A simple method to avoid interference of unwanted mode during tuning of a cavity resonator

When we tune a microwave cylindrical cavity resonator by varying its length with the help of a moving plunger, resonant frequencies of different modes may overlap to each other causing a noise problem. So, tunable range is influenced by the frequency overlapping of different modes. In this paper we describe a simple but effective method to increase the tunable range of a particular mode of a cylindrical cavity resonator. For this purpose we use a curved wall instead of a plane one as the moving wall to vary the length of the cylindrical cavity. Observations have been made with the help of HFSS.