Bulk acoustic wave (BAW) filter having reduced second harmonic generation and method of reducing second harmonic generation in a BAW filter

• US 7,548,140 B2
• Filed: 04/16/2007
• Issued: 06/16/2009
• Est. Priority Date: 04/16/2007
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Inventors: Jamneala, Tiberiu, Bradley, Paul D.
• Primary Examiner(s): Summons; Barbara
• Application Number:
  US11/735,768
• Publication Number:
  US 20080252398A1
• Time in Patent Office: 792 Days
• Field of Search: 333/189, 333/187, 333/133, 310/357
• US Class Current: 333/189
• CPC Class Codes: H03H 9/581 comprising ceramic piezoelectric layers
• CPC Class Codes: H03H 9/60 Electric coupling means therefor H03H9/0095 takes precedence
• CPC Class Codes: H03H 9/605 consisting of a ladder configuration

Abstract

In a filter having a half-ladder structure comprising an alternating series of series branches and shunt branches, including a signal input and a signal output related to a common ground, at least one series branch or one parallel branch of the filter is configured as a BAW device comprising a first BAW resonator and a second BAW resonator connected either antiparallel or antiseries. The second harmonic emission generated by the first BAW resonator substantially cancels the second harmonic emission of the second BAW resonator and the second harmonic emission of at least one other series branch or one other parallel branch of the filter. By this method, the filter'"'"'s second harmonic emissions are reduced.

Claims

1. A filter having a half-ladder structure comprising an alternating series of series branches and shunt branches, including a signal input and a signal output related to a common ground, wherein at least one series branch or one parallel branch of the filter is configured as a BAW device comprising a first BAW resonator and a second BAW resonator connected either antiparallel or antiseries, wherein a second harmonic emission generated by the first BAW resonator substantially cancels a second harmonic emission of the second BAW resonator and a second harmonic emission of at least one other series branch or one other parallel branch of the filter.

2. The filter of claim 1, wherein a first electrode of the first BAW resonator is electrically connected to a second electrode of the second BAW resonator and to a first electrical terminal of the BAW device, and a second electrode of the first BAW resonator is electrically connected to a first electrode of the second BAW resonator and to a second electrical terminal of the BAW device, and wherein, the first and second BAW resonators have the same polarizations with regard to their first electrodes and their second electrodes.

3. The filter of claim 1, wherein a resonance frequency of the first BAW resonator and a resonance frequency of the second BAW resonator are substantially identical.

4. The filter of claim 1, wherein a capacitance of the first BAW resonator is greater than a capacitance of the second BAW resonator.

5. The filter of claim 1, wherein a series branch is configured as the BAW device, and wherein the second harmonic emission generated by the first BAW resonator substantially cancels the second harmonic emission of the second BAW resonator and a second harmonic emission of at least one other series branch of the filter.

6. The filter of claim 5, wherein the second harmonic emission generated by the first BAW resonator substantially cancels the second harmonic emission of the second BAW resonator and second harmonic emissions of all other series branches of the filter.

7. The filter of claim 5, wherein the BAW device is configured in a first series branch directly connected to the signal input.

8. The filter of claim 5, wherein the first and second BAW resonators of the BAW device are connected antiseries.

9. The filter of claim 5, wherein the first and second BAW resonators of the BAW device are connected antiparallel.

10. The filter of claim 1, wherein a shunt branch is configured as the BAW device, and wherein the second harmonic emission generated by the first BAW resonator substantially cancels the second harmonic emission of the second BAW resonator and a second harmonic emission of at least one other shunt branch of the filter.

11. The filter of claim 10, wherein the second harmonic emission generated by the first BAW resonator substantially cancels the second harmonic emission of the second BAW resonator and second harmonic emissions of all other shunt branches of the filter.

12. The filter of claim 10, wherein the BAW device is configured in a first shunt branch directly connected to the signal input.

13. The filter of claim 10, wherein the first and second BAW resonators of the BAW device are connected antiseries.

14. The filter of claim 10, wherein the first and second BAW resonators of the BAW device are connected antiparallel.

15. A method of reducing a harmonic emissions within BAW filter having a half-ladder structure comprising an alternating series of series branches and shunt branches, including a signal input and a signal output related to a common ground, the method comprising configuring at least one series branch or one parallel branch of the filter as a BAW device comprising a first BAW resonator and a second BAW resonator connected either antiparallel or antiseries, and configuring the first BAW resonator and the second BAW resonator such that a second harmonic emission generated by the first BAW resonator substantially cancels a second harmonic emission of the second BAW resonator and a second harmonic emission of at least one other series branch or one other parallel branch of the filter.

16. The method of claim 15, further comprising electrically connecting a first electrode of the first BAW resonator to a second electrode of the second BAW resonator and to a first electrical terminal of the BAW device, and electrically connecting a second electrode of the first BAW resonator to a first electrode of the second BAW resonator and to a second electrical terminal of the BAW device, wherein, the first and second BAW resonators have the same polarizations with regard to their first electrode and their second electrode.

17. The method of claim 15, further comprising configuring a series branch as the BAW device, and wherein the second harmonic emission generated by the first BAW resonator substantially cancels the second harmonic emission of the second BAW resonator and a second harmonic emission of at least one other series branch of the filter.

18. The method of claim 17, wherein the second harmonic emission generated by the first BAW resonator substantially cancels the second harmonic emission of the second BAW resonator and second harmonic emissions of all other series branches of the filter.

19. The method of claim 15, further comprising configuring a shunt branch as the BAW device, and wherein the second harmonic emission generated by the first BAW resonator substantially cancels the second harmonic emission of the second BAW resonator and a second harmonic emission of at least one other shunt branch of the filter.

20. The method of claim 19, wherein the second harmonic emission generated by the first BAW resonator substantially cancels the second harmonic emission of the second BAW resonator and second harmonic emissions of all other shunt branches of the filter.