The use of millimeter-wave technology for imaging and remote sensing has expanded significantly in recent years. Due to the small size of millimeter-wave antennas and electronics combined with the ability of millimeter-wave propagation through fog, smoke, clothing, and some building materials, millimeter-wave sensors are becoming critically important tools in areas such as security sensing, medical imaging, autonomous vehicle sensing, and scientific research. Millimeter-wave imaging furthermore enables imaging and sensing in an electromagnetic regime that is presently underutilized, and is thus becoming increasingly important in the areas stated above. Antenna arrays in particular are becoming of greater interest due to their smaller size and greater flexibility than mechanically-scanned millimeter-wave imagers. This project will develop a new method of millimeter-wave array imaging called active incoherent imaging. The proposed incoherent imaging approach has the potential to significantly reduce the cost of millimeter-wave and sub-millimeter-wave imaging without sacrificing image resolution. Furthermore, the image quality of the proposed approach does not degrade significantly even if part of the receiver array elements fail, which improves its long-term utility over pixel-based imaging methods. The results of this project will enable millimeter-wave imagers to become more accessible to society and to be easily implemented in a broad range of applications. Furthermore, the results of this research will be used to enhance existing courses and develop new courses in radar and millimeter-wave technology at Michigan State University.
Combining aspects of sparse array theory and spatial frequency sampling, the proposed active incoherent millimeter-wave imaging utilizes a spatio-temporal incoherent transmitter array combined with a sparse, coherent receiver array. While resolution is the primary limiting factor in millimeter-wave imaging in many applications, sparse receiver arrays using spatial frequency sampling can be utilized to generate images with resolution equivalent to a fully filled array with at least an order of magnitude fewer elements. Incoherent imaging has the additional benefit of improved efficiency because fewer receiver elements are needed and incoherent transmitter arrays are more energy efficient to implement than coherent transmitter arrays. This project will also investigate a novel modular packaging format, where individual transceiver chips are wirelessly phase locked and the received data is wirelessly downlinked. This distributed approach enables the new imaging method to be directly scalable and easily implemented in future millimeter-wave imaging systems.
