IMPROVED REFLECTION LOSS PERFORMANCE OF DRIED BANANA LEAVES PYRAMIDAL MICROWAVE ABSORBERS BY COAL FOR APPLICATION IN ANECHOIC CHAMBERS

Agricultural waste is produced at agricultural premises as a result of an agricultural activity. Agriculture residue is made up of organic compounds from the living plants like rice straw, oil palm empty fruit bunch, sugarcane bagasse, coconut shell, banana leaves and others. This research has highlighted their eco-friendly nature and high microwave absorption properties, developing a new and improved form of pyramidal absorbers including high carbon content coal in it. Software simulation is done using CST Microwave studio. Samples are developed using a new technique by adding cobalt as an accelerator, and its performance is analyzed in terms of its reflection loss performance using free space measurement method in the frequency range of 8.2 to 12.4 GHz. This research gives a different definition to microwave absorbers as it is based on environmental and eco- friendly materials unlike commercial absorbers which use polyurethane and polystyrene plastic based materials that pose harm to the surroundings as well as human beings by releasing toxic gases when operating under high temperatures (1). Basic material used is dried banana leaves which comes under the category of agricultural wastes and have a great potential of being used as a good microwave absorber. They are the most essential elements of an anechoic chamber to reduce signal interference. In order to increase the absorption properties of the basic material, finely powdered coal is added due to its high porosity and carbon content. A comparison is shown between banana leaves and banana plus coal as microwave absorbers enhancing the absorption capacity of basic material. The results for these unique types of absorbers are even better than the commercial absorbers. Abandoned agricultural wastes pose a risk to the environmental and public health. While effectively absorbing microwave signals, polyurethane material particulates over time adding contaminants to clean rooms and reducing absorber lifetime. An alternative to these absorbers is found using agricultural wastes like banana leaves, sugarcane bagasse, rice husk etc. for the same purpose. These absorbers are composed of renewable materials and eliminate the toxic gas release problem for polyurethane materials under high power test conditions. They are cost effective materials and can be used to make environment friendly microwave absorbers with desired results. India is the largest producer of the bananas in the world contributing to 28% of world's banana production. Around 20-30% of the by products including banana leaves get wasted every year (9). This waste can be effectively utilized in development of microwave absorbing materials due to presence of high amounts of carbon content (43.5%) in it (2). Macro pores in carbon help in absorption. Table 1 shows weight percentages of different elements in banana leaves.