Aliasing Suppression in Synthetic Aperture Interferometric Radiometers Using Subarray-Based Antenna Architecture

Synthetic aperture interferometric radiometers (SAIRs) have emerged as a promising technology for high-resolution remote sensing and target detection by synthesizing spatially distributed antenna elements into a large virtual aperture. To achieve high angular resolution and radiometric sensitivity, SAIR systems often employ sparse antenna arrays composed of antenna elements with large apertures and high gain, resulting in element spacings exceeding half a wavelength. Such undersampling violates the Nyquist sampling criterion, generating grating lobes in the array factor (AF) and resulting in spatial aliasing artifacts in reconstructed brightness temperature (TB) images, which degrade imaging and detection performance. To mitigate this problem, this paper proposes an aliasing suppression method based on a subarray-based antenna architecture. First, the grating lobe directions of the sparse array are identified through AF analysis. Each conventional antenna element is then replaced with a properly designed subarray antenna whose radiation pattern introduces nulls are placed near the grating lobe directions, thereby reducing the corresponding aliasing artifacts in reconstructed TB images. Simulation results and an equivalent experimental emulation demonstrate that the proposed method reduces aliasing artifacts while maintaining competitive spatial resolution and radiometric sensitivity. Additional analyses investigate the effects of subarray layout, the number of subarray elements, and wideband operation, as well as the direction dependence of grating lobe suppression, providing practical guidance for SAIR system design.