A Unified Approach to the Design Measurement and Tuning of Coupled-Resonator FiltersIEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 46, NO. 4, APRIL 1998 343 A Unied Approach to the Design, Measurement, and Tuning of Coupled-Resonator Filters John B. Ness Abstract― The concept of coupling coefcients has been a very useful one in the design of small-to-moderate bandwidth microwave lters. It is shown in this paper that the group delay of the input reection coefcients of sequentially tuned resonators contains all the information necessary to design and tune lters, and that the group-delay value at the center frequency of the lter can be written quite simply in terms of the low-pass prototype values, the LC elements of a bandpass structure, and the coupling coefcients of the inverter coupled lter. This provides an easy method to measure the key elements of a lter……