Electroacoustic filter comprising low-pass characteristics
An electroacoustic filter has improved low-pass characteristics. The filter includes a first electroacoustic converter, an electroacoustic element and a grid structure between the converter and the element. The grid structure is acoustically active in one frequency range that lies above the acoustically active frequency range of the first electroacoustic converter.
1. An electroacoustic filter, comprising:
an acoustic track;
a first electroacoustic transducer arranged in the acoustic track, the first electroacoustic transducer being acoustically active in a frequency range around a center frequency f 1 ;
an acoustic element arranged in the acoustic track, the acoustic element being acoustically active in the frequency range around the center frequency f 1 ;
a grid structure arranged in the acoustic track between the first electroacoustic transducer and the acoustic element, wherein the grid structure is acoustically active in a frequency range around a center frequency f 2 , where f 2 >f 1 and wherein the grid structure has a grid pitch P G , which is selected in order to dissipate energy of a frequency component f>f 1 ; and
wherein the grid structure is arranged as a bulk wave conversion structure, wherein the electroacoustic filter functions using acoustic surface waves or guided bulk acoustic waves.
2. The electroacoustic filter according to claim 1 , wherein the acoustic element comprises a second electroacoustic transducer, a reflector, and/or a deflecting structure.
3. The electroacoustic filter according to claim 1 , wherein f 2 lies in a range around 2*f 1 .
4. The electroacoustic filter according to claim 1 , wherein
the first electroacoustic transducer includes an area having a grid pitch of P 1 ;
the acoustic element includes an area having the grid pitch of P 1 ; and
the grid pitch of the grid structure P G <P 1 .
5. The electroacoustic filter according to claim 4 , wherein the grid pitch of the grid structure P G comprises a pitch selected from the group consisting of a pitch P>0.5*P 1 , a pitch P>0.5*1.030*P 1 , and a pitch P>0.5*1.035*P 1 .
6. The electroacoustic filter according claim 1 , wherein the acoustic element includes split fingers having an area of split fingers having a grid pitch of P 1 , and wherein the grid pitch of the grid structure comprises a pitch selected from the group consisting of a pitch P>P 1 , a pitch P>1.030*P 1 , a pitch P>1.035*P 1 , and a pitch P>1.20*P 1 .
7. The electroacoustic filter according to claim 1 , wherein the first electroacoustic transducer, the acoustic element, and/or the grid structure is designed as fan-shaped structures of a FAN filter.
8. The electroacoustic filter according to claim 1 , wherein the grid structure comprises a metallization, a dielectric material, or recesses in the material of the acoustic track.
9. The electroacoustic filter according to claim 1 , further comprising a phase structure in the acoustic track between the first electroacoustic transducer and the grid structure and/or between the grid structure and the acoustic element, wherein the velocity of an acoustic wave in the phase structure deviates from the velocity of the acoustic wave in the acoustic track outside the phase structure.
10. An electroacoustic filter, comprising:
an acoustic track;
a first electroacoustic transducer arranged in the acoustic track, the first electroacoustic transducer being acoustically active in a frequency range around a center frequency f 1 ;
an acoustic element arranged in the acoustic track, the acoustic element being acoustically active in the frequency range around the center frequency f 1 ; and
a grid structure arranged in the acoustic track between the first electroacoustic transducer and the acoustic element, wherein the grid structure is acoustically active in a frequency range around a center frequency f 2 , where f 2 lies in a range around 2*f 1 .
11. The electroacoustic filter according to claim 10 , wherein the acoustic element comprises a second electroacoustic transducer, a reflector, and/or a deflecting structure.
12. The electroacoustic filter according to claim 10 , wherein
the grid structure is a reflecting structure and/or a bulk wave conversion structure; and
the electroacoustic filter functions using acoustic surface waves or guided bulk acoustic waves.
13. The electroacoustic filter according to claim 10 , wherein the grid structure has a grid pitch P G , which is selected in order to dissipate acoustic energy of a frequency component f>f 1 .
14. The electroacoustic filter according to claim 10 , wherein
the first electroacoustic transducer includes an area having a grid pitch of P 1 ;
the acoustic element includes an area having the grid pitch of P 1 ; and
the grid structure includes an area having a grid pitch of P G , where P G <P 1 .
15. The electroacoustic filter according to claim 14 , wherein the grid pitch P G of the grid structure comprises a pitch selected from the group consisting of a pitch P>0.5*P 1 , a pitch P>0.5*1.030*P 1 , and a pitch P>0.5*1.035*P 1 .
16. The electroacoustic filter according claim 10 , wherein the acoustic element includes an area of split fingers having a grid pitch of P 1 and wherein a grid pitch of the grid structure comprises a pitch selected from the group consisting of a pitch P>P 1 , a pitch P>1.030*P 1 , a pitch P>1.035*P 1 , and a pitch P>1.20*P 1 .
17. The electroacoustic filter according to claim 10 , wherein the first electroacoustic transducer, the acoustic element, and/or the grid structure is designed as fan-shaped structures of a FAN filter.
18. The electroacoustic filter according to claim 10 , wherein the grid structure comprises a metallization, a dielectric material, or recesses in the material of the acoustic track.
19. The electroacoustic filter according to claim 10 , further comprising a phase structure in the acoustic track between the first transducer and the grid structure and/or between the grid structure and the acoustic element, wherein the velocity of an acoustic wave in the phase structure deviates from the velocity of the acoustic wave in the acoustic track outside the phase structure.