High Isolation Wideband Multiple-Input Multiple-Output Antennas for Millimeter Wave Applications

Abstract

A planar 2×2 and 4×4 multiple-input multiple-output (MIMO) antennas are designed and analyzed in thisstudy. The individual antenna elements that form the MIMO structure are located perpendicular to eachother in order to facilitate polarization diversity. Except a notch band at 4.3 GHz, the 2×2 antenna nearlycovers the entire 2.41-31.4 GHz frequency band. It is similar for the 4×4 antenna that has tri-bandcharacteristic, where the impedance bandwidth (|S11| ≤ −10 dB) values are determined as 1.4, 10.05 and16.26 GHz. Beside these high bandwidth results, both MIMO antennas have perfect isolationcharacteristic which is important to prevent coupling in MIMO systems. The proposed MIMO antennasare convenient to be used in all S (2-4 GHz), C (4-8 GHz), X (8-12 GHz), Ku (12-18 GHz) and K-bands(18-27 GHz). Furthermore, omnidirectional radiation patterns are observed at the resonance frequencies,and the reported 2×2 and 4×4 antennas have compact sizes of 80×40×1 mm3(64.5𝜆×32.25𝜆 ×0.8𝜆) and80×80×1 mm3 (64.5𝜆×64.5𝜆 ×0.8𝜆), respectively.