MIMO-SA-Based 3-D Image Reconstruction of Targets Under Illumination of Terahertz Gaussian Beam—Theory and Experiment

Abstract

For the 3-D terahertz (THz) holographic imaging, this work proposes an extended phase-shift migration (PSM) reconstruction algorithm based on multiple-input-multiple-output (MIMO) array with an orthogonal synthetic aperture (SA). For this MIMO-SA-based imaging mechanism, the accurate expression of the signal spatial spectrum can also be obtained by utilizing the method of stationary phase (MSP). Meanwhile, the analytical expression of the reconstructed 3-D point-spread function (PSF) for target under the illumination of MIMO-SA-based THz Gaussian beam is derived to provide the theoretical spatial resolutions quantitatively. A serial of simulation results with fairly good agreement were given to verify the accuracy of the proposed MIMO-SA-based PSM reconstruction algorithm. Meanwhile, due to the PSM’s characteristic of phase shift compensation along the range direction, the image reconstruction process can also be implemented and accelerated by a GPU solution. Finally, two types of MIMO-SA-based prototype imagers are applied for the proof-of-principle experiments. The first prototype imager is configured with one transmitter and two receivers in 0.3-THz band. The MIMO linear array including arbitrary number of transmitters/receivers can be realized by controlling their positions in a low-cost way with the help of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$x$</tex-math> </inline-formula> -axis of a 2-D scanner. The second prototype imager is configured with eight transmitters and eight receivers in 0.2-THz band. The experimental results from the two prototype imagers can validate the effectiveness on image reconstruction quality.