A tuning method using a dummy cavity for dual-mode cavity filters

A tuning method using short-ended dummy cavity is presented for dual-mode cavity filters. Tuning is based on the match of the computed and measured phase response of reflection coefficient. Equivalent circuit model is adopted for computing required phase response of reflection coefficient. This proposed method is applied to 4-pole in-line type dual-mode elliptic response filter for demonstration of this new method. It is shown that this method shows good agreement between the experimental and computed result, and no additional tuning procedure is required.