Mutual coupling arises in an antenna array because of 1. Signal leakage via conducting currents on the metallic background or surface wave along substrates 2. Leakage received from space between antenna elements. The first one can be suppressed by changing the distribution of surface currents. But in the 2nd case the radiation-leakage caused coupling can be minimized by conventional approaches using circuit manipulation. In this research work, we propose and design a decoupling module, which is planer frequency-selective surface structure. FSS structure has the ability to suppress the surface wave propagation by providing an extra coupling path which will oppose the signal goes directly from element to element. In this design it has been observed that after implementing FSS structure between antenna elements, it causes significant suppression of mutual coupling with a reduction of more than 50dB at the designed frequency of 3.7GHz.