A novel frequency reconfigurable 4G Multiple-Input Multiple-Output (MIMO) handset antenna is presented and verified with experimental results. Frequency tuning is used to minimize the antenna volume and to compensate for the losses related to user-originated impedance detuning. Both antenna elements are independently frequency reconfigurable and can cover most of the LTE-A bands. The study compares the losses of CMOS- and MEMS-based digitally tunable capacitors (DTC). In addition, two prototypes with total antenna volumes of 1170 and 3900 mm3 have been studied. The results show that the larger antenna structure operates with an efficiency better than 49% across the frequencies of 698-960 MHz and better than 56% across the frequencies of 1430-2690 MHz, when a MEMS-based DTC is used. In addition, a new method is introduced to estimate the suitability of the antenna geometry for frequency tunable antennas.
2. Dioum, I., A. Diallfo, S. Farssi, and C. Luxey, "A novel compact dual-band LTE antenna-system for MIMO operation," IEEE Trans. Antennas Propag., Vol. 62, No. 4, 2291-2296, April 2014.
3. Zhang, S., K. Zhao, Z. Ying, and S. He, "Adaptive quad-element multi-wideband antenna array for user-effective LTE MIMO mobile terminals," IEEE Trans. Antennas Propag., Vol. 61, No. 8, 4275-4283, August 2013.
4. Ren, Y.-J., "Ceramic based small LTE MIMO handset antenna," IEEE Trans. Antennas Propag., Vol. 61, No. 2, 934-938, February 2013.
5. Kuonanoja, R., "Low correlation handset antenna configuration for LTE MIMO applications," IEEE Int. Symp. Antennas and Propagation (APSURSI), 1-4, 2010.
6. Ilvonen, J., R. Valkonen, J. Holopainen, and V. Viikari, "Design strategy for 4G handset antennas and a multiband hybrid antenna," IEEE Trans. Antennas Propag., Vol. 62, No. 4, 1918-1927, April 2014.
7. Manteuel, D. and M. Arnold, "Considerations for reconfigurable multi-standard antennas for mobile terminals," Proc. Int. Workshop Antenna Technology (iWAT), 231-234, 2008.
8. Valkonen, R., M. Kaltiokallio, and C. Icheln, "Capacitive coupling element antennas for multistandard mobile handsets," IEEE Trans. Antennas Propag., Vol. 61, No. 5, 2783-2791, May 2013.
9. Caporal Del Barrio, S., A. Tatomirescu, G. Pedersen, and A. Morris, "Novel architecture for LTE world-phones," IEEE Antennas Wireless Propag. Lett., Vol. 12, 1676-1679, 2013.
10. Payandehjoo, K. and R. Abhari, "Compact multi-band PIFAs on a semi-populated mobile handset with tunable isolation," IEEE Trans. Antennas Propag., Vol. 61, No. 9, 4814-4819, September 2013.
11. Ogawa, K., T. Matsuyoshi, and K. Monma, "An analysis of the performance of a handset diversity antenna influenced by head, hand, and shoulder effects at 900MHz: Part II --- Correlation characteristics," IEEE Trans. Veh. Technol., Vol. 50, No. 3, 845-853, May 2001.
12. Tian, R., B. K. Lau, and Z. Ying, "Multiplexing efficiency of MIMO antennas," IEEE Antennas Wireless Propag. Lett., Vol. 10, 183-186, 2011.
13. Villanen, J., J. Ollikainen, O. Kivekas, and P. Vainikainen, "Coupling element based mobile terminal antenna structures," IEEE Trans. Antennas Propag., Vol. 54, No. 7, 2142-2153, July 2006.
14. Peregrine, Digitally Tunable Capacitors, Peregrine Semiconductor, San Diego, USA, Online Available: http://www.psemi.com/content/products/product.php?product=PE64904/.,.
15. WiSpry, "Tunable digital capacitor arrays," WiSpry inc., Irvine, USA, Online Available: http://www.wispry.com/products-capacitors.php/.
16. Ilvonen, J., O. Kivek¨as, J. Holopainen, R. Valkonen, K. Rasilainen, and P. Vainikainen, "Mobile terminal antenna performance with the user’s hand: Effect of antenna dimensioning and location," IEEE Antennas Wireless Propag. Lett., Vol. 10, 772-775, 2011.
17. Rahola, J., "Bandwidth potential and electromagnetic isolation: Tools for analysing the impedance behaviour of antenna systems," Proc. 3rd European Conf. Antennas and Propagation (EuCAP), 944-948, 2009.
18. Zhang, S., K. Zhao, Z. Ying, and S. He, "Diagonal antenna-chassis mode for wideband LTE MIMO antenna arrays in mobile handsets," Proc. Int. Workshop Antenna Technology (iWAT), 407-410, 2013.
19. Optenni Lab Matching circuit generation and antenna analysis software, Optenni Ltd., Espoo, Finland, Online Available: http://www.optenni.com/.
20. Lehtovuori, A., R. Valkonen, and J. Ilvonen, "On designing dual-band matching circuits for capacitive coupling element antennas," Proc. 8th European Conf. Antennas and Propagation, (EuCAP), 3909-3913, 2014.
21. Rahola, J., "Effect of antenna Q to the radiation efficiency of tunable antennas," Proc. 8th European Conf. Antennas and Propagation, (EUCAP), 3905-3908, 2014.
22. Zhao, K., S. Zhang, Z. Ying, T. Bolin, and S. He, "SAR study of different MIMO antenna designs for LTE application in smart mobile handsets," IEEE Trans. Antennas Propag., Vol. 61, No. 6, 3270-3279, June 2013.
23. Ilvonen, J., R. Valkonen, O. Kivekas, P. Li, and P. Vainikainen, "Antenna shielding method reducing the interaction between user and mobile terminal antenna," Electronics Letters, Vol. 47, No. 16, 896-897, 2011.
24. Foschini, G. and M. Gans, "On limits of wireless communications in a fading environment when using multiple antennas," Wireless Pers. Commun., Vol. 6, No. 3, 311-335, 1998.