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Tytuł:
Ahead looking sonar with cylindrical array
Autorzy:
Elminowicz, A.
Powiązania:
https://bibliotekanauki.pl/articles/332419.pdf
Data publikacji:
1999
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Cylindrical arrays are widely used in omnidirectional or very wide sector sonars. These arrays utilise horizontal phasing for compensation of geometrical phase-delays, which form a narrow beam. The cylindrical symmetry of the array provides beam rofation around the array. The ahead looking sonar using the above method needs an array with a large number of staves and a larger number of receiver channels. This paper presents the design approach to ahead looking sonars with a cylindrical arc array using delay of the staves signals for equalising of the array and a beamforming processor for beam steering. This sonar performance is determined by array parameters and a processing method used to form the beams. There is no simple closed form of mathematical expression for a delayed signals and steered beam of such arrays so the array and method of beamforming have to be analysed by considering the elements spacing, weighting and directivity. The angular aperture and radius of array curvature are analysed. The results of a computer simulation of beam patterns for such sonars are presented. The indication for design of ahead looking sonars with cylindrical arc array using equalising and beam steering processing are presented.
Źródło:
Hydroacoustics; 1999, 2; 139-144
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Multi-beam side-scan sonar
Autorzy:
Elminowicz, A.
Powiązania:
https://bibliotekanauki.pl/articles/332735.pdf
Data publikacji:
2001
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Conventional single beam side-scan sonars with beams at about 1o are not well suited for the detection and identification of very small objects TS < -25 dB - e.g. minelike objects. Sonars of very high angular resolution at 0.1o - 0.2o operate in the nearfield and the speed of the sonar's transducer towing has to be reduced significantly. The paper presents a design approach to a multi-beam side-scan sonar where the above mentioned drawbacks have been removed. The sonar has several narrow parallel (not conical) beams simultaneously formed using the method of beam shaping in the nearfield. Two methods of beam shaping in the nearfield are presented. Thanks to them sonars of various quality and cost can be designed. Selected beam patterns for the two methods of beam forming in the nearfield are presented and compared.
Źródło:
Hydroacoustics; 2001, 4; 57-60
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Wideband beamformer in the frequency domain
Autorzy:
Elminowicz, A.
Powiązania:
https://bibliotekanauki.pl/articles/332683.pdf
Data publikacji:
2003
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
acoustics
wideband sonar
beamforming
Opis:
In modern high resolution wideband sonars using linear array, beamforming constitutes one of the most difficult problems. This paper presents a new efficient method of beamforming in the frequency domain. Applying fast Fourier transforms: to transfer into the frequency domain - temporal FFT (TFFT); to make spatial filtration spatial FFT (SFFT) and to transfer from the frequency domain - inverse FFT (IFFT), as well as fast convolution in the frequency domain correlating the conjugated and corrected replicas for each beam with picked up samples of SFFT for each frequency and each beam we obtain a processing that is less calculations burdened than other known processing algorithms.
Źródło:
Hydroacoustics; 2003, 6; 235-242
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Correction of frequency distortion of the DDS signals
Autorzy:
Elminowicz, A.
Zajączkowski, L.
Powiązania:
https://bibliotekanauki.pl/articles/331959.pdf
Data publikacji:
2010
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The Diver Detection Sonar (DDS) as a surveillance system has been designed to monitor the threat of underwater attacks against harbours, ships, naval bases, coastal industrial installations, oil platforms etc. This paper describes technical complexity of designing wideband DDS, with increased coverage effectiveness and following additional advantages: improved range resolution, high signal to noise and reverberation ratio and possibility operation of several sonars in the same frequency band using different type of modulation. The article presents technological principles and problems related to the wideband sig-nals transmitting and receiving by cylindrical piezocomposite transducer as well as implementation of the broadband compression technique for correction of frequency distortion.
Źródło:
Hydroacoustics; 2010, 13; 83-88
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Doppler effect in wideband sonars
Autorzy:
Elminowicz, A.
Zajączkowski, L.
Powiązania:
https://bibliotekanauki.pl/articles/332069.pdf
Data publikacji:
2004
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
To increase sonar range and to improve the range resolution and SNR, modern sonars use a matched filtration what corresponds to correlation between replica of transmitted sig-nal and received echoes. Motion of sound source or/and object causes frequency Doppler shift of received signals, thereby generating the distortion of the correlation processing of echo with signal replica. In the paper, the results of studies of sonar signals (CW, LFM and HFM) immunity to correlation distortions due to Doppler effect are presented. It has been demonstrated that only HFM signals are immune to adverse Doppler effect in correlation processing.
Źródło:
Hydroacoustics; 2004, 7; 31-36
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
High resolution multi-beam side looking sonar
Autorzy:
Elminowicz, A,
Zajączkowski, L.
