Patent ID: 8729982

Claim:
Elementary filter of the HBAR type which is intended to operate at a predetermined operating frequency, comprising: a first resonator ( 20 , 220 ) and a second resonator ( 22 , 222 ) of the HBAR type and a coupling element ( 28 , 228 ) for electroacoustic coupling by means of overlapping of evanescent waves, the first resonator ( 20 , 220 ) and the second resonator ( 22 , 222 ) each comprising a first electrical excitation electrode ( 4 ) and a first connection element ( 14 ) and a second electrical excitation electrode ( 6 ) and a second connection element ( 16 ), respectively, the first and second electrical excitation electrodes being discrete and separated by a channel ( 18 ), a common reference electrode ( 10 ) and a common monobloc piezoelectric transducer ( 8 , 208 ), the first and second connection elements being connected to the common reference electrode ( 10 ), and wherein the elementary filter is an electric quadripole, the coupling element ( 28 , 228 ) comprising an intermediate zone ( 26 , 226 ) of the piezoelectric transducer ( 8 , 208 ) that is arranged between the first resonator and the second resonator ( 20 , 22 ; 220 , 222 ), the piezoelectric transducer ( 8 , 208 ) being constituted by a layer of a first thickness of a first material which is orientated in accordance with an angle φ defined by nomenclature (YXw)/φ of the IEEE standard Std-176 (1949 revision), and which is cut in accordance with a first cutting angle θ1 defined by nomenclature (YXl)/θ of the IEEE standard Std-176 (1949 revision), such that the electroacoustic coupling of the waves in accordance with a longitudinal mode or a transverse mode within the first material alone is greater than 5%, and wherein the first resonator ( 20 , 220 ), the second resonator ( 22 , 222 ) and the coupling element ( 28 , 228 ) comprise a common monobloc acoustic substrate ( 12 , 212 ) which is arranged facing and coupled to the piezoelectric transducer ( 8 , 208 ) by waves having the same longitudinal or transverse vibration mode through the common reference electrode ( 10 ).