In this paper, a tunable multiband LTE antenna is designed for metal-rimmed smartphone applications. The antenna only uses a broken metal ring, which comprises an IFA (Inverted-F antenna) section and a parasitic section, and generates three resonant modes through this layout for the feeding point and shorting point. In addition, loading a matching circuit at the feeding point and a RF switch at shorting point of the IFA is used to switch low frequency to lower frequency. The bandwidth can completely cover 824-960 and 1710-2690 MHz. So the proposed antenna can work at GSM850, 900; DCS1800; PCS1900; WCDMA band 1, 2, 4, 5, 8; TD-SCDMA band 34, 39; CDMA BC0,BC1 and LTE band 1, 3, 7, 38, 39, 40, 41. Also, the total size of the cellphone is 150 mm×75 mm×3.5 mm, which is very suitable for 4G slim smart mobile phone applications.
2. Lin, C. C., G. Y. Lee, and K. L. Wong, "Surface-mount dual-loop antenna for 2.4/5 GHz WLAN operation," Electronics Letters, Vol. 39, 1302-1304, 2003.
3. Chen, W. S. and K. Y. Ku, "Broadband design of a small nonsymmetrical ground λ/4 open slot antenna," Microwave Journal, Vol. 50, 110-120, 2007.
4. Guo, Q. X., "Interaction between internal antenna and external antenna of mobile phone and hand effect," IEEE Transactions on Antennas and Propagation, Vol. 61, No. 2, 862-870, Feb. 2013.
5. Yuan, B., et al., "Slot antenna for metal-rimmed mobile handsets," IEEE Antennas and Wireless Propagation Letters, Vol. 11, 1334-1337, 2012.
6. Ilvonen, R. J. and C. Icheln, "Inherently non-resonant multi-band mobile terminal antenna," Electronics Letters, Vol. 49, 11-13, 2013.
7. Wong, K. L., Y. W. Chang, and S. C. Chen, "Bandwidth enhancement of small-size planar tablet computer antenna using a parallel-resonant spiral slit," IEEE Transactions on Antennas and Propagation, Vol. 60, 1705-1711, 2012.
8. Wong, K. L., P. W. Lin, and H. J. Hsu, "Decoupled WWAN/LTE antennas with an isolation ring strip embedded therebetween for smartphone application," Microwave and Optical Technology Letters, Vol. 55, 1470-1476, 2013.
9. Valkonen, R., M. Kaltiokallio, and C. Icheln, "Capacitive coupling element antennas for multi-standard mobile handsets," IEEE Transactions on Antennas and Propagation, Vol. 61, 2783-2791, 2013.
10. Wahid, P. F., M. A. Ali, B. C. DeLoach, and Jr., "A reconfigurable Yagi antenna for wireless communications," Microwave and Optical Technology Letters, Vol. 38, 140-141, 2003.
11. Zhou, L., S. K. Sharma, and S. K. Kassegne, "Reconfigurable microstrip rectangular loop antennas using RF MEMS switches," Microwave and Optical Technology Letters, Vol. 50, 252-256, 2008.
12. Al-Dahleh, R., C. Shafai, and L. Shafai, "Frequency-agile microstrip patch antenna using a reconfigurable mems ground plane," Microwave and Optical Technology Letters, Vol. 43, 64-67, 2004.