Compact pseudo-highpass filters formed by cavity and iris resonators

A new class of broadband waveguide filters for pseudo-highpass applications is presented. The cavities are initially designed for TM₁₁₀-mode operation with TE_10-mode bypass coupling to create transmission zeros below the passband. The broadband characteristic is achieved by utilizing the coupling irises as additional resonances, thus achieving a pseudo-highpass operation with a minimum of physical cavities. Several designs for passbands starting at around 10 and 12 GHz are presented, and bandwidths of up to 41 percent are achieved. The design process allows for implementation of either vertical or horizontal (inline) I/O ports. Both types are verified by measurements.