Capacitively fed annular ring microstrip antenna with reconfigurable circular polarisation

A single fed polarisation reconfigurable antenna that can provide orthogonal circular polarisations is presented in this paper. The antenna consists of an annular ring that is excited capacitively in positions which enable orthogonal modes. Correct phase conditions are provided by an incorporated feeding network located on the bottom side of the antenna ground plane. The feeding network employs four pin diodes which enable switching between RHCP and LHCP. Details of the antenna structure are shown and simulated and measured results are presented and discussed.