A four port circularly polarized printed multiple-input multiple-output antenna with enhanced isolation

In this article, a four-port circularly polarized printed multiple-input multiple-output (MIMO) antenna is designed to cover Wi-Fi/WLAN (5 GHz), Wi-MAX (3.4–3.6), and C band applications, which consists of four trapezoidal shaped patches with microstrip feed. To achieve high isolation between the ports, the antenna elements are located orthogonally to each other. The antenna elements are separated by placing diagonal lines to further enhance the port isolation. Circular polarization is achieved by modifying the ground plane and trimming the edges of the trapezoidal patch. The proposed MIMO antenna works between 3.2 and 6.2 GHz and has a 63.83% impedance bandwidth (IBW) for S11 ≤ −10 dB. It also offers a good diversity performance with envelope correlation coefficient (ECC) < 0.04 and diversity gain of ≈10 dB. The antenna is fabricated on a low-cost FR4 material with 1.6 mm thickness and has dimensions of 50 mm × 50 mm. This article also clarifies some of the prior literature's misconceptions about MIMO antenna metrics. The measured results show that the proposed MIMO antenna is circularly polarized, has a similar IBW, and axial ratio bandwidth (ARBW) to the simulated results, and has >25-dB isolation.