Powiązania:
https://bibliotekanauki.pl/articles/332745.pdf
Data publikacji:
2005
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The conventional side–scan sonars does not ensure sufficient angular and range resolution to detect very small objects with small target strength. Decrease of beam width leads to the increase of angular resolution but requires the decrease of towing speed what means reduction of searched area. Other method of the angular resolution increased is designing multi–beam sonar or sonar with synthetic aperture. The paper presents a design of effective multi–beam side looking sonars with a large angular and range resolution operates with 100 kHz, 200 kHz, 400 kHz and 600 kHz. The sonar, described in the paper, operates with 200 kHz frequency; LFM modulation – 20 kHz and 40 kHz band; array provides 32 elements with d/ë spacing what ensure a shaping of 5 or 9 beams with 0,40° width. The range of sonar is from 250 m to 300 m, the level of side lobes are smaller than -20 dB and level of grating lobes for 5 beams are smaller than -30 dB. The principle of sonar performance and wideband effective processing are presented. Effectiveness of processing depends on beams number and decrease of beams number, together with the range increased, leads to increase of processing effectiveness.
Źródło:
Hydroacoustics; 2005, 8; 37-46
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of DDS and magnetic barrier cooperating with acoustic barriers and tethered sonobuoys for harbour and anchorage underwater protection
Autorzy:
Elminowicz, A.
Zajączkowski, L.
Powiązania:
https://bibliotekanauki.pl/articles/331708.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The underwater protection system that consists of wideband Acoustic Barriers (WAB) and wideband DDS (WDDS) is a very suitable acoustic device to operate in Littoral Water (LW) and Extremely Littoral Water (ELW). A new approach to underwater protection harbour and task group on the anchorage against AUV, DDV and torpedos is focused on designed stationary tethered sonobuoys with passive sonar, active multistatic sonar, intercept sonar and also possibility of jamming intercepted underwater objects. Passive omnidirectional sonar may be used for initial detection of intruder on the long distance (up to 5 km) and active multistatic sonar will be applied for detection and precise location of detected object. Intercept sonar is waiting for homing sonar signals generated by AUV, DDS, torpedos or submarines and received signals are basis generating jamming signals. The paper describes the WAB, WDDS and magnetic barrier integrated to short range (up to 1000 m) protection systems. The long range (up to 5000 m) sonobuoy – for various technical parameters and environmental conditions – has been studied.
Źródło:
Hydroacoustics; 2011, 14; 39-46
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Badanie przetwornika o nierównomiernie rozmieszczonych elementach
Autorzy:
Elminowicz, A.
Porosińska, E.
Powiązania:
https://bibliotekanauki.pl/articles/332235.pdf
Data publikacji:
2000
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
General object of nonuniform array design is the approximation of desired beam pattern with reduced number of elements which are required for uniform array of d/α=0,5. This work intends to study possibilities of design procedures lead to useful, nonuniform arrays with elements situated in raster d/α=0,5. Options of spacing elements for nonuniform arrays presented beneath are reduced to the raster d/α=0,5, which enable easier technical realisation of the beamformer. Arrays with equal excited elements have been used, what is highly practical, both for transmission and receiving. Many designs of arrays have been proposed and tested The beam patterns for steered beams are presented.
Źródło:
Hydroacoustics; 2000, 3; 135-140
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Multistatic systems
Autorzy:
Elminowicz, A.
Zajączkowski, L.
Powiązania:
https://bibliotekanauki.pl/articles/332386.pdf
Data publikacji:
2006
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
This paper describes key features of a multistatic operation in the littoral beginning from multistatic system (MS) configuration, his performance model and constraints imposed by environment of shallow water. The architecture of MS, features and requirements of MS basic subsystem has been presented. Essential role as during MS operation is fulfilled by data fusion and tracking methods as well a communication between MS units, has been protruded. The application of MS, especially for underwater protection systems, in the form of barriers protecting anchorage, harbour, straits or entries to the harbour has been presented. Other applications are connected with military operation, especially Anti–Submarine Warfare (ASW) in littoral areas. Attention was paid on possibility of cooperation among the different acoustics devices in MS.
Źródło:
Hydroacoustics; 2006, 9; 57-64
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mutual interferences reduction between sonars or barrier modules operating in the same area
Autorzy:
Elminowicz, A.
Zajączkowski, L.
Powiązania:
https://bibliotekanauki.pl/articles/332459.pdf
Data publikacji:
2007
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
This paper describes key features of a Mutual Interference Reduction (MIR) in sea area, especially in shallow water, where some acoustic devices may operate simultaneously. MIR is an essential problem in mono– and multistatic systems. Receivers of sonars or barrier modules, operating in these systems, can receive signals from other acoustic devices by direct track, as echoes from the targets or as reverberations. The mutual sonars interference level depends on many parameters, like: the transmitting signal parameters (modulation, SL, B, T) and bands aliasing, mutual sectors coverage, the distance and mutual localization of trans-mitting transducers and receiving arrays, as well as type of matched filtration. The degrada-tion of mutual interferences by matched filtration has been determined. Influence of modula-tion type, B and T parameters on MIR at the matched filtration output have been presented also.
