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    Wyświetlanie 1-12 z 12
    Tytuł:
    An Experimental Study of Conducted EMI Mitigation on the LED Driver using Spread Spectrum Technique
    Autorzy:
    Yanuar, M. H.
    Hidayat, R.
    Firmansyah, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/226428.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    LED driver
    conducted
    EMI
    luminance
    spread spectrum
    Opis:
    LED driver has the potential to interfere the system of electronic devices if the voltage and current change rapidly. Several previous studies presented various solutions to overcome this problem such as particular converter design, component design, electromagnetic interference (EMI) filters, and spread-spectrum techniques. Compared to other solutions, the spread-spectrum technique is the most potential way to reduce the EMI in LED applications due to its limited cost-size-weight. In this paper, the effectiveness of conducted EMI suppression performance and the evaluation of its effect on LED luminance using spread-spectrum techniques are investigated. Spread-spectrum is applied to the system by modifying the switching frequency by providing disturbances at pin IADJ. The disorder is given in the form of four signals, namely square, filtered-square, triangular, and sine disturbance signals. The highest level of the EMI suppression of about 31.89% is achieved when the LED driver is given 800 mVpp filtered-square waveform. The highest reduction power level occurs at fundamental frequency reference, when it is given 700 mVpp square disruption signal, is about 81.77% reduction. The LED luminance level will reduce by 85.2% when it is given the four waveforms disruption signals. These reductions occur as the switching frequency of the LED driver does not work on a fixed frequency, but it varies in certain bands. LED brightness level has a tendency to generate a constant value of 235 lux when it is given the disruption signals. This disturbance signal causes the dimming function on the system that does not work properly.
    Źródło:
    International Journal of Electronics and Telecommunications; 2016, 62, 3; 293-299
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Velocity measurement using the FDOA Method in ground-based radio navigation system
    Autorzy:
    Sadowski, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/221491.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    radio navigation
    spread spectrum
    velocity estimation
    FDOA
    Opis:
    Velocity is one of the main navigation parameters of moving objects. However some systems of position estimation using radio wave measurements cannot provide velocity data due to limitation of their performance. In this paper a velocity measurement method for the DS-CDMA radio navigation system is proposed, which does not require full synchronization of reference stations carrier frequencies. The article presents basics of FDOA (frequency difference of arrival) velocity measurements together with application of this method to an experimental radio navigation system called AEGIR and with some suggestions about the possibility to implement such FDOA measurements in other kinds of asynchronous DS-CDMA radio networks. The main part of this paper present results of performance evaluation of the proposed method, based on laboratory measurements.
    Źródło:
    Metrology and Measurement Systems; 2014, 21, 2; 363-376
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Conducted EMI mitigation in switched mode dc-dc converters by spread spectrum techniques
    Autorzy:
    Knitter, A.
    Łuszcz, J.
    Chrzan, P. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/262735.pdf
    Data publikacji:
    2005
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
    Tematy:
    spread spectrum
    carrier frequency modulation
    EMI suppression
    electromagnetic compatibility
    Opis:
    In this paper effectiveness of spread spectrum modulation techniques to the electromagnetic interference (EMI) suppression is investigated. Comparative evaluation of spread spectrum methods is reviewed and demonstrated with the aid of function generator and EMI receiver. Obtained results indicate advantageous features of random carrier frequency modulation (CFM), which results in more steady spectral distribution. For a switch mode dc-dc converter, random and periodical sinusoidal CFM is systematically tested. Based on disturbance voltage measurements using Line Impedance Stabilization Network (LISN) and EMI receiver, conducted emission spectra are evaluated in function of the defined randomness index R and frequency range. For the acceptable range of R variations up the 20dB EMI suppression level was reached.
    Źródło:
    Electrical Power Quality and Utilisation. Journal; 2005, 11, 2; 49-55
    1896-4672
    Pojawia się w:
    Electrical Power Quality and Utilisation. Journal
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On a method to improve correlation properties of orthogonal polyphase spreading sequences
    Autorzy:
    Wysocki, B. J.
    Wysocki, T. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/307741.pdf
    Data publikacji:
    2003
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    spread spectrum communications
    orthogonal sequences
    wireless communications
    wireless LAN
    correlation
    Opis:
    In this paper, we propose a simple but efficient method for improving correlation properties of polyphase spreading sequences for asynchronous direct sequence code division multiple access (DS CDMA) applications. The proposed method can be used to reduce the mean square value of aperiodic crosscorrelation or the mean square value of aperiodic autocorrelation, the maximum value of aperiodic crosscorrelation functions, merit factor or other properties of the sequence set. The important feature of the method is that while it modifies correlation properties of the sequence set, it preserves sequence orthogonality for perfect synchronization, if this is the property of the original sequence set.
    Źródło:
    Journal of Telecommunications and Information Technology; 2003, 2; 99-105
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Optimum double-matched detection and its application to SSMA systems
    Autorzy:
    Pawelec, J.J.
    Powiązania:
    https://bibliotekanauki.pl/articles/309576.pdf
    Data publikacji:
    2001
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    optimum detection
    spread spectrum multiple access systems
    NB interference
    adaptation
    Opis:
    This paper is concerned with the issue of optimum detection of known signal in nonwhite noise and/or narrow-band interferences. The detection is carried out in three steps. First, some function related to the power spectrum of interfering process I(z) is estimated via adaptation. Second, the signal + interference is withened due to I(z). Third, the replica of signal is filtered via I(z) to match it to the deformed signal in the previous step. The simulation of SS reception in presence of NB interference shows a high gain in comparison to classical single-matched detection.
