Electromagnetic characteristics measurement of organic material absorber

Electro Magnetic Compatibility (EMC) Chamber requires high performance absorber material to assure the quality of EMC chamber related to Radio Frequency (RF) shielding effectiveness of the corresponding chamber. RF shielding effectiveness is measured following EN 50147-1 testing method. EMC laboratory of BPPT (Indonesian Agency for the Assessment and Application of Technology uses polyurethane absorber material which absorbs the carbon-neoprene mixture to maintain consistent RF performance over a broad frequency band, especially in the frequency range of CISPR 22 radiated emission test between 30 MHz to 6 GHz, limits in CISPR 22 (Information technology equipment-radio disturbance characteristics-limits and methods of measurement). Measurement test for rice husk and wood saw husk with VNA for absorption capability has shown that a mixed layer of rice husk without any additional carbon (50 grams weight) may absorb radiated emission in 900 MHz by reflection loss of -21.779 dB. But the cotton based absorber has better reflection loss of -32.93 dB in 900 MHz. In contrary the 1800 MHz radiated emission will be absorbed more with 30% coconut husk. In order to have a better absorber based on these organic materials for both mobile phone frequencies (900 MHz and 1800 MHz), a mixture of coconut husk and wood saw husk may be used. In addition, rice husk and coconut husk may become a potential alternative for mobile phones casing to reduce ‘unwanted radiated emission’ from mobile phones and at the same time will reduce the SAR values. Results has shown a mixture of 50% coconut husk with resin absorb the most radiated emission in 900 MHz, while 30% of coconut husk will absorb the most radiated emission in 1800 MHz.(EMS2022)