A novel high-gain polarization reconfigurable antenna composed of a polarization conversion metasurface (PCM) and a linearly polarized source patch antenna is presented in this article. The PCM is placed above the source patch antenna with an air gap. The proposed PCM can convert the linear polarization (LP) wave radiated by the source patch antenna to LP wave, right-hand circular polarization (RHCP) wave, and left-hand circular polarization (LHCP) wave by rotating the PCM around the center of the antenna. Meanwhile, the proposed PCM can serve as the partially reflective surface (PRS) of a Fabry-Perot (FP) resonant cavity which can achieve gain enhancement. In order to validate the performance of the proposed design, a prototype antenna is fabricated and measured. Simulated and measured results agree well. From 10.43 GHz to 11.2 GHz, the polarization reconfiguration can be achieved by rotating the PCM to different angles while maintaining the high gain performance simultaneously.

For microwave computational imaging (MCI), the reduction of measurement matrix's coherences permits better reconstruction performance. Therefore, frequency diverse apertures (FDAs) have become a major option of antennas for MCI due to thier frequency-varying radiation patterns. The frequency diversity in the patterns reduces coherences; however, the losses in practical materials and the finite sizes of apertures impose upper limits on frequency diversity. For further coherence reduction, the polarization diversity (PD) of aperture elements is as a new approach introduced in this paper. We present an electromagnetic formulation of scattering aperture elements' PD. In the formulation, the PD brings an additional degree of freedom in the generation of the measurement matrix, given the apertures being illuminated with varying polarizations. This new degree of freedom enables a potential of reducing the coherences. Two complementary electric-field-coupled (cELC) scattering apertures, which differentiate in the polarizations of elements, are fabricated for validation. A set of comparisons yielded by the near-field scanning data of these apertures shows that the PD effectively reduces coherences and improves reconstruction performance.