Antenna Mutual Coupling and Ground Reflection Effects on the Performance of a VHF phased array

This paper investigates the effects of antenna mutual coupling and ground reflection on the performance of very high frequency (VHF) phased array radars. A uniform linear array that consists of four horizontally polarized dipole antennas operating in VHF band is used to demonstrate the influence. The ground is considered infinitely large, perfectly flat, and as a perfect electric conductor, which is a reasonable assumption for such a low-frequency electromagnetic problem. The image theory can therefore be used and the ground is replaced with four image dipoles. The simulation results show that the mutual coupling and the ground reflection can strongly influence the performance of the VHF phased array, including the radiated power, the radiation pattern. The ground reflection introduces deep nulls into the elevation coverage, especially in the middle-angle and low-angle regions. This research implies that designers of VHF radar systems should carefully deal with antenna mutual coupling and ground reflection issues, or the benefit of VHF radars in detecting small targets will not hold anymore.