A Steerable Dual-Polarized Monopulse Reflector Antenna With Gap-Waveguide Adaptive Phase Shifters for E-Band Backhaul

This letter presents an E-band monopulse feed with broadband gap-waveguide adaptive phase shifters for Gregorian reflector antennas tailored for 5G backhaul communications. The monopulse functionality is achieved using a gap-waveguide-based $2\times 2$ step-horn-array feed with a feeding network comprising 3 dB couplers and adaptive phase shifters. The antenna achieves an ultrahigh-gain of 50 dBi through integration of the feed with a Gregorian reflector antenna and employs beamsteering by offsetting the feed from the subreflector focus. However, the feed offsetting degrades the null depth in difference ($\Delta$) patterns. Therefore, a new phase compensation strategy is proposed, involving a codesign of adaptive phase shifters with the offset by using a numerical phase compensation function quantified in this work based on simulation data through GRASP and CST. The fabricated antenna demonstrates reflection coefficients below $-10$ dB for both polarizations over 71 GHz to 86 GHz. The measured radiation patterns and gains align closely with the simulated results. The system achieves a maximum gain of 50.48 dBi, with beamsteering within $\pm 2^\circ$ from boresight and a maximum steering loss of 0.96 dB. The null depth of all $\Delta$-beams is maintained above 20 dB. These results highlight the significant potential of this antenna for 5G backhaul communications.