A novel non-uniform superstrate resonant cavity antenna (RCA) design method was proposed. The non-uniform superstrate was constructed by changing the reflection coefficient at different location of the aperture. The values of the reflection coefficients were determined by a given function. Metallic via was chosen as the unit of superstrate, whose reflection coefficient can be determined by changing via diameters or by changing unit length between vias. According these two ways, two kinds of non-uniform superstrate RCAs were designed, both followed the same reflection coefficient function. The performances of two kinds of antennas were very similar, and both satisfy the results forecasted by the reflection coefficient function. The results indicated that reflection coefficient characteristic was the important impact factor for non-uniform superstrate RCA. Two prototype antennas were fabricated and measured. The measured |S11|
