Design of a Compact Wideband Omnidirectional Circularly Polarized Antenna

A design of a compact wideband omnidirectional circularly polarized antenna is presented in this letter. In order to achieve the wideband implementation, TM₀₁,top-loaded Monopole and TM₀₂modes are simultaneously excited by the capacitive feeding technique. For the seek of compact size, the antenna is operated in TM₀₁mode and has no redundant stubs. The monopole composed of coaxial probe and copper sheet produces vertical polarization waves. Horizontal polarization is formed by connecting the upper and lower sectors through via holes. The simulated results indicate that this antenna has an impedance bandwidth of 57.8% (2.09 - 3.78 GHz) for| S₁₁|≤ -10 dB and 31% (2.06 - 2.81 GHz) for AR s 3dB. The overall size of the antenna is 0.41 λ_L× 0.41 λ_L × 0.1 λ_L (λ_Lis the wavelength at the minimum operating frequency).