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Tytuł:
General analysis of broadband signal spatial filtration
Autorzy:
Salamon, R.
Rudnicki, M.
Schmidt, J.
Powiązania:
https://bibliotekanauki.pl/articles/332491.pdf
Data publikacji:
2003
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
acoustics
spatial filtration
underwater acoustic
Opis:
The majority of underwater acoustic systems use narrow band sounding signals. Consequently, there is extensive knowledge on how the relevant spatial filters should be analysed and designed. The difficulty begins when the sounding signal has a broad spectrum. Applying the results of narrow band signal analysis to broadband signals leads to serious errors. The same is true for spatial filtration methods when applied to narrow band signals. The article presents a general method for analysing spatial filters designed for broadband signals. It also gives an assessment of the errors caused by applying spatial filtration methods designed for narrow band signals.
Źródło:
Hydroacoustics; 2003, 6; 251-260
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of the vertical distribution of the sound speed of the Gulf of Gdansk in the years 2000-2010
Autorzy:
Grelowska, G.
Witos, D.
Powiązania:
https://bibliotekanauki.pl/articles/332481.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
shallow water acoustics
underwater acoustic climate
Opis:
The conditions of the acoustic wave propagation in the southern Baltic are much more complex than in other shallow waters. In the typical shallow water, seasonal changes in acoustical conditions in the upper layer, of the depth of about 60-70 m, are observed. They are caused by variation of the annual meteorological conditions. Most often, in the deep water layer, acoustical conditions are stable throughout the year. However, in the Southern Baltic they change during the year also in the deep water layer. They depend on the inflows of highly saline water from the Northern Sea through the Danish Straits, which evoke a dense bottom current increasing the salinity at the bottom. The vertical sound speed distribution in the Southern Baltic is strongly dependent on the hydrological conditions. In the paper the characteristic elements of acoustic climate of the Southern Baltic will be considered, based on data concerning the Gulf of Gdansk. Averaged characteristics of temperature, salinity and sound speed for the years 2000-2010, as well as anomalies, have been determined.
Źródło:
Hydroacoustics; 2016, 19; 129-137
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Shallow Water Experiment of OFDM Underwater Acoustic Communications
Autorzy:
Kochańska, Iwona
Schmidt, Jan H.
Marszal, Jacek
Powiązania:
https://bibliotekanauki.pl/articles/177592.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
underwater acoustic communications
UAC
orthogonal frequency-division multiplexing
OFDM
Opis:
The large variability of communication properties of underwater acoustic channels, and especially the strongly varying instantaneous conditions in shallow waters, is a challenge for the designers of underwater acoustic communication (UAC) systems. The use of phase modulated signals does not allow reliable data transmission through such a tough communication channel. However, orthogonal frequency-division multiplexing (OFDM), being a multi-carrier amplitude and phase modulation technique applied successfully in the latest standards of wireless communications, gives the chance of reliable communication with an acceptable error rate. This paper describes communication tests conducted with the use of a laboratory model of an OFDM data transmission system in a shallow water environment in Wdzydze Lake.
Źródło:
Archives of Acoustics; 2020, 45, 1; 11-18
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Emergence Angle on Acoustic Transmission in a Shallow Sea
Autorzy:
Lu, Yanyang
Yang, Kunde
Liu, Hong
Huang, Chunlong
Powiązania:
https://bibliotekanauki.pl/articles/177665.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
underwater acoustic
emergence angle
transmission loss
active sonar detection
Opis:
In this study, the effect of the emergence angle of a source array on acoustic transmission in a typical shallow sea is simulated and analyzed. The formula we derived for the received signal based on the Normal Mode indicates that the signal is determined by the beamform on the modes of all sources and the samplings of all modes at the receiving depth. Two characteristics of the optimal emergence angle (OEA) are obtained and explained utilizing the aforementioned derived formula. The observed distributions of transmission loss (TL) for different sources and receivers are consistent with the obtained characteristics. The results of this study are valuable for the development and design of active sonar detection.
