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Wyświetlanie 1-10 z 12
Tytuł:
Velocity measurement using the FDOA Method in ground-based radio navigation system
Autorzy:
Sadowski, J.
Tematy:
radio navigation
spread spectrum
velocity estimation
FDOA
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Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:
https://bibliotekanauki.pl/articles/221491.pdf  Link otwiera się w nowym oknie
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.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An Experimental Study of Conducted EMI Mitigation on the LED Driver using Spread Spectrum Technique
Autorzy:
Yanuar, M. H.
Hidayat, R.
Firmansyah, E.
Tematy:
LED driver
conducted
EMI
luminance
spread spectrum
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Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:
https://bibliotekanauki.pl/articles/226428.pdf  Link otwiera się w nowym oknie
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.
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.
Tematy:
spread spectrum
carrier frequency modulation
EMI suppression
electromagnetic compatibility
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Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
Powiązania:
https://bibliotekanauki.pl/articles/262735.pdf  Link otwiera się w nowym oknie
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.
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.
Tematy:
spread spectrum communications
orthogonal sequences
wireless communications
wireless LAN
correlation
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Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Powiązania:
https://bibliotekanauki.pl/articles/307741.pdf  Link otwiera się w nowym oknie
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.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimum double-matched detection and its application to SSMA systems
Autorzy:
Pawelec, J.J.
Tematy:
optimum detection
spread spectrum multiple access systems
NB interference
adaptation
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Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Powiązania:
https://bibliotekanauki.pl/articles/309576.pdf  Link otwiera się w nowym oknie
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.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The development of an underwater telephone for digital communication purposes
Autorzy:
Schmidt, J.
Tematy:
digital signal processor
spread spectrum
DDC
DUC
STANAG 1074/1475
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Wydawca:
Polskie Towarzystwo Akustyczne
Powiązania:
https://bibliotekanauki.pl/articles/331641.pdf  Link otwiera się w nowym oknie
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.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Walsh-chirp sequences for wireless applications
Autorzy:
Wysocki, B. J.
Wysocki, T. A.
Zepernick, H.-J.
Tematy:
spread spectrum communications
polyphase spreading sequences
multi-access interference
Walsh sequences
aperiodic correlation functions
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Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Powiązania:
https://bibliotekanauki.pl/articles/309560.pdf  Link otwiera się w nowym oknie
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.
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.
Tematy:
fractal
signal analysis
spread spectrum communication
fraktal
analiza sygnału
komunikacja (łączność).za pomocą widma (rozproszonego) (szerokiego)
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Wydawca:
Politechnika Lubelska. Wydawnictwo Politechniki Lubelskiej
Powiązania:
https://bibliotekanauki.pl/articles/408873.pdf  Link otwiera się w nowym oknie
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.
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
Tematy:
underwater acoustic communications
UAC
direct sequence spread spectrum
DSSS
akustyczna komunikacja podwodna
bezpośrednie modulowanie nośnej sekwencją kodową
Pokaż więcej
Wydawca:
Politechnika Poznańska. Instytut Mechaniki Stosowanej
Powiązania:
https://bibliotekanauki.pl/articles/2146643.pdf  Link otwiera się w nowym oknie
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.
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-10 z 12

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