An FM-Cavity Filter Designed and Analyzed with the Use of N+2 Coupling Matrix Synthesis

This paper presents a filter design technique of the FM-cavity filter by using the N+2 coupling matrix synthesis. The proposed calculation can be used to predict the frequency response of filter before realizing the cavity filter. The filtering performance of the realized filter shows very low passband insertion loss and also shows good agreement results with the calculated results. The proposed filter can be used in a practical work of an FM transmitting station in order to resolve the RIM problem. The proposed FM-cavity filter can be well used in the FM broadcasting system at any FM station in Thailand.