Pseudo-elliptic dual-band filters based on TM dual-mode cavities

This paper presents possible configurations of dual band filters based on transverse magnetic (TM) Dual mode cavities. The concept is to useTMdual-mode cavities in order to design compact dual band filters. High flexibility is obtained in terms of transmission zero (TZ) positioning. By using this approach a number of TZs up to the number of poles is attainable. Zeros can be placed in both the lower and upper stop-bands as well as between the two pass-bands to increase their insulation. The use of TM cavities allows a dramatic reduction of the filter length without significantly reducing the RF performances. Two three-cavity TM dual-band filters with six symmetric and asymmetric TZs have been designed and manufactured to validate the proposed geometry.