An RF signal filter includes an elongate block of dielectric material having a transmit electrode, an antenna electrode and an array of spaced resonators extending between the transmit electrode to the antenna electrode. A signal trap resonator is positioned adjacent to the transmit electrode but opposite...http://www.google.com/patents/US6570467?utm_source=gb-gplus-sharePatent US6570467 - Cost effective dual-mode shiftable dielectric RF filter and duplexer
