A dual-band dual-element multiple-input-multiple-output (MIMO) antenna system with enhanced isolation is proposed. The MIMO antenna system is based on printed 4-shaped antenna elements. Dual band isolation is achieved by using an array of printed capacitively loaded loops (CLLs) on the top side of the board for high band isolation improvement and a complementary CLL structure on the GND plane of the antenna for lower band isolation improvement. The lower band of operation covers 827-853 MHz and the higher band covers 2.3-2.98 GHz. Two prototypes were investigated to access the effect of the isolation mechanism. Measured isolation improvement of 10 dBs was observed in the lower operating band while the improvement in the higher band was approximately 2.5 dBs. The isolation improvement was at the expense of 5% reduction in efficiency. The measured gain patterns as well MIMO figures of merits such as the correlation factor, TARC and MEG were investigated as well.
2. 3GPP TS 36.101, V8.3.0, , "EUTRA User Equipment Radio Transmission and Reception,", Septembe 2008.
3. Gesbert, D., S. Mansoor, S. Da-shan, P. J. Smith, and A. Naguib, "From theory to practice: An overview of MIMO space-time coded wireless systems," IEEE J. Sel. Areas Commun., Vol. 21, No. 3, 281-302, Apr. 2003.
4. Yoo, S. and S. Kahng, "A compact MIMO antenna using ZOR split ring resonator radiators with a decoupling structure," Microwave Journal, Vol. 54, No. 11, S26-S31, November 2011.
5. Li, H., J. Xiong, Z. Ying, and S. He, "High isolation compact four-port MIMO antenna systems with built-in filters as isolation structure," Proceedings of the Fourth European Conference on Antennas and Propagation (EuCAP), 1-4, 2010.
6. Chou, H. T., H. C. Cheng, H. T. Hsu, and L. R. Kuo, "Investigations of isolation improvement techniques for Multiple Input Multiple Output (MIMO) WLAN portable terminal applications," Progress In Electromagnetics Research, Vol. 85, 349-366, 2008.
7. Zhu, F., J. Xu, and Q. Xu, "Reduction of mutual coupling between closely-packed antenna elements using defected ground structure," Electronics Letters, Vol. 45, No. 12, 601-602, 2009.
8. Han, M. and J. Choi, "Multiband MIMO antenna with a band stop filter for high isolation characteristics," Antennas and Propagation Society International Symposium, 1-4, 2009.
9. Yeom, I., J. Kim, and C. Jung, "Compact dual-band MIMO antenna with high isolation performance," Asia-Pacific Microwave Conference Proceedings (APMC), 766-769, 2010.
10. Li, Z., M. Han, X. Zhao, and J. Choi, "MIMO antenna with isolation enhancement for wireless USB dongle application at WLAN band," Antennas and Propagation Society International Symposium, 758-761, 2010.
11. Lee, C., S. Chen, and P. Hsu, "Integrated dual planar inverted-F antenna with enhanced isolation," IEEE Antennas and Wireless Propagation Letters, Vol. 8, 963-965, 2009.
12. Min, K., D. Kim, and Y. Moon, "Improved MIMO antenna by mutual coupling suppression between elements," The European Conference on Wireless Technology, 125-128, 2005.
13. Karaboikis, M., C. Soras, G. Tsachtsiris, and V. Makios, "Compact dual-printed inverted-F antenna diversity systems for portable wireless devices," IEEE Antennas and Wireless Propagation Letters, Vol. 3, No. 1, 9-14, 2004.
14. Hsu, C., K. Lin, H. Su, H. Lin, and C. Wu, "Design of MIMO antennas with strong isolation for portable applications," IEEE Antennas and Propagation Society International Symposium, 1-4, 2009.
15. Lee, Y., H. Chung, J. Ha, and L. Choi, "Design of a MIMO antenna with improved isolation using meta-material," International Workshop on Antenna Technology (iWAT'11), 231-234, 2011.
16. Sarabandi, K. and Y. J. Song, "Subwavelength radio repeater system utilizing miniaturized antennas and metamaterial channel isolator," IEEE Transactions on Antennas and Propagation, Vol. 59, No. 7, 2683-2690, 2011.
