Temat: frequency modulation

Skocz do pozycji: 1.

Tytuł:: The diagnosis of onboard generators (alternators)
Autorzy:: Gębura, A.
Radoń, T.
Tematy:: technical diagnostics
frequency modulation; Pokaż więcej
Wydawca:: Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Powiązania:: https://bibliotekanauki.pl/articles/258804.pdf Link otwiera się w nowym oknie
Opis:: In the paper selected problems related to diagnostics of onboard generators and alternators fitted with control systems are discussed. Problems refer to commutator generators and synchronous single- and threephase alternators. Special attention is paid to commutation effects. Results of incorrectness and possibility to detect them are discussed. There are also discussed effects associated with changes in a character of pulsation, which occur during shortings or insulation clearances in rotor or stator wiring. Possibility of diagnosis of generator’s or alternator’s parts by means of analysis of pulsation component parameters is indicated. In the case of alternators a number of diagnostic methods based on observation of changes in shape of voltage or frequency modulation, is discussed. This allows to detect many mechanical or electrical faults of generators, alternators or their control systems.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: The simple analysis method of nonlinear frequency distortions in FMCW radar
Autorzy:: Kulpa, K. S.
Wojtkiewicz, A.
Nałęcz, M.
Misiurewicz, J.
Tematy:: radar
nonlinear frequency distortions
linear frequency modulation; Pokaż więcej
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Powiązania:: https://bibliotekanauki.pl/articles/309080.pdf Link otwiera się w nowym oknie
Opis:: The paper presents a simple method for estimating nonlinear frequency distortions of linear frequency modulated (LFM) signals used in FMCW radars. This method, derived from the polynomial model of the nonlinear FM signal phase, is based on finding the maximum of two-dimensional chirp-like transform of the IF video signal. The IF signal is obtained by mixing transmitted FM signal with its delayed copy. Using suggested transform we show that the presented method is able to detect and classify signal distortions.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Transmission Perspective on the Mechanism of Coarse and Fine Crackle Sounds
Autorzy:: Lu, Bing-Yuh
Hsueh, Meng-Lun
Wu, Huey-Dong
Tematy:: crackles
computer simulation
lung sound
respiration
amplitude modulation
frequency modulation; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czasopisma i Monografie PAN
Powiązania:: https://bibliotekanauki.pl/articles/1953484.pdf Link otwiera się w nowym oknie
Opis:: The possibility of a normal distribution indicates that few particles are in the same phase during a breath and their reflections can be observed on the chest wall, then a few explosive waves with relatively large power occurr occasionally. Therefore, the one-cycle sine wave which is simulated as a single burst of the explosive effect phenomenon penetrates through the chest wall and was analysed to explore the reason of the crackle sounds. The results explain the differences between the definitions of crackle proposed by Sovijärvi et al. (2000a). The crackles in the lungs were synthesised by a computer simulation. When the coarse crackles occur, the results indicate that higher burst frequency carriers (greater than 100 Hz) directly penetrate the bandpass filter to simulate the chest wall. The simulated coarse crackle sounds were low pitched, with a high amplitude and long duration. The total duration was greater than 10 ms. However, for a lower frequency carrier (approximately 50 Hz), the fundamental frequency component was filtered out. Therefore, the second harmonic component of the lower frequency carrier, i.e., the fine crackle, penetrated the chest wall. Consequently, it is very possible that the normal lung sounds may contain many crackle-shaped waves with very small amplitudes because of the filtering effects of the chest wall, environment noises, electric devices, stethoscopes, and human ears, the small crackles disappear in the auscultations. In addition, our study pointed out that some unknown crackles of the very low frequency under the bandwidth of the human ears cannot penetrate the airways and be detected by medical doctors. Therefore, it might be necessary to focus advanced electronic instrumentation on them in order to analyse their possible characteristics for diagnosis and treatment of the respiration system.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

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; Pokaż więcej
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

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Skocz do pozycji: 5.

Tytuł:: Nonlinear magneto-optical rotation with amplitude modulated light
Autorzy:: Krzemień, Leszek
Sushkov, A. O.
Budker, D.
Sangla, D.
Gawlik, Wojciech
Pustelny, Szymon
Zachorowski, Jerzy
Graf, M.
Opis:: The technique of nonlinear magneto-optical rotation with amplitude modulated light is developed. The technique is an alternative to its counterpart with frequency modulated light and can be applied to sensitive measurements of magnetic fields ranging from microgauss to the Earth-field level. The rotation signals exhibit nontrivial features such as narrowed non-Lorentzian line shapes and multicomponent resonances.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 6.

Tytuł:: Microwave frequency modulation in CW EPR at W-band using a loop-gap resonator
Autorzy:: Sidabras, Jason W.
Anderson, James R.
Strangeway, Robert A.
Hyde, James S.
Camenisch, Theodore G.
Froncisz, Wojciech
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

Artykuł

na półce

Skocz do pozycji: 7.

