Multitarget 3-D Indoor Localization Using Virtual Element (VE) Digital Beamforming Technique With SIMO-FMCW Radar

This study proposed a virtual element (VE) technique for a single-input-multiple-output frequency-modulated continuous-wave (SIMO-FMCW) radar with one transmitting and three receiving antennas, which achieved multitarget 3-D indoor localization with a high spatial resolution. In the conventional method, it increases the angular resolution by increasing the antenna array size in the spatial domain, thereby increasing the complexity of the hardware and calibration processes for multichannel data. In contrast, the application of the proposed VE technique to three-channel received data improved the angular resolution, which achieved a narrower 3-dB beamwidth, enabling more accurate distinction of the direction of arrivals (DOA) of multiple targets. In addition, the theory of the VE with digital beamforming (DBF) technique for 1D-DOA (azimuth) and 2D-DOA (azimuth and elevation) estimation was derived and validated through simulation for feasibility verification. In addition, side-view and top-view radar sensing experiments were conducted to demonstrate the localization performance of the 1D-VE and 2D-VE techniques. Subsequently, multiperson indoor localization was achieved with a minimum azimuth spacing of 15° and measured errors of less than 5° when the 1T3R FMCW radar was used.