Isolation Enhancement of Wideband Vehicular Antenna Array Using Fractal Decoupling Structure

Wideband vehicular planar inverted-F antenna (PIFA) array with high isolation by using a fractal structure is presented in this letter. The PIFA antenna elements are placed face to face, and the decoupling structure (DS) consisting of four fractal unit slots and a narrow line slot is inserted between elements to reduce the mutual coupling. The proposed structure is fabricated, and the suppression effect of mutual coupling is verified by both the simulation and measurement. Measured results show that the impedance bandwidth is from 3.02 to 3.96 GHz, which covers the 5G working frequency. An enhanced isolation of 8-32 dB in the frequency band of 3.17-4.15 GHz is obtained compared to without DS when the distance is only 0.17λ ₀ (λ ₀ is the free-space wavelength at the center frequency of 3.5 GHz) between two PIFA elements.