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Wyświetlanie 1-15 z 27
Tytuł:
Reliable underwater communication system for shallow coastal waters
Autorzy:
Schmidt, J.
Powiązania:
https://bibliotekanauki.pl/articles/332091.pdf
Data publikacji:
2014
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
This paper presents a reliable and robust low data rate spread spectrum approach which is implemented in the acoustic underwater communication system for shallow coastal waters. It shows operation assumptions of spread spectrum techniques based on the wellknown Shannon equation. It describes two methods of spread spectrum: frequency hopping spread spectrum and direct sequence spread spectrum; their block diagram and their characteristics are then listed to make comparisons. In short, adverse channel effect is analyzed on the expected operation of the system. I present the platform for the target implementation of the acoustic underwater communication system, which now has to allow continuous and easy development of stable algorithms.
Źródło:
Hydroacoustics; 2014, 17; 171-178
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The development of an underwater telephone for digital communication purposes
Autorzy:
Schmidt, J.
Powiązania:
https://bibliotekanauki.pl/articles/331641.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
digital signal processor
spread spectrum
DDC
DUC
STANAG 1074/1475
Opis:
The underwater telephone HTL-10 has been designed to provide voice and data communication between helicopter and submarines using acoustic waves. It works in a halfduplex mode and uses analogue power-efficient modulation in the form of a single side-band, suppressed carrier, in a wide range of frequencies. It generates the transmitted signal, and processes the received signals. It is implemented with the use of digital signal processing techniques. Although it was designed several years ago, the flexible structure of the underwater telephone ensures a convenient platform for the implementation of various types of communication, as well as testing. This ability is due to the particular characteristics of the digital signal-processing module, which was designed by the author, both in hardware and software. The main elements of the module consist of the fixed-point signal processor, and the floating-point high performance digital signal processor. The article demonstrates the ability to adapt HTL-10 to implement digital communication in shallow waters, with a robust low data rate spread spectrum approach.
Źródło:
Hydroacoustics; 2016, 19; 341-352
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Implementation of the digital receiver in multibeam long-range sonar
Autorzy:
Schmidt, J.
Schmidt, A.
Powiązania:
https://bibliotekanauki.pl/articles/331768.pdf
Data publikacji:
2013
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The article presents the implementation of a digital receiver in multibeam long-range sonar. Developed by the authors of the article, the implementation was part of sonar modernisation on large Polish Navy ships. The article explains the structure of the receiver, its design details and requirements affecting the architecture. The technical solutions regarding the equipment and signal processing algorithms for determining receiving beams for the active and passive mode are discussed. Key to the receiver design is the signal processing module responsible for determining the multibeam spatial filter (beamformer). Aspects of modern data transmission as used in the device are also discussed.
Źródło:
Hydroacoustics; 2013, 16; 203-210
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
High resolution methods of the analysis of acoustic signals in medicine
Autorzy:
Lis, W.
Schmidt, J.
Powiązania:
https://bibliotekanauki.pl/articles/332161.pdf
Data publikacji:
1999
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The paper describes an analysis of the possible parametric methods used to estimate the spectrum of short acoustic signals of law oscillations. These kinds of signals often appear in acoustic waves emitted by the temporomandibular joint as it moves [1-2,5]. There is reason to suppose that the frequency which is characteristic of these oscillations could be an essential parameter confirming the pathology of the joint under examination. The measurement of low oscillations is difficult and not accurate, especially when nonparametric methods are used. The paper presents the results of analysis of a simulated short oscillating pulse using the DFT non-parametric method and the parametric method of linear prediction, using Burg algorithm. Finally, results of patient analysis are given, using the FFT and parametric methods.
Źródło:
Hydroacoustics; 1999, 2; 335-340
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Measuring the impedance of ultrasonic transducers
Autorzy:
Lis, W.
Schmidt, J.