    Źródło:
    Journal of Telecommunications and Information Technology; 2001, 3; 80-85
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    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:
    Walsh-chirp sequences for wireless applications
    Autorzy:
    Wysocki, B. J.
    Wysocki, T. A.
    Zepernick, H.-J.
    Powiązania:
    https://bibliotekanauki.pl/articles/309560.pdf
    Data publikacji:
    2001
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    spread spectrum communications
    polyphase spreading sequences
    multi-access interference
    Walsh sequences
    aperiodic correlation functions
    Opis:
    This paper deals with a new method to design polyphase spreading sequences for DS CDMA wireless applications. The method is based on weighting symbols of the orthogonal Walsh sequences by the complex factors being symbols of baseband chirp sequences. The resulting sequences possess good aperiodic correlation properties, while maintaining the orthogonality. Because of the parametric design, the sequences can be optimized to achieve desired characteristics.
    Źródło:
    Journal of Telecommunications and Information Technology; 2001, 3; 24-28
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analysis of correlation and spectral characteristics of fractal comb-structured signals
    Analiza charakterystyk korelacyjnych i spektralnych sygnałów fraktalnych o strukturze grzebieniowej
    Autorzy:
    Politanskyi, R.
    Veryga, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/408873.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Lubelska. Wydawnictwo Politechniki Lubelskiej
    Tematy:
    fractal
    signal analysis
    spread spectrum communication
    fraktal
    analiza sygnału
    komunikacja (łączność).za pomocą widma (rozproszonego) (szerokiego)
    Opis:
    The paper presents theoretical and experimental investigations of the spectra of fractal comb-structured signals for different values of their coefficient of generation, as well as analyzes autocorrelation characteristics and phase portraits depending on the coefficient of generation. It is established that signal base increases with increasing fractal order and with decreasing coefficient of generation.
    W pracy przedstawiono teoretyczne i eksperymentalne badania widm sygnałów fraktalnych o strukturze grzebieniowej dla różnych wartości ich współczynnika generowania, a także przeprowadzono analizę charakterystyk autokorelacji i portretów fazowych w zależności od współczynnika generowania. Ustalono, że baza sygnału wzrasta wraz ze wzrostem rzędu fraktali oraz ze spadkiem współczynnika generowania.
    Źródło:
    Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska; 2016, 1; 44-46
    2083-0157
    2391-6761
    Pojawia się w:
    Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska
    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:
    Performance of the Direct Sequence Spread Spectrum Underwater Acoustic Communication System with Differential Detection in Strong Multipath Propagation Conditions
    Autorzy:
    Schmidt, Jan H.
    Kochańska, Iwona
    Schmidt, Aleksander M.
    Powiązania:
    https://bibliotekanauki.pl/articles/31339747.pdf
    Data publikacji:
    2024
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    direct sequence spread spectrum
    DSSS
    m-sequences
    Kasami codes
    shallow-water channel
    multipath propagation
    underwater acoustic communications
    UAC
    Opis:
    The underwater acoustic communication (UAC) operating in very shallow-water should ensure reliable transmission in conditions of strong multipath propagation, significantly disturbing the received signal. One of the techniques to achieve this goal is the direct sequence spread spectrum (DSSS) technique, which consists in binary phase shift keying (BPSK) according to a pseudo-random spreading sequence. This paper describes the DSSS data transmission tests in the simulation and experimental environment, using different types of pseudo-noise sequences: m-sequences and Kasami codes of the order 6 and 8. The transmitted signals are of different bandwidth and the detection at the receiver side was performed using two detection methods: non-differential and differential. The performed experiments allowed to draw important conclusions for the designing of a physical layer of the shallow-water UAC system. Both, m-sequences and Kasami codes allow to achieve a similar bit error rate, which at best was less than 10−3. At the same time, the 6th order sequences are not long enough to achieve an acceptable BER under strong multipath conditions. In the case of transmission of wideband signals the differential detection algorithm allows to achieve a significantly better BER (less than 10−2) than nondifferential one (BER not less than 10−1). In the case of narrowband signals the simulation tests have shown that the non-differential algorithm gives a better BER, but experimental tests under conditions of strong multipath propagation did not confirm it. The differential algorithm allowed to achieve a BER less than 10−2 in experimental tests, while the second algorithm allowed to obtain, at best, a BER less than 10−1. In addition, two indicators have been proposed for a rough assessment which of the detection algorithms under current propagation conditions in the channel will allow to obtain a better BER.
    Źródło:
    Archives of Acoustics; 2024, 49, 1; 129-140
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Simulation of direct-sequence spread spectrum data transmission system for reliable underwater acoustic communications
    Autorzy:
    Kochańska, Iwona
    Schmidt, Jan H.
    Powiązania:
    https://bibliotekanauki.pl/articles/128008.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Poznańska. Instytut Mechaniki Stosowanej
    Tematy:
    underwater acoustic communications
    UAC
    direct sequence spread spectrum
    DSSS
    PRBS
    akustyczna komunikacja podwodna
    bezpośrednie modulowanie nośnej sekwencją kodową
    pseudolosowa sekwencja bitów
    Opis:
    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.
    Źródło:
    Vibrations in Physical Systems; 2019, 30, 1; 1-8
    0860-6897
    Pojawia się w:
    Vibrations in Physical Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-12 z 12

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