Frequency reconfigurable planar ultra-wide band multiple-input multiple-output (MIMO) antenna array designs are presented in this paper. To achieve Frequency Reconfigurability, Four stub are used to introduce the narrow band feature connected to the Micro strip feed line via pin diodes. The dielectric substrate used is an FR4 substrate with a dielectric constant ϵr = 4.3, thickness of 1.52 mm, and a loss tangent of 0.02 fed by a 50 Ω micro strip lines. The designed antenna operates at ultra-wide band frequency ranging from 3.1 GHz to 10.6 GHz and Narrow band ranging from 4.5 GHz to 5.93 GHz which is suitable for high speed WLAN applications with isolation better than 15 dB. © 2017 IEEE.