Abstract-The need to find ways to effectively utilize the large quantities of agricultural waste that are produced is indicative of the huge potential associated with producing an alternative pyramidal microwave absorber for anechoic chamber-testing applications. We propose the development of a pyramidal microwave absorber that can use sugar cane bagasse (SCB), a byproduct from the production and processing of sugar cane, as the absorbent. In this paper, we report the results of our use of dielectric probe measurement to determine the dielectric constant and loss tangent of SCB. These values were used to model and simulate an SCB pyramidal microwave absorber in Computer Simulation Technology's (CST's) Microwave Studio. This absorber was operated in the microwave frequency range between 0.1 GHz and 20.0 GHz.

Although solid, geometrically tapered microwave absorbers are preferred due to their better performance, they are bulky and must have a thickness on the order ofλor more. The goal of this study was to design lightweight absorbers that can reduce the electromagnetic reflections to less than −10 dB. We used a very simple approach; two waste materials, that is, rice husks and tire dust in powder form, were used to fabricate two independent samples. We measured and used their dielectric properties to determine and compare the propagation constants and quarter-wave thickness. The quarter-wave thickness for the tire dust was 3 mm less than that of the rice husk material, but we preferred the rice-husk material. This preference was based on the fact that our goal was to achieve minimum backward reflections, and the rice-husk material, with its low dielectric constant, high loss factor, large attenuation per unit length, and ease of fabrication, provided a better opportunity to achieve that goal. The performance of the absorbers was found to be better (lower) than −20 dB, and comparison of the results proved that the hollow design with 58% less weight was a good alternative to the use of solid absorbers.

Abstract-Composites of rice husks and carbon nanotubes (RHCNTs) are an innovation in improving the absorption of microwave signals. Rice husks, which are an agricultural waste material, have been found to possess a significant propensity for absorbing microwave signals. Studies have shown that both rice husks and carbon nanotubes (CNTs) have high percentages of carbon. Thus, in this paper, we present the results of our experimental study in which we varied the ratios of rice husks and CNTs in the composite materials and determined the dielectric properties of the composites and measured their abilities to absorb microwave signals. The experimental microwave

This paper presents a calculation of the dielectric properties of low-loss materials using the transmission phase-shift method. This method can provide calibration-independent and position-insensitive features, and it was verified experimentally by measuring several well-known samples using X-band rectangular waveguides.

In this paper, we propose a very simple technique that offers an extra degree of freedom to optimize the design of a tire dustbased absorber with reduced height. Cladding is a technique that is used to enhance the surface properties of a part, and it has been used in many applications for many years. In this technique, a clad layer is created on the core material, and the composition of the clad layer is adjusted to enhance the performance of the core material. We use a rice husk-clad layer to enhance the impedance matching characteristics of the low-loss, tire-dust core, microwave absorber. The overall design is a two-layer, geometrically-tapered, pyramidal structure composed of two lossy waste materials. Our main goal was to make the front surface less reflective (impedance matched), hence the material of the outer layer (clad) of the absorber was selected on the basis of the analysis of the dielectric properties of the candidate materials. Optimum thickness of the clad was obtained by using CST simulation software and found to be 12 mm, for which a reflectivity performance of less than −20 dB was