Źródło:
Archives of Acoustics; 2020, 45, 1; 3-9
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Statistical Optimization of Underwater Lower-Frequency Sound Insulation for Locally Resonant Sonic Material Using Genetic Algorithm
Autorzy:
Yuan, Bo
Chen, Yong
Tan, Bilian
Li, Bo
Powiązania:
https://bibliotekanauki.pl/articles/177461.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
underwater acoustic
sound insulation
local resonance
statistical optimization
global optimum
Opis:
The locally resonant sonic material (LRSM) is an artificial metamaterial that can block underwater sound. The low-frequency insulation performance of LRSM can be enhanced by coupling local resonance and Bragg scattering effects. However, such method is hard to be experimentally proven as the Best optimizing method. Hence, this paper proposes a statistical optimization method, which first finds a group of optimal solutions of an object function by utilizing genetic algorithm multiple times, and then analyzes the distribution of the fitness and the Euclidean distance of the obtained solutions, in order to verify whether the result is the global optimum. By using this method, we obtain the global optimal solution of the low-frequency insulation of LRSM. By varying parameters of the optimum, it can be found that the optimized insulation performance of the LRSM is contributed by the coupling of local resonance with Bragg scattering effect, as well as a distinct impedance mismatch between the matrix of LRSM and the surrounding water. This indicates coupling different effects with impedance mismatches is the Best method to enhance the low-frequency insulation performance of LRSM.
Źródło:
Archives of Acoustics; 2019, 44, 2; 365-374
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Underwater target direction of arrival estimation by small acoustic sensor array based on sparse bayesian learning
Autorzy:
Wang, B.
He, C.
Powiązania:
https://bibliotekanauki.pl/articles/260588.pdf
Data publikacji:
2017
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
DOA
underwater acoustic signal processing
sparse Bayesian learning
temporally correlated source
Opis:
Assuming independently but identically distributed sources, the traditional DOA (direction of arrival) estimation method of underwater acoustic target normally has poor estimation performance and provides inaccurate estimation results. To solve this problem, a new high-accuracy DOA algorithm based on sparse Bayesian learning algorithm is proposed in terms of temporally correlated source vectors. In novel method, we regarded underwater acoustic source as a first-order auto-regressive process. And then we used the new algorithm of multi-vector SBL to reconstruct the signal spatial spectrum. Then we used the CS-MMV model to estimate the DOA. The experiment results have shown the novel algorithm has a higher spatial resolution and estimation accuracy than other DOA algorithms in the cases of less array element space and less snapshots.
Źródło:
Polish Maritime Research; 2017, S 2; 95-102
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modeling the Geometry of an Underwater Channel for Acoustic Communication
Autorzy:
Naman, Hala A.
Abdelkareem, A. E.
Powiązania:
https://bibliotekanauki.pl/articles/2174453.pdf
Data publikacji:
2022
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
channel impulse response
geometry channel model
multipath propagation
underwater acoustic communication
Opis:
The achievement of efficient data transmissions via underwater acoustic channels, while dealing with large data packets and real-time data fed by underwater sensors, requires a high data rate. However, diffraction, refraction, and reflection phenomena, as well as phase and amplitude variations, are common problems experienced in underwater acoustic (UWA) channels. These factors make it difficult to achieve high-speed and long-range underwater acoustic communications. Due to multipath interference caused by surface and ocean floor reflections, the process of modeling acoustic channels under the water’s surface is of key importance. This work proposes a simple geometry-based channel model for underwater communication. The impact that varying numbers of reflections, low water depth values, and distances between the transmitter and the receiver exert on channel impulse response and transmission loss is examined. The high degree of similarity between numerical simulations and actual results demonstrates that the proposed model is suitable for describing shallow underwater acoustic communication environments.
Źródło:
Journal of Telecommunications and Information Technology; 2022, 4; 3--12
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Methods to Estimate the Channel Delay Profile and Doppler Spectrum of Shallow Underwater Acoustic Channels
Autorzy:
Nguyen, Van Duc
Nguyen, Tien Hoa
Ho, Hoa Xuan Thi
Powiązania:
https://bibliotekanauki.pl/articles/176670.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
shallow underwater acoustic
channel parameters detection
channel delay profile
Doppler spectrum
Opis:
In this paper, we present the methods to detect the channel delay profile and the Doppler spectrum of shallow underwater acoustic channels (SUAC). In our channel sounding methods, a short impulse in form of a sinusoid function is successively sent out from the transmitter to estimated the channel impulse response (CIR). A bandpass filter is applied to eliminate the interference from out-of-band (OOB). A threshould is utilized to obtain the maximum time delay of the CIR. Multipath components of the SUAC are specified by correlating the received signals with the transmitted sounding pulse with its shifted phases from 0 to 2π. We show the measured channel parameters, which have been carried out in some lakes in Hanoi. The measured results illustrate that the channel is frequency selective for a Barrow band transmission. The Doppler spectrum can be obtained by taking the Fourier transform of the time correlation of the measured channel transfer function. We have shown that, the theoretical maximum Doppler frequency fits well to that one obtained from measurement results.
