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

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.

Linear and Circular UWB Millimeter-Wave and Terahertz Monostatic Near-Field Synthetic Aperture Imaging

“…We denote the field produced by a transmitting element located at r ⃗_(t_i) at a frequency f in the field point ⃗ as ⃗ ⃗, ; ⃗ . According to the principle of equivalence [5], the illuminating field induces in the object a current distribution proportional to the electric contrast, which can be expressed as ⃗ ⃗, ; ⃗ = ⃗) ⃗ ⃗, ; ⃗…”

“…According to the principle of equivalence [5], the illuminating field induces in the object a current distribution proportional to the electric contrast, which can be expressed as…”

“…In Reference [4], a terahertz inspection system for radome polymer object inspection operating from 70 to 110 GHz and from 110 to 170 GHz was presented with very good resolution results, proposing the use of higher frequencies around 300 GHz for better resolution. In Reference [5], a terahertz three-dimensional (3D) linear frequency modulated (LFM) SAR imaging system for security detection at the 340 GHz band was tested using a two-dimensional (2D) Fourier transform. In Reference [6], a radar operating at 522 GHz was presented in order to explore this band.…”

Semantic Fusion and Joint Analysis of Terahertz and 3d Video Images by the Means of Object-Oriented Logic Programming

“…Active terahertz video surveillance is historically associated with such areas as radar and holography [39,41]. At present, in the field of active terahertz observation, it has been proposed to use the mechanical and digital beam formation [20,42,43], terahertz holography [44,45], time-of-flight terahertz tomography [46], synthesized apertures [47] to obtain information on the threedimensional surface of the object under study -49], coding apertures [50][51][52][53][54], frequency modulation of the signal [55], antennas from metamaterials [56], etc.…”

Modulus Stretch-Based Circular SAR Imaging with Contour Thinning

“…Farhadi et al proposed a distributed compressed sensing algorithm for circular SAR imaging, which improves the resolution and reduces the side-lobe effect in the full-aperture 3D image, and meanwhile reduces the computation [25]. In recent years, the research on Circular SAR imaging mainly focuses on Deep Learning, Compression Sensing, 3D imaging and other aspects [26][27][28][29][30][31][32][33][34]. Many excellent research results and algorithm theories have emerged.…”