A novel approach for miniaturization of circularly polarized patch antennas

A novel approach for highly miniaturizing a patch antenna with circular polarization is presented in this paper. It is shown that the antenna is fabricated by using an anisotropic conductor supporting the proper electric current paths and extreme miniaturization can be accomplished by manipulating its geometry. Anisotropic conductivity is achieved by removing strips of metal from the ordinary patch parallel to direction of desired electric current but keeping two metallic strips at each end connecting all parallel strips. Next, the straight metallic traces are replaced by meandered metallic traces for size reduction. This in effect increases the inductance per unit length of the thin strips. This antenna can only produce linear polarization. To achieve circular polarization a second mode is excited by elongating end strips in a proper fashion and feeding the structure accordingly. It turns out that this miniaturization method enables the ease to control two resonant frequencies corresponding to two orthogonal polarizations, and the size reduction of about 72% as compared to the conventional corner-truncated square microstrip antenna fabricated on the same substrate.