Resonator filter working with surface acoustic waves

A filter working with surface acoustic waves and constructed as a resonator filter, the filter comprising:

• a first sub-filter;
• and
• a second sub-filter interconnected with the first sub-filter;
• wherein the filter has a transfer function with a phase rotation of at least 400° within a passband;
• wherein the first and second sub-filters both have a passband that is narrower than a passband, of the resonator filter;
• wherein the first and second sub-filters each, have at least three or more terminal transducers, and wherein the three or more terminal transducers comprise at least one input transducer and at least two output transducers, or wherein the three or more terminal transducers comprise at least two input transducers and at least one output transducer;
• wherein each sub-filter is divided into first and second acoustic tracks;
• wherein the terminal transducers of the at least three or more terminal transducers located in each first track are input transducers;
• wherein the terminal transducers of the at least three or more terminal transducers located in each second track are output transducers;
• wherein each terminal transducer of the first and second tracks are arranged between two coupler transducers;
• and
• wherein the first and the second tracks are electrically connected in series by connecting corresponding coupler transducers.