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

Jubo Hao,  Jin Li, Yiming Pi,

http://www.mdpi.com/1424-8220/18/8/2477/xml

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

Abstract-Dynamic Gesture Recognition with a Terahertz Radar Based on Range Profile Sequences and Doppler Signatures

Zhi Zhou, , Zongjie Cao,    Yiming Pi

http://www.mdpi.com/1424-8220/18/1/10

The frequency of terahertz radar ranges from 0.1 THz to 10 THz, which is higher than that of microwaves. Multi-modal signals, including high-resolution range profile (HRRP) and Doppler signatures, can be acquired by the terahertz radar system. These two kinds of information are commonly used in automatic target recognition; however, dynamic gesture recognition is rarely discussed in the terahertz regime. In this paper, a dynamic gesture recognition system using a terahertz radar is proposed, based on multi-modal signals. The HRRP sequences and Doppler signatures were first achieved from the radar echoes. Considering the electromagnetic scattering characteristics, a feature extraction model is designed using location parameter estimation of scattering centers. Dynamic Time Warping (DTW) extended to multi-modal signals is used to accomplish the classifications. Ten types of gesture signals, collected from a terahertz radar, are applied to validate the analysis and the recognition system. The results of the experiment indicate that the recognition rate reaches more than 91%. This research verifies the potential applications of dynamic gesture recognition using a terahertz radar.

Abstract-Three-Dimensional Imaging of Space Debris with Space-Based Terahertz Radar

 Xu Yang, Yiming Pi,  Tong Liu,   Haijiang Wang

http://ieeexplore.ieee.org/document/8207424/


The increasing natural or man-made space debris could pose a serious threat to orbital space-based systems and their operators. Consequently, their detection, reorganization, and tracking are of considerable significance. However, the traditional solutions, including ground-based radar and optical telescope, can not exactly observe the debris with small diameter. Imaging with space-based terahertz (THz) radar in combination with inverse synthetic aperture radar (ISAR) technique enables us to obtain high-resolution three-dimensional (3-D) image. In this paper, we have developed a high-resolution THz radar that operates at 340 GHz with a bandwidth of 28.8 GHz and the output peak power of 5 mW for proof-of-concept. In addition, using the characteristic that space debris rotates its main axis, we have established a 3-D ISAR imaging geometry as well as its corresponding signal model. Then, a 3-D wavenumber-domain image formation algorithm is presented and has been validated by point target simulation. The experimental results have confirmed that the THz radar can effectively achieve high-resolution 3-D imaging of the spinning space debris.

Abstract-Terahertz active imaging radar: preprocessing and experiment results

Gang Yao and Yiming Pi,

EURASIP Journal on Wireless Communications and Networking 2014, 2014:10  doi:10.1186/1687-1499-2014-10

http://jwcn.eurasipjournals.com/content/2014/1/10/abstract

A terahertz (THz) radar provides the possibility of higher precision imaging due to the wider bandwidth. A summary of a THz imaging radar system is presented with emphasis on THz radar component design, system design, and detective imaging. In this article, we introduce a linear frequency-modulated continuous wave (LFMCW) radar system with a 4.8-GHz bandwidth and theoretical resolution of 3.125 cm. The heterodyne RF receiver structure is applied to the system to reduce the sampling rate. A non-linear correction method is applied to compensate the range backscatter signal. With the presented LFMCW radar system, high-resolution images (3.5 cm ? 3.5 cm) are achieved using the ISAR imaging technique. The experiments performed on the real LFMCW radar data have shown the capability of high-resolution imaging.