Computer analysis and optimization of radiation characteristics of vibrator and microstrip antennas

Abstract

Problems of antenna system optimization from the view point of decreasing the size, and the lateral and back radiation are very important at present in connection with the necessity of miniaturization and electromagnetic compatibility in compact ranges. In case of vibrator and microstrip antennas, these problems can be solved to a great extent by optimizing a screen’s shape. Therefore one has to carry out a computer analysis of dependencies of lateral and back radiation of the analyzed system on the size (W, L) and the shape of the screen (a ratio of screen sides being P = W/L). As a parameter with respect to which optimizing electromagnetic and geometric antenna characteristics takes place, there has been taken the Back-to-Front Ratio of analyzed radiating systems: V = 20lg(E_back/E_max).

In the report, by using the Uniform Geometrical Theory of Diffraction, there is considered in detail the methodology of calculating a spatial field distribution of the vibrator and microstrip antenna backed with a plane rectangular screen, vibrator being arbitrarily oriented with respect to the screen. Numerically efficient algorithms and programs have been developed. The computed directive patterns have been compared with the known ones calculated for the same geometrical parameters by means of the integral equation method. This comparison shows that the accuracies of the both methods are in good agreement up to a resonant size of antenna. The developed programs allow to calculate the Back-to-Front Ratio (V) for the main field polarization, when changing L from 0.5 to 10 wavelengths, and P from 0.2 to 20. From the detailed analysis of the obtained three-dimensional data, there have been constructed and illustrated the dependences of optimum ratios of the screen size P providing minimum values of V, that may be approximated by a hyperbolic function.