Frequency selective surface superstrate for wideband code division multiple access system

A single layer frequency selective surface (FSS) for the gain enhancement of a wideband code division multiple access (WCDMA) frequency bands (1.92 GHz-2.17 GHz) is built and tested. The proposed FSS is made up of a 2-D periodic array of rectangular slots and rings with very small unit cell dimensions. Each unit cell is printed on the two side of a substrate. By combining with slots and rings structures, the first center frequency of the pass-band can be lowered. As a result, the size of unit cell is miniaturized as 0.14 lambda₀ at 2.02 GHz. To verify the gain enhancement performance of the FSS, a FSS-dipole complex antenna is made. Although the FSS layer enhances the gain of a primary radiation source of the dipole antenna, the FSS-dipole complex antenna cannot show a uniform gain all over the desired frequency band. To achieve the enhanced gain for transmitting and receiving bands in WCDMA system, the resonant frequency of the dipole (2.18 GHz) and the first center frequency of the FSS pass-band (2.02 GHz) are designed differently. Experimental results show a gain enhancement of 3 dBi with a FSS in WCDMA frequency band.