Simple inverted-F antenna based on independent control of resonant frequency for LTE/wireless wide area network applications

In this study, a simple inverted-F antenna (IFA) that can independently tune resonant frequency is proposed. The proposed antenna covers the hexa-band (long term evolution/wireless wide area network (LTE700/WWAN)) for mobile handset applications. The proposed structure consists of four radiating branches. Each branch operates as an IFA and has a resonant length of quarter-wavelength at the fundamental frequency. One remarkable feature of the proposed antenna is that all four resonant frequencies can be tuned independently without affecting the other resonant frequencies. The independent resonant control is explained through analysis based on parameter study and simulated electric field distribution. The occupied antenna volume of the proposed design is 50 × 15 × 3 mm³, which is appropriate for the smart phone applications. A prototype of the proposed antenna is fabricated and measured, and the obtained results, including the reflection coefficient, efficiency and gain, are presented. A stable and omni-directional radiation pattern with a reasonable gain has been observed over the operating bandwidth.