Wireless communication systems in the modern world are bonded to everyone’s live in many circumstances every day. The number of times that one will encounter wireless devices has grown to be larger than the number of people on the planet. Therefore, the world’s demand on mobile systems, wireless devices, and electronics is creating a large market. Based on the raising communication network, more advanced technology is required to support higher data rate, faster speed, and wider coverage. New technologies will have no limit to continue growing and providing greater communication experience for users in the world. This thesis presents a body of work that designed active antenna system to work with the high data throughput wireless networks and reconfigurable resonance response to make this modern communication possible. Four elements antennas were designed as the objective of this thesis. Their development, fabrication, and analysis is presented in the thesis. Antenna design is built off a planar inverted F antenna (PIFA) with a combination of loop and monopole antenna. This antenna design was chosen for its near omnidirectional pattern, high efficiency, ease in tuning the resonances individually, low cost of fabrication, and dual-band nature. The four elements multiple inputs and multiple outputs (MIMO) is intended to cover all 4G/LTE, 3G, 2G operating in the 700-960 MHz and 1710-2690 MHz frequency bands by using four RF switches to make lower frequency band reconfigurable while maintaining the same matching performance for the higher frequency band. MIMO antenna systems use multiple antennas at the transmit and receive modes along with encoding and decoding algorithms in order to achieve high data rate connections while maintaining robust data links in complex urban environments. This thesis includes an introduction to MIMO system, important parameters used to describe MIMO system and shows the design simulation, and experimental measurement of these MIMO antennas. The MATLAB code for computing MIMO performance parameters has been developed. The MIMO parameters are envelope correlation coefficient (ECC), total active reflection coefficient (TARC), capacity loss, and mean effective gain (MEG). Comparison results for the antenna parameters between simulation and experimental measurement are included in the end.