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1

Simulation of direct-sequence spread spectrum data transmission system for reliable underwater acoustic communications

Kochańska Iwona, Schmidt Jan H.

Vibrations in Physical Systems

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2019

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Vol. 30, nr 1

art. no. 2019108

EN

Underwater acoustic communication (UAC) system designers tend to transmit as much information as possible, per unit of time, at as low as possible error rate. It is a particularly difficult task in a shallow underwater channel in which the signal suffers from strong time dispersion due to multipath propagation and refraction phenomena. The direct-sequence spread spectrum technique (DSSS) applied successfully in the latest standards of wireless communications, gives the chance of reliable data transmission with an acceptable error rate in a shallow underwater channel. It utilizes pseudo-random sequences to modulate data signals, and thus increases the transmitted signal resilience against the inter symbol interference (ISI) caused by multipath propagation. This paper presents the results of simulation tests of DSSS data transmission with the use of different UAC channel models using binary spreading sequences.

2

Measurement of impulse response of shallow water communication channel by correlation method

Schmidt J., Kochańska I., Schmidt A.

Hydroacoustics

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2017

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Vol. 20

149--158

EN

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.

3

Assessment of the accuracy of synchronous generator model parameter estimation based on noisy dynamic waveforms

Berhausen S., Paszek S.

Przegląd Elektrotechniczny

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2015

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R. 91, nr 7

16-20

EN

In the paper, there are presented the results of parameter estimation of the mathematical model of a synchronous generator operating in a single-machine power system. Noisy dynamic waveforms caused by introducing a disturbance in the form of a step change in the reference voltage or a pseudorandom signal to the generator voltage regulator system were the basis of estimation. It was assumed that the generator load was close to the rated one. Finite and infinite impulse response zero-phase digital filters were used for filtering the waveforms. The least squares method was used for parameter estimation, and the gradient method was applied to minimization of the mean square error.

PL

W artykule przedstawiono wyniki estymacji parametrów modelu matematycznego generatora synchronicznego pracującego w jednomaszynowym systemie elektroenergetycznym. Podstawą estymacji są zaszumione przebiegi dynamiczne wywołane wprowadzeniem do układu regulacji napięcia generatora zakłócenia w postaci skokowej zmiany napięcia zadanego lub sygnału pseudolosowego. Założono, że generator pracuje blisko znamionowego obciążenia. Do filtracji przebiegów wykorzystano filtry cyfrowe o zerowym przesunięciu fazowym o skończonej i nieskończonej odpowiedzi impulsowej. Do estymacji parametrów wykorzystano metodę najmniejszych kwadratów, a do minimalizacji błędu średniokwadratowego metodę gradientową.

4

Diagnostyka rezystancyjnych czujników temperatury za pomocą wymuszeń wewnętrznych

Wojturski J., Kowalczyk A.

Zeszyty Naukowe Politechniki Rzeszowskiej. Elektrotechnika

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2002

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z. 22 [192]

249-255

PL

W artykule przedstawiono podstawowe metody wyznaczania statycznych i dynamicznych charakterystyk rezystancyjnych czujników temperatury (RTD). Omówiono identyfikację właściwości dynamicznych czujników metodą wymuszeń wewnętrznych: LCSR, PRBS-, MBS- oraz SH-test. Wskazano na możliwość zastosowania wymuszeń wewnętrznych do kontroli statycznej charakterystyki przetwarzania czujnika.

EN

In this article, the basic methods of determination ar static and dynamic characteristics of resistance temperature detectors (RTD) were presented. Methods of internal heating tests (PRBS, MBS, LCSR and SH) for sensor identification were discussed. Attention to the possibility of control the static characteristic or resistive sensor was drawn.