Źródło:
Archives of Acoustics; 2019, 44, 2; 375-383
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Performance of coherent modulation scheme used in acoustic underwater communication system
Autorzy:
Schmidt, Jan H.
Schmidt, Aleksander M.
Kochańska, Iwona
Powiązania:
https://bibliotekanauki.pl/articles/127757.pdf
Data publikacji:
2019
Wydawca:
Politechnika Poznańska. Instytut Mechaniki Stosowanej
Tematy:
underwater acoustic communications
shallow underwater channel
coherent modulation
akustyczna komunikacja podwodna
płytki kanał podwodny
modulacja koherentna
Opis:
The development of an acoustic underwater communication system for shallow waters is still a big scientific and construction challenge. Currently, non-coherent modulations in combination with strong channel coding are used to achieve reliable communication with low rate in such a channel. To obtain transmission with a higher transmission rate, it is required to use coherent modulation. This paper presents the assumptions of such a transmission system and the results of data transmission carried out by this system in the channel with the Rician fading, which reflects the short range shallow water channel. A digital version of the carrier phase modulation known as Phase-Shift Keying was selected for simulation.
Źródło:
Vibrations in Physical Systems; 2019, 30, 1; 1-8
0860-6897
Pojawia się w:
Vibrations in Physical Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Underwater Acoustic Sensor Node Scheduling using an Evolutionary Memetic Algorithm
Autorzy:
Sivakumar, V.
Rekha, D.
Powiązania:
https://bibliotekanauki.pl/articles/307911.pdf
Data publikacji:
2018
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
broadcast UASN scheduling
memetic algorithm
time division multiple access
underwater acoustic sensor network
Opis:
Underwater Acoustic Sensor Networks (UWASNs) play an important role in monitoring the aqueous environment which has created a lot of interest for researchers and scientists. Utilization of underwater acoustic sensor node (UASN) scheduling for transmission remains, due to the limited acoustic bandwidth available, a challenge in such an environment. One of the methods to overcome this problem is to efficiently schedule UASN data using time division multiple access (TDMA) protocols the parallel transmissions, simultaneously avoiding interference. The paper shows how to optimize the utilization of acoustic sensor node bandwidth by maximizing the possible node transmissions in the TDMA frame and also by minimizing the node's turnaround wait time for its subsequent transmissions by using an evolutionary memetic algorithm (MA). The simulation of MA-TDMA proves that as the size of the network increases, every node in UWASN transmits with an average minimal turnaround transmission time. It also proves that as the TDMA cycle repeats, the overall network throughput gets maximized by increasing the possible node transmissions in the MA-TDMA frame.
Źródło:
Journal of Telecommunications and Information Technology; 2018, 1; 88-94
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Synchronization system for underwater acoustic communications using in shallow waters
Autorzy:
Schmidt, Jan H.
Schmidt, Aleksander M.
Powiązania:
https://bibliotekanauki.pl/articles/24201990.pdf
Data publikacji:
2023
Wydawca:
Politechnika Poznańska. Instytut Mechaniki Stosowanej
Tematy:
synchronization system
underwater acoustic communications
shallow water
układy synchronizacji
akustyczna komunikacja podwodna
wody płytkie
Opis:
A reliable synchronization system of the transmitted data frame has a significant impact on the efficiency of the underwater communication system. This applies in particular to communication systems dedicated to work in shallow waters, where the phenomenon of multipath permanently occurs. To overcome these difficulties, the concept of a synchronization system consisting of two broadband signals of opposite monotonicity was presented. The method of receiving these signals has been described in detail. The stochastic channel model with Rician fading and the Watermark simulator was used to test the efficiency of the synchronization system in the underwater multipath channel.
Źródło:
Vibrations in Physical Systems; 2023, 34, 1; art. no. 2023102
0860-6897
Pojawia się w:
Vibrations in Physical Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Interaction of Resonance And Bragg Scattering Effects for the Locally Resonant Phononic Crystal with Alternating Elastic and Fluid Matrices
Autorzy:
Yuan, B.
Chen, Y.
Jiang, M.
Tang, S.
He, M.
Tu, M.