17. Marques, R., F. Martin, and M. Sorolla, Metamaterials with Negative Parameters: Theory, Design and Microwave Applications, John Wiley and Sons, 2011.
18. Guo, Y. and R. Xu, "Planar metamaterials supporting multiple left-handed modes," Progress In Electromagnetics Research, Vol. 66, 239-251, 2006.
19. Hrabar, S., Z. Eres, and J. Bartolic, "Capacitively loaded loop as basic element of negative permeability meta-material," 32nd European Microwave Conference, 1-4, 2002.
20. Goussetis, G., A. P. Feresidis, S.Wang, Y. Guo, and J. C. Vardaxoglou, "Uniplanar left-handed artificial metamaterials," J. Opt. A: Pure Appl. Opt., Vol. 7, No. 2, S44, 2005.
21. Guo, Y., G. Goussetis, A. P. Feresidis, and J. C. Vardaxoglou, "Efficient modeling of novel uniplanar left-handed metamaterials," IEEE Transactions on Microwave Theory and Techniques, Vol. 53, No. 4, 1462-1468, 2005.
22. Jan, M. A., D. N. Aloi, and M. S. Sharawi, "A 2 x 1 compact dual band MIMO antenna system for wireless handheld terminals," IEEE Radio and Wireless Symposium (RWS 2012), Santa Clara, California, January 2012.
23. Sharawi, M. S., M. A. Jan, and D. N. Aloi, "A 4-shaped 2 x 2 multi-standard compact MIMO antenna system for LTE mobile handsets," IET Microwaves, Ant. and Prop., Vol. 6, 685-696, June 2012.
24. Sonkki, M., E. Antonino-Daviu, M. Cabedo-Fabres, M. Ferrando-Bataller, and E. T. Salonen, "Improved planar wideband antenna element and its usage in a mobile MIMO system," IEEE Antennas and Wireless Propagation Letters, 1, 2012.
25. Lee, C. J., W. Huang, A. Gummalla, and M. Achour, "Small antennas based on CRLH structures: Concept, design, and applications," IEEE Antennas and Propagation Magazine, Vol. 53, No. 2, 10-25, 2011.
26. Han, M.-S. and J. Choi, "MIMO antenna using a decoupling network for next generation mobile application," 9th International Symposium on Communications and Information Technology (ISCIT'09), Icheon, South Korea, September 2009.
27. Lopez, N., C. Lee, A. Gummala, and M. Achour, "Compact metamaterial antenna array for Long Term Evolution (LTE) handset application," IEEE International Workshop on Antenna Techcnology (iWAT'09), Santa Monica, California, March 2009.
28. Lee, S. and J. Lee, "Electrically small MNG ZOR antenna with multilayered conductor," IEEE Antennas and Wireless Propagation Letters, Vol. 9, 724-727, 2010.
29. Yoo, S. and S. Kahng, "Negative permeability metamaterial structure based electrically small loop antenna," International Conference on Advanced Communication Technology (ICACT), 769-773, 2008.
30. Paul, H., "The significance of radiation efficiencies when using S-parameterss to calculate the received signal correlation from two antennas," IEEE Antennas and Wireless Propagation Letters, Vol. 4, No. 1, 97-99, June 2005.
31. Chae, S. H., S. K. Oh, and S. O. Park, "Analysis ofmutual coupling, correlations, and TARC in WiBro MIMO array antenna," IEEE Antennas and Wireless Propagation Letters, Vol. 6, 122-125, 2007.
32. Browne, D. W., M. Manteghi, M. P. Fitz, and Y. Rahmat-Samii, "Experiments with compact antenna arrays for MIMO radio communications," IEEE Transactions on Antennas and Propagation, Vol. 54, No. 11, 3239-3250, 2006.
33. Ding, Y., Z. Du, K. Gong, and Z. Feng, "A novel dual-band printed diversity antenna for mobile terminals," IEEE Transactions on Antennas and Propagation, Vol. 55, No. 7, 2088-2096, July 2007.
34. Ko, S. C. K. and R. D. Murch, "Compact integrated diversity antenna for wireless communications," IEEE Transactions on Antennas and Propagation, Vol. 49, 954-960, June 2001.