340-GHz 3-D Imaging Radar With 4Tx-16Rx MIMO Array
A standoff 3-D imaging radar for security body scan at 340 GHz has been described. This terahertz imager incorporates a multiple input multiple output (MIMO) array as an electronic beam former in a horizontal dimension and an elliptic cylinder as a focusing reflector in elevation. Frequency-modulated continuous-wave (FMCW) emission with 16-GHz bandwidth caused a 10-mm-range resolution after calibration for nonlinearities of the distorted radar signals. The horizontal MIMO array contains 4 transmitters and 16 receivers (4Tx-16Rx) to generate a 64-Tx/Rx full virtual array corresponding to an antenna size of approximately 128 mm, which caused a horizontal resolution of about 14 mm at a distance of 3 m. FMCW signals were transmitted from the 4-Tx sequentially and focused as narrow beam lines by the elliptic reflector to get a 12-mm vertical resolution at 3 m. A fast-scanning mirror swings in the light path to make these beam lines screen in the vertical direction. A 4-Hz frame rate is now possible for a personal screen with a field of view of 2 m × 0.6 m.