Design of an Optical Transparent Absorber and Defect Diagnostics Analysis Based on Near-Field Measurement

Abstract

To reduce the electromagnetic wave interference caused by cavity resonance or electromagnetic wave leakage, herein, an optical transparent radar absorbing structure (RAS) was designed using transparent conductive oxides (TCOs) with a high optical transmittance and electrical conductivity, and a procedure was proposed for detecting possible defects in the fabrication and operation and for assessing the influence of the defects on the electromagnetic performance. To detect locally occurring defects in planar and three-dimensional absorbing structures, a measurement system based on an open-ended near-field antenna capable of producing small beam spots at a close distance was constructed. Moreover, the reflection characteristics of the transparent RAS were derived from a simplified multiple reflection equation, and the derived results were compared with the analysis results of an equivalent circuit model to predict the surface resistance of the TCO coating layer, based on which the presence of defects could be confirmed. By using the experimental results, the predicted surface resistance results of the coating layer and the results measured using a non-contact sheet resistance meter were compared and were found to correspond, thereby confirming the effectiveness of the proposed defect detection method.

Material Thickness Classification Using Scattering Parameters, Dielectric Constants, and Machine Learning

“…The NIST iterative method provides accurate outputs as well as helps to prevent the inconsistent results caused by the significant deterioration of S11 if using the NRW method [17]. The results of the methods are slightly similar, which can confirm that the simulation structure in [21] is suitable for our research. The small differences may occur due to the equipment errors, but this is negligible.…”

“…In each simulated structure, 101 X-Band frequency points in the range of 7 GHz to 13 GHz are taken into account as a signal goes through the structure. The MUTs are According to the multilayer structure above, the ABCD matrix of the equivalent circuit for the two-port network is obtained for the whole structure by the following equations [21]:…”

“…where: From the ABCD matrix, the scattering parameters can be deduced by the equivalent circuits for the two-port network [21] as follows:…”

“…The structure includes three layers of air and MUT with the incidence angle θ as 0 , as illustrated in Figure 2. According to the multilayer structure above, the ABCD matrix of the equivalent circuit for the two-port network is obtained for the whole structure by the following equations [21]:…”

RCS Estimation of Singly Curved Dielectric Shell Structure with PMCHWT Method and Experimental Verification

“…However, it also has high electromagnetic transparency, so that the RCS of the inner cockpit has large scattering as a corner reflector. An acrylic-based material with a thin multilayered surface composed of a transparent conductive oxide (TCO) has been researched for its microwave absorption properties [17,18]. To reduce the RCS of an aircraft, a proper method for the RCS reduction of a singly curved dielectric object is required.…”