A compact printed hybrid-mode antenna for dual-band dual-sense circular polarisation

A compact printed hybrid-mode antenna for dual-band dual-sense circular polarisation (CP) has been proposed. To achieve dual-band dual-sense CP, a hybrid mode produced by an L-shaped element and a loop element is used. In the lower frequency band, the left-handed CP is radiated by a vertical electric field from the L-shaped element and a horizontal electric field from the loop element. In the higher frequency band, the right-handed CP is radiated by a horizontal electric field from the L-shaped element and a vertical electric field from the loop element. Both the L-shaped and the loop elements produce resonances in the lower and higher frequency bands. The operational principle for dual-band dual-sense CP is clarified using the simulated orthogonal components of the electric fields and the simulated electric current distributions. Parametric studies are discussed in the design procedure. The simulated and measured input reflection coefficient, axial ratio, absolute gain, and radiation pattern are presented. The measured bandwidths of -10dB-input reflection coefficient with a 3dB-axial ratio are 2.37-2.55 GHz (7.32%) in the lower frequency band and 3.38-3.70 GHz (9.04%) in the higher frequency band. The antenna size is 0.0741 & lambda;(2)(2.45) and 0.151 & lambda;(2)(3.5) (& lambda; (f) is a wavelength at f GHz).