Powiązania:
https://bibliotekanauki.pl/articles/177103.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
locally resonant phononic crystals
effective speed of sound
coupling band gaps
underwater acoustic materials
Opis:
Three-dimensional (3D) locally resonant phononic crystals (LRPCs) are studied with the aim of optimising the sub-wavelength band gaps of such composites. By analysing their effective acoustic properties, it has been found that the effective acoustic speed of the composite will drop to zero when local resonance arise, and will increase monotonically when Bragg scattering effects occur. Moreover, if the matrix is a low-shear-speed medium, local resonators can significantly reduce the effective acoustic speed of the composite and, therefore, lower the frequency where Bragg scattering effects occur. Hence, a specific LRPC with alternating elastic and fluid matrices is proposed, whose resonance and Bragg gaps are already close in frequency. The fluid matrix behaves as a wave filter, which prevents the shear waves from propagating in the composite. By using the layer-multiple-scattering theory, the coupling behaviour of local resonance and Bragg scattering band gaps has been investigated. Both gaps are enhanced when they move closer to each other. Finally, a gap-coupled case is obtained that displays a broad sub-wavelength band gap. Such proposal excels at the application of underwater acoustic materials since the arrangement of structure can be handily adjusted for tuning the frequency of coupled gap.
Źródło:
Archives of Acoustics; 2017, 42, 4; 725-733
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new direct-sequence spread spectrum signal detection method for underwater acoustic communications in shallow-water channel
Autorzy:
Kochańska, Iwona
Powiązania:
https://bibliotekanauki.pl/articles/2146643.pdf
Data publikacji:
2021
Wydawca:
Politechnika Poznańska. Instytut Mechaniki Stosowanej
Tematy:
underwater acoustic communications
UAC
direct sequence spread spectrum
DSSS
akustyczna komunikacja podwodna
bezpośrednie modulowanie nośnej sekwencją kodową
Opis:
Direct-Sequence Spread Spectrum (DSSS) is one of the modulation and coding techniques used in Underwater Acoustic Communication (UAC) systems for reliable data transmision even at low signal levels. However, in a shallow water channel, there is a strong multipath propagation which causes a phase fluctuation of the received signal, affecting the performance of the spread-spectrum system. The article presents a differential method for DSSS signal detection. It is based on the calculation of the correlation coefficient of adjacent segments of signal at the output of filter matched to the spreading sequence used in the transmitter. A positive value of the correlation coefficient means that a given modulation symbol carries the same information bit as the previous one; a negative value means that the opposite bit has been transmitted. The reliability of the proposed method has been compared to classical method of DSSS signal detection, which consists in detecting the information directly from the signal at the output of the matched filter. Simulation and measurement tests of underwater acoustic communications in strong multipath propagation conditions have shown that the proposed method allows obtaining lower values of the DSSS transmission Bit Error Rate (BER) than the classical detection technique while maintaining the same data transmission rate.
Źródło:
Vibrations in Physical Systems; 2021, 32, 1; art. no. 2021106
0860-6897
Pojawia się w:
Vibrations in Physical Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Erratum: A new direct-sequence spread spectrum signal detection method for underwater acoustic communications in shallow-water channel (DOI: 10.21008/j.0860-6897.2021.1.06)
Autorzy:
Kochańska, Iwona
Powiązania:
https://bibliotekanauki.pl/articles/2146666.pdf
Data publikacji:
2022
Wydawca:
Politechnika Poznańska. Instytut Mechaniki Stosowanej
Tematy:
underwater acoustic communication
UAC
direct sequence spread spectrum
DSSS
akustyczna komunikacja podwodna
bezpośrednie modulowanie nośnej sekwencją kodową
Źródło:
Vibrations in Physical Systems; 2022, 33, 1; art. no. 2022114
0860-6897
Pojawia się w:
Vibrations in Physical Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Underwater acoustic communication system using broadband signal with hyperbolically modulated frequency
Autorzy:
Schmidt, Jan H.
Schmidt, Aleksander M.
Powiązania:
https://bibliotekanauki.pl/articles/2146694.pdf
Data publikacji:
2021
Wydawca:
Politechnika Poznańska. Instytut Mechaniki Stosowanej
Tematy:
underwater acoustic communication
shallow water
hyperbolic modulation frequency signals
akustyczna komunikacja podwodna
wody płytkie
hiperboliczna modulacja sygnałów częstotliwościowych
Opis:
The implementation of reliable acoustic underwater communication in shallow waters is a scientific and engineering challenge, mainly due to the permanent occurrence of the multipath phenomenon. The article presents the concept of a transmission system using a broadband signal with hyperbolically modulated frequency (HFM) to transmit data symbols and synchronize data frames. The simulation tests were carried out in channels with Rician fading, reflecting the short- and medium-range shallow water channels. The simulation also took into account the presence of additive Gaussian noise in the channel on the functioning of the receiver. The obtained results prove the high reliability of the underwater communication system based on broadband HFM signals.
Źródło:
Vibrations in Physical Systems; 2021, 32, 1; art. no. 2021116
0860-6897
Pojawia się w:
Vibrations in Physical Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 27

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