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ECE PhD Proposal Review: Weite Zhang
July 29, 2021 @ 3:00 pm - 4:00 pm
PhD Proposal Review: High Sensing-capacity Multi-dimensional-coded Millimeter-wave MIMO Imaging System
Location: Microsoft Teams Link
Abstract: Millimeter-wave (mm-wave) MIMO imaging systems have been explored to use more and more complicated radar waveforms to achieve advanced multiplexing and high-performance imaging. As the complexity of the radar waveform increases, conventional systems inevitably suffer from higher design difficulty and cost. In spite of the radar waveform design, existing mm-wave imaging systems are still suboptimal due to the fact that the sensing matrix is not tailored properly to achieve its maximum capacity, which often results in large mutual information between successive measurements, and limited imaging performance.
As the first contribution of this proposal, high sensing-capacity mm-wave MIMO imaging systems with multi-dimensional-coding are built. In the first prototype, a 70-77 GHz frequency-modulated continuous wave (FMCW) MIMO imaging system with massive channels is studied. To enhance the sensing-capacity, a compressive reflector antenna (CRA) is added to perform randomized spatial wavefront coding to increase the measurement diversity. Both static and on-the-move experiments are carried out to show the functionality of the imaging system. In the second prototype, an 81-86 GHz software-defined mm-wave MIMO imaging system is designed, which makes use of cost-effective software-defined radios (SDRs) with mm-wave mixers. Due to the baseband flexibility of SDRs, efficient orthogonal frequency-division multiplexing (OFDM) with binary phase coding is designed as the radar waveform to achieve simultaneous MIMO transmission, where high receiving signal-to-noise ratio and spectrum efficiency are achieved. Again, a CRA is designed and applied to increase the measurement diversity. Primary simulation and experimental results show good imaging performance with reduced side lobe effect.
As the second contribution of this proposal, a material characterization method is developed, which is vital in some important mm-wave imaging applications, such as security screening, where both object profile and material information are required for potential threats prediction. Specifically, a Geometrical Optics (GO) forward model based on a reflectarray imaging system is developed. The GO forward model can be adapted to any other imaging systems as long as their geometrical configurations are known. Both simulations and experiments are performed to show the effectiveness and efficiency of the proposed material characterization method, where the complex relative permittivity as well as a more accurate shape of the object is retrieved.