Tuning ports in the middle of resonators

Port tuning is a form of space mapping that allows rapid optimization of filters and other microwave circuits. An initial electromagnetic (EM) analysis of the filter with tuning ports inserted in all resonators is performed. Then small circuit theory components (e.g., inductors, transmission lines) are connected to the tuning ports and filter optimization takes place at circuit theory speed with nearly full EM accuracy. Once a port tuning model is in place, design time can be reduced to almost zero. This paper discusses the effect of internal port calibration and illustrates the additional port tuning techniques allowed when good port calibration is available. While the technique can work in some cases without port calibration, the range, accuracy, and efficiency is vastly improved with good port calibration.