A Microwave/Millimeter-Wave Shared-Aperture Filtering Antenna With Reused via Structure

A microwave (MW) and millimeter wave (MMW) shared-aperture filtering antenna reused via structure for 5G application is proposed in this communication. The antenna is composed of a 3.5 GHz filtering patch antenna and a 28 GHz substrate-integrated filtering cavity antenna (SIFCA) array. The shorting via structure of the patch antenna, which designed to generate a lower-edge radiation null in the MW band, is repurposed as metallized grooves for 28 GHz cavity antenna array radiation in the MMW band. Then, two parasitic patches are applied to produce an upper-edge radiation null at the MW band. For the 28 GHz SIFCA element, a stub-loaded microstrip feed line is employed to generate a controllable radiation null. Moreover, for the extension of MMW antenna array, two additional SIFCA elements are further inserted. The antenna array extension is realized as a <inline-formula> <tex-math notation="LaTeX">$1\times 2$ </tex-math></inline-formula> patch array for MIMO system and a <inline-formula> <tex-math notation="LaTeX">$1\times 12$ </tex-math></inline-formula> SIFCA array for high-gain and beam-steering applications. A dual-band antenna array prototype for validation is fabricated and tested. The measured results demonstrate a reasonable agreement with the simulated ones.