Symmetrical response filter design applying the Bartlett´s theorem and using Riblet´s couplers

This paper presents the design of a six-order elliptic response filter with two transmission zeros implemented by means of a 3 dB coupler loaded with two reactive loads related to the two halves of a symmetrical network. With this alternative structure, the cross couplings are avoided, simplifying the topology and reducing the sensitivity. In addition, a Riblet-modified coupler including a λ/4 transmission line has been designed to carry out the concept. The structure implemented in H-plane waveguide configuration for Ku-band applications (center frequency at 12 GHz and 54 MHz bandwidth) reduces dramatically the milling cost.