SURFACE ACOUSTIC WAVES FILTERS WITH OPTIMISED SYMMETRY

摘要

The invention concerns a surface acoustic wave filter comprising at least an i<th> cascaded input acoustic path (VAi) to an i + 1 output acoustic path (VAi + 1), each acoustic path comprising interdigital electrode transducers and in particular: at least a central transducer (TCi); at least a pair of coupling transducers consisting of a first lateral transducer (T1Li) and a second lateral transducer (T2Li). The invention is characterised in that it comprises a first electrical connection with a first potential (V1) connecting the first lateral transducer (T1Li) of the i<th> acoustic path and a second electrical connection to a second potential (V2) connecting the second lateral transducer of the (i + 1)<th> acoustic path (T2Li+1) and the potentials are out of phase. The central transducer of the i<th> acoustic path being connected to at least an input voltage (ViN). The central transducer of the i + 1<th> acoustic path being connected to at least an output voltage (Vout). Said filter structure enables to reduce cross couplings and to obtain in differential structures very good symmetry, in the field of double mode filters.