In this paper two types of three-layer mushroom-like electromagnetic band-gap (EBG) surfaces with circular patches are investigated. One of them consists of a square array of circular patches and the other one consists of a triangular array of circular patches in upper and lower layers. Guidelines for designing a ground plane for low pro¯le antenna applications are presented using the re°ection phase characteristics. The e®ect of some parameters of the three-layer structures on the re°ection phase characteristic is studied. The frequency band in which a wire antenna adjacent to the three-layer EBG surface has good matching is determined by investigating the reflection phase characteristics of the EBG ground plane.

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