Design and Analysis of a W-Band Metasurface-Based Computational Imaging System

We design and numerically analyze a coherent computational imaging system that utilizes a sparse detector array of planar, frequency-diverse, metasurface antennas designed to operate over the W-band frequency range (75-110 GHz). Each of the metasurface antennas consists of a parallel plate waveguide, into which a center coaxial feed is inserted into the lower plate, launching a cylindrical guided wave. A dense array of metamaterial resonators patterned into the upper plate couples energy from the waveguide to free space radiative modes. The resonance frequency of each element, determined by its specific geometry, can be positioned anywhere within the W-band. The geometry of each element is chosen to produce a resonance frequency selected randomly from the W-band. Since a random subset of elements is resonant at any given frequency, the metasurface antenna forms a sequence of spatially diverse radiation patterns as a function of the excitation frequency. We analyze the metasurface aperture as an imaging system, optimizing key parameters relevant to image quality and resolution, including: aperture size; density and quality factor of the metamaterial resonators; number of detectors and their spatial distribution; bandwidth; and the number of frequency samples. A point-spread function analysis is used to compare the metasurface imager with traditional synthetic aperture radar. The singular value spectrum corresponding to the system transfer function and the mean-square-error associated with reconstructed images are both metrics used to characterize the system performance.