Spectral analysis belongs to widely used method frequency spectrum of ECG signal instead of usual analysis for biomedical data exploration. In order to interpret based on cardiotachogram (RR interval sequences) derived spectrum correctly, prior knowledge how various from measured ECG. phenomena affect the spectrum of analyzed signal is desirable. Spectrum ofECG signal is affected by waveform component shapes, their time positions within cardiac . cycle as well as by regularity of heart period. This paper 2 Signal Models deals with effect of heart rate variability on ECG signal Impulse sequence, whose parameters are random spectrum. Three representations are proposed to model variables, is called a random impulse process. These variable heart timing in the case of normal sinus rhythm impulse processes can be divided into two classes in (pulse process with time jitter, random inter-pulse interval dependency on statistic attributes of the impulse formation: and integral pulse frequency modulation model).Properties of corresponding spectra are theoretically a Pulse process with time jitter studied and compared with real-world signals from * Pulse process with random interbeat interval PhysioBank data archive.(for ECG) Random impulse process is described by various parameters, which can be stochastic. Impulse sequences Keywords with different properties are analyzed on the basis of these EGG spectrum, heart rate variability, random pulse parameters. In the next, we consider only sequences with process, integral pulse frequency modulation model. constant width and amplitude of the impulse. Pulse Process with Time Jitter

In this paper, the dependence of radio-frequency (RF) field absorption on human body dimensions is investigated. The resonance properties of an ellipsoidal homogeneous human model have been investigated in frequency range from 10 MHz to 500 MHz with assistance of CST Microwave Studio program environment. In the article, the simulation of RF field absorption in the ellipsoidal body model has been performed for three various body heights, as well as three widths for a given body height.

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This article is devoted to an investigation of electrophysicalparameters ofbiological tissue influence on 2. Numerical Method its absorption of microwave energy. The specific There are several methods for the computing the absorption rate (SAR) is the dosimetric quantity for electromagnetic field induced inside the biological objects. evaluation of microwave energy absorbed in biological One of the numerical methods, which makes a spatial tissue. Many parameters have effect on the SAR value, such discretization scheme of Maxwell's equations is FIT. It is as geometry of the part of the body, which is exposed to suitable method for computers and can solve various microwave energy, electrical parameters of body tissues, electromagnetic field problems in modeled situations that distance between the source ofenergy and surface ofbody, simulate real conditions. In contrast to some other geometry of the antenna etc. In this article, homogeneous numerical methods, FIT is applied to the integral form of spherical model of the human head is modeled in CST Maxwell's equations [1]: Microwave Studio program environment. The tissue parameters variation influence on SAR values is evaluated aB for 900 MHz, 1800 MHz and 2450 MHz frequencies JdEd=-df dA (1) utilized in communication, medical and other applications. AA A at fH.ds=||' +i 4rd (2) Keywords AA A t )( Microwaves, CST Microwave Studio, SAR, fjjdA =|PedV (3) modeling, biological objects. e av v