Single Feed Broadband Circularly Polarized Antenna With Parasitic Patch

A single feed broadband circularly polarized (CP) antenna is proposed. The antenna is composed of single feeding loop structure which provides sequential phase, four driven patches, and one parasitic patches. The driven patches, which are capacitively coupled by the feeding structure, generate one CP mode due to the sequentially rotated structure. One parasitic patch produces additional CP mode. By combining single feeding loop structure with four driven patches and one parasitic patch, the axial ratio (AR) bandwidth is greatly broadened. The results of the simulation show that the antenna achieves a broad impedance bandwidth of 20.7% (4.38–5.39 GHz) and a 3-dB AR bandwidth of 14.2% (4.65–5.36 GHz). In addition, the proposed antenna has a flat gain within the operating frequency band and a size of $\boldsymbol{\Phi} 0.97\boldsymbol{\lambda}_{0}\times 0.15\boldsymbol{\lambda}_{0}$ at 5.0 GHz.