Highly Selective Microstrip Filters Based on Multi-Step Comb Structures with Additional Cross-Coupling

In this paper, we study the selective capabilities of highly selective three- and four-resonator microstrip filters based on multi-step comb structures with additional electromagnetic cross-coupling between non-adjacent resonators. The effect of impedance steps in different parts of the length of the resonators on the working attenuation poles formation and their location on the frequency axis is shown. The possibilities of various methods for controlling the degree of the splitting of the attenuation poles and their location relative to the passband are demonstrated.