W-band frequency-polarization-port-diverse cavity imager with bunching random beams

Abstract

A frequency-polarization-port-diverse (FPPD) cavity imager with bunching random beams working in the W-band (from 76 GHz to 81 GHz) is proposed in this paper. A random-coherent-superposition design method is utilized to design the bunching random beam. Low-correlated radiation patterns can be generated when excited either at different frequencies or by different ports. Orthogonal polarized radiation patterns also vary from each other, which can enlarge measurement modes from the polarization dimension. The FPPD cavity imager is composed of a disordered cavity, a lid etched with elliptical holes and a dual-polarized horn antenna. Frequency-port-diverse electric field distributions of the disordered cavity are achieved by loading irregular structures and FPPD radiation patterns are realized by etching elliptical holes with various minor axis lengths and rotation angels. A dual-polarized horn antenna is used to generate the bunching radiation patterns, on which we superpose the random radiation patterns. Definitions of the bunching angle and the correlation coefficient are also given to evaluate the performance of the FPPD cavity imager. Finally, a coincidence imaging experiment is used to investigate the FPPD cavity imager under different conditions and the target image has been reconstructed successfully. Advantages of the bunching characteristic are also proved by comparative experiments using the bunching radiation patterns and the normal radiation patterns. High-quality reconstruction of the target image demonstrates the feasibility of the multi-dimension joint (i.e. frequency, polarization and port) design method. The proposed method is verified by simulations and measurements.