Oldrich Ondracek

RF Field Orientation Influence on the Specific Absorption Rate in a Biological Object

The influence of radio-frequency (RF) field orientation on specific absorption rate (SAR) in a human body is investigated in this paper. Three basic field orientations have been simulated: electric field vector, magnetic field vector and Poynting vector parallel to the longitudinal axis of a human body. The influence has been investigated in frequency range from 10 MHz to 2450 MHz with assistance of CST Microwave Studio program environment. Here the homogeneous ellipsoid, as a human body model, is irradiated by plane wave, representing far-field zone of antenna.

Comparison of methods for edge detection with sub-pixel accuracy in 1-D images

Edge detection is often used procedure in digital image processing. For some practical applications is desirable to detect edges with sub-pixel accuracy. In this paper we present comparison of four methods for edge detection with sub-pixel accuracy in 1-D images: method based on approximation of real image function with erf function, moment-based edge operator, technique using spatial moments of the image function and the method based on wavelet transform of image. The paper presents results of simulations as well as of experiments to compare methods in terms of accuracy, the standard deviation of the edge localization error is chosen as precision criterion.

Spectrum of counts computation for HRV analysis

Heart rate variability (HRV) analysis provides noninvasive way for assessment of neural activity that control cardiovascular system. Contributions of sympathetic and parasympathetic autonomous nervous system that modulate instantaneous heart rate are studied by means of spectral analysis. The objective is to recover modulating signal spectrum from beat occurrence times. In this paper, properties of so called spectrum of counts with respect to artifact arising in practical application of this method are described. Specifically, spectral leakage and beat time detection precision are discussed. Phenomena are analyzed on theoretical basis of integral pulse frequency modulation (IPFM). Computer simulations and recommendations for artifact rejection are presented.

Digital Group Delay Equalizer

This paper deals with problem of digital group delay equalizer for various types of digital filters. Proposed method of equalization is evaluated for a set of digital allpass filters. Whole system is analyzed in Matlab environment. Genetic algorithm has been used to design group delay equalizer. In this paper, the method of genetic algorithm is applied to group delay correction of digital IIR bandstop filters. Three examples are presented to demonstrate efficiency of the proposed method. This genetic algorithm method is suitable also for basic types of digital filters with nonlinear phase frequency response.

Sub-pixel localization of edges in JPEG images

Many methods for edge detection have been proposed in the last two-three decades. Sometimes is desirable to increase resolution of system for edge detection. There are two ways how to deal with this problem. Either a sensor with a greater number of pixels is used or method for edge detection with sub-pixel accuracy is applied. In some cases, only JPEG pictures are used as incoming data. In this paper we analyze how JPEG compression of picture changes the accuracy of edge localization. JPEG pictures with different compression quality were used to test three methods for edge localization in 1-D images with sub-pixel accuracy: method that approximates real 1-D picture with function erf (EFA) and edge detectors based on statistical moments (STM) or spatial moments (SPM) of the image function. This paper presents results of simulations of noiseless pictures and pictures with Gaussian noise. Lower and upper 5% quantiles are chosen as the accuracy criterion.

Detecting edges with sub-pixel precision in JPEG images

Edge localization is one of the mostly used procedures in image processing. In some applications it is desirable to improve edge detector precision to sub-pixel values. The input data for precise edge detector are usually in the form of uncompressed image. Sometimes, only JPEG images are available for processing. In our paper we deal with this situation, we focus on the question how lossy JPEG compression of image can change the precision of edge detection. We used JPEG images with different quality to test three methods for edge localization with accuracy at the sub-pixel level for 1-D images. First two algorithms are based on spatial and gray level moments of the image function. Third method used in our experiments approximates samples of real image with erf function. To compare these three methods we used noiseless and noisy JPEG images, two types of noise were used: Gaussian noise and ‘salt & pepper’. The standard deviation of edge position error was chosen as the precision criterion.

Integrated radio communication systems based on IT

Paper deals with complex solutions of radio communication systems for special application especially in air traffic control ATC and integrated rescue systems IRS area. Basic customer demands for such applications are briefly described and discussed from point of view of multi band antenna systems and SW transceivers. The architecture design of an ATC and an IRS system is demonstrated including remote monitoring and control RMC system. High contribution of IT is demonstrated to solve the problem of the mobile communication system infrastructure with connectivity based on standard interfaces