The aim of this paper is to prove that the power generated by a wearable textile patch antenna experiences reduced absorption in the phantom when the antenna ground-plane is increased. First, the dedicated human torso-equivalent phantom and two antennas were fabricated, which are multi-layered, with orientation normal to the body and made of the same materials. One of the antennas has a double in size ground-plane with regards to the other antenna, while the rest of their dimensions are identical. According to the proposed measurement procedure, once the radiation efficiencies of both antennas are measured in free space and with the phantom, the total absorption coefficient and the phantom losses are evaluated. The comparison of the measurement results proves that the increased ground-plane reduces the absorption on the phantom body of the antenna EM power (by 30.5%). Simulations and measurements were found in good agreement, with maximum deviation between the two up to 6% in terms of radiated efficiency. Hence, the proposed experimental evaluation of the impact of the ground-plane size of a wearable textile patch antenna on the reduction of the power absorbed by the user's body can be considered as a simple, reliable and cost-effective measurement method.
2. Meier, K., V. Hombach, R. Kastle, R. Y.-S. Tay, and N. Kuster, "The dependence of electromagnetic energy absorption upon human head modeling at 1800 MHz," IEEE Trans. Microwave Theory Tech., Vol. 45, 2058-2062, Nov. 1997.
3. Balzano, Q., O. Garay, and T. Manning, "Electromagnetic energy exposure of simulated users of portable cellular telephones," IEEE Trans. Veh. Technol., Vol. 44, 390-403, Aug. 1995.
4. Kobayashi, T., T. Nojima, K. Yamada, and S. Uebayashi, "Dry phantom composed of ceramics and its application to SAR estimation," IEEE Trans. Microwave Theory Tech., Vol. 41, 136-140, Jan. 1993.
5., , URL: https://indexsar.com/..
6., , URL: https://www.speag.com/products/isar2/isar2-systems/..
7. Sager, M., M. Forcucci, and T. Kristensen, "A novel technique to increase the realized efficiency of a mobile phone antenna placed beside a head-phantom," IEEE Antennas and Propagation Society International Symposium, Vol. 2, 1013-1016, Columbus, Ohio, USA, Jun. 2003.
8. Holopainen, J., J. Ilvonen, O. Kivekas, R. Valkonen, C. Icheln, and P. Vainikainen, "Near field control of handset antennas based on inverted top wavetraps: Focus on hearing-aid compatibility," Antennas and Wireless Propagation Letters (AWPL), Vol. 8, 592-595, 2009.
9. Picher, C., et al., "Analysis of the human head interaction in handset antennas with slotted ground planes," IEEE Antennas Propag. Mag., Vol. 54, No. 2, 36-56, 2012.
10. Andujar, A., J. Anguera, C. Picher, and C. Puente, "Ground plane booster antenna technology. Human head interaction: Functional and biological analysis," European Conference on Antennas and Propagation, EuCAP 2012, Prague, Czech Republic, 2012.
11. Nishikido, T., Y. Saito, M. Hasegawa, H. Haruki, Y. Koyanagi, and K. Egawa, "Multi-antenna system for a handy phone to reduce influence by user's hand," 6th International Symposium on Antennas, Propagation and EM Theory, 2003, Proceedings, 348-351, Beijing, China, 2003.
12. Hirata, A., T. Adachi, and T. Shiozawa, "Folded-loop antenna with a reflector for mobile handset at 2.0 Hz," Microwave & Opt. Tech. Lett., Vol. 40, No. 4, 272-275, 2004.
13. Islam, M. T., M. R. I. Faruque, and N. Misran, "Design analysis of ferrite sheet attachment for SAR reduction in human head," Progress In Electromagnetics Research, Vol. 98, 191-205, 2009.
14. Wang, J., J., O. Fujiwara, and T. Takagi, "Effects of ferrite sheet attachment to portable telephone in reducing electromagnetic absorption in human head," 1999 IEEE International Symposium on Electromagnetic Compatability, Vol. 2, 822-825, Symposium Record (Cat. No.99CH36261), Seattle, WA, 1999.
15. Hanafi, N. H. M., M. T. Islam, N. Misran, and M. R. I. Faruque, "Numerical analysis of aluminium sheet for SAR reduction," Proceeding of the 2011 IEEE International Conference on Space Science and Communication (IconSpace), 281-285, Penang, 2011.
16. Kwak, S. I., D. U. Sim, J. H. Kwon, and H. D. Choi, "Comparison of the SAR in the human head using the EBG structures applied to a mobile handset," 2007 European Microwave Conference, 937-940, Munich, 2007.
17. Hwang, J. N. and F. C. Chen, "Reduction of the peak SAR in the human head with metamaterials," IEEE Transactions on Antennas and Propagation, Vol. 54, No. 12, 3763-3770, Dec. 2006.
18. Rani, R., P. Kaur, and N. Verna, "Metamaterials and their applications in patch antenna: A review," International Journal of Hybrid Information Technology, Vol. 8, No. 11, 199-212, 2015.
