Synthesis and design of N‐order filters with N‐transmission zeros by means of source–load direct coupling

An extension is made to the synthesis of microwave filters with cross couplings between nonadjacent cavities to the case where there is a direct coupling between the input and output ports, i.e., the source and the load of the device. This coupling extends to N‐order filters the possibility to accomplish responses with N finite transmission zeros. In addition, symmetric and asymmetric rejection slopes out of band and equalized group delay can be obtained simultaneously. Several examples of filter synthesis are presented to validate the proposed synthesis procedure. Finally, to show the applicability of the load–source direct coupling, a second‐order Ku‐band filter with two transmission zeros has been designed using three physical structures: two different rectangular waveguide E‐plane configurations and one H‐plane.