A single-layer compact four-element quasi-Yagi MIMO antenna design for super-wideband response

Abstract

In this article, a new configuration of a multiple-input-multiple-output (MIMO) antenna system for super-wideband response is presented. The proposed antenna consists of four microstrip line-fed compact 3-elements quasi-Yagi antennas placed perpendicularly to each other. Each element has a bow-tie-driven monopole element over a finite ground plane backed by a flared truncated ground reflector and a diamond-shaped director. The end-fire radiation pattern over the wider bandwidth has been achieved using a bow-tie monopole-driven element. The measured impedance bandwidth (for |S11| ≤ −10 dB) is from 1.37 to 16 GHz (168.5% at 8.68 GHz mid-frequency), and port isolation is better than 16 dB with a common ground plane. The measured gain and efficiency variations are between 3.5 and 5.4 dBi and 56–90%, respectively. These characteristics are in good agreement with theoretical results. The calculated envelope correlation coefficient and capacity loss are less than 0.01 and 0.25 bit/s/Hz, respectively, over the entire operating band. The overall size of the proposed MIMO antenna is 110 × 110 × 1.6 mm3. The novelty of the proposed antenna system is the four directive beams and good diversity performance over super-wide bandwidth with a simple single-layer compact design, which makes it a promising candidate for large-capacity and high-speed communication systems.