A broadband microstrip-CPW fed circular-polarized antenna

Abstract

A broadband circularly polarized antenna with a compact size is proposed based on a microstrip-to-CPW fed rectangular slot antenna. With the designed wideband power divider (PD) combined by a Wilkinson power divider and a 90° phase difference comparator, the even modes of four CPW feed lines are generated to provide equal amplitudes but in phase quadrature. Circular polarizations can be generated in a very broad frequency band. A reflector is added to the antenna structure to improve the antenna gains. The measured impedance bandwidth for |S11|<;-10dB is 74.4% and a broad 3-dB axial ratio (AR) bandwidth of 70.8% is also obtained. The measured 3-dB gain bandwidth is 53.65% with the peak gain of 7.4dBic.