This research work focuses on design and characterization of a compact reconfigurable band notch UWB-MIMO Antenna. The analysis of two different designs of UWB antenna elements is presented in this thesis. The reconfigurable performance of these antenna elements is analyzed for 2 × 2 and 4 × 4 MIMO scenarios as well. In first design a miniaturized antenna element exhibiting reconfigurable notched band functionality is presented for UWB-MIMO applications. The antenna element consists of rectangular lower half, fed by a rectangular feed line. Antenna elements shows a good impedance match over frequency band of 3.1 GHz - 10.6 GHz. To achieve enhanced isolation in MIMO communication, a slotted circular shaped decoupling structure is designed on the ground plane. Decoupling structure provides isolation above 20 dB for radiating elements operating in ultra wideband. Electronically reconfigurable bandnotch characteristic at WLAN (5.15 - 5.825 GHz) is achieved by inserting PIN diodes in inverted L-shaped slots present in the main radiating elements. In second design MIMO antenna element exhibiting electronically reconfigurable WiMAX (3.2 - 3.8 GHz) band notch capability is proposed for ultra wideband MIMO applications. Isolation of more than 25 dB among all radiating elements over entire ultra wideband is achieved using rectangular slotted decoupling structure. Finite Element Method (FEM) based simulations have been carried out in Ansys High Frequency Structural Simulator (HFSS)™ for the design and optimization of antenna. The equivalent circuit analysis of proposed designs is performed in Advanced Design System (ADS) software and for Characteristic Mode Analysis (CMA), CST Studio Suite® is used. Characteristic Mode Analysis (CMA) of UWB band notch antennas explains the availability of resonant modes linked to the surrounded narrowband slot structure (notch modes). The proper placement and location of slot within the geometry of the UWB antenna determines the effect over the rest of the radiating modes of the wideband structure, and consequently, over the behavior of the antenna. Elements are fabricated and tested on FR-4 laminates of thickness 0.8 mm and 1.6 mm. The diversity parameters for all MIMO design configurations are well within desired limits. Moreover, simulated results are verified through measurements. S-parameters are measured using vector network analyzer (VNA), while radiation patterns are measured in anechoic chamber. The measured results are in good agreement with the simulated results.