Wideband tilted beam end-fire antenna using double semi-circular rings

This article presents a novel wideband (WB) tilted-beam end-fire planar antenna for microwave and millimeter-wave (mmWave) applications. The antenna comprises of a microstrip fed double semi-circular rings over a curvilinear slotted ground plane. It is impedance matched over a broad frequency range from 11.5 to 62.5 GHz, covering the 5G New Radio (NR) mmWave bands n257, n258, n260, n261, and partly covering the unlicensed 60 GHz band. Across this entire band, the antenna exhibits a return loss better than 12 dB and a gain exceeding 6.5 dBi, with a peak gain of 11.6 dBi at 40 GHz. The overall electrical size of the antenna is 1.28 × 1 × 0.08 λ ₀³ , where λ ₀ corresponds to the free-space wavelength at 32 GHz. Within the 24–40 GHz frequency range, corresponding to a 50% fractional bandwidth and covering the four 5G NR bands, end-fire radiation is achieved with a tilted beam angle of 65∘ ± 10∘ . A prototype of the antenna is fabricated and experimentally characterized. The measured results show good agreement with full-wave simulations, validating the proposed design. Owing to its compact planar geometry, wide bandwidth, and high gain, the antenna is a strong candidate for future high-data-rate wireless communication systems.