Finline and Metal Insert Filters with Improved Passband Separation and Increased Stopband Attenuation

A new class of optimized finline and metal insert filters is introduced. In these filters, the ladder-type insert is located in a waveguide section which is either wider or narrower than the embedding standard waveguide. A step junction at each end forms the transition to the standard waveguide and is included in the analysis. Both filter types provide a better suppression of spurious passbands and have significantly improved stop-band attenuation. Filters with enlarged sections are useful for design at the lower end of the waveguide band, whereas the narrower version is appropriate for bandend design.