Sparse Array Radiometric Imaging (SARI) using an Electronic Mirror

A high resolution, millimeter-wave radiometric imaging system with the ability to penetrate obscurants (rain, clouds, dust, sand and smoke) is a highly attractive surveillance tool with broad application to satellite, uninhabited aerial vehicle (UAV) and other military and commercial platforms. Achievement of such a system through application of conventional interferometric or sparse aperture techniques has been shown impractical for many potential applications. This is due to the inherent difficulty of simultaneously satisfying field of view (FOV) and image quality requirements while also maintaining acceptable weight, power and computational limits - this is especially true for satellites and UAV platforms. In response, IR&T has developed an innovative solution to this severe limitation through the use of an w concept of a beam-steerable, sparse array imaging interferometer for application to millimeter-wave radiometric imaging. The electronic mirror allows fewer, higher gain elements thereby reducing the overall antenna weight, power consumption and data analysis complexity. The electronic mirror provides the necessary control to increase the FOV while also providing flexibility to optimize image acquisition and quality in varying weather and tactical situations. The electronic mirror consists of an array of monolithic, solid-state, varactor diodes together with antennas and bias lines. The incident electromagnetic wave is steered through a progressive phase shift introduced across the array through a simple bias voltage. Monolithic fabrication results in the low-cost, high reliability essential for both the proposed military as well as commercial applications.