Mutual coupling between two circular window elements has been reported in various papers and the results indicate that mutual coupling level is greater for the window patch antennas than for the normal patches due to cylindrical waves which are trapped by the metal of the low frequency element and these cylindrical waves are added to the radiative waves to increase the mutual coupling level. Since mutual coupling between antenna elements in an array can be problematical, some techniques will be presented in this paper to reduce the mutual coupling between elements in a multi-band window element depending on the phase cancellation between the radiative and the trapped waves.