Dual-Polarized Isolation-Improved MIMO Inverted-F Antenna Through an L-Shaped Decoupler

This paper introduces a compact MIMO antenna system designed for WLAN applications, offering dual polarization, strong isolation, and pattern diversity. The system includes two orthogonally positioned inverted-F antenna (IFA) elements operating in the 2.4 GHz WLAN band. To achieve polarization diversity, each element is designed and excited with a perpendicular feed. An L-shaped metallic parasitic element is placed close to the antennas to significantly reduce mutual coupling and enhance isolation. The antenna's layout is straightforward and planar, making it easy to fabricate without requiring complex manufacturing steps. A prototype of the design was built and tested, and the experimental results show good agreement with simulated data. The fabricated antenna achieves a wide operating bandwidth from around 2.2 to 2.7 GHz and exhibits excellent port isolation, with S₂₁ better than -30 dB at 2.4 GHz. The proposed antenna with L-parasitic provides an efficiency of around -0.53 dB (89%) and a peak gain of 3.3 dBi at 2.4 GHz. Further, it offers an exceptionally low envelope correlation coefficient (ECC), approximately 0.0004, and diversity gain of nearly 10 dB, ensuring robust diversity and MIMO performance. These characteristics make the proposed design a promising option for use in low-profile modern WLAN MIMO systems.