Bandpass filtering coupler based on dual-mode dielectric resonators

This paper proposes an approach to implement a bandpass filtering quadrature coupler. Motivated by the excellent properties of dielectric resonators (DRs), four cylindrical dielectric resonators operating at HE11 mode are utilized to implement a quadrature coupler with additional bandpass filtering function integrated. The coupling coefficient can be easily controlled by the cross irises between the DRs. For demonstration purposes, a quadrature coupler was designed to exhibit the 6 dB coupling coefficient together with bandpass filtering characteristics over an operating frequency of 5.2 GHz.