Near-Field Image Restoration for Rotman Lens by Localized Angle-Time Spread Function-Based Filtering Method

Rotman lens is a prospective device for real-time microwave/millimeter-wave imaging by virtue of its parallel multibeam functionality. For imaging purposes, a Rotman lens intrinsically requires that the scattered waves arriving at the array be plane waves. However, this requirement cannot be met in near-field imaging applications, as the scattered waves from targets in the near field defocus at the beam ports of the lens because of the nonplane wave scattering. As a result, out-of-focus blurs appear in the near-field images, thus leading to degradation of picture quality. To address this problem, we propose a localized angle-time spread function (ATSF)-based filtering method to reduce out-of-focus blurs. With the proposed method, the deblurring process becomes simple for a Rotman lens. Both simulations and experiments were performed. The results show that the proposed method significantly improves the quality of near-field images with enhanced resolutions in both angular and radial directions.