A Broadband Circularly Polarized Antenna With Triple-Mode Characteristics

A novel circularly polarized (CP) antenna based on the triple-mode characteristics is presented in this paper. First, by utilizing three resonant modes, a compact antenna element is designed to realize a wide impedance bandwidth of 80%. Then, for the purpose of obtaining broadband CP radiation, the sequential feeding method is employed in the design. By sequentially exciting four antenna elements with a progressive 90 phase shift, a wideband CP windmill-shaped antenna is developed. The proposed antenna exhibits a wide impedance bandwidth (104%), a wide axial ratio (AR) bandwidth (80%), and a low profile (0.18 lambda, lambda is the wavelength in free space at the lowest operating frequency). Such a wideband and low-profile CP antenna is a promising candidate for modern broadband CP applications.