Enhancing Microwave Metamaterial Aperture Radar Imaging Performance With Rotation Synthesis

Microwave metamaterial aperture imaging radar (MMAIR) is a new radar system, which is capable of generating forward-looking image without using mechanical scanning or antenna arrays. In MMAIR, metamaterial elements are specifically embedded into a top plate of a parallel plate waveguide, whose resonance frequencies vary among a wide frequency bandwidth. Different MMAIR radiation fields can be motivated by a wide-band waveform, and the forward-looking image is reconstructed with the measurements excited by a set of frequency radiation modes. According to the compressed sensing (CS) theory, the imaging performance of an MMAIR system is restricted by the diversity of the frequency-agility radiation modes. In general, abundant radiation modes are difficult to achieve and require special design of the metamaterial aperture and waveform of extremely wide frequency bandwidth. In this paper, we propose a rotation-synthesis approach to enhance the diversity of the radiation modes without the increase of the system complexity. By rotating the metamaterial aperture panel around the panel axis, the approach exploits the pseudo-randomness characteristics of the MMAIR radiation field. The rotation motion is capable of dramatically improving the abundance of the MMAIR measurements at a price of consuming more measurement time. As a result, the image performance of MMAIR using the CS reconstruction optimization can be crucially enhanced. Extensive simulations verify the effectiveness of the proposed approach.