Design and analysis of a step-by-step ultra-wideband MIMO antenna with band-rejection features

In this study, we present the design, fabrication, and analysis of a step-by-step Ultra-Wideband (UWB) Multi-Input Multi-Output (MIMO) antenna operating from 3 to 14 GHz. The antenna consists of four elements, each characterized by high isolation and equipped with four band-rejection features. These elements are implemented on a Rogers substrate with ϵr = 3. Each antenna element is a modified rectangular patch, incorporating partial ground etching to achieve wider bandwidth. Two sets of U-Shape and H-L shape slots are integrated into the patch to act as band-reject filters. The assigned four-band rejections target frequencies at 5.5 GHz (WLAN), 7.5 GHz (lower X-band), 9.5 GHz (upper X-band), and 12.9 GHz (KU-band). Isolation between antenna elements exceeds 15 dB, effectively reducing mutual coupling. We simulate and calculate MIMO diversity parameters across the entire frequency band which showed acceptable results. Our measured data closely aligns with simulation results, validating the accuracy of this antenna design.