Nikolai N. Voitovich

Reducing the Backscattering via Complex Impedance Coating

A method for reducing the back scattering from bodies with complex impedance boundaries is developed. A nonlinear integral equation system providing zero backscattering is obtained for determining the impedance distribution on the boundaries of infinite cylinders. Numerical results for circular and elliptic cylinders are given. Frequency dependence of backscattering at obtained optimal impedance is discussed on the example of circular cylinder.

Antenna synthesis according to prescribed amplitude radiation pattern and the phase problem

Connection between the so-called phase problem in optics and the antenna synthesis problem according to prescribed amplitude pattern is noted. Using the zeros properties of the entire functions of exponential type, the variational antenna synthesis problem solutions are expressed in the analytical form and the problem is reduce to a limited transcendental equation set.

Calculation of Complex Impedance Coating for the Back Scattering Minimization

A method for decreasing the back scattering from bodies having complex impedance boundaries is developed. A system of nonlinear integral equations is given for determining the impedance distribution which provides minimal back scattering. Numerical results for a model problem of scattering on the infinite circular cylinder are given. Frequency dependencies of scattering at obtained impedance distributions are shown.

New closed solutions of the linear antenna synthesis problem according to amplitude radiation pattern

In the linear antenna case, the synthesis problem according to prescribed amplitude pattern is solved analytically with a limited numbers of complex parameters to be calculated. These parameters are defined from the set of transcendental equations. As they are nonunique, the optimal solution is chosen from the all obtained solutions. A measure of the synthesis effectivity is offered. The case, when the given amplitude pattern is constant inside the limited angle, is considered in detail and numerical results are presented.

Comparing different approaches to linear antenna synthesis problems according to power radiation pattern

The antenna synthesis problem according to the prescribed power radiation pattern with the equality norm condition is solved by the approach based on the concept of generating polynomials. The variational formulation, supplied by the Lagrange method of multipliers, is applied. The modified Newton method is used for numerical solving of the respective integro-transcendental equation systems. The approach was numerically tested on the example of the antenna synthesis problem, recently solved directly by the Newton method. Numerical results are compared and analyzed.

Calculation of waves scattered in irregular waveguides

Wave scattering problems in irregular waveguides are investigated. The proposed algorithm for solving such problems is based on the reduction of the scattering problem to an interior boundary value problem in the irregular section. This problem is solved in general form by the boundary integral equation method and then the solutions in regular and irregular sections are matched. The scalar Dirichlet problem with excitation by a wave, incident from infinity, is considered. The approach is applied to a test problem and numerical results are compared with the ones obtained by the cross section method.

Structure of phase-asymmetric solutions of circular antenna synthesis problem by amplitude radiation pattern with axially independent data

The synthesis problem by the amplitude radiation pattern is considered for the circular aperture antennas. The prescribed pattern is assumed to be axially-symmetric. The solutions with asymmetric phase patterns are analyzed numerically.

Synthesis of circular aperture antenna by amplitude radiation pattern of Fourier harmonics

The synthesis problem by the amplitude radiation pattern is considered for the circular aperture antennas. The conception of circular harmonics is used. The representation by generating polynomials is used for each harmonic separately. The numerical results are presented for the harmonic of the first order (infundibular pattern).

Polynomial approach to linear antenna array synthesis problem according to power radiation pattern with restriction on its norm

The synthesis problem for equidistant linear antenna array according to the prescribed power radiation pattern (RP) is generalized by taking into account an additional restriction on the norm of the synthesized RP. The variational approach supplemented by the Lagrange method of multipliers is applied for the formulation of problem. The phase RP is uniquely represented by the complex polynomial of high degree. The modified Newton method is used for numerical solving the respective integral-transcendental equation system. The approach was numerically applied to an example of the antenna array synthesis problem.

Complex zeros of solutions to the synthesis problem of irregular linear antenna array by amplitude radiation pattern

The synthesis problem for nonuniformly spaced linear antenna arrays by the amplitude radiation pattern is considered. Distribution of complex zeros of its solutions is numerically analyzed. Results partially confirm the hypothesis that these zeros describe the minimal complex factor of the solutions. Distribution of complex zeros of its solutions is numerically analyzed. Results partially confirm the hypothesis that these zeros describe the minimal complex factor of the solutions.