Computational Microwave Imaging Relying on Orbital Angular Momentum Transmitarrays for Improved Diversity

TL;DR

This paper introduces a novel microwave imaging approach using orbital angular momentum waves to enhance measurement diversity, reduce bandwidth needs, and improve image quality, validated by a Ka-band prototype.

Contribution

It demonstrates that OAM waves significantly improve imaging performance and bandwidth efficiency in computational microwave imaging systems.

Findings

Multiple OAM waves increase measurement diversity.

OAM-based system achieves high-quality images with less bandwidth.

Complex targets are reconstructed only with multiple OAM modes.

Abstract

This work proposes the use of orbital angular momentum (OAM) waves to improve the performance of a computational imaging (CI) system. Specifically, in contrast to a solely frequency-diverse operation, leveraging multiple OAM waves leads to a significant increase in the diversity of the measurement modes of a CI system. This significantly reduces the frequency bandwidth required to achieve high-quality image reconstructions. A proof-of-concept prototype working at Ka-band frequencies is used to validate the proposed approach. The prototype consists of two metalized three-dimensional (3D) printed cavities, with fully-dielectric transmitarrays inside that generate OAM waves. Imaging results from various targets reveal that the CI system achieves superior imaging quality when multiple OAM waves are considered, compared to when it solely relies on frequency-diversity. This is specially noticeable in the case of complex distributed targets, which can only be reconstructed with the prototype when multiple OAM waves are used. Furthermore, it is shown that accurate image reconstructions can be obtained employing only one eighth of the operational bandwidth of the frequency-diverse system.