Characterization of a carbon fiber based broadband microwave absorber

This paper reports the development and characterization of a novel ultra-wideband microwave absorber material (MAM) based on vertically aligned carbon fibers and ferrite beads. This specific material combination and manufacturing process allows MAM design that is thin, lightweight, and broadband. The material is prepared using a flocking process in which its components are electrostatically deposited on top of an adhesive substrate. Distinct material properties of the substrate and materials layers require characterization done with two separated layers. The microwave absorption characteristics are studied first by rectangular waveguide measurements at X and Ku bands that yield complex electric permittivity and magnetic permeability of the MAM samples without any metal backing. Here, the sample is measured under transverse electric waves (TE10\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {TE}_{10}$$\end{document}). Additional analysis is accomplished with full electromagnetic (EM) simulation using a high-frequency structure simulator (HFSS). The scattering parameters (S-parameters) from waveguide measurements and HFSS simulations are compared and excellent agreement is achieved. Extracted material parameters are also used to analytically calculate the reflection loss (RL) based on the transmission line model. The transmission line model shows excellent agreement with the full EM simulation results which should speed up future studies. Finally, the broadband RL performance of MAM was investigated using a free space spot probe system. The results show a MAM with broadband performance of - 10 dB RL over the entire X and Ku bands. Overall, this study demonstrates that MAM developed using magnetically loaded flocked carbon fiber (MLF-CF) has a promising combination of low-cost, lightweight, and broadband performance.