CAD Procedure for High-Performance Composite Corrugated Filters

The design of waveguide low-pass filters is accomplished with a new method, where focus is on the upper stopband performance rather than passband or roll-off requirements. Using an efficient multimode variational formulation, composite filters are generated by direct optimization from an arbitrary number of partial corrugated subelements, each showing mutual TE₁₀-mode passband and different nonintersecting passbands corresponding to higher order modes. The flexibility of this method leads to optimal filter solutions, having the designer full control over key dimensional features, i.e., minimum gap and cavity length. It is therefore possible to design low-pass filters exhibiting broad stopbands free of spurious propagation, without penalties of higher losses, lower power handling capability, larger size, and/or increased manufacturing complexity. Simulated and measured results demonstrate significant advantages over filters designed with conventional methods.