Directional and Band Properties of Dipole Antennas with Square-Shaped Screens

The paper presents a quantitative analysis of the directivity characteristics and the operating frequency band of a resonant dipole antenna parallel to a perfectly conducting square-shaped screen. This analysis considers the effect of in-phase diffracted fields at all four edges of the screen with a geometrooptical field in the direction normal to the screen, the dimensions of which ensure the in-phase operation of these fields. The paper uses the solution of the three-dimensional vector problem of diffraction of dipole radiation on a rectangular screen obtained within the framework of the method of uniform geometric theory of diffraction (UGTD). The programs developed in the FORTRAN environment were used to calculate radiation patterns (RP), directed action coefficient (DAC) in the direction normal to the screen and the direction of the main maximum of RP, radiation resistance of the resonant half-wave dipole, and optimal dimensions of a square screen in terms of the DAC maximum for varying the operating wavelengths and screen dimensions in a wide range. It is shown that the optimal dimensions of the square screen amount to 0.7–1.3 of dipole resonant wavelength, and the resonance of the antenna radiation resistance occurs at the electrical dimensions of the square screen in the range of 0.7–0.9. The width of the main lobe of antenna RP in the plane of the electric field vector is about 60° and about 100° in the plane of the magnetic field vector, and it is slightly dependent on the screen size. The band of operating wavelengths is limited by the radiation resistance and the identity of the main lobe of antenna RP; this band varies from 0.75 to 1.5 of the resonant wavelength depending on the screen size. The bandwidth index of the dipole antenna with a square screen can reach unity.