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Millimeter-wave (mm-wave) multiple-in-multiple-out (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 radar waveforms increases, conventional radars inevitably suffer from higher design difficulty and cost. This work presents a software-defined mm-wave (SDMMW) multistatic radar design by making use of cost- effective commercial software-defined radios (SDRs) and additional radio-frequency/mm-wave modules. Due to the great baseband flexibility of the SDRs, the efficient space-time-coded (STC) orthogonal frequency-division multiplexing (OFDM) is developed as the radar waveform to achieve simultaneous MIMO transmission at the same time and frequency. The radar is designed at 83:5 GHz with a frequency bandwidth of 4:8 GHz, where an 8-by-8 waveguide array is specially designed to form 64 virtual channels with a small element-separation of 9 mm for three-dimensional imaging applications. To further enhance the sensing capacity and improve the imaging resolution of the SDMMW radar, the spatial coding created by the compressive reflector antenna is combined with the efficient multiplexing based on the STC OFDM. Preliminary experimental results show good imaging performance, giving great potential for developing future high-performance mm-wave imaging systems with advanced multiplexing.
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