Wideband Dual-Polarized Hollow-Waveguide Slot Array Antenna

A wideband dual-polarized slot array antenna based on hollow waveguide (HW) is presented in this article. Its wide bandwidth and high performance are enabled by two separate feeding networks, from the side and the bottom, using square coaxial line and ridge waveguide structures, respectively. The full-corporate-feed networks excite the radiation slots in a one-to-one fashion without using backed cavities. Tight element spacing is made possible, suppressing the grating lobe and maintaining high cross-polarization discrimination (XPD) across the wideband. This resolves a usual tradeoff between bandwidth and grating lobe. A double-ridge rectangular waveguide cavity is devised as an orthogonal mode splitter for isolation enhancement. Several design features are used to minimize the signal path length and facilitate routing. An $8\times8$ element prototype in K-band is designed, fabricated, and measured. Experimental results show that the antenna has a wide bandwidth of 23.4% (from 17 to 21.5 GHz) free from grating lobes. More than 25.5 dBi peak gain higher than 51.2 dB isolation and over 43.6 dB XPD are also obtained for the dual polarizations.