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Multi-frequency printed dipoles based on antipodal printed dipoles loaded with metamaterial particles are presented. Split ring resonators (SRRs) are used as metamaterial particles in order to obtain fully printed and planar antennas. First, a simplified model of these antennas is developed. This model is based on a printed dipole loaded with the equivalent circuit of the SRRs. This model shows that...
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This article describes development of a versatile periodic structure simulation program. The program is written in Matlab and performs analysis of a planar multilayer frequency selective surfaces by method of moments. Analysis reflection/transmission from a FSS compromised from arbitrarily shaped metal elements and having several dielectric layers is possible. The biggest advantage of the program...
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Nowadays microwave thermotherapy belongs to methods of treatment for cancer diseases. This method is often used in combination with classical therapies, which brings more success during treatment of tumors. The area is heated by microwave energy through microwave applicator. This paper deals with design, modelling and testing of planar spiral type of applicator for local microwave thermotherapy.
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Article is concerned to the problem of assessment of occupational exposition to EMF of medical personnel of physiotherapy departments. The results of measurements close to the appliances and in the whole room are shown. Confirming dangerous levels of EMF near apparatus the study also aims precise exposition evaluation in real conditions of work. An attempt to represent new method of examining of complex...
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This article is devoted to an investigation of electrophysical parameters of biological tissue influence on its absorption of microwave energy. The specific absorption rate (SAR) is the dosimetric quantity for evaluation of microwave energy absorbed in biological tissue. Many parameters have effect on the SAR value, such as geometry of the part of the body, which is exposed to microwave energy, electrical...
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In this paper is presented our longstanding experience with combination of teleradiotherapy and superficial hyperthermia in the treatment of patients with head and neck cancers, especially in cases with superficial tumors or lymph node metastases, in the Institute of Radiation Oncology in Prague. Microwave thermotherapy - hyperthermia in combination with other treatment methods (mainly with teleradiotherapy)...
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The use of electromagnetic fields in biomedicine for cancer treatment and diagnostics, nowadays begin to be quite widespread. This paper describes the design and the evaluation of a microwave applicator for treatment of small subcutaneous tumours implanted on animal model. The support of computer simulations was used to evaluate and optimise the fundamental parameters of the applicator and the SAR...
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This paper presents results from the measurement of the electrical activity cold sensitive beta-tubulin mutant tub2-401 of yeast cells in frequency region 0.4 - 1.6 kHz. 25 measurements of both synchronized and nonsynchronized cells show that the synchronized cells have higher electrical activity which corresponds to the findings of Pohl et al. Local nanomechanical vibrations of yeast cell membrane...
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Microwave hyperthermia is a promising method of cancer treatment used to increase the temperature within the interval of 40 - 44degC. The goal of this paper is to introduce the possibility of treatment planning for superficial hyperthermia using COMSOL Multiphysics. The real model of the patient with recurrent breast cancer was developed. The waveguide horn applicator with aperture of 10 x 10 cm was...
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A numerical dosimetry procedure is applied to a biological tissue in order to evaluate the temperature increase produced by RF exposure. The originality of the proposed method regards the application of the bio-heat equation in a vascularized region considering a discrete blood vessel structure which operates as a cooling system in the biological region. First, the blood structure is assumed to be...
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Frohlich postulated coherent polar oscillations as a fundamental biophysical property of biological systems. Pelling et al. detected recently mechanical vibrations of yeast cell membrane in the frequency range 0.5-2 kHz with atomic force microscope (AFM). This paper describes the measurement of electric activity of yeast cells at frequencies around 1 kHz and of mechanical vibrations of cell membrane...
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In this paper the temperature distribution inside WPC is done. As most of biological effects caused by RF electromagnetic radiation are thermal, it was necessary to separate temperature rise because of WPC construction itself and temperature rise due to electromagnetic field levels. WPC is very popular structure for EMC tests because it is easy to build at very affordable cost. And what should not...
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The paper presents a comparison of three approaches for analyzing spherical lens antennas - spectral-domain method, ray-tracing method, and time- domain finite integration technique (FIT) implemented in commercial software CST Microwave Studioreg. The spectral-domain method takes advantage of transforming the three-dimensional problem into a set of one- dimensional problems. The spherical lens antenna...
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A novel microstrip patch antenna miniaturization technique based on multilayer meanderly folded shorted- patch structure is introduced. The technique enables a decrease of the original shorted (quarter-wavelength) patch dimension by the factor l/N where N is a number of vertically placed patch plates above the ground plane while maintaining a quarter wavelength resonant length. The antenna operational...
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This paper describes the design of a highly effective parabolic dish antenna primary feed based on backward radiation. This assembly, comprising a dielectric lens and reflecting plate, supports both linear and circular polarization and may be directly attached to a circular waveguide. The current design is intended to work in the 10 GHz band with the specified parabolic dish antenna.
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Design procedure and experimental verification of linearized power detector, suitable for measurement purposes, are presented. Good linearity, fast response and wide dynamic range of the detector are achieved by using a zero-bias Schottky diode with 16-bit analog to digital converter and 60 MHz 32-bit RISC processor. Linearity error better than plusmn 2 % has been achieved in 40 dB dynamic range with...
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For the problem of boxed printed circuits embedded within a stratified media, efficient formulations based on the Method of Moments have been suggested which involve the computation of modal series appearing in the representation of Green's functions in this context. This paper suggests an efficient truncation criterion in computing these modal series which guarantees attaining an acceptable accuracy...
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This paper presents a new analysis of a polarizer composed of N sections of frequency selective surfaces (FSS). Each FSS is composed of periodic array of conducting wires. The structure is analyzed with the use of the exact full-wave theory based on the the mode-matching method, and also an efficient numerical technique based on the T- matrix approach and the lattice sums is utilized to investigate...
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In this paper two kinds of orthogonal polynomials - weighted Laguerre and Hermite polynomials - are used as temporal basis functions for the approximation of the transient responses of wire structures. Numerical schemes with these polynomials are derived and their properties are compared on an analysis of straight wires of different lengths. The comparisons and investigations show that the scheme...
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The paper deals with the reconstruction method of the radiation pattern of directional antennas. The method is based on the amplitude near-field measurement (or simulation) on two plane surfaces, and consists of two steps. First, a global optimization is used to find an initial estimation. Second, a common Fourier iterative algorithm is created to iteratively improve the initial estimation. The genetic...
