Three-Dimensional Imaging of Terahertz Circular SAR with Sparse Linear Array.

Jubo Hao,Jin Li,Yiming Pi

doi:10.3390/s18082477

Abstract

Due to the non-contact detection ability of radar and the harmlessness of terahertz waves to the human body, three-dimensional (3D) imaging using terahertz synthetic aperture radar (SAR) is an efficient method of security detection in public areas. To achieve high-resolution and all aspect imaging, circular trajectory movement of radar and linear sensor array along the height direction were used in this study. However, the short wavelength of terahertz waves makes it practically impossible for the hardware to satisfy the half-wavelength spacing condition to avoid grating lobes. To solve this problem, a sparse linear array model based on the equivalent phase center principle was established. With the designed imaging geometry and corresponding echo signal model, a 3D imaging algorithm was derived. Firstly, the phase-preserving algorithm was adopted to obtain the 2D image of the ground plane for each sensor. Secondly, the sparse recovery method was applied to accomplish the scattering coefficient reconstruction along the height direction. After reconstruction of all the range-azimuth cells was accomplished, the final 3D image was obtained. Numerical simulations and experiments using terahertz radar were performed. The imaging results verify the effectiveness of the 3D imaging algorithm for the proposed model and validate the feasibility of terahertz radar applied in security detection.

Highlights

Terrorist attacks have increased substantially in recent years on a global scale, and they pose a great threat to public safety
The imaging results verify the effectiveness of the 3D imaging algorithm for the proposed model and validate the feasibility of terahertz radar applied in security detection
A benefit pf the high center frequency is that a large bandwidth can be achieved for terahertz radar, which is set as 28 GHz here

Summary

Introduction

Terrorist attacks have increased substantially in recent years on a global scale, and they pose a great threat to public safety. Because of the pitch angle, resolutions between range and height directions are coupled, which makes it difficult to improve both resolutions simultaneously To address this issue, much research has been conducted by scholars, including studies on multipass SAR, linear array SAR, etc. SAR imaging, where the array distributes along the needed direction to provide a sampling aperture. The targets of interest in security detection behave with spatial sparsity generally, the sparse recovery method can be employed to form the image. The imaging geometry of CSAR with sparse linear sensor array was first established, and the echo signal model in the terahertz band was developed.

Imaging Geometry

Scattering Coefficient Reconstruction along the Height Direction

Simulation Results and Analysis

Experiment Results and Analysis

Conclusions