Theory for the design of a filter having one cross coupling path to realize poles of attenuation in its stopband

A general circuit model of a filter having one cross coupling path is analyzed, and a new theory is developed for the design of a filter with poles of attenuation in its stopband. By using the derived formulas, the reactance element values in the cross coupling path are determined readily. The attenuation poles can thus be assigned at desired frequencies. Various design examples are provided, together with simulated results, which validate the proposed theory.