A parameter extraction method for microwave direct-coupled-resonator filters with the consideration of component losses

In this paper, a method is proposed to extract the parameters of direct-coupled-resonator filters such as the resonant frequencies, coupling coefficients, and Q factors. The ABCD matrix is firstly built from the simulation or measured response. The components of the filter in each stage can then be decomposed based on the derived functions. Since lossy components can be individually extracted, this method is applicable to lossy filter designs with non-uniform Q distribution. From the extracted parameters, it is clear to indicate the detuned components and is more efficient for them to be fine-tuned. Two filter examples are given finally to validate the proposed method.