Inline TM110-mode filters with high-design flexibility by utilizing bypass couplings of nonresonating TE1001/ modes

This paper presents a new class of pseudoelliptic function filters that are based on compact inline TM₁₁₀-mode cavity configurations. No structural folding is required. The bypass couplings are implemented through the nonresonating TE₁₀01/ modes so that arbitrarily positioned transmission zeros can be implemented. Design guidelines to generate a given transmission zero on the desired side of the passband and how to control it are presented. To demonstrate its flexibility, the approach is illustrated at examples of four-pole inline filters providing Chebyshev, elliptic-function-type, and asymmetric characteristics. Performance comparisons with different numerical codes validate the designs. A fourth-order pseudoelliptic filter with four transmission zeros is then designed, constructed, and measured. Excellent agreement between simulated and experimental results verifies the approach.