Gain-Enhanced Wideband Circularly Polarized Antenna with a Non-Uniform Metamaterial Reflector

In this paper, a gain-enhanced wideband circularly polarized (CP) antenna with a non-uniform metamaterial (NUM) reflector is presented, which is composed of a modified wide S-shaped slot antenna and a NUM reflector. To achieve a wideband CP operation, a modified S-shaped slot is fed by an L-shaped microstrip feedline that ends with a triangular patch to improve axial ratio (AR) bandwidth and impedance bandwidth. A NUM reflector composed of rectangular metal units with different sizes is employed and its units are unevenly distributed. The proposed CP antenna is designed, fabricated, and measured. The measured results show that the impedance bandwidth covers 3.0-6.0 GHz (66.7%) and a 3-dB AR bandwidth covers 3.1-5.6 GHz (57.4%). A peak gain of 6.0 dBi is obtained at 3.8 GHz by using the reflector. The advantages of the proposed antenna are the simple structure, high gain, and broad CP bandwidth.