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Page 749 of 936 Results 7481 - 7490 of 9356

J.F.M.L. Mariano, Helena Ramos
SOME RESULTS ON THE VALIDATION OF WIDROW’S MODEL FOR SINUSOIDAL SIGNALS

Some results on the validity of Widrow’s model of quantizing sinusoidal signals in a uniform quantizer are presented. Sripad and Snyder’s formulation is used to derive a general equation for the probability density function of the quantization noise, for a generic sinusoidal signal, which is applied to different types of sinusoids. The equations obtained in this way are numerically evaluated to characterize the quantization noise by means of its average and variance. In this calculation, a novel method to accelerate the series convergence has been used. The results obtained provide a confirmation that Widrow’s model can only be applied to sinusoids when their amplitudes are much larger then the quantization step.

Leopoldo Angrisani, Mauro D’Arco, Rosario Schiano Lo Moriello, Michele Vadursi
OPTIMAL SAMPLING STRATEGIES FOR BAND-PASS MEASUREMENT SIGNALS

Data Acquisition Systems (DAS) play a fundamental role in a lot of modern measurement solutions. One of the parameters characterizing a DAS is its maximum sampling frequency. As well known from Nyquist theorem, for a correct digitization of analog signals, sampling frequency must be greater than a limit value, related to signal bandwidth. With regard to band-pass signals, which are very common in telecommunications, it is possible to single out some separated ranges of licit sampling frequencies that are significantly lower than such threshold. But, how to choose the sampling frequency conveniently? It seems that there is no instrument currently on the market that selects it properly, given the signal characteristics. The paper proposes a criterion of choice aimed at optimising the DAS resources and two algorithms that perform an automatic selection of the optimal sampling frequency.

Tomas Andersson, Peter Händel
TOWARD A STANDARDIZED MULTI-SINEWAVE FIT ALGORITHM

Multi-sinewave test methods require algorithms for multiple-tone parameter estimation. There exist a vast amount of imeko_proceedings on the topic. This paper presents a generalization of the IEEE four-parameter sinewave fit algorithm suitable to handle data comprising multiple sinewaves. The proposed method directly estimates the 3 p + 1 parameters of a p-tone model. The algorithm is analyzed numerically with emphasize on its convergence properties and statistical efficiency. The initialization of the algorithm is of major importance and an attempt to formulate a proper initialization procedure is presented.

Pier Andrea Traverso, Domenico Mirri, Gaetano Pasini, Gaetano Iuculano
CASCADED RECTANGULAR WINDOWS FOR LEAKAGE REDUCTION IN SPECTRAL ANALYSIS

A novel family of windows are proposed for digital spectrum analysis and the main figures of merit compared to those associated with both well-known and state-of-the-art windows available in the literature. The elements of the family, which are obtained by means of successive linear convolutions between elementary rectangular windows, present a very good side-lobe behaviour if a moderately high order of convolution is considered and allow for a strong reduction of the spectral leakage effect at the output of the analysis. The growth of the main-lobe within the spectrum of the proposed windows is acceptable for most of the applications, and the benefits deriving from the rapidly fading side-lobe signature can be appreciated even in presence of the need for a quite high frequency resolution, when the large storage capabilities and computational efficiency provided by modern sampling instrumentation are properly exploited.

Janusz Sawicki
ADAPTING MEDIAN FILTERING TO MEASUREMENT SIGNALS

Filtering out disturbances from transmitted or recovered measurement signals is one of the most important tasks of analog and digital signal processing for many decades. Removing of specific disturbances, having form of separate pulses (impulsive disturbances), requires specific algorithms because of very wide spectra of such pulses. The use of median procedures, especially of weighted medians, is particularly effective in such filtering procedures. According to the applied algorithm, signal samples, which include disturbances, are eliminated and replaced by some values resulting from neighbouring nondisturbed samples. The optimum weights of median filter depend on signal shape of deterministic signals. An analysis of frequency responses of medians is given in the contribution.

Dorota Rabczuk, Beata Pałczyńska, Ludwik Spiralski
DECODING OF THE FSK SIGNAL WITH NOISE AND DISTORTION WITH THE USE OF COEFFICIENTS OF THE TIME-FREQUENCY TRANSFORM

The coefficients of wavelet packet decomposition of the signal represent the components of the instantaneous spectrum. For the FSK signal which consists of two instantaneous frequencies f0 + df and f0 - df thresholding and weighing of the absolute values of decomposition coefficients at properly selected nodes shows which of the two frequencies was present in the spectrum at a time interval. In the proposed algorithm more than one vector of coefficients represent each frequency for better distinguishing the instantaneous frequencies.

Artur Wollek
A PROPOSED METHOD FOR DECREASING THE LOSSES OF THE SAMPLE NUMBER DURING A WEIGHT FILTRATION

Weight filtration is one of the methods for weakening the effect of noise exerted on dis-crete signals. The wider is the weight window, the higher is the filtration quality. However, weight fil-tration produces an undesirable side effect, namely a certain number of samples relative to the input is lost. This may be attributed to the concept of weight filtration itself. The number of lost samples is the greater, the wider is the weight window. So, the desire to get a well-filtered signal comes into conflict with the number of samples being lost by virtue of filtration. In the paper an approach is suggested that enables the sample losses occurring during the weight filtration to be reduced.

Emil Vremera, Luciano Brunetti
IMPROVEMENT OF MICROCALORIMETER MEASUREMENTS THROUGH DATA CORRECTION

The paper describes the most important uncertainty sources in the microcalorimeter measurement technique. Analyzing data obtained from automated measuring systems, the correlation factors between measured quantities and error sources are carried out. With appropriate corrections on the raw data the final results show significant accuracy improvement.

Milan Stork
VOLTAGE TO FREQUENCY CONVERTER AND FRACTIONAL FREQUENCY DIVIDER BASED ON MODIFIED SIGMA-DELTA CONVERTER

Voltage to frequency converter (VFC) is an oscillator whose frequency is linearly proportional to control voltage. In this paper, the New Synchronous Voltage to Frequency Converter (NSVFC) or "sigma delta" (Σ-Δ) voltage to frequency converter is described. This NSVFC works similarly as conventional synchronous voltage to frequency converter (SVFC), but it has a better frequency spectral property then other SVFC and therefore it is possible to used as fractional frequency divider and also building block in fractional phase locked loop (PLL). An experimental NSVFC was constructed and simulated to verify operation of the converter. Analysis and prototype of NSVFC is described.

Milan Stork
CAPACITANCE MEASURING SYSTEM BASED ON MODIFIED SIGMA-DELTA CONVERTER

The paper brings new information about capacitance measuring system based on modified sigma-delta converter (MSDC) with compensated loop based on phase locked loop (PLL). The consist of the 2 current sources and can be used for non-electrical quantity which will break the value symmetry in circuit, e.g. light intensity can be also measured with photodiode connected parallel to current source. Measuring system can work in open loop (direct sigma-delta converter) or closed loop (PLL). The system has the voltage and digital output and in closed loop can be supposed as a voltage controlled oscillator which is locked to input clock frequency. The simple flip-flop sensor for capacitance, or some other measuring is also described. In this paper, short information concerning of the system and experimental results are shown.

Page 749 of 936 Results 7481 - 7490 of 9356