content available Digital signal processing applied to the modernization of Polish Navy sonars
Marszal J.
Polish Maritime Research
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2014
|
nr 2
65--75
EN
The article presents the equipment and digital signal processing methods used for modernizing the Polish Navy’s sonars. With the rapid advancement of electronic technologies and digital signal processing methods, electronic systems, including sonars, become obsolete very quickly. In the late 1990s a team of researchers of the Department of Marine Electronics Systems, Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology, began work on modernizing existing sonar systems for the Polish Navy. As part of the effort, a methodology of sonar modernization was implemented involving a complete replacement of existing electronic components with newly designed ones by using bespoke systems and methods of digital signal processing. Large and expensive systems of ultrasound transducers and their dipping and stabilisation systems underwent necessary repairs but were otherwise left unchanged. As a result, between 2001 and 2014 the Gdansk University of Technology helped to modernize 30 sonars of different types.
9
Content available Experimental Study of Silent Sonar
Marszal J.
Archives of Acoustics
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2014
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Vol. 39, No. 1
103--115
EN
Stealth is a frequent requirement in military applications and involves the use of devices whose signals are difficult to intercept or identify by the enemy. The silent sonar concept was studied and developed at the Department of Marine Electronic Systems of the Gdansk University of Technology. The work included a detailed theoretical analysis, computer simulations and some experimental research. The results of the theoretical analysis and computer simulation suggested that target detection and positioning accuracy deteriorate as the speed of the target increases, a consequence of the Doppler effect. As a result, more research and measurements had to be conducted to verify the initial findings. To ensure that the results can be compared with those from the experimental silent sonar model, the target’s actual position and speed had to be precisely controlled. The article presents the measurement results of a silent sonar model looking at its detection, range resolution and problems of incorrect positioning of moving targets as a consequence of the Doppler effect. The results were compared with those from the theoretical studies and computer simulations.
10
Content available Detection Range of Intercept Sonar for CWFM Signals
Marszal J., Salamon R.
Archives of Acoustics
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2014
|
Vol. 39, No. 2
215--230
EN
Stealth in military sonars applications may be ensured through the use of low power signals making them difficult to intercept by the enemy. In recent years, silent sonar design has been investigated by the Department of Marine Electronic Systems of the Gdansk University of Technology. This article provides an analysis of how an intercept sonar operated by the enemy can detect silent sonar signals. To that end a theoretical intercept sonar model was developed with formulas that can numerically determine the intercept ranges of silent sonar sounding signals. This was tested for a variety of applications and water salinities. Because they are also presented in charts, the results can be used to compare the intercept ranges of silent sonar and traditional pulse sonar.
11
Content available Implementation of contemporary technologies in naval sonars modernization
Marszal J.
Hydroacoustics
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2013
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Vol. 16
167--180
EN
Today’s fast technological advancement in electronics and signal processing methods makes electronic systems, including sonars, obsolete very quickly. The Polish Navy seems to be particularly affected as its ships were built in the 1970s and 1980s. Researchers at the Gdansk University of Technology have developed a methodology for modernising Navy sonars which involves the use of new electronic sub-systems and modern, bespoke methods of digital signal processing. Thanks to that, the existing large and expensive ultrasonic transducers and their systems for deployment and stabilisation remain unchanged. Between 2001 and 2013 this methodology was used by the Gdansk University of Technology to modernise 26 sonars of different types for the Polish Navy. The projects have significantly improved the technical and utility parameters of the sonars, while keeping the expenditure at about 20% of the value of new equipment.
12
Content available Distance measurement errors in silent FM-CW sonar with matched filtering
Marszal J., Salamon R.
Metrology and Measurement Systems
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2012
|
Vol. 19, nr 2
321-332
EN
The secretiveness of sonar operation can be achieved by using continuous frequency-modulated sounding signals with reduced power and significantly prolonged repeat time. The application of matched filtration in the sonar receiver provides optimal conditions for detection against the background of white noise and reverberation, and a very good resolution of distance measurements of motionless targets. The article shows that target movement causes large range measurement errors when linear and hyperbolic frequency modulations are used. The formulas for the calculation of these errors are given. It is shown that for signals with linear frequency modulation the range resolution and detection conditions deteriorate. The use of hyperbolic frequency modulation largely eliminates these adverse effects.
13
Content available Application of maximum length sequence in silent sonar
Marszal J., Salamon R., Kilian L.
Hydroacoustics
|
2012
|
Vol. 15
143-152
EN
Silent sonars are designed to reduce the distance over which their sounding pulses can be detected by intercept sonars. In order to meet this objective, we can use periodical sounding signals that have low power, a very long duration and wide spectrum. If used in the silent sonar’s receiver, matched filtration ensures very good detection of motionless or slow moving targets. However, it is more difficult to detect echo signals of fast moving targets with Doppler effect causing significant error in target distance measurements. In an effort to find signals that can better resist Doppler effect, maximum length sequence was tested for its application in silent sonar. It has an elementary signal which includes linear frequency modulation. It was demonstrated that the signal produces much better results than those obtained with simple frequency modulation signals.
