Reducing the downward radiation of slanted dipole array

In an attempt to satisfy some government-imposed policies and at the same time optimize the coverage of an FM antenna system, this paper describes the radiation pattern of the most commonly employed FM broadcast antenna system, the shunt fed slanted dipole array. The description involves computations of the radiation pattern. It describes one simple and practical method of reducing the downward radiation due to the minor lobes in the array radiation pattern. Free space radiation is assumed in these computations and a simplified model of the antenna structure is used. The basic theory of uniform linear antenna array analysis is first presented. A commercially available simulation and analysis software is used for all gain pattern calculations. Results show that the common inter-bay distance of one wavelength produces downward radiation with a high percentage of the maximum permissible amount. However, by simply varying the distance between the identical elements in the array, improvements to reduce the downward radiation are possible. The service areas with reception related problems can also be controlled using this method. In reducing the downward radiation of the antenna system, though, the total gain generally decreases.