A wideband omnidirectional circularly polarized (CP) patch antenna is proposed in this paper. The proposed antenna is composed of a disk-loaded coaxial probe and four pairs of modified Γ-shaped strips loaded with shorting pins. Each pair of modified Γ-shaped strips consists of an inner Γ-shaped strip and an outer Γ-shaped strip. The approach employed in this design to improve the impedance bandwidth is to add an inner Γ-shaped strip and make it couple to the outer one. By introducing the two coupled Γ-shaped strips, two different monopole modes can be achieved simultaneously and controlled separately by two different corresponding parts of these two Γ-shaped strips, respectively, and they can be merged to realize a wide-band impedance matching. Meanwhile, the dual minimum axial ratio (AR) points around the resonance frequency of the antenna are excited by the coupled Γ-shaped strips, and they can be reallocated closely to each other for wide AR bandwidth. In the design, the monopole mode of the patch antenna is excited by the disk-loaded coaxial probe for generating the θ-polarization and the Γ-shaped strips are utilized for achieving the φ-polarization. Omnidirectional CP radiation pattern is obtained once the two orthogonal components are equal in amplitude but in phase quadrature. is conducted to further verify the proposed design.
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