Unitary Condition, Group Delay and Quality Factor in Microwave Filters
Year: 2025
Type: article
Abstract: In this paper, the unitary condition of scattering parameters for lossless and lossy filters is investigated. The primary objective is to establish a mathematical framework that explains the limitations observed in filter amplitude response sharpness at passband edges during practical measurements. It is achieved by analytically evaluating the unitary condition using a closed form coupling matrix model. Various numerical examples are presented to demonstrate the impact of loss on the unitary condition and filter sharpness in practical scenarios. Moreover, we propose a mathematical form of the T term based on the extension to the unitary condition, serving as a gauge to quantify the rounded passband edges in filter response. This T term is related to filter design parameters and the resonators' quality factor, enabling a deeper understanding of filter performance in real-world conditions. The developed theory implication is discussed in analyzing the measurement results of three different filter in different frequency bands.
Source: IEEE Journal of Microwaves
Authors: Ali Kheirdoost, Maysam Haghparast, Behzad Ahmadi, Matteo Oldoni
Institutions: ICT Research Institute, Politecnico di Milano
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,075
OpenAlex ID: W4407948367