Array of coupled oscillators generating circular polarization

This paper presents a 4-element array of linearly polarized active antennas generating circular polarization. The loop arrangement with unidirectional coupling of the four oscillators is theoretically investigated and we find four possible modes of steady-state operation depending on the coupling phase. An array has been designed and realized in order to achieve the /spl pi//2-mode required to generate circular polarization. Measurements have shown a wide axial ratio beamwidth for a 2% axial ratio bandwidth.