Double mode symmetric filter for mobile telephone, has two pairs of coupling transducers each in one acoustic path, where transducers of each path are respectively coupled between opposite polarities of input and output voltages

摘要

The filter has two acoustic paths (VA1, VA2) each with a central transducer (TC1, TC2), and a pair of coupling transducers (T1L2, T2L2). The acoustic paths are coupled in parallel to a non-differential input and output, and the acoustic paths are in series to the differential input and output. Coupling transducers of the two paths are respectively connected between the opposite polarities of input and output voltages.