Terahertz reflection imaging using virtual arrays and MUSIC in a synthetic aperture array

Terahertz imaging using synthetic aperture arrays (SAAs) is an attractive nondestructive measurement method, as it can increase the spatial resolution while reducing the restrictions on target placement. MUltiple SIgnal Classification (MUSIC), which is a high-resolution direction of arrival estimation method, is also attractive because it increases the resolution of terahertz imaging. However, the resolution of the MUSIC spatial spectrum deteriorates when correlated signals are received. Spatial smoothing (SS) can reduce the correlation of incoming waves; however, this technique is only applicable to equispaced linear arrays in plane wave reception environments. This paper introduces MUSIC with SS to THz imaging using an arcuate SAA by applying array interpolation using virtual arrays. The imaging results and position estimation accuracy using simulated or measured arcuate synthetic array responses of two metal wire targets demonstrate the effectiveness of the method compared with the conventional beamformer and MUSIC methods.