Compact Filtering Planar Inverted-F Antenna Array with Enhanced Isolation

This paper presents a filtering Planar Inverted-F Antenna (PIFA) array with an edge-to-edge distance of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${0.042} {\lambda}_{0}$</tex>. This design features a traditional PIFA with a U-shape slot etched on the upper layer and three parasitic strips on the bottom. The antenna has total dimensions of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${0.12} {\lambda}_0 \times {0.38} {\lambda}_0 \times {0.012}{\lambda_{0}}$</tex>. Its simulated average realized gain and out-of-band suppression level are 1.5 dBi and over 19 dB, respectively. Based on the element, a filtering MIMO array by using a neutralization line (NL) is obtained. Simulated results indicate that the isolation between two elements is improved from 10 dB to 20 dB, with a −10 dB impedance bandwidth of 13.3%. Meanwhile, a stable omnidirectional radiation pattern is also obtained.