In this paper, a 60-GHz broadband 8-by-1 gap-coupled microstrip antenna array is presented and experimentally investigated. The proposed antenna array has been implemented using a Miniature Hybrid Microwave Integrated Circuits (MHMIC) fabrication process on a thin ceramic substrate with εr = 9.9, and h = 127 μm. For a comprehensive characterization and to accurately evaluate losses, as well as manufacturing tolerances, the proposed antenna array structure has been implemented using two different feeding techniques. The first one adopts a grounded broadband via-hole less transition from coplanar to microstrip line (GCPW-to-MS), while the second one has involved a broadband waveguide (WR12) to microstrip transition, based on a ridged waveguide concept. The obtained results have demonstrated that the proposed gap-coupled array configuration provides an improved bandwidth (4.56%) and an enhanced gain (11.8 dBi), while maintaining a lower side-lobe level (13.4 dB). These outstanding performances make the proposed WR12 gap-coupled array structure a potential candidate for the future emerging 60-GHz short-range point-to-point wireless communication systems.
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