Wideband dual-mode planar endfire antenna with circular polarisation

A novel wideband dual-mode planar endfire antenna with circular polarisation is presented. The antenna consists of a semicircular disk radiator and a concentrically, stub-loaded annular sector dipole. A pair of stubs is symmetrically loaded along the annular sector dipole so that the second odd-order dipole mode is excited and moved downwards to the fundamental mode. Thus, a wideband, planar endfire circularly polarised antenna with dual-resonant characteristic is achieved. It is shown that the prototype has an impedance bandwidth of more than 24.8%, and a 3 dB axial ratio bandwidth of 18.8%.