Canceling the Cross-Polarization of the Difference Modes in a Circular Aperture Multimode Monopulse Feed

摘要

A highly efficient circular aperture multimode monopulse feed is proposed.$mathbf {TE_{01}}$and$mathbf {TM_{01}}$modes in the circular waveguide are added in a circular waveguide$mathbf {TE_{21}}$mode dual-channel monopulse feed. Optimal mode ratios (both amplitude and phase) are realized conveniently to cancel the cross-polarization of the difference modes on the feed’s aperture, which changes a low-efficient funnel-shaped difference beam to an azimuth or elevation difference beam with the efficiency of which highly improved. The fundamental$mathbf {HE_{11}}$mode of the corrugated waveguide is adopted as the sum mode. The simulation and measured results show that this feed is of low voltage standing-wave ratio, high sum–difference isolation, high transmitter–receiver isolation, high efficiency, and broadband.