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In this paper, a K-band antenna with ±60 • beam scanning is proposed for a mmWave (millimeter-Wave) radar sensor. Especially, we take advantages of the magnetic dipole principle, and design the antenna by employing via holes in three sides, so as to form a cavity which can be equivalently considered as magnetic dipole, resulting in the 3 dB beam width as wide as 140 • in E-plane. We cascade the mmWave antenna to 1×4 and 4×4 arrays for radar transmitting and receiving, respectively. The antenna array is fabricated and implemented to a K-band radar and its wide-angle beam scanning performance is evaluated by the radar's distance and angular detections. INDEX TERMS Wide-angle beam scanning, antenna array, magnetic current antenna, K-band radar.

A wideband dual-polarized antenna is proposed for 4G and 5G communication applications. The antenna element consists of a pair of opened-loop dipoles for dual-polarization and its three inherent resonant modes are shifted closer to form a wide bandwidth. With additional U-shaped slots etched around the feed point, the input impedance of the antenna element is matched to 50 Ohm. The fabricated antenna element operates from 1.8 to 4.0 GHz, having 75.9% (VSWR ≤ 2) impedance bandwidth and high port-toport isolation (> 25 dB). It also achieves a 67±1 • beamwidth in H-plane and 68.7 ± 3.3 • in V-plane with 8.5 ± 1 dBi gain across the supported bands. By using six antenna elements and designing RF phase shifting module (RFPSM) based on vector modulators, a six-element dual-polarized array with electrically downtilt is also fabricated and measured, realizing a peak gain of 16.8 dBi, a similar beamwidth in H-plane as single antenna element and an electrically downtilt in V-plane from 0 • to 12 • which is preferred in communication applications. This antenna array could be used for future 5G communication and other applications. INDEX TERMS Wideband, dual-polarized, electrically downtilt, opened-loop dipoles, 5G.

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