An Integrated Radiating and Decoupling Surface for MIMO Antenna Array

An integrated radiating and decoupling surface (IRDS) is proposed for multiple-input multiple-output (MIMO) antenna arrays. The IRDS is placed close (0.16<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula>) above the MIMO antenna array and consists of many electrically small pixel elements. These elements can be specially connected to form a large resonant scatterer geometry. By well designing the impedance distribution on the IRDS, it can control the MIMO antenna radiation patterns in the far-field region, while utilizing multiple scattering effects in the near-field region to cancel the mutual couplings between antenna ports. A numerical inverse design method to find the optimal impedance distribution on the IRDS is also introduced. Three design examples are investigated to verify the design method: a 2-port antenna array in the E-plane, a 2-port antenna array in the H-plane, and a 4-port antenna array in the H-plane. Experimental results show that the proposed IRDS can increase the antenna bandwidth by three times, while simultaneously reducing mutual coupling (below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 20dB) and maintaining the antenna radiation patterns. The proposed method is promising for future compact wireless systems where both <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$S$</tex-math></inline-formula>-parameters and radiation patterns need to be decoupled.