A terahertz (THz) wave is widely used in nondestructive detection, remote sensing, communications, and other fields. It is proved important in the field of radar cross section (RCS) measurements[
Chinese Optics Letters, Volume. 15, Issue 11, 112201(2017)
Cross section measurements of scale-model tactical targets by using 0.1 THz compact radar system
We present a new compact radar system to measure a terahertz radar cross section (RCS) of metal plates, trihedral corner reflectors, and an aircraft scaled model with a 0.1 THz continuous wave. We both numerically and experimentally investigate the terahertz RCS of the metal plates and trihedral corner reflectors. The numerical simulations are obtained by using commercial software, i.e., computer simulation technology, which agree well with the experimental results. Then, the RCS of an aircraft scaled model is measured, and the experimental results are in good agreement with the physical characteristics of the scaled model. The effectiveness of our compact radar system is verified to get the RCS of complex targets, such as the scaled models of the tactical targets.
A terahertz (THz) wave is widely used in nondestructive detection, remote sensing, communications, and other fields. It is proved important in the field of radar cross section (RCS) measurements[
The traditional ways to get the RCS are THz frequency-domain systems, which are typically applied in the Submillimeter-Wave Technology Laboratory (STL)[
Obtaining low-phase noise, high power THz waves is a major issue for real applications[
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According to the relative locations of the radar transmitter and receiver, the RCS can be divided into monostatic and bistatic RCS[
The metal plates and trihedral corner reflectors have long been used as calibrators[
Based on the theory of RCS calculation, the RCS analytical calculations of the plates and trihedral corner reflectors are given by numerical simulations. Furthermore, measurements are performed in a 0.1 THz compact radar system. Compared with the numerical simulations, it can be found that it is feasible to use the 0.1 THz compact radar system to obtain the RCS of the plates and trihedral corner reflectors. Lastly, we studied the RCS of an aircraft scaled model by the 0.1 THz compact radar system.
Figure
Figure 1.(a) Geometry of a metal plate. (b) The geometry of a triangular trihedral corner reflector. (c) The geometry of a square trihedral corner reflector.
For a metal plate, its main scattering procurements include the reflection of its surfaces, diffraction of the edges, and the backscattering from surface traveling wave effects[
As shown in Fig.
Figure 2.Schematic diagram of the 0.1 THz compact radar system.
Using the commercially available software CST Studio Suite, which is one of the most reliable softwares in the field of RCS simulation[
Before simulation, a concept that should be clear is that the electric size means that the geometric dimension is divided by the wavelength. In this Letter, the simulated models are
So, in this Letter, the solver chosen for generating solutions is the integral equation solver based on the MoM method and in the monostatic scattering mode. The models include plates, triangular trihedral corner reflectors, and square trihedral corner reflectors in different sizes, which are coincident with the targets measured in the experiment.
The 0.1 THz compact radar system, shown in Fig.
Figure 3.(Color online) Comparison of the experimental results and the numerical simulations for different sizes of metal plates: (a)
The Gunn diode generates electromagnetic radiation at 0.1 THz. Then, the Gaussian beam is propagated in a polymethylpentene (TPX) lens behind the source, which is used for collimation[
The models are mounted on a support structure, which is made from Vero White materials that have low reflection. Moreover, there are anechoic materials specifically designed for THz around the experimental table. This is to minimize the amount of radiation scattered back into the receiver by objects other than the targets[
In the experimental section, two groups of experiments are accomplished. One group uses the plates, and the other group uses the trihedral corner reflectors when the elevation angle
The monostatic RCS of the metal plates are shown in Fig.
As it illustrated in Fig.
For a certain size of the plates, there is a principal lobe and many side lobes, and when the
From Figs.
The monostatic RCS of the trihedral corner reflectors are shown in Figs.
Figure 4.(Color online) Comparison of the experimental results and the numerical simulations for different sizes of triangular trihedral corner reflectors: (a)
Figure 5.(Color online) Comparison of the experimental results and the numerical simulations for different sizes of square trihedral corner reflectors: (a)
From Figs.
For Fig.
For Fig.
As we can see, the RCS of the trihedral corner reflectors include the main scattering region and the side lobes. The main scattering region is a result of the internal reflections among the trihedral corner reflectors, and the side lobes are caused by the direct reflection from the single plates[
Comparing the data from Figs.
For the plates, when the
What is more, from Figs.
From the above three groups’ data, it can be found that the RCSs of trihedral corner reflectors are larger than that of the plates, and the scattering pattern is wider. This is because of the three times internal reflections among the three plates of the trihedral corner reflectors.
From the errors of the metal plates and trihedral corner reflectors, we can see that the errors of the trihedral corner reflectors are larger. The reason is that the trihedral corner reflectors are assembled by three plates manually, which are not strictly vertical. So, the symmetry of the trihedral corner reflectors is not as good as that of the plates, and the measurement peak RCS of the main scattering region is much lower than that of the numerical simulations. Besides, the errors related to the accuracy of the optical path adjustment in which the targets should be illuminated precisely.
Next, we will take an aircraft scale-model, for example, to study the RCS of the aircraft. The size of the model is
Figure 6.RCS of an aircraft scaled model by using the 0.1 THz compact radar system.
The Fig.
In conclusion, we both numerically and experimentally investigate the RCS of the metal plates and trihedral corner reflectors with a 0.1 THz compact radar system. By comparing the numerical and experimental results, it can be deduced that the 0.1 THz compact radar system is practical for the RCS measurement. Then, we investigate the RCS of an aircraft scaled model, and the experimental results are in good agreement with the physical characteristics of the scaled model, which verifies the effectiveness of this system. So, our compact radar system can be used to measure the RCS of the scaled models of the tactics targets, and thus can be beneficial for acquiring the RCS of full-scaled tactic targets in microwave.
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Xueying Nie, Yuli Zhang, Feidi Xiang, Jianguo Lu, Xin Huang, Kejia Wang, Jinsong Liu, Zhengang Yang. Cross section measurements of scale-model tactical targets by using 0.1 THz compact radar system[J]. Chinese Optics Letters, 2017, 15(11): 112201
Category: Optical Design and Fabrication
Received: May. 31, 2017
Accepted: Aug. 18, 2017
Published Online: Jul. 19, 2018
The Author Email: Kejia Wang (wkjtode@sina.com)