Diagnosis of individual cell frequencies in a coupled cavity chain without introducing objects into the cavity

This paper presents a new method to diagnose cell frequencies in a cavity without a probe inside the cavity. The equivalent circuit model of a coupled cavity chain is used to estimate the cell frequencies and couplings between cells in terms of the measured passband performance. Two assumptions used to simplify the numerical process are that the next nearest neighbor couplings between the cells are taken as zero and the quality factors of cells are unchanged in the tuning procedure and defined in advance. This method can simplify the tuning process and makes possible the tuning of a sealed cavity. The procedure has been verified with numerical and experimental examples and can be used as a guide to adjust the normal modes and field flatness in a real cavity.