A Low-Profile Wideband PIFA Based on Radiation of Multiresonant Modes

Abstract

In this letter, a low-profile and wideband planar inverted-F antenna (PIFA) based on multiresonant modes is proposed for wireless local area networks and the Internet of Vehicles applications. Through cutting a rectangular slot at the zero-current position of the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3/2,0</sub> mode, a resonant slot mode (TMRS) is excited. Meanwhile, to enhance the impedance bandwidth (IBW), the frequency of TMRS (fRS) is decreased to close to the frequency of TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3/2,0</sub> (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3/2,0</sub> ) by enlarging the length of the rectangular slot. To further enhance the IBW, the frequency of TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2,2</sub> (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2,2</sub> ) is increased with little change on that of TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3/2,0</sub> and TMRS modes by reducing the length of the rectangular patch. Moreover, capacitive coupled feed is used by loading a small rectangular strip (SRS) on the top of the feeding probe connected with the bottom of the substrate and the ground plane, and the impedance can be matched through adjusting the size of the SRS. To verify the predicted results, the proposed low-profile wideband PIFA is fabricated and measured. The measured results show that the IBW of the proposed PIFA is enhanced to about 33.33% (from 5 to 7 GHz) at the profile of 0.036λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> by combining three resonant modes, and it is 7.41 times of 4.5% of the traditional PIFA.