14
Content available Silent sonar with matched filtration
Salamon R., Marszal J., Schmidt J., Rudnicki M.
Hydroacoustics
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2011
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Vol. 14
199-208
EN
Radars with continuous wave frequency (CW FM sonars) are used in radiolocation as ‘silent radars’. They determine the distance to target by measuring the difference between the frequency of the sounding signal and echo signal. The article presents the principle of operation and parameters of silent CW FM sonars. Target distance determined by these sonars is based on the signal at the output of the matched filter. The Doppler effect is studied in detail to identify its effect on the sonar’s parameters. The results of theoretical calculations are presented together with the results of the sonar’s computer simulation.
15
Content available Doppler effect in the cw fm sonar
Marszal J., Salamon R., Zachariasz K., Schmidt A.
Hydroacoustics
|
2011
|
Vol. 14
157-164
EN
When sonars are used for military purposes they have to ensure unobtrusive operation, afeature that can be potentially secured by ‘silent sonars’ or continuous wave frequency modulation sonars (CW FM sonars). The article presents how these sonars operate and identifies the relations between their parameters. The Doppler effect and its impact on the CW FM sonar are studied to identify how it affects the sonar’s parameters. The results of simplified theoretical calculations are supported with results of computer simulations of a more realistic model.
16
Content available Modernization of ASW sonar SQS-56 at Gdansk University of Technology
Marszal J., Schmidt J., Salamon R., Kilian L., Raganowicz A., Zachariasz K., Ostrowski Z., Jedel A., Rudnicki M., Sidorko T.
Hydroacoustics
|
2010
|
Vol. 13
191-196
EN
The fast development of electronic technology and digital signal processing methods makes electronic devices, including sonar systems ones, obsolete very quickly. On the other hand the ships mechanical components including mechanical parts of sonars are operational for a few dozens of years. It makes good opportunity to modernize these devices by using modern electronic devices and new digital signal processing methods with application of existing antenna and mechanical systems. The paper presents the modernization of ASW sonar SQS-56 on the Polish frigate ORP “Kościusko”. The aim of modernization, the new parameters of the sonar and block diagram after modernization are presented.
17
Content available Doppler estimation method for moving target location
Salamon R., Marszal J.
Hydroacoustics
|
2010
|
Vol. 13
225-234
EN
The article presents an algorithm for target location based solely on Doppler shift of echo acoustic signals of a moving underwater object. The algorithm is designed for use in multi-static systems for protecting bodies of water from terrorist attacks by divers or submerged vehicles. The original source of signals is a transmitter emitting continuous acoustic waves. The echo signals from moving object are received by hydrophones located at fixed and known points in the water. Doppler shifts are determined from discrete Fourier transforms of hydrophone signals. The proposed iterative algorithm for target location calculates the approximate values of target speed vector and target coordinates which correspond to speed vectors as calculated previously.
18
Content available Workstation for training ASW helicopter navigators and analysing real flight data
Raganowicz A., Kilian L., Marszal J., Schmidt A., Sidorko T., Rudnicki M.
Hydroacoustics
|
2009
|
Vol. 12
181-188
EN
The article presents a training and diagnostic workstation designed for Polish Navy ASW helicopter navigators. Installed at the helicopter base, the workstation is used for training and instruction in operating the device and analysing information gathered by navigators during the flight using the ASW onboard sonar, sonobuoy receiver and magnetometer. The workstation allows instructors to task two operators and monitor their performance under conditions resembling those onboard a plane. The tasks involve the operation of the consoles and collecting information during tactical situations, diagnosing damage and analysing flight data in office environment. The objective is to ensure proper helicopter navigator training and experience given the limited possibility of training flights.
19
Content available Method for improving multibeam sonar bearing accuracy
Leśniak W., Marszal J., Salamon R., Zachariasz K., Schmidt J.
Hydroacoustics
|
2009
|
Vol. 12
98-108
EN
The paper presents a simple method for improving multibeam sonar bearing accuracy. The principle proposed here is similar to the monopulse method, a solution commonly used in radars and sonars. With no manual or automatic beam rotation, the method offers a substantial reduction in the demand for sonar computational effort. It significantly reduces bearing error for a relatively high signal to noise ratio. The paper gives a boundary value of the output signal to noise ratio which when exceeded satisfactorily improves bearing accuracy.
20
Content available Bearing errors in passive sonar stationary target location
Schmidt A., Marszal J., Salamon R., Jedel A., Ostrowski Z.
Hydroacoustics
|
2009
|
Vol. 12
189-200
EN
The paper presents a method for determining the coordinates of stationary targets using passive sonar bearing. It identifies the requirements sonar movements must meet to keep the incorrect determination of coordinates to a minimum. It gives the relations, which help determine coordinate errors analytically. Numerical experiments are used to demonstrate the success of the analysis.
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