Low-profile broadband circularly polarized short-circuited dipole antenna with backed cavity

A broadband circularly polarized (CP) dipole antenna with a backed cavity is presented in this letter. The proposed antenna consists of a pair of rotational symmetric short-circuited branches and a & UGamma;-shaped feed structure. Each branch is designed to be axe-shaped so that the antenna can achieve a broad 3-dB axial ratio (AR) bandwidth. The coupled feeding method assures the antenna is wideband, and the shorting-to-the-ground technique miniaturizes the lateral dimensions of the antenna. The profile of the proposed antenna is around 0.16 & lambda;(L) (& lambda;(L) denotes the wavelength of the lower bound frequency). The introduction of a back cavity effectively enhances the boresight gain and improves the isolation level if the antenna is used to form an array. Finally, the design is prototyped, and the measurement results agree well with the simulation. The fractal voltage standing wave ratio (VSWR)<2 bandwidth and 3-dB AR bandwidths are 61.15% (2.725-5.125 GHz) and 45.9% (3.15-5.03 GHz), respectively. The antenna's efficiency exceeds 91.5% over the target frequency band.