A Broadband Dual-Polarization Filtering Array Antenna With Dual-OAM Beam Based on Low-Profile Multimode Resonator

This letter presents a broadband, dual-polarized filtering array antenna capable of generating dual-orbital angular momentum (OAM) beam using a low-profile multi-mode resonator (MMR). The broadband MMR is realized by integrating four shorting vias and a slotted patch into a rectangular substrate to excite the dielectric modes$\text{TE}_{111}$,$\text{TE}_{121}$,$\text{TE}_{211}$, and the patch mode$\text{TM}_{10}$. By coupling the spurious$\text{TE}_{211}$with the in-band resonant modes, two transmission zeros are introduced on both sides of the passband, thereby improving bandwidth and frequency selectivity. To implement the filtering array, the patch is co-designed as a radiating metasurface (MTS), serving as the final stage of the polarization-shared filtering circuit. A fabricated 2×2 array sequentially generates three dual-OAM beams with topological charges ($l_{1}$,$l_{2}$) = (+1,-1), (0,+1), and (-1,0) by feeding phase shifts, each exhibiting two radiation nulls. The prototype achieves an active VSWR below 2 over a 32.7% (2.92-4.05 GHz) bandwidth, peak realized gains of 8.2, 10.1, and 10.0 dBi for the three dual-OAM beams, and out-of-band suppression$\geq$17.1 dB.