Improved technique for radar absorbing coatings characterization with rectangular waveguide and numerical modeling

Abstract

For materials characterization, several methods have been developed. Most of them need a sample to be machined prior to testing process. Hence, they are destructive and cannot be used for in-situ radar absorbing coatings testing. This requires employing a suitable measurement technique to extract their electromagnetic properties quickly and accurately. In this paper, the swept frequency of probe reflection technique is proposed for broadband nondestructive radar absorbing coatings characterization using finite flange open-ended rectangular waveguide. The technique is based on the fact that the frequency of measurement is an independent variable of probe’s reflection coefficient by which its data set of selected frequency points can be directly measured in one step by varying the frequency. Finite-difference time-domain (FDTD) method was adopted to calculate probe reflection coefficients at different test conditions. Simple interpolation approximation was employed since they are frequency dependent parameters. Error analysis was numerically performed to evaluate the influences of both flange size and coated material thickness on the accuracy of the measurements, which are carried out on several samples of radar absorbing coatings at X-band to verify the proposed technique. Comparing with the existing methods, the proposed technique simplifies and speeds up measurement process and improves its repeatability and accuracy.