W-band Frequency-Polarization-Diverse Metasurface Antenna for Coincidence Imaging

A W-band frequency-polarization-diverse metasurface antenna (FPDMA) that can be used for coincidence imaging is proposed in this paper. Diverse radiation patterns can be generated by the FPDMA in both the frequency-domain and the polarization-domain, which can be used as different measurement modes in the coincidence imaging system. The working frequency of the FPDMA is extended to the W-band (76 GHz-81 GHz) to obtain higher resolution. The FPDMA is composed of a feeding module and a phase-random-modulation metasurface. The feeding module is a disordered-cavity, which can generate different internal field distributions at different working frequencies. The frequency-diverse feature of the field distribution would be inherited by the coupling slots and passed on to the radiation patterns of the FPDMA. The phase-random-modulation metasurface contains a variety of different metamaterial elements with different transmission phases and diverse polarization characteristics, which could generate polarization-diverse radiation patterns when excited by electromagnetic waves with different polarization. Therefore, when the disordered-cavity and the metasurface work together, radiation patterns show a dual sensitivity in both the frequency-domain and the polarization-domain. Performances of the FPDMA including the reflection coefficient $(S_{11})$, the radiation efficiency and correlation coefficients of radiation patterns generated under different conditions are evaluated through simulations. A simulated coincidence imaging experiment using the proposed FPDMA is also carried out and the target image is reconstructed successfully. The design is validated through simulated results.