In this paper, a flexible compact Jeans gap filled metamaterial inspired antenna is proposed to operate at 2.4 GHz in the Industrial Scientific and Medical (ISM) band. This designed antenna is flexible having size of about 27×23 mm2 with substrate of thickness 0.3 mm. The proposed antenna comprises two complementary split ring resonators at ground plane and one circular ring and complementary rectangular split ring resonator. The top patch consists of two rectangular split ring resonators etched inside the rectangular patch. The use of SRR and CSRR on top and bottom of patch has helped to reduce the size of antenna along with maintaining performance of antenna. Further enhancements are done to make it jeans gap filled antenna with jeans filled between main patch and superstrate. The superstrate top patch consists of a square EBG structure. The simulation results have shown an increase in return loss due to the use of square EBG structure on superstrate. The simulated directivity obtained on antenna is 2.0775 dB. The measured and simulated results are in a good agreement. The motivation of this work is to design a compact metamaterial based antenna for wireless body area network with gap coupled jeans material to nullify effects of human body. Effects of air gap coupled and jeans gap coupled are analyzed in terms of performance. While the final antenna (Antenna-4) is designed, several iterations are tried to optimize and maintain good performance. Step 1 (Antenna-1) consists of two complementary split ring resonators along with a circular ring placed in ground plane with thickness of polyamide substrate as 0.3 mm. Step 2 (Antenna-2) consists of two split ring resonators along with a circular ring placed in ground plane. An air gap coupled superstrate is designed having gap between main patch and superstrate as 1 mm. Step 3 (Antenna-3) has the same configuration as Antenna-2, and the only difference is the air gap between main patch and superstrate which is replaced by jeans material. Step 4 (Antenna-4) is the final designed antenna with miniaturized size of 27×23 mm2 as compared with previous antenna configurations. This research work has identified the challenges involved for designing an antenna in a wireless body area network. Practical aspect of design needs to consider: a) Bending effect on performance as movement and physiological changes might affect the performance. b) Performance degrades when antenna comes in contact with human body. Bending Effect: This work has also analyzed effect of bending on return loss. For final designed antenna (Antenna-4) maximum bending up to bend 30˚ is possible. Further bending would break the substrate. After maximum bending, the measured return loss is about -16.7071 dB at 2.28 GHz. Body area network: The designed final antenna (Antenna-4) is tested on different parts of human body such as human-arm and leg. No major difference is seen on return loss when it is tested on different parts of body. The designed final antenna (Antenna-4) is tested on direct contact with human-arm as well as with different cloths (cotton jeans, cotton, curtain cloth, floor cloth, polyester and Turkish cloth) having different permittivities with the distance between cloth and antenna as 0 cm and 1 cm. Wearable antennas should be carefully constructed to avoid causing harm to the human body when being worn. The Low Specific Absorption Rate is one of the criteria that should be considered while developing a wearable antenna. The maximum allowable SAR limit is 1.6 W/kg. The specific absorption rate for Antenna-4 is 0.2 W/kg when input power is 1 watt and is 0.036 W/kg when input power is 100 milli watt. The results obtained show that the proposed antenna is both safe and acceptable for use in compliance with the World Health Organization's ICNIRP requirements.
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