Metasurface based MIMO microstrip antenna with reduced mutual coupling.

Abstract

In this thesis, a negative permeability (μ) metasurface is used to reduce the mutual coupling of a 2-port Multiple-Input Multiple-Output (MIMO) rectangular inset fed microstrip antenna. That was designed using the transmission model of analysis, simulated and optimized using CST microwave studio. The microstrip antenna that operates at the (5.9-6.1) GHz band is designed for 5G applications, at the extended 6 GHz band (5.925-7.125) GHz. The extended band was chosen because of its new additional spectrum, which results in less noise interference. Three metasurface wall based antenna designs and two metasurface superstrate based antenna designs are conducted. The metasurface wall based antenna designs are formulated by placing a metasurface wall vertically between the two radiating antenna elements. The metasurface superstrate based antenna designs are formulated by suspending a metasurface superstrate above the 2-port microstrip antenna. Both the metasurface wall and superstrate are made up metasurface unit cells, which are formulated by periodic split ring resonators printed on a FR-4 dielectric substrate. The metasurface cells are responsible for introducing a negative permeability medium, which converts the electromagnetic propagating waves into evanescent hence rejecting mutual coupling. In the first metasurface based antenna design, a single metasurface wall is vertically placed between the two microstrip antenna elements. A slight increase of 0.5 dB in mutual coupling is observed. In the second design, a double metasurface wall is vertically placed between the two antenna elements. A mutual coupling reduction of 11 dB is achieved. In the third design a triple metasurface wall is also placed between the two antenna elements, a mutual coupling reduction of 25 dB and up to 17 % bandwidth enhancement is achieved. In the fourth design a single metasurface superstrate is suspended above the 2-port microstrip antenna. A mutual coupling reduction of 32 dB is achieved. Lastly, in the fifth design a metasurface superstrate is also suspended above the 2-port microstrip antenna. A mutual coupling reduction of 22 dB, a 38% bandwidth enhancement and a 2.09 dB gain enhancement is achieved.