Design and development of pyramidal microwave absorber using agricultural waste

Abstract

Agriculture waste has potential to be used as an alternative material for the microwave absorber that used in the RF anechoic chamber. Compared to the current material that used in the commercial market such as polystyrene and polyurethane, the agricultural waste is low cost material and environmental friendly. This rice husk pyramidal microwave absorber can operate effectively in the microwave frequency range from 7 GHz to 13 GHz. In this research, agricultural waste of rice husks from paddy is used as the main material that mixed with resin and hardener agent for the pyramidal microwave absorber design. Other agricultural waste like rice straw and kenaf are also used to compare its reflection loss performance with rice husk absorber. Polyester is used as resin that mixed with agricultural waste and methyl ethiyl ketone peroxide (MEKP) hardener. Other resin like Urea Formaldehyde (UF) and Phenol Formaldehyde (PF) are also used to compare its reflection loss performances. There are six main stages in designing and development of the rice husk pyramidal microwave absorber. The first stages are fabricating the agricultural waste particle board. Secondly, the stage is continuing with deriving the dielectric properties value of the agricultural waste mixture particle board using the free space measurement technique. The third stage is to define the best reflection loss result of the agricultural waste pyramidal microwave absorber using CST Microwave Studio simulation software. The dielectric properties that used in this simulation are taken from the free space measurement technique result that had been done before. Various parameters that affect the performance of the pyramidal microwave absorber are investigated in the parametric study section. The parametric study that taken care in this simulation are different shape, dimension, resin percentage, carbon coating thickness, distance of source signal, angle of source signal, and polygonal side. Then, it continued by fabrication process of the rice husk pyramidal microwave absorber using pyramidal shape with square base mould. The last stage is to measure the reflection loss performances of the fabricated rice husk pyramidal microwave absorber. In this section, the result of the simulation and fabrication of the pyramidal microwave absorber are compared. Measurement results show close agreement with the simulation result. In the other side, the commercial and fabricated absorber is also considered to compare it reflection loss. It show that the reflection loss performance is better than - 30 dB in the range between 7 GHz and 13 GHz.