Agriculture waste has huge potential to be used as an alternative material for constructing microwave absorber which is typically used in an anechoic chamber. The existing microwave absorbers are normally manufactured from chemical substances. This project is proposing the use of a new composite biomass material namely coconut coir, for constructing microwave absorbers. Generally, pyramidal shape is chosen since it is commonly used in the industry. The major part of this project involves an intense study in designing and developing the best techniques to construct pyramidal shape microwave absorber. The frequency range investigated in this work is between 1GHz to 12GHz. Referring to the commercial absorber as the standard, the reflectivity performance of this coconut coir pyramidal absorber was thoroughly investigated in this research. It is then proven that the biomass material used in this study is found to have a significant impact on the microwave absorber performance.
<span>Electromagnetic interference (EMI) is an undesired electromagnetic (EM) wave by nearby electronic devices, process equipment, and measuring instruments. In this work, a novel multi-slot technique is applied to the hollow biomass pyramidal microwave absorber to study its absorption properties thoroughly. Two different slot arrangements in horizontal and vertical configuration are designed for the proposed microwave absorbers. Both slot design concepts have identical shape and size. This work aims to study, compare and analyze the absorption performance of the proposed designs at L, S, C and X frequency bands. The biomass material is used to form as absorbent material. The characteristics performance of the multi-slot design on biomass hollow pyramidal microwave absorbers are measured by using naval research laboratory (NRL) Arch space-free method. The frequency range set up for the measurement is in between 1 GHz to 12 GHz. The multi-vertical slots design exhibits better absorption performance at <br /> C-band and X-band which is -63.67 dB and -46.78 dB respectively while the multi-horizontal slots design provides better absorption performance at <br /> S-band which is -16.92 dB. The results shows that both design performances are frequency-dependent since horizontal slots design improve maximum absorption performance at low frequency while vertical slots design delivers better performance at high frequency. </span>
In recent year, the development of the electronic devices is rapidly growing and that was used in entire world but electronic devices generate the electromagnetic wave (EM) radiation. That radiation can affect the people’s health and interference normal operation of other electronic devices. Hence the researchers have conducted studies in the field of microwave absorption to reduce the risk of electromagnetic (EM) radiation. Microwave absorber comes with many form and material to enhance the absorption performance. This study aims to improve absorption performance of pyramidal geopolymer microwave absorber by using slotted design. The slotted design used on pyramidal geopolymer microwave absorber is triangular shape and that shape was isosceles triangle type. The hollow pyramidal was coated with a geopolymer absorbing material to form hollow pyramidal microwave absorber. Geopolymers are formed by a process called geopolymerization, which involves the chemical bonding of the ingredients together. This study used sodium silicate (Na2SiO3), sodium hydroxide (NaOH), and Powder Activated Carbon (PAC) to make geopolymer absorbing material. Measurement had been done successfully via far field measurement using arch method at 1 GHz to 12 GHz. The absorptivity of hollow pyramidal triangular slotted geopolymer microwave absorber is observed at each frequency band covering the L, S, C and X bands. The result is compared with their maximum absorption in each frequency band and also shows geopolymer material produces good absorption performance. The result shows triangular slotted design is capable of achieving very high absorption performance which is -26.32 dB.
Microwave absorber is commonly used in defense, electromagnetic compatibility (EMC)/electromagnetic interference (EMI) reduction and anechoic chamber application. Conventional electromagnetic (EM) absorbers have some constraints in practical handling due to its heavy weight. In this paper, the research focuses on the development of high performance and lightweight microwave absorber. A lightweight and simple design configuration of different rectangular slot size array implemented on hollow pyramidal microwave absorber are carried out. There are two different designs of different slot size array calculated based on 3GHz, 6GHz and 9GHz frequency slot size. The two designs have an opposite slots size array arrangement namely different slot size 3GHz, 6GHz, 9GHz order design array and different slot size 9GHz, 6GHz, 3GHz order design array. The absorption is measured using the Naval Research Laboratory (NRL) arch free space method in the frequency range of 1GHz to 12GHz covering L, S, C and X band. In the measurement result, the maximum absorption performance is obtained by the different slot size 9GHz, 6GHz, 3GHz order design array which is up to -44.23dB at X-band. The measurement results for both designs array show good absorption performance which exhibit below than -20dB especially at high frequency band. The proposed designs have been identified as the new approach to increase absorption improvement over a broad frequency range application.
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