A Study of the Emc Performance of a Graded-Impedance, Microwave, Rice-Husk Absorber

Abstract

Abstract-Biomass used for energy, whether it is extracted from forest residues or agricultural waste, contributes in many areas, such as power production, the construction industry, and also as a major source of different organic and inorganic compounds in the petrochemical industry. In recent years, research has identified a very remarkable use of agricultural waste, especially rice husks, as a microwave absorber in a pyramidal shape. However, absorbers built in this shape are fragile and require a very high degree of care, especially near the access panels, doors, and high traffic areas of the anechoic facility. This paper presents the results of a detailed experimental investigation of a more-robust, new design that is based on the concept of impedance or dielectric grading of rice-husk material. The absorber was fabricated using multiple layers of rice-husk material with increasing dielectric loss along the incident wave propagation axis. This type of fabrication technique provides more robust design of the microwave, rice-husk absorber with less thickness, as compared to the geometricallytapered, pyramid, or wedge absorbers. Free-space transmission and radar cross section (RCS) methods have been used, to study the electromagnetic compatibility (EMC) performance over the frequency range of 4-8 GHz. After the receiving equipment was calibrated by the thru-reflect-line (TRL) calibration technique, the experiments were performed inside the anechoic chamber. The performance of the absorber was evaluated by incorporating the effects of circular-hole perforation, cross-polarized seams, and different metallic back plates. The proposed absorber demonstrated good performance (< −10 dB) for normal and 60 • off the normal incident angles over the frequency range of 4-8 GHz. Reflectivity performance also was found to be comparable to one of the commercially-available absorbers.

The Use of a Human Body Model to Determine the Variation of Path Losses in the Human Body Channel in Wireless Capsule Endoscopy

“…The conductivity of body tissue increases with frequency and consequence to high absorption loss [42,43]. Likewise some of the tissues (fat, skin, muscle, blood, intestine) show high dissimilar dielectric property with each other that result high impedance mismatch and high reflection loss [44,46,47] at the interface of these layer.…”

Experimental Determination of the Performance of Rice Husk-Carbon Nanotube Composites for Absorbing Microwave Signals in the Frequency Range of 12.4-18 GHZ

“…Such environmental pollution would be reduced if the rice husks were used in other applications rather than burned. Recently, several research projects involving rice husks have shown that the properties of rice husks make this waste material potentially useful as a microwave absorber and for other applications [2][3][4][5][6]. This is because 35-37% of the rice husks is carbon, which has the ability to attenuate/absorb microwave radiation [5].…”

Compact Electromagnetic Absorbers for Frequencies Below 1 GHZ

“…Consequently, in dealing with practical enclosures having openings along their sides, the amount of EM field leaking into (or exiting from) the enclosure can be greatly increased in the proximity of such resonant frequencies [3,5]. Therefore, it is a common practice to line internal surfaces of cabinets with properly designed absorbers in order to damp resonances [11][12][13].…”