Papers by Author: Albinas J. Marcinkevičius

Abstract: The architectural scheme of the designed Sigma-Delta DAC on the FPGA is considered. The place of the interpolator in Sigma-Delta DACs is briefly discussed. The summarized structure of the most common interpolators is presented. More applicable structures of interpolators were suggested and analyzed, providing the comparison with [1]. Having changed the structure of the incomplete interpolator and having optimized the stages, it was possible to improve the characteristic of amplitude frequency response with a smaller number of non-zero coefficients and much lower FPGA resources. The paper provides simulated results of the interpolator filter transmission characteristics as well as Sigma-Delta modulator quantization noise parameters. It is demonstrated that simulation of the complete converter system (interpolator + modulator + output filter) allows to identify places of the interpolator, where hardware resources could be saved, thereby reducing the chip area occupied by the converter, which is not always obvious when analyzing nodes separately. Therefore another version of the interpolator was proposed for the system ensuring larger suppression of the additional frequency band in the whole system compared with the previous interpolator. Simulated results related to occupied chip resources are also confirmed by the experiment, which was implemented in Xilinx Spartan FPGA.

Abstract: Precision and wide-band analog-to-digital converters (ADC) are used for information processing in mechatronic systems. The analog signal transformation circuits, such as sample, and hold circuit (SHC) and an analog signal interpolation circuit (ASIC), are applied with the aim of increasing the precision of converters. These circuits allow for reducing the quantity of comparators in the converter and increase their dynamic stability. The models of SHC and ASIC as well as the results of the calculation precision and dynamic parameters of such circuits are presented in this paper. Equations for the calculation of the aperture error in the Gaussian and a sinusoidal input signal were derived. The structural model, proposed for SHC, evaluates the nonlinearity of a transfer characteristic, and the influence of noise in the signal and strobe channels. The results of the theoretical research and analytical equations for the evaluation of the number of signal interpolation block differential amplifiers, which depends on the analog signal’s maximal frequency and the number of segments of the converter, are presented. The results of this work allow one to estimate the main precision and dynamic parameters of ADC transformation circuits.

Abstract: Most of researchers at research of "self evicted vibrations" in machining state that they are resulted by passing of force stability boundaries of the mechanical system at which oscillations increase hardly. Explanations of process development from the point of view of grinding dependencies are absent. The article is allotted to analyze the process in time, it is shown how in result of action of forced vibrations with frequencies different from any natural frequency of the system new vibrations with some natural frequency of the system are propagated. New properties of the system are formed. Equations are deduced and calculation results are presented in the article.