Broadband crossed dipole circularly polarized antenna with parasitic round-metal pillars

A broad crossed dipole circularly polarized antenna (CPA) with modified and parasitic elements is presented. The crossed dipole CPA is consisted of a pair of vacant-quarter printed rings as continuous phase feeding structure, four L-shaped strips as radiated patch, four grounded round-metal pillars as parasitic element and a circular ground as a reflector. Note that two deformed trapezoid-microstrip lines as impedance matching element are used to feed the crossed dipole CPA, which is different from the traditional rectangular-microstrip lines. Moreover, the rotated L-shaped strips as radiated patch are used to realize CP radiation, but four rotated grounded round metal pillars as the only parasitic element are arranged at the edge of the L-shaped strips to improve the CP bandwidth. Through making use of these elements, multiple CP resonant modes could be together stimulated, which leads to an increase in the CP bandwidth. The antenna prototype is fabricated and tested to verify the rationality of the design. Finally, the designed crossed dipole CPA features a broad 3-dB axial ratio bandwidth of 78% (1.25-2.85, 2.05 GHz), and a wide -10-dB impedance bandwidth of 107.4% (0.94-3.12, 2.03 GHz), which could include the WiBro (2.3-2.39 GHz) and GPS (L1 1.575 GHz) band. Thus, the presented crossed dipole CPA would be a very promising candidate in the wireless communication systems.