Sidelobe Suppression in Resonant Cavity Antennas through Near-field Analysis

This paper describes an effective approach to reduce the high sidelobe levels (SLLs) in resonant cavity antennas (RCAs) with small footprints. The objective is to first understand the reason behind the high SLL in compact RCAs and than improve its radiation characteristics. For this, a near-field to far-field transformation routine is implemented in MATLAB, which allows to understand the individual effects of near-field amplitude and phase distributions on the SLL in the far-field patterns. This approach resulted in an optimal electric-field distribution, which is realized by a dielectric partially reflecting superstructure (PRS) exhibiting a broadside directivity of 19.5 dBi with significantly low sidelobe levels of -30dB in both the principle planes. It is important to note that the proposed approach can be linked easily with global optimization techniques to fit the radiation patterns within specific pattern masks.