Abstract- A Side-Lobe Suppression Method Based on Coherence Factor for Terahertz Array Imaging

Yanwen Jiang,  Yuliang Qin,  Hongqiang Wang,  Bin Deng,  Kang Liu, Binbin Cheng

An imaging method with side-lobe suppression based on coherence factor is proposed to improve the image quality of Terahertz (THz) array imaging, which is validated by simulation and experiments. The imaging results of real-world data demonstrate that the side-lobe can be suppressed by 29 dB using the proposed method.

http://ieeexplore.ieee.org/document/8272383/

Terahertz (THz) arrays can be used to improve the data acquisition speed considerably in realtime imaging applications. However, the THz array imaging usually suffers from the side-lobe artifacts, which leads to a severe decline in the image quality. In this paper, a side-lobe suppression method based on coherence factor is proposed to improve the image quality. The influences of signal-to-noise ratio on the imaging results are analyzed by simulation. Furthermore, the results based on the real-world data validate the effectiveness of the proposed method, which indicates that the side-lobe is suppressed by 29 dB. This paper can benefit the development of THz imaging technique and its applications in real-time imaging realms.

Abstract-A Fast Terahertz Imaging Method Using Sparse Rotating Array

Yanwen Jiang, Bin Deng, Yuliang Qin, Hongqiang Wang,  Kang Liu

http://www.mdpi.com/1424-8220/17/10/2209


For fast and standoff personal screening, a novel terahertz imaging scheme using a sparse rotating array is developed in this paper. A linearly sparse array is designed to move along a circular path with respect to an axis perpendicular to the imaging scenario. For this new scheme, a modified imaging algorithm is proposed based on the frequency-domain reconstruction method in circular synthetic aperture radar. To achieve better imaging performance, an optimization method of the sparse array is also proposed, according to the distribution of the spectral support. Theoretical and numerical analysis of the point spread function (PSF) is provided to demonstrate the high-resolution imaging ability of the proposed scheme. Comprehensive simulations are carried out to validate the feasibility and effectiveness of the array optimization method. Finally, the imaging results of a human-scattering model are also obtained to further demonstrate the good performance of this new imaging scheme and the effectiveness of the array optimization approach. This work can facilitate the design and practice of terahertz imaging systems for security inspection

Abstract-Research on imaging of precession targets based on range-instantaneous Doppler in the terahertz band

 Qi Yang,  Bin Deng,  Hongqiang Wang,   Wenxia Ding,   Kang Liu,

http://ieeexplore.ieee.org/document/7968798/

In this paper, a 0.32 THz imaging radar system was built and experiment on a precession warhead model is presented. The imaging algorithm based on range-instantaneous Doppler algorithm is adopted and high resolution ISAR imaging results are obtained. From these imaging results, we can easily recognize structures and even the subtle structures of the precession target, which verify the advantages of terahertz radar in high resolution imaging.

Abstract-Toward Standoff Sensing of CBRN with THz Waves

• Kang Liu, 
• Xi-Cheng Zhang
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https://link.springer.com/chapter/10.1007/978-94-024-1093-8_1

With the soaring demands for remote spectroscopy in homeland security and environmental monitoring, terahertz (THz) wave sensing has drawn a significant amount of attention because of its capability to acquire chemical spectral signatures non-invasively. THz-Radiation-Enhanced-Emission-of-Fluorescence (THz-REEF) makes broadband stand-off remote spectroscopy possible, due to its omni-directional emission pattern of the fluorescence and minimal ambient water vapor absorption of THz wave near the target. Two years ago, we have demonstrated coherent THz wave detection at a distance of 30 m. The development of intense broadband table-top THz source is imperative to all the extreme THz science research, including THz remote sensing. Recently, we have also demonstrated an enhanced THz radiation using dual-color ring-Airy beam induced air-plasma compared to a Gaussian beam induced plasma. It is believed that the great tunability of ring-Airy beam, its wavepacket stability at nonlinear focus regime, and the strong resilience to turbulent medium of the Airy beam family, make the plasma induced by this novel wave a promising broadband THz source for THz remote sensing and spectroscopy.

Abstract-An Effective Nonlinear Phase Compensation Method for FMCW Terahertz Radar

Yanwen Jiang 
Bin Deng ; Hongqiang Wang ; Yuliang Qin ; Kang Liu

http://ieeexplore.ieee.org/xpl/abstractAuthors.jsp?arnumber=7460187&filter%3DAND%28p_IS_Number%3A4581641%29

The nonlinearity of signal usually leads to the range profile blurring and defocusing in the terahertz (THz) radar ranging, which should be compensated to achieve a well-focused range profile. In this paper, an effective nonlinear phase compensation method is proposed to compensate for the signal distortion caused by the radar waveform nonlinearities. It comprises two processing steps, namely, coarse phase compensation and precise phase compensation, which are based on the time-frequency (TF) distribution and the phase gradient autofocus (PGA) algorithm, respectively. The proposed method is a nonparametric method and can eliminate the errors caused by phase discontinuity of the dechirped frequency modulated continuous wave (FMCW) signal. Furthermore, the compensation method can be used in the processing of multi-period real data which are obtained from the FMCW THz radar.