Affiliations: [a] Key Laboratory of Electromagnetic Wave Information Technology and Metrology of Zhejiang Province, College of Information Engineering, China Jiliang University, Hangzhou, China | [b] Institute of Flexible Electronics Technology of THU, Jiaxing, China | [c] Key Laboratory of Wireless Power Transmission of Ministry of Education, College of Electronics and Information Engineering, Sichuan University, Chengdu, China
Correspondence:
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Corresponding authors: M. Zhu, Key Laboratory of Electromagnetic Wave Information Technology and Metrology of Zhejiang Province, College of Information Engineering, China Jiliang University, Hangzhou 310018, China. E-mail: mzhu@cjlu.edu.cn; H.-M. Zhou, Key Laboratory of Electromagnetic Wave Information Technology and Metrology of Zhejiang Province, College of Information Engineering, China Jiliang University, Hangzhou 310018, China; and Institute of Flexible Electronics Technology of THU, Jiaxing 314006, China. E-mail: zhouhm@cjlu.edu.cn
Note: [†] T. Wu, G. Yu and J. Pang contributed equally to this work.
Abstract: This work presents an easy way to improve the low-frequency properties in a small-size LTE/WWAN smartphone antenna by just loading a soft magnetic ferrite film on the strong radiation area. The base non-magnetic antenna, which only takes up an 11 mm × 30 mm no-ground space, can achieve hexa-band operation covering 822–914/1710–3244 MHz bands by co-designing a meandering strip and a T-shaped feeding strip. With loading a small-size ferrite film (2 mm × 15 mm) at the strong radiation strip, the frequencies can be shifted to cover the range of 692–1191/1698–3020 MHz, which shows a fully covering of octa-band operation, especially including the best long-term-evolution band, LTE700, without enlarging the size of base antenna. In addition, the radiation characteristics of the magnetic antenna with ferrite film loading show a limited change at upper bands (1710–2690 MHz) but an acceptable level at lower bands (698–960 MHz). Both experimental and simulated results have been taken out and shown the consistent tendency. This optimization method of low-frequency properties by introducing a commercial ferrite film on the antenna has provided a simple and convenient way to solve the frequency deviation in the practical smartphone applications.
Keywords: Multiband antenna, ferrite loading, frequency modulation, LTE700 band
