Mutual Coupling Reduction in Microstrip Phased Array Using Stacked-Patch Reduced Surface Wave Antenna

Surface waves excitation in conventional microstrip patch antennas causes strong mutual coupling between adjacent elements in an array. Reduced surface wave (RSW) antennas are a solution to reduce mutual coupling in arrays. However, these arrays are suffered from large size of RSW elements. In this paper, stacking technique is applied on a rectangular RSW antenna and 33% size reduction is achieved at 5.8 GHz. The mutual coupling in a two-element array of this antenna is examined. With 0.7 lambda(0) element spacing, the mutual coupling is 4 dB better than the conventional one and for spacing larger than 1.1 lambda(0), this improvement rises to 10 dB. In addition, investigation of radiation characteristics of a 1x 5 linear phased array verifies that in contrast to conventional patch array, the side lobe level is better than -9 dB over the entire scan range and no grating lobe happens. Simple fabrication, low cost and easy installation are the other benefits of this structure.