A compact H-shaped defected ground structure (DGS) is applied to reduce the mutual coupling between array elements and eliminate the scan blindness in a microstrip phased array design. The proposed DGS is inserted between the adjacent E-plane coupled elements in the array to suppress the pronounced surface waves. A two-element array is measured and the results show that a reduction in mutual coupling of 12 dB is obtained between elements at the operation frequency of the array. The scan properties of microstrip phased arrays with and without DGS are studied by the waveguide simulator method. The analysis indicates that the scan blindness of the microstrip phased array can be well eliminated because of the effect of the proposed DGS. Meanwhile, the active patterns of the array centre element in 7×3 element arrays with and without the H-shaped DGS are simulated, and the results agree with those obtained by the waveguide simulator method.