Compact 2.5–2.7 GHz two element MIMO antenna system for modern USB dongle

This paper presents design of a compact two element planar MIMO antenna system for a modern USB dongle operating in the 2.5-2.7 GHz frequency band. The proposed MIMO antenna consists of two monopole antenna elements. High isolation between the antenna elements needed to realize the required diversity properties is achieved by using a decoupling technique that utilizes a lumped capacitance introduced between the antenna elements. The designed MIMO antenna has a compact size of 10 mm×20 mm (that is 6 and 12 times lower in a corresponding dimension than the operating wave length), more than 200 MHz bandwidth for return loss S₁₁ and insertion loss S₂₁ simultaneously, and exhibits pattern diversity when different antenna elements are excited. The performed analysis of the envelope correlation coefficient (that is equal to 0.06) shows superior MIMO antenna system characteristics. The designed antenna has planar structure with the standard FR4 PCB technology and, therefore, low production cost. Experimental measurements of a fabricated antenna system prove the characteristics obtained from electromagnetic simulation.