Threefold Rotationally Symmetric SIW Antenna Array for Ultra-Short-Range MIMO Communication

A high-performance, three-element substrate-integrated-waveguide (SIW) cavity-backed slot antenna array that covers the (5.15-5.85) GHz band is designed for integration inside or underneath the worktop of a desk, to set up a stable, high data-rate ultra-short-range 3 × 3 multiple-input multiple-output (MIMO) wireless communication link with a mobile user (MU) positioned on top of that worktop. The antenna topology and array geometry are carefully selected to maximally exploit the multiplexing capabilities of the ultra-short-range 3 × 3 MIMO channel over a wide bandwidth, yielding an increased channel capacity and/or reduced power consumption. In addition, special care was taken to guarantee a channel capacity that is less dependent on the relative orientation of the MU. Furthermore, the SIW implementation technology is combined with innovative antenna materials to guarantee a low-profile, low-cost, stable, and high-performance broadband array design that maintains its excellent performance after integration. A prototype of the antenna array was fabricated, integrated according to two different integration scenarios, and validated. Measurements prove that the antenna array allows integration into a worktop with only a minor influence on its return loss and mutual coupling, guaranteeing a bandwidth of at least 1.078 GHz and a minimum isolation between antenna elements of 30 dB within the entire (5.15-5.85) GHz band.