A new planar multiple-input–multiple-output (MIMO) antenna for ultra wideband (UWB) applications is presented. The proposed antenna operates over the frequency band from 3.1 to 10.6 GHz and it consists of two identical circular monopoles on an FR4 substrate. The wide isolation is achieved through a novel planar decoupling structure that is being inserted between the dual antennas. Moreover, a center slot is etched on the common ground to further increase isolation. The effectiveness of the decoupling structure is analyzed, and performance study has been performed to investigate the mutual coupling reduction. A good isolation of more than 31 dB has been achieved through the entire UWB band (more than 12 dB improvement over the reference antenna). The proposed UWB antenna with and without the wideband decoupling structure has been investigated and verified both numerically and experimentally. The measurement results of the proposed UWB–MIMO antenna are in good agreement with the simulation results. The proposed UWB antenna has been compared with previous works regarding antenna size, geometric complexity, bandwidth, and isolation level. The proposed antenna has some outstanding characteristics such as a geometric simplicity, compact size, broad bandwidth, and low correlation which give the antenna an excellent diversity performance and a good candidate for UWB applications.

This paper describes a new configuration of frequency-selective structure (FSS) structures to reduce mutual coupling between the radiating elements. Also, the antenna performance before and after the implementation of FSS have been investigated. The proposed configuration provides an improvement in mutual coupling by 14 dB (measured value) with a reduced edge-to-edge spacing of 23 mm. The reduction of mutual coupling between antenna elements is interesting in the electromagnetic and antenna community. The use of electromagnetic band-gap structures constructed by microstrip technology is a way to appease the mutual coupling problem. Periodic structures such as FSS can help in the reduction of mutual coupling using their ability of suppressing surface waves propagation in a given frequency range. The goal of this present study is to use it in patch antenna arrays, keeping both the element separation smaller than λ0 for grating lobes evasion and the patch antenna size large enough to have good antenna directivity. The results showed that the proposed configuration eliminates disadvantages of similar structures presented in the previous works.