Abstract— Mutual coupling is a critical issue in the design of MIMO antennas as it deteriorates MIMO and diversity system performance. This work presents a novel approach and guideline for the design of a compact parasitic decoupling element between two element MIMO antennas. It is based on a stepped impedance resonator circuit theory, where the antenna impedance bandwidth, the level of isolation and compactness can all be controlled and optimized. Using this theory, a compact planar inverted-L dual-element antenna with a parasitic decoupling element is proposed for handset terminal applications. Measurement results show that this design has a good performance over the frequency range 1700-2700MHz, which covers most of cellular frequency bands, such as DCS 1800, PCS 1900, UMTS, and LTE-advanced between 1700-2700MHz. Finally, diversity performance parameters are obtained and evaluated based on both the simulated and measured results.