Technique for designing acoustic microwave filters using LCR-based resonator models

Patent metadata

Field	Value
Publication number	US-10657305-B2
Application number	US-201916400717-A
Country	US
Kind code	B2
Filing date	May 1, 2019
Priority date	Nov 13, 2015
Publication date	May 19, 2020
Grant date	May 19, 2020

Abstract

A method for designing a narrowband acoustic wave microwave filter including: generating a modeled filter circuit design having circuit elements including an acoustic resonant element defined by an electrical circuit model that includes a parallel static branch, a parallel motional branch, and one or both of a parallel Bragg Band branch that models an upper Bragg Band discontinuity and a parallel bulk mode function that models an acoustic bulk mode loss; and generating a final circuit design. Generating the final circuit design includes optimizing the modeled filter circuit design to generate an optimized filter circuit design; comparing a frequency response of the optimized filter circuit design to requirements; selecting the optimized filter circuit design for construction into the actual acoustic microwave filter based on the comparison; and transforming the optimized filter circuit design to a design description file for input to a construction process.

First claim

What is claimed is:

1. A non-transitory computer-readable medium having stored thereon instructions that, when executed by a processing device, enable the processing device to perform a method for designing a narrowband acoustic wave microwave filter to satisfy predetermined frequency response requirements, comprising the steps of
generating a modeled filter circuit design having a plurality of circuit elements comprising an acoustic resonant element defined by an electrical circuit model that comprises a parallel static branch, a parallel motional branch, and one or both of a parallel Bragg Band branch that models an upper Bragg Band discontinuity and a parallel bulk mode function that models an acoustic bulk mode loss; and
generating a final circuit design for construction into an actual acoustic microwave filter, wherein generating said final circuit design comprises:
optimizing the modeled filter circuit design to generate an optimized filter circuit design;
comparing a frequency response of the optimized filter circuit design to the frequency response requirements;
selecting the optimized filter circuit design for construction into the actual acoustic microwave filter based on the comparison; and
transforming the optimized filter circuit design to a design description file that serves as an input to a construction process.

2. The medium of claim 1 , wherein the parallel static branch comprises a static capacitance, and the parallel motional branch comprises a motional inductance and a motional capacitance.

3. The medium of claim 1 , wherein the electrical circuit model comprises at least one resistor that models an electrical loss of the acoustic resonant element.

4. The medium of claim 1 , wherein the electrical circuit model comprises the Bragg Band branch.

5. The medium of claim 4 , wherein the Bragg Band branch comprises a series LRC circuit.

6. The medium of claim 1 , wherein the electrical circuit model comprises the parallel bulk mode function.

7. The medium of claim 6 , wherein the bulk mode function is a hyperbolic tangent function.

8. The medium of claim 7 , wherein the hyperbolic tangent function is

Y
=

h
*

(

1
-

1

10

(

freq

w
⁡

(

10
6

-

F
b

)

+
1

)

)

,

where Y is the bulk mode loss in dB; h is a scaling factor used to match the loss of the bulk mode; F b is a frequency in Hz used to match the onset frequency of the bulk mode, w is a scaling factor used to match the steepness of the onset of the bulk mode, and freq is the frequency of the input signal.

9. The medium of claim 1 , wherein the frequency response requirements comprise one or more of a frequency dependent return loss, insertion loss, rejection, and linearity.

10. The medium of claim 1 , wherein the acoustic resonant element is 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.

11. The medium of claim 1 , wherein the frequency response requirements comprise a pass band.

12. The medium of claim 11 , wherein the passband is in the 500-3500 MHz range.

13. The medium of claim 11 , wherein the passband is in the 300 MHz to 10.0 GHz range.

14. The medium of claim 11 , wherein the passband is in the 300 MHz to 300 GHz range.

15. The medium of claim 1 , wherein the modeled filter circuit design has an Nth order ladder topology.

16. The medium of claim 1 , wherein generating the modeled filter circuit design comprises:
defining a physical model of the acoustic resonant element;
simulating the physical model of the acoustic resonant element to generate a first frequency response;
simulating the electrical circuit model of the acoustic resonant element to generate a second frequency response;
comparing the first and second frequency responses; and
modifying at least one parameter in the electrical circuit model based on the comparison prior to the optimization of the modeled electrical filter circuit design.

17. The medium of claim 16 , wherein the physical model of the acoustic resonant element is simulated using a Finite Element Model (FEM).

18. The medium of claim 16 , wherein defining the physical model of the acoustic resonant element comprises selecting a parameter consisting of at least one of a material, one or more of a number of finger pairs, aperture size, mark-to-pitch ratio, and transducer metal thickness.

19. The medium of claim 16 , wherein defining the physical model of the acoustic resonant element comprises:
defining a first set of resonator characteristics for the acoustic resonant element;
simulating the physical model of the acoustic resonant element to generate a second set of resonator characteristics;
comparing the first and second sets of resonator characteristics; and
modifying at least one parameter of the physical model of the acoustic resonant element based on the comparison.

20. The medium of claim 19 , wherein each of the first and second sets of resonator characteristics comprises one or both of a resonant frequency and a static capacitance.

21. The medium of claim 20 , wherein optimizing the modeled filter circuit design comprises optimizing the one or both of a resonant frequency and a static capacitance.

22. The medium of claim 19 , wherein comparing the frequency response of the optimized filter circuit design to the frequency response requirements, comprises:
simulating the electrical circuit model of the acoustic resonant element of the optimized filter circuit design to generate a third set of resonator characteristics;
simulating the physical model of the acoustic resonant element to generate a fourth set of resonator characteristics;
comparing the third set of resonator characteristics to the fourth set of resonator characteristics;
modifying the parameter of the physical model of the acoustic resonator ba

Assignees

• Resonant Inc

Inventors

• Raihn Kurt F
• Turner Patrick J
• Fenzi Neal O

Classifications

• G06F30/36

  Circuit design at the analogue level · CPC title

• H03H9/54

  comprising resonators of piezoelectric or electrostrictive material (comprising resonators using surface acoustic waves H03H9/64) · CPC title

• G06F30/367

  Design verification, e.g. using simulation, simulation program with integrated circuit emphasis [SPICE], direct methods or relaxation methods · CPC title

• H03H9/605

  consisting of a ladder configuration · CPC title

• H03H9/6483 Primary

  Ladder SAW filters · CPC title