Sub-mm Resolution Indoor THz Range and SAR Imaging of Concealed Object

Abstract

In radar systems, the frequency range is being extended to high frequencies such as THz for sub-mm resolution. The spectrum offers high resolution but on the contrary, propagation distance and penetration depth are limited because of smaller wavelength. It suffers from higher atmospheric absorption in comparison to sub-GHz systems. In comparison to optical technology, the radar technique majorly benefits with respect to the penetration property such as cloud/smoke cover penetration and detection of concealed objects. However, the THz range and synthetic aperture radar (SAR) imaging of concealed objects are not very well established. Therefore, this paper examines this property at THz. A testbed has been set up with a bandwidth of 110 GHz at a carrier frequency of 275 GHz. The imaging is performed of a very small metal object. Firstly, the sub-mm resolution is validated with the experiment after that the range and SAR imaging are performed in which this object is covered with different types of materials. The backscattered data is processed with the image reconstruction algorithms and the results are presented in this paper with respect to sub-mm resolution and detection.

Terahertz Three-Dimensional SAR Imaging Using Time- and Frequency-Domain Algorithms

“…The main parameters for the simulations are summarized in the upper part of Table I. The frequency span for the simulations 220GHz − 330GHz are chosen by the parameters of the experimental THz indoor testbed [8] and [9]. With this frequency span, the fractional bandwidth is B/f c = 0.4 and larger the limit for ultrawideband (B/f c ≥ 0.25).…”

“…The research on THz SAR has been emerged recently. Several novel THz SAR testbeds based on radar frontends [4]- [6] and vector network analyzer (VNA) [7]- [9] have been experimented. In [8], a VNA based testbed has been setup for the measurements at a center frequency of 275 GHz with a bandwidth of 110 GHz to investigate the resolution and quality of THz SAR images.…”

Fourier Transform of SAR Data Cube and 3-D Range Migration Algorithm

“…The main parameters for the simulations are summarized in the upper part of Table I. The frequency span for the simulations 220GHz − 330GHz are chosen by the parameters of the experimental THz indoor testbed [17] and [18]. With this frequency span, the fractional bandwidth is B/f c = 0.4 and larger the limit for ultrawideband (B/f c ≥ 0.25).…”

Interpolation Methods for SAR Backprojection at THz Frequencies

“…As a case study, we consider a two-dimensional indoor THz SAR imaging for a point target. Assume that a point target is in the center of SAR scene and that the minimal range distance between the imaging system and the target is R 0 = 0.12 m. Furthermore, assume that the THz SAR system has characteristics similar to the system described in [4]. The system transmits frequencymodulated signals (1) of duration T p = 0.1 µs with the baseband bandwidth [0.22, 0.33] THz and the corresponding center frequency f c = 0.275 THz.…”

“…THz SAR imaging is a new and an active research area, where the objective is to design THz SAR imaging systems that can be mounted on different platforms, especially fying platform. For the experimental SAR systems operating at 300 GHz [2]- [4] and 600 GHz [5], mounting them on fying platform leads to several technical issues. One of foreseen issue is that at the THz frequencies, the SAR imaging system becomes sensitive to vibrations of the fying platform [6].…”