NETWORK SYNTHESIS DESIGN OF MICROWAVE ACOUSTIC WAVE FILTERS

• US 20140282311A1
• Filed: 03/14/2014
• Published: 09/18/2014
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Resonant Inc. (Murata Manufacturing Co Limited)
• Inventors: Turner, Patrick J., Silver, Richard N., Willemsen Cortes, Balam Quitze Andres, Raihn, Kurt F., Fenzi, Neal O., Hammond, Robert B.
• Granted Patent: US 8,990,742 B2
• Time in Patent Office: Days
• US Class Current: 716/104
• CPC Class Codes: G06F 30/36 Circuit design at the analogue level
• CPC Class Codes: H03H 9/46 Filters multiple-port electromechanical filters H03H9/70
• CPC Class Codes: H03H 9/465 in combination with other electronic elements
• CPC Class Codes: H03H 9/542 including passive elements H03H9/545 takes precedence
• CPC Class Codes: H03H 9/6483 Ladder SAW filters

Abstract

A method of designing an acoustic microwave filter in accordance with frequency response requirements. The method comprises selecting an initial filter circuit structure including a plurality of circuit elements comprising at least one resonant element and at least one other reactive circuit element, selecting lossless circuit response variables based on the frequency response requirements, selecting a value for each of the circuit elements based on the selected circuit response variables to create an initial filter circuit design, transforming the resonant element(s) and the other reactive circuit element(s) of the initial filter circuit design into at least one acoustic resonator model to create an acoustic filter circuit design, adding parasitic effects to the acoustic filter circuit design to create a pre-optimized filter circuit design, optimizing the pre-optimized filter circuit design to create a final filter circuit design, and constructing the acoustic microwave filter based on the final filter circuit design.

Claims

1. A method of designing an acoustic microwave filter in accordance with frequency response requirements, comprising:

selecting an initial filter circuit structure including a plurality of circuit elements comprising at least one resonant element and at least one other reactive circuit element;

selecting lossless circuit response variables based on the frequency response requirements;

selecting a value for each of the circuit elements based on the selected lossless circuit response variables to create an initial filter circuit design;

transforming the at least one resonant element and the at least one other reactive circuit element of the initial filter circuit design into at least one acoustic resonator model to create an acoustic filter circuit design;

adding parasitic effects to the acoustic filter circuit design to create a pre-optimized filter circuit design;

optimizing the pre-optimized filter circuit design to create a final filter circuit design; and

constructing the acoustic microwave filter based on the final filter circuit design.

2. The method of claim 1, wherein the frequency requirements comprises one or more of a frequency dependent return loss, insertion loss, rejection, and linearity.

3. The method of claim 1, wherein the frequency response requirements comprise a passband in 500-3500 MHz range.

4. The method of claim 1, wherein the frequency response requirements comprise a passband and a stopband.

5. The method of claim 1, wherein each of the at least one resonant element comprises a parallel L-C resonator combination of a capacitor and an inductor.

6. The method of claim 1, wherein the at least one other reactive circuit elements comprises a capacitor.

7. The method of claim 1, wherein the initial filter circuit structure is an in-line non-resonant-node circuit structure.

8. The method of claim 1, wherein the lossless circuit response variables are in the form of a ratio between numerator polynomials defining transmission zeroes and denominator polynomials defining reflection zeroes multiplied by a scale factor.

9. The method of claim 8, wherein the total number of transmission zeroes are equal to or greater than the total number of reflection zeroes.

10. The method of claim 1, wherein each of the at least one acoustic resonator model is a Butterworth-Van Dyke (BVD) model.

11. The method of claim 10, wherein one of the at least one resonator comprises an in-shunt parallel L-C resonator combination, one of the at least one other reactive circuit element comprises an in-shunt admittance inverter in series with the in-shunt parallel L-C resonator combination, and an in-shunt non-resonant susceptance in parallel with the in-shunt parallel L-C resonator combination, and wherein the in-shunt parallel L-C resonator combination, in-shunt admittance inverter, and in-shunt non-resonant susceptance are transformed into one of the at least one BVD model.

12. The method of claim 11, wherein the in-shunt parallel L-C resonator combination and the in-shunt admittance inverter are transformed into an in-shunt series L-C resonator combination, and the in-shunt series L-C resonator combination and in-shunt non-resonant susceptance are transformed into the one BVD model.

13. The method of claim 11, wherein the BVD model is an in-shunt BVD model.

14. The method of claim 13, wherein the at least one reactive circuit element further comprises two in-line admittance inverters coupled to a node between the in-shunt parallel L-C resonator combination and the in-shunt non-resonant susceptance, and wherein the in-shunt BVD model and the two in-line admittance inverters are transformed into an in-line BVD model and a reactance in series with the in-line BVD model.

15. The method of claim 1, wherein the at least one resonant element comprises a plurality of resonant elements, the at least one other reactive circuit elements comprises a plurality of reactive circuit elements, and the at least one acoustic resonator model comprises a plurality of resonator models.

16. The method of claim 15, further comprising dividing the initial filter circuit design into a plurality of sub-set circuit designs, each of which includes one of the resonant elements and one or more of the plurality of reactive circuit elements, wherein, for each sub-set circuit design, the resonant element and the one or more reactive circuit elements are transformed into a respective one of the acoustic resonator models.

17. The method of claim 1, further comprising selecting the structural type of each of the at least one resonant element from one of a surface acoustic wave (SAW) resonator, a bulk acoustic wave (BAW) resonator, a film bulk acoustic resonator (FBAR), and a microelectromechanical system (MEMS) resonator.

18. The method of claim 1, further comprising:

mapping the frequency response requirements to a normalized design space, wherein the circuit element values are normalized values that are determined based on the mapped frequency response requirements; and

unmapping the normalized circuit element values of the acoustic filter circuit design to a real design space.

19. The method of claim 1, wherein the at least one resonant element comprises a plurality of resonant elements.

20. The method of claim 19, changing the order in which the plurality of resonant elements in the pre-optimized filter circuit design are disposed along a signal transmission path to create a plurality of filter solutions;

computing a performance parameter for each of the filter solutions;

comparing the performance parameters to each other; and

selecting one of the filter solutions as the pre-optimized circuit design based on the comparison of the computed performance parameters.

21. The method of claim 1, further comprising performing an element removal optimization of the pre-optimized filter circuit design to create the final filter circuit design.

22. The method of claim 1, wherein the final circuit design comprises a plurality of acoustic resonators, and wherein the difference between the lowest resonant frequency and the highest resonant frequency of the plurality of acoustic resonators in the final filter circuit design is at least one time the maximum frequency separation of a single resonator in the plurality of acoustic resonators.

23. The method of claim 22, wherein the difference between the lowest resonant frequency and the highest resonant frequency of a plurality of resonators in the final filter circuit design is at least two times the maximum frequency separation of a single resonator in the plurality of resonators.

24. The method of claim 22, wherein the difference between the lowest resonant frequency and the highest resonant frequency of a plurality of resonators in the final filter circuit design is at least three times the maximum frequency separation of a single resonator in the plurality of resonators.

25. The method of claim 1, wherein optimizing the pre-optimized filter circuit design comprises inputting the pre-optimized filter circuit design into a filter optimizer to create the final filter circuit design.