A Hybrid Synthetic Aperture and Time-Reversal MUSIC Algorithm for Subwavelength Radar Imaging

A promising chipless RFID approach uses millimeter-wave synthetic aperture radar (SAR) to image metal ink-printed ID tags from a meter or more away. Due to printing cost, it is desirable to minimize the size and spacing of metal patches within a tag, preferably into the subwavelength regime. Although circular SAR (CSAR) has a sharply peaked point response in 2D, its side lobes of closely-spaced targets interfere strongly with each other to distort the image. An alternative 2D subwavelength imaging approach with minimal side lobes is Time-Reversal MUSIC (TR-MUSIC). Traditional TR-MUSIC, however, requires a large number of transmitters and receivers. We propose a hybrid synthetic aperture TR-MUSIC algorithm (SATR-MUSIC) that combines the benefits of both approaches. Using relatively few transceivers, SATR-MUSIC is able to resolve objects separated by approximately in 2D with minimal background artifacts. It does so by averaging TR-MUSIC’s imaging kernel incoherently over the synthetic aperture.

Superlensing property of 2-D glass photonic crystal

A two dimensional square lattice photonic crystal (PhC) formed by placing glass matrix in air is proposed for subwavelength imaging around 840 nm. The superlensing behavior at relatively lower wavelength compared to other reported PhC superlens is obtained by this configuration. Other advantages of using glass is that they have lower optical absorption at this wavelength and is relatively cheap. By placing the proposed PhC arrangement between the object and the objective of a conventional optical microscope, superlensing effect can be realized. Moreover, any change in radius of glass rod during fabrication process can result in the shift of superlensing wavelength.