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CN-121706503-B - 13GXBAR filter design method based on lithium niobate thin film

CN121706503BCN 121706503 BCN121706503 BCN 121706503BCN-121706503-B

Abstract

The invention relates to the technical field of radio frequency filters, in particular to a design method of a 13GXBAR filter based on a lithium niobate thin film. The Euler angle of the lithium niobate thin film is simulated and set in finite element simulation software to obtain admittance responses under different cutting angles, so that an admittance curve with a larger electromechanical coupling coefficient is obtained, meanwhile, the admittance curve with a complete suppression of stray modes is simulated by using the cutting angle, electrode materials, interdigital pairs, interdigital intervals, thin film thickness and metallization rate to obtain the impedance of each resonator, material parameters of the corresponding resonators are obtained, a three-dimensional force-electric coupling model of the lithium niobate resonator is constructed, the physical model is subjected to layout design in the finite element simulation software through a field path coupling method, the force-electric-acoustic multi-physical field coupling is carried out, the S parameter curve of the designed XBAR filter is obtained, whether the S parameter result is consistent with a target is verified, and the forward design of full simulation driving is realized.

Inventors

  • CHEN SHITAO
  • Xue Xingtong
  • Yin Qiupeng
  • WANG WEI
  • HUANG ZHIXIANG

Assignees

  • 安徽大学
  • 中国电子科技集团公司第三十八研究所

Dates

Publication Date
20260512
Application Date
20260209

Claims (10)

  1. 1. The design method of the 13GXBAR filter based on the lithium niobate thin film is characterized by comprising the following steps: Step S1, crystal tangential optimization, in which parameterized scanning and optimization are carried out on the Euler angle of the crystal of the lithium niobate thin film in finite element simulation software, so that the optimal electromechanical coupling coefficient is obtained in a target frequency band, and the spurious mode is completely inhibited as a judgment basis, and the crystal tangential direction is determined; Step S2, structural parameter determination, namely establishing a three-dimensional model of the XBAR resonator in finite element simulation software based on the determined crystal tangential direction, carrying out parameterization simulation on electrode materials, interdigital structural parameters and film thickness, and determining an optimal structural parameter combination meeting the requirement of a target center frequency; s3, finite element modeling and verification, namely constructing a three-dimensional force-electric coupling finite element model of the XBAR resonator by utilizing the optimal structural parameter combination, obtaining complex impedance data of the XBAR resonator along with the change of frequency through frequency domain solving, and verifying the accuracy of the model; S4, acoustic-electric-magnetic joint simulation, namely calculating the complex impedance data of the resonator obtained in the step S3 through an equivalent dielectric constant formula to obtain an equivalent relative dielectric constant changing along with frequency, constructing a layout model of the XBAR filter in three-dimensional electromagnetic simulation software, importing the calculated equivalent dielectric constant into the material property of the piezoelectric layer in the model, performing acoustic-electric-magnetic joint simulation, obtaining the S parameter of the filter, and verifying and optimizing the design according to the simulation result.
  2. 2. The method for designing a 13GXBAR filter based on a lithium niobate thin film according to claim 1, wherein the finite element simulation software is COMSOL Multiphysics.
  3. 3. The method for designing a 13GXBAR filter based on a lithium niobate thin film according to claim 1, wherein the euler angle is determined by: And rotating an X axis to an N axis by taking a primary crystal axis Z as a rotating axis, rotating a Z axis to an X3 axis by taking N as a rotating axis, rotating an N axis to an X1 axis by taking X3 as a rotating axis, at the moment, enabling a Y axis to reach an X2 axis position to obtain a new crystal coordinate system (X1, X2 and X3), carrying out parameterization scanning on Euler angles in a preset range in finite element simulation software, simulating to obtain an admittance frequency response curve of the XBAR resonator under each Euler angle combination, extracting series resonance frequency and parallel resonance frequency from each admittance curve, calculating corresponding electromechanical coupling coefficients according to a formula, taking Euler angles meeting preset conditions as candidates, obtaining candidate Euler angles, and selecting a combination with the largest electromechanical coupling coefficient from the candidate Euler angles as an optimal Euler angle.
  4. 4. The method for designing a 13GXBAR filter based on a lithium niobate thin film according to claim 3, wherein the electromechanical coupling coefficient is calculated by the following formula: ; Wherein, the Representing the coefficient of electromechanical coupling, Representing the parallel resonant frequency of the antenna, Representing the series resonant frequency.
  5. 5. The method for designing a 13GXBAR filter based on a lithium niobate thin film according to claim 3, wherein the preset conditions are specifically: and for the admittance frequency response curve corresponding to each Euler angle combination, in the target frequency band, the amplitude of all stray resonance modes is lower than the amplitude of the main resonance peak by a preset inhibition threshold value.
  6. 6. The method of claim 1, wherein the interdigital parameters include interdigital width, interdigital distance, interdigital logarithm, and metallization ratio.
  7. 7. The method for designing a 13GXBAR filter based on a lithium niobate thin film according to claim 1, wherein the three-dimensional force-electric coupling finite element model includes a solid mechanical physical field, an electrostatic physical field and a piezoelectric effect module.
  8. 8. The method for designing the 13GXBAR filter based on the lithium niobate thin film according to claim 1, wherein the three-dimensional force-electric coupling model is constructed by selecting aluminum as an electrode material, using the lithium niobate thin film as a piezoelectric material, deriving the density, relative dielectric constant, coupling matrix, elastic matrix, poisson ratio and Young's modulus of the material from a belt material library in finite element simulation software, manually inputting the elastic matrix of the lithium niobate, and setting boundary conditions of a solid mechanical physical field, an electrostatic physical field and a piezoelectric effect module.
  9. 9. The method for designing a 13GXBAR filter based on a lithium niobate thin film according to claim 1, wherein the three-dimensional electromagnetic simulation software is ANSYS HFSS.
  10. 10. The method for designing a 13GXBAR filter based on a lithium niobate thin film according to claim 1, wherein the equivalent dielectric constant formula is: ; Wherein, the Indicating the equivalent relative dielectric constant of the dielectric, The area of the active region is indicated, Indicating the thickness of the piezoelectric layer, The dielectric constant of the vacuum is indicated, The impedance is represented by a value representing the impedance, Which represents the angular frequency of the light emitted by the light source, Representing imaginary units.

