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.

中文翻译：

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加载软磁铁氧体薄膜用于多频带天线的低频改进

这项工作提出了一种简单的方法，只需在强辐射区域上加载软磁性铁氧体薄膜，即可改善小型LTE / WWAN智能手机天线的低频特性。基本的非磁性天线仅占用11 mm×30 mm的无地面空间，通过共同设计曲折带和T形天线，可以实现覆盖822–914 / 1710–3244 MHz频段的六频段操作喂食条。在强辐射条上加载小尺寸铁氧体膜（2 mm×15 mm），可以改变频率以覆盖692–1191 / 1698–3020 MHz的范围，这显示了八频带操作的完全覆盖，尤其是包括最佳的长期演进频段LTE700，而又不扩大基础天线的尺寸。此外，带有铁氧体薄膜负载的磁性天线的辐射特性在较高频段（1710–2690 MHz）上显示出有限的变化，但在较低频段（698–960 MHz）上则可以接受。实验结果和模拟结果均已取出，并显示出一致的趋势。通过在天线上引入商用铁氧体薄膜的这种低频特性优化方法，为解决实际智能手机应用中的频率偏差提供了一种简单便捷的方法。