Circularly polarised back-to-back microstrip antenna with an omnidirectional pattern

A new configuration for a circularly polarised microstrip antenna with an omnidirectional pattern is proposed. This antenna consists of two rectangular patches with perturbation segments, which are arranged back-to-back relative to a coplanar waveguide (CPW) on a ground plane. The characteristics of the proposed antenna were clarified by experiments, and the mechanism to produce the circular polarisation was proved by using an electromagnetic simulator. The radiation patterns and input impedances were measured as a parameter of the width of the perturbation segment. Good circularly polarised radiation patterns with an omnidirectional pattern and input impedance characteristics were obtained.