US Patent 7915977 Tuneable bandpass filter

A tuneable bandpass filter includes a plurality of coupled resonators. A common structure of the filter includes at least one common coupling or one common resonator. An upper loop includes first and second end resonators coupled together by a signal path and further includes at least one further signal path extending between end resonators. The further signal path includes at least one further resonator with the end resonators being coupled to the common structure. A lower loop includes first and second end resonators coupled together by a signal path and further includes at least one further signal path extending between end resonators. The further signal path includes at least one further resonator with the end resonators being coupled to the common structure.