High-Isolation Compact MIMO Antenna with Distributed Metamaterial Loading

This paper details the design and realization of a high-isolation multiple-input-multiple-output (MIMO) antenna tailored for fifth-generation (5G) wireless applications. The antenna consists of a 2-element array, with each unit being a patch antenna loaded with six uniformly sized complementary split ring resonators (CSRRs). These CSRRs are strategically etched to minimize the antenna's overall size. In addition, the fragment-type split ring resonators (SRRs) are horizontally positioned between the antenna units to further improve isolation. The placement and structure of these fragment-type SRRs are optimized through a combined use of High-Frequency Structure Simulator (HFSS) and genetic algorithm (GA) techniques, which enables significant isolation levels exceeding -40 dB between antenna units. The proposed MIMO antenna operates within the 5G C-band with a -10 dB bandwidth ranging from 4.84 to 5.00 GHz, while the isolation at 4.9 GHz improves from 14.73 dB to 42.88 dB. Moreover, the maximum Envelope Correlation Coefficient is 0.0042, and the antenna dimensions are 50 mm x 44 mm x 1.6 mm. Antenna samples are fabricated using wet etching on an FR4 substrate. The measured and simulated values are found to be in good agreement. Compared to the traditional antenna design method, which relies on parameters sweeping, the algorithmic approach used in this paper significantly enhances both the design's effectiveness and efficiency.