19. Yimdjo Poffelie, L. A., P. J. Soh, S. Yan, and G. Vandenbosch, "A high-fidelity all-textile UWB antenna with low back radiation for off-body WBAN applications," IEEE Transactions on Antennas and Propagation, Vol. 64, No. 2, 757-760, 2016.
20. Aun, N. F. M., P. J. Soh, A. A. Al-Hadi, M. F. Jamlos, G. A. E. Vandenbosch, and D. Schreurs, "Revolutionizing wearables for 5G: 5G technologies: Recent developments and future perspectives for wearable devices and antennas," IEEE Microwave Magazine, Vol. 18, No. 3, 108-124, May 2017.
21. Gil, I. and R. Fernandez-Garcıa, "SAR impact evaluation on jeans wearable antennas," 2017 11th European Conference on Antennas and Propagation (EUCAP), 2187-2190, Paris, 2017.
22. Bhattacharjee, S., M. Mitra, and S. R. Bhadra Chaudhuri, "An effective SAR reduction technique of a compact meander line antenna for wearable applications," Progress In Electromagnetics Research M, Vol. 55, 143-152, 2017.
23. Zhong, J., A. Kiourti, T. Sebastian, and Y. Bayram J. L. Volakis, "Conformal load-bearing spiral antenna on conductive textile threads," IEEE Antennas and Wireless Propagation Letters, Vol. 16, 230-233, 2017.
24. Wang, K. and J. Li, "Jeans textile antenna for smart wearable antenna," 2018 12th International Symposium on Antennas, Propagation and EM Theory (ISAPE), 1-3, Hangzhou, China, 2018.
25. Wang, M., et al., "Investigation of SAR reduction using flexible antenna with metamaterial structure in wireless body area network," IEEE Transactions on Antennas and Propagation, Vol. 66, No. 6, 3076-3086, Jun. 2018.
26. Pei, R., M. Leach, E. G. Lim, Z. Wang, J. Wang, and Y. Huang, "A belt antenna design with textile aritificial magnetic conductor reflector," 2019 IEEE MTT-S International Wireless Symposium (IWS), 1-3, Guangzhou, China, 2019.
27. Seimeni, M. A., A. Tsolis, A. A. Alexandridis, and St. Pantelopoulos, "Mitigation of end-user’s exposure to EMF of wearable antennas," Proceedings of the 14th Conference on Antennas & Propagation (LAPC2018), 5 pages, Loughborough, UK, Nov. 12–13, 2018.
28. Seimeni, M. A., A. Tsolis, A. A. Alexandridis, and S. A. Pantelopoulos, "The effects of ground-plane of a textile higher mode microstrip patch antenna on SAR," 2020 International Workshop on Antenna Technology (iWAT), 1-4, Bucharest, Romania, 2020.
29. CST Studio Suite, , URL: https://www.3ds.com/products-services/simulia/products/cst-studio-suite/solvers/..
30. Gabriel, C., "Compilation of the dielectric properties of body tissues at RF and microwave frequencies," Brooks Air-Force Base, report No. AL/OE-TR-1996-0037.
31., , URL: http://niremf.ifac.cnr.it/tissprop/htmlclie/htmlclie.php#inizio, accessed May 21st, 2020.
32. Yilmaz, T., R. Foster, and Y. Hao, "Broadband tissue mimicking phantoms and a patch resonator for evaluating noninvasive monitoring of blood glucose levels," IEEE Transactions on Antennas and Propagation, Vol. 62, No. 6, 3064-3075, Jun. 2014.
33. Castello-Palacios, S., A. Valles-Lluch, C. Garcia-Pardo, A. Fornes-Leal, and N. Cardona, "Formulas for easy-to-prepare tailored phantoms at 2.4 GHz ISM band," 2017 11th International Symposium on Medical Information and Communication Technology (ISMICT), Vol. 27, No. 31, Lisbon, 2017.
34. Groumpas, E., M. Koutsoupidou, I. S. Karanasiou, C. Papageorgiou, and N. Uzunoglu, "Real-time passive brain monitoring system using near-field microwave radiometry," IEEE Trans. Biomed. Eng., Vol. 67, No. 1, 158-165, 2020.
35. Mobashsher, A. T. and A. M. Abbosh, "Artificial human phantoms: Human proxy in testing microwave apparatuses that have electromagnetic interaction with the human body," IEEE Microwave Magazine, Vol. 16, No. 6, 42-62, Jul. 2015.
36. Tsolis, A., A. Paraskevopoulos, A. A. Alexandridis, W. G. Whittow, A. Chauraya, and J. C. Vardaxoglou, "Design, realisation and evaluation of a liquid hollow torso phantom appropriate for wearable antenna assessment," IET Microwaves, Antennas & Propagation, Vol. 11, No. 9, 1308-1316, 2017.
37. Zervos, T., et al., "Mobile phone antenna performance and power absorption in terms of handset size and distance from user’s head," Wireless Pers. Commun., Vol. 33, 109-120, 2005.