A cavity-backed aperture-coupled microstrip patch antenna array with sum/difference beams

摘要

This paper presents a new cavity-backed aperture-coupled microstrip patch antenna (ACMPA) array with sum/difference beams. It is composed of a feed network and two aperture-coupled elliptical patch antennas. A metallic cavity is used at the back of the antenna array to minimize the back radiation. The feed network is realized by a planar magic-T, which consists of microstrip and slotline T-junctions coupled by microstrip-slotline transitions. The antenna is designed, manufactured and tested at 35 GHz. Measurements show clean and symmetrical patterns are realized for both the sum and difference beams. The measured -3-dB E-and H-plane beamwidths of the sum pattern are 55.8° and 77.6°, respectively. A deep null of -32.4 dB is achieved for the difference pattern. Meanwhile, the measured return losses for both the sum and difference ports are less than 10 dB from 34.2-36.6 GHz corresponding to a bandwidth of 6.8%. Within this bandwidth, the isolation between the sum and the difference ports is better than 38 dB.