Millimeter-Wave Wideband Endfire Antenna with Small Ground Clearance for 5G Mobile Terminals

A wideband vertically polarized endfire antenna is presented for 5G millimeter-wave mobile terminals. The antenna is implemented with a single-layer SIW structure and has a small ground clearance of only 2.5 mm. A pair of top-hat dipoles, consisting of metallic disks and vias, are loaded in front of the antenna aperture and partially connected with the SIW structure, which can dramatically improve the impedance matching and stabilize the in-band gain fluctuations. Two matching pins are inserted in the SIW to further broaden the bandwidth. The antenna achieves a −10 dB bandwidth of 25.4%, covering the n257, n258, and n261 bands simultaneously. A $1\times 4$ endfire antenna array is constructed for beamforming applications. Good beam scanning performances are obtained.