Generalized TM Dual-Mode Cavity Filters

A new cavity arrangement, namely, the generalized TM dual-mode cavity, is presented in this paper. In contrast with the previous contributions on TM dual-mode filters, the generalized TM dual-mode cavity allows the realization of both symmetric and asymmetric filtering functions, simultaneously exploiting the maximum number of finite frequency transmission zeros. The high design flexibility in terms of number and position of transmission zeros is obtained by exciting and exploiting a set of nonresonating modes. Five structure parameters are used to fully control its equivalent transversal topology. The relationship between structure parameters and filtering function realized is extensively discussed. The design of multiple cavity filters is presented along with the experimental results of a sixth-order filter having six asymmetrically located transmission zeros.