A Compact V-Band Planar Gap-Coupled $4\times 1$ Antenna Array: Improved Design and Analysis

In this paper, a broadband 60-GHz millimeter-wave 4 x 1 microstrip patch antenna array using the gap-coupled technique is presented and analyzed. In order to meet the challenging requirement of reduced size related to this kind of technique, and facilitate the integration with other integrated passive or active devices, the proposed antenna array has been designed on a thin ceramic substrate (ε_r = 9.9 and h = 127 μm), using an miniature hybrid microwave integrated circuits (MHMIC) fabrication process. The proposed structure is based on a modified shape of a gap-coupled patch element with curved radiating edges. For further analysis, the performances of the latter in terms of impedance bandwidth, gain, and radiation efficiency were investigated and compared with a conventional structure of a rectangular gap-coupled patch antenna. The obtained results clearly show that the proposed gap-coupled array structure provides an improved bandwidth (7%) and an enhanced gain (10.7 dB), while maintaining a reduced size (5.2 mm x 9.5 mm). All these benefits make it an attractive candidate for the future integrated millimeter-wave RF front-end circuits; it can, however, be connected directly to various MHMIC passive circuits, or active devices through using the wire bonding technology, on a standard thin-film alumina substrate.