Dual-band surface wave suppression using soft surface structure

In this paper, to suppress the surface waves in dielectric substrate at dual-band (Tx and Rx of UMTS), novel soft surface structures are proposed. By removing the ground plane edges of the patch and forming soft surfaces within the bare substrate, the front-to-back ratio of a patch antenna significantly improved. The proposed new structure has a mushroom type with edged via and two different transposed unit cells are located near the both side of the main ground plane. By using the proposed soft surface structure, backward radiation powers of a microstrip patch antenna show −18 dB at 1.95 GHz and −24 dB at 2.14 GHz, respectively. As a result, the improvement for the front-to-back ratio of a patch antenna can be increased to about 10 dB through the use of the proposed new soft surface structure compared to a conventional patch antenna without soft surface structure.