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...
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 f 0 + d f and f 0 - d f 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.
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...
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.
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...
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...
The main product of the DFT algorithms is the amplitude frequency spectrum while the phase frequency spectrum calculation is mainly unwanted. However, this part becomes relevant in the cases, in which the spectral lines have to be considered as vectors. Since the data record, from which the frequency spectrum is calculated, is usually acquired by non-coherent sampling, a problem of the correct phase determination appears. Time windows minimise the leakage in the amplitude frequency spectrum; their effect on the phase frequency spectrum is unclear. Moreover, the phase of each frequency...
Using wavelet transform (WT) for increasing signal-to-noise ratio (SNR) of discrete-time signals corrupted by additive noise is explained and compared with some other techniques (averaging, frequency filtration, correlation). Signal processing for de-noising is applied to basic periodical signals and repeated transients (in non-destructive ultrasonic testing of welds, where presence of flaws should be detected). Results of both computer simulations and measurements are reported, and some best suitable wavelets, levels of signal decomposition and methods and parameters of thresholding are...
If the RMS value is gained by digital processing of sequence of signal samples, both uncertainty and bias of the measured value depend on the algorithm used. Since in practice signal sampling is usually non-coherent, leakage occurs in signal DFT spectrum and definition of the RMS of periodic signals in time domain is violated. The paper compares three different DSP algorithms of RMS measurement by non-coherent sampling from the point of view of measurement bias and uncertainty for various leakage levels and data window used. Results of simulations and example of measurement are evaluated for...
This paper describes a new sigma delta modulation technique. This technique is used for measurement of changes in half capacitive bridge to detect deflections, which can result from acceleration input in practice. The half bridge is connected to a modified flip-flop circuit, the outputs of which are used for one-bit force feedback. The modification of flip-flop consists in the implementation of a switched capacitor structure to achieve a perfect flip-flop value symmetry and compensation of a flicker noise. Some theoretical considerations are verified by experimental results. An experimental...