Scattering wideband pulse signals by non-smooth surfaces

Processes of scattering and reflection of wideband signals by non-smooth rough surfaces in the frequency range of 38–52 GHz have been investigated. Dependences of reflection coefficient for various non-smooth surfaces versus distance up to the antenna and the degree of roughness of the sample surface have been obtained experimentally. The influence of behavior and the degree of surface heterogeneity on the value of the reflection coefficient has been estimated using results of the measurements, the influence of spatial orientation of the scattering surface on amplitude of the reflected signal has been revealed

Experimental investigation of horn antenna radiation

Horn antennas are widely used in different practical applications. They serve as feed antennas in many types of more complex constructions of antennas. The horn antennas are powerful means of high energy technology, they are used as applicators in medical purposes. The horn antennas are the most popular probing device in non-destructive testing. The horn antennas are also important tools of standards of power gain. In all applications the information about of space distribution of electromagnetic field is very important. For instance in medical and technological applications knowledge of field distribution allow ones to control the depth of heating that is very important for success of operation. The feature of these applications is use of near-field wave. Information about longitudinal distribution of field serves for increasing accuracy in non-destructive testing due to more accurate calibration at the same distances for structure under test and metallic standard mirror. Usually they cannot be positioned in the same place under technological process and displacement courses error in calibration and therefore errors in dielectric constant and thickness. Power gain can be measured using metallic plate but this approach is simple only for far-field zone, for Fresnel zone a few sets of measurements at a few distances are need. This circumstance determines importance of the field description

Analysis of natural frequency and q-factor estimation for open dielectric resonators with variation of coupling by means of fractional-rational approximation of reflection response

The analysis of the natural frequency and estimation of Q-factor of the open resonator by means of fractional-rational approximation of the reflection response has been considered. An advantage of the proposed technique in comparison with the classical methods has been demonstrated. Dependence of Q-factor of the shielded half-disk dielectric resonator and estimations of the poles and the zeros of the resonance response against the coupling coefficient value has been analyzed

Problems of technique of organizing antenna laboratory course

Now our daily life is characterized by wide application of modern means of telecommunications. First of all satellite television and mobile communication means, including cellular ones, must be mentioned. The feature of this means is a wide usage of micro-wave electromagnetic waves especially of the range 11–12 GHz, which has elements with properties and construction distinct from more low frequencies ones in many respects. First of all, this fact concerns antenna devices. The pointed circumstances stipulate necessity of perfection of training the students of radiophysical specialty in the microwave antenna engineering. The learning of antenna engineering can not be restricted by only lecture course and requires such educational component as a laboratory experimental work. This situation is coursed by the following fact that the theoretical approaches allow only common tendencies of antenna devices behavior to be considered, but the problems of their practical tuning and application require experimental skills. In the paper the review of the contents of laboratory exercises with microwave antennas which have received implantation in educational process at a chair of microwave physics of Dnepropetrovsk State University is displayed

Determination of biconical cavity eigenfrequencies using method of partial intersecting regions and approximation by rational fractions

The paper considers the problem of determining the eigenfrequencies of biconical cavity making it possible to simplify the eigenfrequency-based design of devices. We used the solving of the excitation problem for biconical cavity using the method of partial intersecting regions in combination with the collocation method. Based on the concept of the search of quasisolution for determining eigenfrequencies, it was proposed to apply the fractionally rational approximation of cavity response obtained as a result of solving the problem of resonator excitation. The efficiency of finding eigenfrequencies of biconical cavity was substantiated by using the fractionally rational approximation based on the chain fraction interpolation of cavity response calculated only at collocation points. Using the above approach, we have obtained the relationship of eigenfrequencies of azimuth-symmetric oscillations of biconical cavity as a function of the aperture angle, and the typing of lower azimuth-symmetric transverse electric modes of biconical cavity has been performed

Simple technique for biconical cavity eigenfrequency determination

A number of features of biconical cavities make them attractive for various applications. Expressions for the calculation of the eigenfrequencies of a biconical cavity with large cone angles can be derived using the overlapping domain decomposition method in combination with the collocation method; however, the expressions reported in the literature involve only a single pair of collocation points, thus giving no way to estimate the eigenfrequency determination accuracy. The aim of this paper is to calculate the biconical cavity eigenfrequencies for an arbitrary number of collocation point pairs. An equation in the biconical cavity eigenfrequencies for an azimuthally symmetric transverse electric field at an arbitrary number of collocation point pairs is derived. The equation reduces to two equations, whose solution requires far less computational effort in comparison with the original equation. The solution of one of the two equations are based on modes symmetric about the cavity symmetry plane, and the solutions of the other are based on antisymmetric modes. The calculated eigenfrequencies converge rapidly with increasing number of collocation point pairs, while the use of only one collocation point pair may introduce noticeable error. The proposed technique may be used in the development of components and units on the basis of biconical cavities