Turnstile Polarizer: A Broadband Continuously Reconfigurable Polarization Modulator—Part II: Dual-Polarization Reconfigurable Antenna and Experimental Validation

This two-part article proposes a novel waveguide polarizer, referred to as turnstile polarizer (TP), which achieves precise polarization modulation within a full band. In this part, we further present a broadband dual-polarization continuously reconfigurable antenna based on gap waveguide (GW) at the W-band, which consists of a smooth-wall horn integrated with a TP and a turnstile junction orthomode transducer (OMT). Through relative rotation between modules, the antenna’s dual-orthogonal output modes can be dynamically reconfigured among circular polarization (CP), elliptical polarization (EP) with arbitrary axial ratio (AR), and linear polarization (LP). Furthermore, the left-hand/right-hand operational states at both ports can be switched via rotational adjustment. A prototype was fabricated, and its performance was tested under both LP and CP modes. The measurement and simulation results are in good agreement, demonstrating an impedance bandwidth covering 75–110 GHz (37.8%), with the return loss of 20 dB and the isolation of 40/25 dB for LP and CP modes. The measured AR remains below 1 dB across the entire W-band for CP modes. Moreover, stable rotationally symmetric radiation patterns are achieved across the entire operating band, with a measured gain of 17.5 ± 1 dBi(c). The proposed antenna achieves flexible, precise, and efficient dual-polarization regulation across a broad bandwidth, providing a cost-effective passive polarization modulation solution. Additionally, the use of all-GW modules enables its operation in the sub-THz bands.