V. F. Borulko

Wide-band reflection coefficient measurements using direct and inverse frequency-time domain transformations

The problem of measurement of modulus of the reflection coefficient (RC) in wide frequency band in presence of additional reflections such as reflections in a horn antenna is considered. The Pronys method and the method of separation of autocorrelation function of layered structure by windowing in time domain for the restoration of the square modulus of the RC in wide frequency band were compared. The values of the error of restoration methods under consideration in the chosen frequency band have been calculated. It has been shown the advantage of the Pronys method application in sliding frame by the results of the numerical simulations and real measurement data processing. The technique of data extrapolation at the edges of the frequency band for applying Pronys method is proposed.

Inverse problem solution for layered dielectric structures using rational interpolation method

An opportunity of using the rational representation of reflection characteristics in the spectral conjugate domain for determination of parameters of layered dielectric structures has been considered. The algorithm of rational interpolation providing steady estimates is presented. The accuracy properties of proposed method are analysed.

Dual method of minimum spatial extent for processing of antenna measurements

Inverse problem of radiation-sources restoration from near-field measurement data is considered. Case of data distortion by additive noise and spikes is investigated. New approach based on a concept of “spatial extent” is suggested. It states that the weighted sum of spatial extent of solution discrepancy and spatial extent of solution should be a minimum. Thus, the concept of spatial extent is used two times, namely, in an original space (which is the space of solution) and in a conjugate space (which is the space of solution discrepancy). The model of radiation sources is described by a set of ideal Hertzian dipoles. The case, when dipoles are located along a straight line, which is parallel to measurement line of electric field, and when their electric moments are perpendicular to the measurement plane, is considered. Algorithm, based on the conjugate gradient method, is proposed. Numerical simulations of direct and inverse problems are presented.

Asymptotic solution of the second order for corrugated rectangular waveguide

Rectangular waveguides with nonperiodical corrugation of wall are considered. The Krylov-Bogoliubov-Mitropolsky asymptotic method is used for solving boundary-value problem describing electromagnetic wave propagation in the close waveguiding structure. Mutual transformations of a wave modes propagating in such waveguides are investigated. Analytical solutions for some coupling coefficients are obtained.

Eigen parameters of quasiperiodic Bragg nanostructures

The influence of various types of apodization on the eigen parameters of the distributed Bragg reflector, layered Bragg reflectors and resonators has been analyzed. The conditions of reduction of the quality factor of unwanted side Bragg oscillations in quasiperiodic apodized resonators have been determined. It has been proposed the construction of periodic and quasiperiodic structures and apodized Bragg resonators with thin contrast layers, which are relatively easy technologically implemented in the microwave range. The measurement results of reflection coefficient for periodic and quasiperiodic apodized structures and resonators with thin contrast layers are presented.

Properties of complex parameters of five-port reflectometer with E-plane T-junctions

The problem of creating meter of complex reflection coefficient based on the electromagnetic approach using E-plane dividers is studied. Rigorous electromagnetic model of direct and inverse problems of five-port measurements of complex reflection coefficient is derived. Frequency dependencies of model parameters are calculated. Properties of T-junctions are investigated.

Semi-asymptotic analysis of Bragg coupling on quasiperiodic impedance rod

Phenomena of coupling of wave beam and surface wave at impedance rod with spatially oscillating parameters are theoretically considered. Used method is asymptotic with respect to smoothness parameter and is numerical with respect to perturbation amplitudes. It combines advantages of the asymptotic and numeric methods in cases of quasiperiodic structures with large number of “periods”. Obtained coupling coefficients are compared with known asymptotic expressions.

Properties of complex parameters of five-port reflectometer with E-plane oblique X- and T-junctions

The problem of creating meter of complex reflection coefficient based on the electromagnetic approach using E-plane dividers is studied. Rigorous electromagnetic model of direct and inverse problems of five-port measurements of complex reflection coefficient is derived. Frequency dependencies of model parameters are calculated. Properties of oblique X- and T-junctions are investigated.

Dual method of minimum spatial extent

Inverse problem of radiation-sources restoration from near-field measurement data is considered. Case of data distortion by additive noise and spikes is investigated. New approach based on a concept of “spatial extent” is suggested. It states that the weighted sum of spatial extent of solution discrepancy and spatial extent of solution should be a minimum. Thus, the concept of spatial extent is used two times, namely, in an original space (which is the space of solution) and in a conjugate space (which is the space of solution discrepancy). The model of radiation sources is described by a set of ideal Hertzian dipoles. The case, when dipoles are located along a straight line, which is parallel to measurement line of electric field, and when their electric moments are perpendicular to the measurement plane, is considered. Algorithm, based on the conjugate gradient method, is proposed. Numerical simulations are presented.

Modification of pole model for wideband responses of distributed structures

For more effective approximation of wideband responses of the distributed structures the necessity of a modification of pole model is shown. Refinement of the model for the account of beam propagation in an open distributed structure and for the account of frequency dependence of the model parameters is suggested. Efficiency of the considered approach is demonstrated on the numerical example.