Źródło:
Hydroacoustics; 2007, 10; 39-44
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Data processing of broad-band signals received by multi-element cylindrical transducer
Autorzy:
Janowski, T.
Elminowicz, A.
Szworski, K.
Powiązania:
https://bibliotekanauki.pl/articles/331559.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
data processing
multi-element cylindrical transducer
hydroacoustic
Opis:
The sonar based on cylindrical transducer compared with linear transducer has few advantages. Particularly its omni-directional central symmetry enables simplification of the echo signal Direction of Arrival (DOA) estimation. When the number of transducer staves is the power of two the efficient Fast Fourier Transformation can be used to calculate spatial convolution. The article presents theoretical and technological principles of the real time digital data processing of the wideband echo signals received by cylindrical hydroacoustic transducer. Described procedures enable high resolution underwater target location and precise data display. The implementation of effective broadband pulse compression technique with high range resolution will be presented. The results of signal processing modeling and examples of application will be also discussed.
Źródło:
Hydroacoustics; 2008, 11; 113-120
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sonar with electronically steered transmitted beam
Autorzy:
Elminowicz, A.
Janowski, T.
Męciński, W.
Powiązania:
https://bibliotekanauki.pl/articles/332272.pdf
Data publikacji:
1997
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The ahead looking sonar with 60° sector profected by multielement cylindrical array and analog beamforming technique used multielement linear array for selecting 4° x 15 beams is presented. The aim of this paper is to study the pattern directivity of the linear multielement receiving transducer of the sonar SHL-1OOM for application to electronically steered beam profector. This paper presents the result of the computer aided calculations of the beam patterns as the function of the weighting excitation parameters and damaged elements for steered linear array.
Źródło:
Hydroacoustics; 1997, 1; 227-230
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stationary sonar for shallow water
Autorzy:
Elminowicz, A.
Porosińska, E.
Kotłowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/332011.pdf
Data publikacji:
2001
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The aim of the paper is checking possibility of building active stationary sonar designed for work in very shallow water, depth 8 - 10 m. Sonar is designed for monitoring very weak and moving targets by TS about -20 dB at the range up to few hundred metres. This paper presents construction of wide-sector sonar consists of two linear transducers. Beampatterns of the transducers are adjusted to conditions existing in very shallow water, particularly to minimize bottom and surface reverberation and effect of multipath propagation. Below are presented results of tests and measurements made for different types of targets and different environmental conditions - including: state of the sea, strong aeration of the near surface water, and influence of different sound propagation conditions for detection of the targets. The paper contains results of influence few types of signal processing for improvement SNR, thus increasing probability of the targets detection.
Źródło:
Hydroacoustics; 2001, 4; 61-64
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Wideband, modular Diver Detection Sonar (DDS)
Autorzy:
Elminowicz, A.
Męciński, W.
Okuniewski, M.
Powiązania:
https://bibliotekanauki.pl/articles/331870.pdf
Data publikacji:
2010
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The complete protection of naval harbours, port approaches and anchorages requires the underwater continuous monitoring and threat detection such as divers, their delivery vehicles or AUVs from safe distances. R&D Marine Technology Centre (CTM) has began designing and building of the new generation, modular, wideband Diver Detection Sonar (DDS), based on cylindrical multielement piezocomposite transducer made by Materials Systems Inc. (Littleton, USA). The paper describes key features of the DDS technology demonstrator and specific technological principles of the sonar construction. The first DDS harbour trials are planned take place during May 2010.
Źródło:
Hydroacoustics; 2010, 13; 75-82
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Broadband LFM signal source for a module-based diver detection sonar
Autorzy:
Zachariasz, K.
Lis, W.
Elminowicz, A.
Powiązania:
https://bibliotekanauki.pl/articles/332017.pdf
Data publikacji:
2010
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
A new approach to design of the diver detection sonar’s sounding pulse source is pre-sented. It is based on modules comprising 8 or 16 elements of the transducer grouped on the transmitting channel. The basic advantage of this solution is that it reduces significantly the number of group transmitters. The required output power and topology of the transmitters were determined through theoretical estimation and measurements in a four terminal network. Measurements were taken of the frequency characteristics in the transducer modules includ-ing the compensation system used. It is demonstrated that the source level is most irregular in the transducer under examination when the transducer’s voltage has a constant amplitude, i.e. with parallel compensation. It is also demonstrated that by appropriately selecting ele-ments for a series compensation of the transducer, the frequency characteristics becomes more regular and source level is increased at the extreme ends of the working bandwidth. The result is a compensated characteristics on the receiving side.
Źródło:
Hydroacoustics; 2010, 13; 269-278
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 19

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