A Compact Broadband Planar Inverted-F Antenna with Dual-Resonant Modes

In this paper, a compact broadband planar inverted-F antenna (PIFA) with dual-resonant modes (TM1/2,2 and TM3/2,0) is proposed for 5G applications. By loading a pair of horizontal slots on the patch, the TM3/2,0 mode can be shifted downward and combined with the TM1/2,2 mode, leading to a dual-mode operation. Meanwhile, another pair of slots, which are orthogonal to the previous pair, is introduced to improve the impedance matching of the antenna. Moreover, the substrate with a high dielectric constant is used in this design to achieve a compact antenna size. In order to verify the principle and the design method, an antenna prototype was fabricated and measured. Experimental results show that the PIFA has a good performance with a −10 dB impedance bandwidth of 14.5% (3.17–3.67 GHz), a peak gain of 6.23 dBi, a low cross-polarization level of −17.3 dB, and a compact size of 0.45 × 0.26 × 0.03 λ013 (λ01 is the free-space wavelength at 3.5 GHz). The antenna is predicted to be suitable for 5G terminal applications