Omnidirectional oversized annular lens antenna with high gain for 5G millimeter-wave channel measurement

A high gain oversized annular lens antenna for 28-GHz band channel measurement system is presented. The proposed antenna is composed of an omnidirectional feeding source and an oversized annular lens. The feeding source is a compact multi-stepped biconical antenna with a wide impedance bandwidth. By rotating a horizontally placed two-dimensional extended hemispherical lens around the vertical axis, the oversized annular lens is realized, which effectively increases the vertical radiation aperture and maintains high aperture efficiency to enhance the omnidirectional gain. Under the same envelope, the proposed antenna features a higher gain than the biconical antenna and the ordinary annular lens antenna. A prototype is fabricated and measured. The measured results demonstrate that the -10-dB impedance bandwidth is 20.7% (24-29.6 GHz), with stable vertically polarized (VP) omnidirectional radiation patterns and gain over 10.3 dBi within the entire band of interest.