Single-Layer Broadband Vertically Polarized Endfire Magnetoelectric Dipole Loop Antenna and Array for Millimeter-Wave Applications

A single-layer broadband vertically polarized (VP) endfire magnetoelectric dipole (ME-dipole) antenna is investigated for millimeter-wave (mm-wave) applications. The main radiator of this antenna is a substrate-integrated (SI) closed loop, which consists of two horizontal metallic strips printed on the upper and lower surfaces of substrate and a pair of vertical metallic vias. Excited by a double-sided parallel-strip line (DSPSL) at the center of the loop, the metallic vias function as electric dipoles, while the entire loop aperture works as magnetic dipole. Thus, a complementary broadband ME-dipole structure is constructed, generating endfire radiation. To facilitate integration, this SI ME-dipole loop antenna is fed by an open-ended SI waveguide (SIW), which also works as a backed cavity to enhance the front-to-back ratio (FTBR). Moreover, two pairs of rectangular slots are etched at the edges of the SIW aperture to further improve the FTBR and also the cross-polarization performance. This antenna element is then utilized to design a 1×8 antenna array. For validation, both the ME-dipole antenna and array have been fabricated and tested. The measured results show that the antenna/array prototypes have a wide bandwidth of 57.3% (37.2-67.1 GHz)/59.9% (36.1-67 GHz) and a stable gain of approximately 5.8/14.9 dBi. Due to the superior performance and also simple structure, the proposed design would be a promising candidate for mm-wave communication systems.