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Katedra Sygnałów i Systemów WETI

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Katalog Publikacji

Rok 2024
Rok 2023
  • Fast Algorithms for Identification of Time-Varying Systems with Both Smooth and Discontinuous Parameter Changes
    Publikacja

    The problem of noncausal identification of a time-varying linear system subject to both smooth and occasional jump-type changes is considered and solved using the preestimation technique combined with the basis function approach to modeling the variability of system parameters. The proposed estimation algorithms yield very good parameter tracking results and are computationally attractive.

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  • Noise effect on parameters of quiet sonar with code modulation

    Earlier publications of the paper authors have shown that the use of code keying mixed with the CW FM sound signal allows the significant reduction in the distance measurement error, compared to classic silent CW FM sonar. In addition to the code modulation parameters, the magnitude of this error is influenced by the received input acoustic noise. The article shows the dependence of the input signal-to-noise ratio and the sound...

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  • Określanie liczby sygnałów echa w zmodyfikowanej metodzie Prony’ego w zastosowaniu do echosondy interferometrycznej
    Publikacja

    - Rok 2023

    W rozprawie zaprezentowana została analiza możliwości poprawy dokładności określania głębokości w echosondzie interferometrycznej. Analiza dostępnych źródeł wykazała, że jednym ze sposobów na osiągnięcie poprawy dokładności jest zastosowanie zaawansowanych metod określania kierunku. Spośród odstępnych metod wybrano Zmodyfikowaną Metodę Prony’ego i zastosowano ją do przetwarzania sygnałów w echosondzie interferometrycznej. Aby poprawnie...

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  • Synchronization system for underwater acoustic communications using in shallow waters

    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....

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  • Towards Robust Identification of Nonstationary Systems
    Publikacja

    The article proposes a fast, two-stage method for the identification of nonstationary systems. The method uses iterative reweighting to robustify the identification process against the outliers in the measurement noise and against the numerical errors that may occur at the first stage of identification. We also propose an adaptive algorithm to optimize the values of the hyperparameters that are crucial for this new method.

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  • Wake-Up Receiver for Underwater Acoustic Communication Using in Shallow Water
    Publikacja

    A data frame transmitted over the underwater acoustic channel usually begins with a preamble. Therefore, underwater communication systems have a dedicated receiver that constantly listens to the preamble signals. A receiver that is to work effectively in shallow waters must have solutions that effectively reduce the impact of the permanently occurring multipath propagation. The article presents a solution based on complementary...

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Rok 2022
Rok 2021
Rok 2020
Rok 2019
Rok 2018
Rok 2017
  • Analysis of distance measurement errors in CW FM sonar with MLS code modulation
    Publikacja

    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...

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  • Bearing estimation using double frequency reassignment for a linear passive array

    The paper demonstrates the use of frequency reassignment for bearing estimation. For this task, signals derived from a linear equispaced passive array are used. The presented method makes use of Fourier transformation based spatial spectrum estimation. It is further developed through the application of two-dimensional reassignment, which leads to obtaining highly concentrated energy distributions in the joint frequency-angle domain...

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  • Canonical switched capacitor converters. Comments, complements, and refinements
    Publikacja

    - Rok 2017

    Switched Capacitor Converters (SCC) form useful blocks in low/medium power applications as they are suitable for integration, both as off-chip and on-chip IC realizations. However, the problem with SCC is that their voltage conversion ratio is topology-dependent. By changing the SC circuit configuration, we can gain control over voltage conversion but the available ratio remains of a discrete nature, i.e. it maps into a countable...

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  • Chirp Rate and Instantaneous Frequency Estimation: Application to Recursive Vertical Synchrosqueezing
    Publikacja

    - IEEE SIGNAL PROCESSING LETTERS - Rok 2017

    This letter introduces new chirp rate and instantaneous frequency estimators designed for frequency-modulated signals. These estimators are first investigated from a deterministic point of view, then compared together in terms of statistical efficiency. They are also used to design new recursive versions of the vertically synchrosqueezed short-time Fourier transform, using a previously published method (D. Fourer, F. Auger, and...

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  • Estimation of time-frequency complex phase-based speech attributes using narrow band filter banks
    Publikacja

    - Rok 2017

    In this paper, we present nonlinear estimators of nonstationary and multicomponent signal attributes (parameters, properties) which are instantaneous frequency, spectral (or group) delay, and chirp-rate (also known as instantaneous frequency slope). We estimate all of these distributions in the time-frequency domain using both finite and infinite impulse response (FIR and IIR) narrow band filers for speech analysis. Then, we present...

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  • Implementation of DIFAR Processing in ASW Dipping Sonar
    Publikacja

    - Rok 2017

    This paper presents the implementation of the signal processing algorithm used by buoy DIFAR (Directional Frequency Analysis and Recording), that is fully operational on Polish Navy anti-submarine warfare (ASW) helicopters and ships, applied to dipping sonars for detection and tracking of submarines. The development of the DSP algorithms was a part of the modernization of sonars conducted at the Gdansk University of Technology....

  • Measurement of Impulse Response of Shallow Water Communication Channel by Correlation Method

    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...

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  • Probe signal processing for channel estimation in underwater acoustic communication system
    Publikacja

    Underwater acoustic communication channels are characterized by a large variety of propagation conditions. Designing a reliable communication system requires knowledge of the transmission parameters of the channel, namely multipath delay spread, Doppler spread, coherence time, and coherence bandwidth. However, the possibilities of its estimation in a realtime underwater communication system are limited, mainly due to the computational...

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  • Testing the Wide-Sense Stationarity of Bandpass Signals for Underwater Acoustic Communications
    Publikacja

    - Rok 2017

    The Underwater Acoustic Communication (UAC) systems work in communication channels characterized by a large variety of multipath propagation conditions that can additionally change over time. Designing a reliable communication system requires knowledge of the transmission parameters of the channel. There is a need for the development of adaptive signaling schemes that would dynamically optimize the signal parameters of the physical...