Powiązania:
https://bibliotekanauki.pl/articles/332169.pdf
Data publikacji:
2004
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
For ultrasonic transducers whose impedance is usually highly variable with frequency, impedance measurement is quite difficult. Cheap and easy devices which are currently available are not suitable for this purpose. Expensive scientific devices are known to be used; usually, they are designed for such measurements in a wide frequency band, from acoustic to microwave range. Simpler and cheaper devices with a narrower band are not commercially available. For hydroacoustic applications, the frequency range may be reduced to 1MHz or even 250 kHz in most cases. This article discusses the possibilities of building a simple and cheap automated system of measuring electric impedance of ultrasonic transducers used in hydroacoustics. The presented results are based on the concept of using a digital oscilloscope as the basic tool for measuring the impedance magnitude and phase. The results have been verified in the original measurement system.
Źródło:
Hydroacoustics; 2004, 7; 143-148
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of parametric methods of power spectrum estimation in passive sonar signals classification
Autorzy:
Schmidt, J.
Salamon, R.
Powiązania:
https://bibliotekanauki.pl/articles/332824.pdf
Data publikacji:
1999
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The paper presents the signals classification method based on the parametric spectral analysis as applied to the passive sonar. The system's structure is discussed special emphasis is given to the procedure of features selection in which true poles are chosen. Attached are results of tests carried out to evaluate the applicability of parametric methods of spectral estimation for the purpose of creating acoustic portraits and their classification.
Źródło:
Hydroacoustics; 1999, 2; 145-150
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Digital microcontroller for sonar waveform generator
Autorzy:
Schmidt, A.
Schmidt, J.
Powiązania:
https://bibliotekanauki.pl/articles/332754.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
direct digital synthesis (DDS)
digital transmitter
transmitter controller
Opis:
Generating sounding signals is essential for the operation of active sonar. The system should be highly reliable. This can be achieved through architecture, communication between the devices, and a well-designed and self–testing software. The system presented in the article is responsible for the generation of hydroacoustic sounding signals, and ensures proper interaction between power amplifiers and power supplies. Thanks to its structure, the system ensures a very stable generation of many complex sounding signals in the form of linear or hyperbolic frequency modulated pulses (up or down), continuous transmission wave with increasing frequency and others. It is used in the mine-countermeasure sonar, but can also be used in other types of hydroacoustic systems which require complex sounding signals. The article describes possible technical solutions and sounding signals.
Źródło:
Hydroacoustics; 2016, 19; 353-360
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Measurement of impulse response of shallow water communication channel by correlation method
Autorzy:
Schmidt, J.
Kochańska, I.
Schmidt, A.
Powiązania:
https://bibliotekanauki.pl/articles/331786.pdf
Data publikacji:
2017
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
underwater communications
impulse response
delay spread
Doppler spread
coherence time
coherence bandwidth
PRBS
HFM
Opis:
Performances of underwater acoustic communication (UAC) systems are strongly related to specific propagation conditions of the underwater channel; conditions that can additionally change in time due to the movement of the acoustic system transmitter and receiver or to reflection by underwater objects of the transmitted signal. The time-varying impulse response is a comprehensive description of dynamically changing transmission properties of the UAC channel. It is a basis for estimation of stochastic parameters used for designing the signaling scheme of the communication system. The paper presents the results of a measurement experiment conducted in a shallow water environment. The channel impulse response was measured by the correlation method with the use of two kinds of broadband signals: pseudo-random binary sequence (PRBS) and hyperbolic frequency modulation chirp (HFM). For each measurement result statistical transmission parameters, namely delay spread, Doppler spread, coherence time, and coherence bandwidth were estimated.
Źródło:
Hydroacoustics; 2017, 20; 149-158
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Code signals transmission using MFSK modulation in shallow waters
Autorzy:
Zachariasz, K.
Schmidt, J.
Salamon, R.
Powiązania:
https://bibliotekanauki.pl/articles/332705.pdf
Data publikacji:
2001
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The paper presents an acoustic system for the transmission of digital data in shallow coastal waters of which multi-path propagation and intense reverberations are characteristic. To ensure a small error probability of moderate speed transmission, the system uses corrective codes and a technique of incoherent modulation MFSK (Mufti Frequency Shift Keying). To synthesise the transmission signal, estimate the spectrum of the signal received and code and decode the channels, a DSP processor was used. The paper includes the results of a computer simulation in which the system was put to work in the presence of Gaussian noise. The system was tested in shallow coastal waters and the results are discussed in the paper.