Tytuł:: Model flickermetru dla modulacji częstotliwości napięcia wejściowego
A model of the flickermeter for frequency modulation of input voltage
Autorzy:: Wiczyński, G.
Tematy:: flickermetr
model
wskaźnik Pst
modulacja FM
flickermeter
Ps
indicator
frequency modulation; Pokaż więcej
Wydawca:: Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Powiązania:: https://bibliotekanauki.pl/articles/153232.pdf Link otwiera się w nowym oknie
Opis:: Flickermetr jest potoczną nazwą układu do pomiaru uciążliwości odczuwania migotania światła wywołanego wahaniami napięcia. Przetwarzanie toru sygnałowego tego układu jest na tyle złożone, że analityczne wyznaczenie wartości wyjściowych nie jest proste. Założonym celem prac opisanych w artykule jest budowa prostego modelu dla modulacji częstotliwości FM sygnału wejściowego. Obecnie brak specyfikacji normatywnej flickermetru do modulacji FM. W artykule zaproponowano model flickermetru dla modulacji FM sygnałami wolnozmiennymi i w zakresie od 1Hz do 100 Hz. Dokonano ocenę prawidłowości aproksymacji charakterystyk dla modulacji FM przebiegami harmonicznym i prostokątnym, bazując na wynikach symulacji numerycznych. Prezentowany model ułatwia zrozumienie działania badanego toru sygnałowego flickermetru i weryfikację prawidłowości działania rzeczywistych układów pomiarowych w rozpatrywanym zakresie częstotliwości sygnału modulującego FM.
The aim of studies presented in the paper is a structure of the simple model for FM frequency modulation of the input signal. There is a lack of the flickermeter standard specification in this subject. Based on results of numerical simulations, evaluation of approximation correctness of characteristics for FM modulation with harmonic as well as rectangular waveforms has been made. The equations for FM modulation using slowly varying signals and signals in the frequency range from 1 Hz to 100 Hz are proposed. The presented model facilitates understanding the operation of the tested flickermeter signal chain and verification of the operation correctness of real measuring systems in the considered frequency range.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Wpływ metody akwizycji sygnałów częstotliwościowych na dokładność pomiaru
Effect of the method of frequency signal acquisition on the measurement accuracy
Autorzy:: Świsulski, D.
Pawłowski, E.
Tematy:: akwizycja sygnałów
sygnał impulsowy modulowany częstotliwościowo
signal acquisition
pulse frequency modulation signal; Pokaż więcej
Wydawca:: Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Powiązania:: https://bibliotekanauki.pl/articles/155228.pdf Link otwiera się w nowym oknie
Opis:: W artykule przedstawiono metody przetwarzania impulsowego sygnału częstotliwościowego. Opisane metody pozwalają na odtworzenie wartości wielkości mierzonej w stałych odstępach czasu w trybie on-line i off-line. Przeprowadzono symulację pomiaru prędkości obrotowej przetwornikiem obrotowo-impulsowym, wyznaczając wartości błędu pomiaru i efektywnej liczby bitów. Wykazano mniejszą wartość błędu i większą wartość efektywnej liczby bitów dla metody wykorzystującej dwa przedziały między-impulsowe.
Methods for processing a frequency-modulated pulse signal are presented in this paper. The methods allow acquiring information about the frequency of a pulse signal with constant sampling frequency. These methods, depending on the time instant for which the measurement result is determined, can be divided into two groups. In measurements on-line the measured value is determined based only on the position of pulses preceding the moment of measurement. The method in which the measured value is determined from the last period and that in which the measured value is determined from extrapolation of two last periods (Fig. 1) are described. In measurements off-line, first there is saved the location of all pulses in the time of recording, and after there is determined the value measured in the assumed moments of the measurement. Therefore, in this case the measured value is determined not only by the position of pulses before the moment of measurement, but also those occurring after this time. The method in which the measured value is determined from the current period and that in which the measured value is determined from interpolation of two periods (Fig. 2) are described in the paper. The accuracy of conversion is determined by a relative error or the number of bits, and thus by the resolution. The noise added to the useful signal has a significant impact on the processing accuracy in real measurements. Therefore the ENOB (Effective Number of Bits), the number of digital signal bits above the noise, is more useful than the resolution. The paper presents examples of simulation results for speed measurements (Tables 1, 2). As it can be seen from the results, increase in the standard generator frequency allows increasing the effective number of bits only to a certain limit. Further increase in the frequency does not increase the ENOB value due to the noise being a result of the method used.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Distance measurement errors in silent FM-CW sonar with matched filtering
Autorzy:: Marszal, J.
Salamon, R.
Tematy:: silent sonar
frequency modulation
continuous wave
matched filtering
distance measurement
errors
Doppler effect; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/220637.pdf Link otwiera się w nowym oknie
Opis:: The secretiveness of sonar operation can be achieved by using continuous frequency-modulated sounding signals with reduced power and significantly prolonged repeat time. The application of matched filtration in the sonar receiver provides optimal conditions for detection against the background of white noise and reverberation, and a very good resolution of distance measurements of motionless targets. The article shows that target movement causes large range measurement errors when linear and hyperbolic frequency modulations are used. The formulas for the calculation of these errors are given. It is shown that for signals with linear frequency modulation the range resolution and detection conditions deteriorate. The use of hyperbolic frequency modulation largely eliminates these adverse effects.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Passivity-based control strategy for resonant converterbased on Euler–Lagrange model
Autorzy:: Zhang, Yajing
Liang, Weihao
Wang, Xiuteng
Li, Lifen
Tematy:: LLC resonant converter
passivity based control
PWM
pulse width modulation
fixed frequency modulation
soft switching technology; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czasopisma i Monografie PAN
Powiązania:: https://bibliotekanauki.pl/articles/59111827.pdf Link otwiera się w nowym oknie
Opis:: The LLC resonant converter is a widely used DC/DC converter that offers the benefit of enabling soft switching compared to classical DC/DC converters. However, traditional PI control strategy based on a linear model has drawbacks such as slow dynamic response and poor anti-interference performance. To overcome the shortage, a passivity based control strategy based on the Euler–Lagrange (EL) model is proposed in this paper to improve the dynamic performance of the half-bridge LLC resonant converter. In addition, the stability of the system based on the proposed strategy is analyzed and verified. Further, the effectiveness and performance of the proposed strategy is verified in the simulation by comparing with the traditional PI controller. Finally, a prototype was built to verify the dynamic performance of the LLC resonant converter based on the proposed control strategy.
Dostawca treści:: Biblioteka Nauki

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