Switch-Reconfigurable Metal Rim MIMO Handset Antenna With Distributed Feeding

A new antenna design method together with a novel metal rim antenna is presented in this paper. The design method transforms an electromagnetic synthesis problem into a circuit problem, which can be solved in a straightforward manner. The new metal rim antenna is based on switches and the antenna cluster concept. The antenna cluster concept uses several, differently fed radiating elements together as one antenna. The proposed method is used to design a handset antenna with small ground clearance of 5 mm capable of <inline-formula> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula> MIMO operation in the 698–960 MHz low band with 30–40 % efficiency and <inline-formula> <tex-math notation="LaTeX">$4\times 4$ </tex-math></inline-formula> MIMO in the 1.7–2.7 GHz middle-high band with better than 50 % efficiency, and the 3–4 GHz high band with efficiency up to 75 %. The proposed optimization method leads to a novel way of distributing the antennas over the entire available volume.