Źródło:
Hydroacoustics; 2001, 4; 261-264
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Determining the impedance of ultrasonic transducers by the added elements method
Autorzy:
Lis, W.
Schmidt, J.
Wojan, Z.
Powiązania:
https://bibliotekanauki.pl/articles/332719.pdf
Data publikacji:
2005
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
There are a number of problems involved in measuring complex electrical impedance of ultrasonic transducers. This is because in the frequency function impedance tends to change values rapidly, in particular where resonances are involved. Measuring impedance using accurate bridge methods is a tedious and time-consuming process. While modern automated systems offer shorter test periods and high accuracy, they are very costly. This is why the project aims to implement new methods for computing impedance without these limitations. The article proposes a new, simplified method for measuring the electrical impedance of ultrasonic transducers. In the method complex impedance is calculated from results of two measurements of the transducer’s impedance magnitude only: with the known reactance and without it. To demonstrate the practicality of this method the authors included in the article the value of complex electrical impedance computed using the method and compared these with the results of measurements taken with an automated typical measurement system.
Źródło:
Hydroacoustics; 2005, 8; 99-104
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Acoustic signal processing in passive sonar system with towed array
Autorzy:
Raganowicz, A.
Rudnicki, M.
Schmidt, J.
Powiązania:
https://bibliotekanauki.pl/articles/331645.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
sonar system
acoustic signal processing
towed array
Opis:
The aim of this document is to introduce acoustic signal processing in passive sonar system with towed array. The concept of the "acoustic signals processing" includes all possible operations on analogue signals such as amplifying, filtering, sampling and most importantly - operations on digital signals obtained in the sampling process. Digital operations executed in the system include: synchronizing, conversion, sorting, creating deflected beams sets, plotting the power density spectrum received signals and imaging the results. Apart from digital signals processing, we focus on reciprocal connections between microcontrollers and processors in which processing is performed. At the end of this document some exemplary imagings of the output are presented, obtained at the marine testing of this system.
Źródło:
Hydroacoustics; 2008, 11; 329-338
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
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:
Underwater communication system for shallow water using modified MFSK modulation
Autorzy:
Schmidt, J.
Zachariasz, K.
Salamon, R.
Powiązania:
https://bibliotekanauki.pl/articles/332663.pdf
Data publikacji:
2005
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The paper describes the design and operation of the Modified MFSK system for underwater communication. Its function is to transmit data and commands from ships to underwater objects in shallow coastal waters and lakes. The system was primarily required to ensure energy efficiency in its underwater section and the minimum of transmission errors. The emphasis was on non-linear distortions produced in piezoelectric transducers, an untypical source of errors.
Źródło:
Hydroacoustics; 2005, 8; 179-184
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Acoustic processor of the mine countermeasures sonar
Autorzy:
Rudnicki, M.
Schmidt, J.
Schmidt, A.
Leśniak, W.
Powiązania:
https://bibliotekanauki.pl/articles/331928.pdf
Data publikacji:
2012
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
This paper presents the concept of an acoustic processor of the mine countermeasure sonar. Developed at the Department of Marine Electronics Systems, Gdansk University of Technology, the acoustic processor is an element of the MG-89, an underwater acoustic station. The focus of the article is on the modules of the processor. They are responsible for sampling analogue signals and implementing the algorithms controlling the measurement cycle and digital signal processing. As it performs the above functions, the device should be highly reliable and resistant to mechanical and weather conditions and ensure a user friendly operation. The functions of the processor software should help with object detection and classification. The results of measurements should be displayed with the shortest possible delay in relation to sounding signals to allow the operator to take decisions quickly and establish if the object poses a risk. The article demonstrates that the acoustic processor designed for and used by the Navy meets these requirements.
Źródło:
Hydroacoustics; 2012, 15; 179-186
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Silent sonar with matched filtration
Autorzy:
Salamon, R.
Marszal, J.
Schmidt, J.
Rudnicki, M.
Powiązania:
https://bibliotekanauki.pl/articles/331754.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
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.
Źródło:
Hydroacoustics; 2011, 14; 199-208
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 27

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