David Slepicka

Uncertainty Analysis of the RMS Value and Phase in the Frequency Domain by Noncoherent Sampling

The determination of RMS value and phase of harmonic components belongs to the most important tasks of signal analysis in the frequency domain. Evaluation of these parameters is frequently performed using a discrete Fourier transform (DFT) algorithm. In practice, signals are mostly sampled noncoherently. This leads to the well-known effect called leakage, i.e., spreading energy of signal harmonic components into signal frequency neighboring frequency bins. Signals are multiplied by tapering time windows for leakage suppression. This paper is focused on the uncertainty analysis of the RMS value and phase computed from the DFT spectrum of the noncoherently sampled signal using cosine windows. The analysis is focused on investigating the influence of quantization noise

Accurate Amplitude Estimation of Harmonic Components of Incoherently Sampled Signals in the Frequency Domain

This paper focuses on estimating the amplitude of harmonic components of a harmonically distorted sine wave by the interpolated discrete Fourier transform (IpDFT) method with maximum sidelobe decay windows. The expression of the maximum of the interference error caused by the fundamental sine-wave component on the amplitude estimation of harmonic components is derived. In addition, for a signal corrupted by stationary white noise, the statistical efficiency of the IpDFT method is investigated with respect to the single-tone unbiased Crame¿r-Rao lower bound (CRLB). Based on the derived expressions, a constraint is derived ensuring that interference from the fundamental component could practically be neglected. Finally, the performance of the IpDFT method is compared with that of the energy-based method on the basis of theoretical, simulation, and experimental results and with that of a state-of-the-art method according to simulation and experimental results.

Comparison of nonparametric frequency estimators

This paper deals with the performance of several up-to-date nonparametric frequency estimators. The algorithms of frequency estimation are introduced and their bias, standard deviation and consumption time are compared with regard to the most common signal parameters.

ADC nonlinearity correction based on INL(n) approximations

One of the most important parameter of ADC which negatively influence its quality is its nonlinearity. The correction of this imperfection can be accomplished in the output data but only if the nonlinearity is well characterized. Two methods — application of look-up table or an analytical inverse function of INL(n) curve — from other possibilities can be used for the ADC nonlinearity correction. The first results of correction using look-up table were published in [5]. The application of inverse function, which is dependent on the possibility to derive the inverse function to the function approximating the INL(n) curve, is published in the paper.

Analysis of frequency stability of 16.7 Hz railways

In this paper the stability of the fundamental frequency of 16.7 Hz of European railway networks is observed and its influence on processing higher order harmonics is evaluated. The stability is analyzed by means of amplitude frequency spectrum, short-time Fourier transform and residuals of sine-wave fitting.

Evaluation of ADC testing systems using ADC transfer standard

A transportable high stable reference AD device was designed and built for a comparison of systems for testing of the dynamic quality of ADCs or modules. Three different input modules enable its use in the frequency range up to 5 MHz. First, this paper refers to the results of the AD device application in the frequency range of the testing signal up to 100 kHz (comparison of four ADC testing systems in different laboratories, evaluation of a short time amplitude and/or frequency instability of testing signal generators). Second, it describes the first experience of its application in the frequency range from 100 kHz to 5 MHz.

Estimating the Uncertainty in the Frequency Domain Characterization of Digitizing Waveform Recorders

New propagation formulas for the uncertainty evaluation for the characterization of digitizing waveform recorders are proposed in this paper. The frequency domain figures of merit, as defined in IEEE Std. 1057, have been considered to present useful addenda to the standard. The proposed formulas have been validated on simulated and actual signals.

Models of the ADC transfer function - sensitivity to noise

This paper describes several approaches of modeling nonlinearities of analog to digital converters (ADC). First results of three approximations are introduced and compared - the common polynomials, Chebyshev polynomials Fourier series.

Phase Noise in Time Domain ADC Testing

The results of ADC dynamic testing are strongly dependent on test signal purity. From this reason, the spectral purity of the most common ADC test signal, sine wave, is often improved mostly by analog filters. Such analog signal processing can essentially suppress harmonic and spurious components but not phase noise. The effects of phase noise are therefore discussed in this paper and a possible way of low-frequency phase noise suppression in the time domain is proposed and an example shown.

System for Testing Middle-Resolution Digitizers using Test Signal up to 20 MHz

A system for the testing of ADCs at the frequency range of 1 MHz, which was designed and prototyped at the Dept. of Measurement, CTU FEE last year, was extended up to 20 MHz. Low-cost as well as high-quality filters for frequencies about 4.4, 9.5 and 19.5 MHz were manufactured. Experimental results showed that the system is directly applicable for the testing of ADCs with the ENOB up to 11-13 in case of low-cost filters and up to 20 in case of high-quality filters