Broadband Near‐Field Computational Microwave Imaging Enabled by Nonperiodic Dispersive Unit‐Cell Loading in a Passive Metasurface

Computational microwave imaging can reduce reliance on dense antenna arrays and mechanical scanning by encoding scenes using spatially diverse electromagnetic masks. Metasurface apertures are attractive for producing such masks; however, many implementations rely on active tuning, cavity‐backed apertures, folded propagation paths, mechanical reconfiguration, or multiple feeds. This work presents a passive single‐layer randomized leaky‐wave metasurface aperture for broadband near‐field computational microwave imaging. The aperture uses a single feeding port and an integrated 16‐way microstrip power divider to launch guided waves along nonperiodic rows composed of six dispersive H‐shaped unit‐cell types. Eigenmode‐based analysis guides the selection of these unit‐cell types and clarifies how their nonperiodic loading produces frequency‐dependent near‐field masks through leaky‐wave radiation. The fabricated prototype integrates the aperture and feed network on a PCB, demonstrating broadband operation over 18–28 GHz, corresponding to 43.5% fractional bandwidth. Measured near‐field masks confirm broadband low‐redundancy spatial encoding. Imaging experiments demonstrate recovery of test targets and 5 mm two‐target separability in both transverse directions. These results show that static nonperiodic unit‐cell loading and broadband dispersion provide a compact, hardware‐efficient passive route to near‐field computational microwave imaging.