An original resonant Y-junction for compact waveguide diplexers

This paper presents an innovative resonant Y-junction for the design of compact rectangular waveguide diplexers. The junction contains an elliptic ridge which serves as common dual-mode resonator for both channel filters. The junction itself constitutes therefore the first resonators of the filters, thus allowing for considerable size reduction with respect to the conventional diplexer implementation. The orientation of the input branch and the insertion of irises and ridge taps are used to control the coupling coefficients within the junction. An X-band diplexer employing the proposed junction in combination with H-plane cavity filters has been designed, manufactured, and successfully tested.