Integrated Microwave and mm-Wave MIMO Antenna Module With 360° Pattern Diversity for 5G Internet of Things

Abstract

The complete coverage of the operating frequency bands from microwave bands to millimeter (mm-wave) is required for the realization of the fifth-generation (5G) Internet of Thing (IoT) systems. Here, we present a multiband antenna operating at the microwave (2.5/3.5/5.5/7.5 GHz) and mm-wave bands (23–31 GHz), and its 12-port MIMO configuration with pattern diversity affording 360° coverage for 5G IoT applications. The multiband characteristics are obtained by adding well-designed quarter-wavelength stubs. The antenna operates at the important frequency bands from 2.37–2.65, 3.25–3.85, 5.0–6.1, and 7.15–8.5 GHz (|S11| <–10 dB), while it resonates from 23–31 GHz at the mm-wave band with the desired radiation characteristics. Moreover, the antenna has more than 95% radiation efficiency and a stable gain (> 2.5 dBi at microwave band and 6.5 dBi at mm-wave bands) characteristics. In addition, the single-element antenna is translated to design a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\,\,\mathbf {\times }\,\,2$ </tex-math></inline-formula> MIMO antenna. This MIMO unit is further utilized in the formation of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\,\,\mathbf {\times }\,\,4$ </tex-math></inline-formula> and the proposed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\,\,\mathbf {\times }\,\,4$ </tex-math></inline-formula> (12-port) MIMO configurations to achieve spectral and pattern diversity. Considering the unique three-dimensional arrangement of the antenna elements, the 12-port MIMO system is the only one of its kind that offers the codesign of microwave and mm-wave antenna, good isolation, and pattern diversity, providing complete 360° space coverage in elevation and azimuth planes. The proposed antenna module is suitable for 5G IoT, especially in an indoor scenario for smart houses, offices, and vehicle-to-everything communications.