Description

13GXBAR filter design method based on lithium niobate thin film Technical Field The invention relates to the technical field of radio frequency filters, in particular to a design method of a 13GXBAR filter based on a lithium niobate thin film. Background With the rapid development of wireless communication systems, from early 2G, 3G and 4G networks to the current new generation mobile communication networks, communication spectrum resources are increasingly tense, frequency band allocation is increasingly complex, performance requirements on a radio frequency front-end filter are continuously improved, and a radio frequency acoustic wave filter with high frequency and large bandwidth becomes a research hotspot in the field. The XBAR resonator has received a lot of attention in the design of acoustic wave resonators due to the combination of the advantages of bulk acoustic wave and surface acoustic wave. Lithium niobate (LiNbO 3) has stronger piezoelectric effect and higher coupling coefficient than aluminum nitride (AlN) by means of ion cutting novel film transfer technology, is expected to realize an ultra-large bandwidth filter, and can obtain a high quality factor by utilizing the mode isolation and energy limitation characteristics of a release mechanical structure of the ultra-large bandwidth filter, so that an XBAR resonator based on a lithium niobate film becomes an important research direction of a radio frequency front end of wireless communication. The existing filter design method has the obvious defects that the design process depends on process manufacturing, a resonator model parameter library covering different film materials, thicknesses, structures and different working frequencies is required to be established through a large number of flow sheets and tests, the time consumption is long, the design efficiency is low, the process manufacturing cost is high, in addition, the filter manufactured through the equivalent model fitting process has reliability and poor robustness only for the filter manufactured by the same material, and once the material is replaced, a large number of fitting works are required to be carried out again. Disclosure of Invention The invention aims to provide a 13GXBAR filter design method based on a lithium niobate thin film, so as to solve the problems in the prior art. In order to achieve the above purpose, the invention aims to provide a design method of a 13GXBAR filter based on a lithium niobate thin film, which comprises the following steps of S1, crystal tangential optimization, wherein in finite element simulation software, parameterized scanning and optimization are carried out on the Euler angle of the crystal of the lithium niobate thin film so as to obtain an optimal electromechanical coupling coefficient in a target frequency band, and spurious modes are completely inhibited as judgment basis, so that the crystal tangential direction is determined. And S2, determining structural parameters, namely establishing a three-dimensional model of the XBAR resonator in finite element simulation software based on the determined crystal tangential direction, carrying out parameterization simulation on electrode materials, interdigital structural parameters and film thickness, and determining an optimal structural parameter combination meeting the requirement of a target center frequency. And S3, finite element modeling and verification, namely constructing a three-dimensional force-electric coupling finite element model of the XBAR resonator by utilizing the optimal structural parameter combination, obtaining complex impedance data of the XBAR resonator along with the change of frequency through frequency domain solving, and verifying the accuracy of the model. S4, acoustic-electric-magnetic joint simulation, namely calculating the complex impedance data of the resonator obtained in the step S3 through an equivalent dielectric constant formula to obtain an equivalent relative dielectric constant changing along with frequency, constructing a layout model of the XBAR filter in three-dimensional electromagnetic simulation software, importing the calculated equivalent dielectric constant into the material property of the piezoelectric layer in the model, performing acoustic-electric-magnetic joint simulation, obtaining the S parameter of the filter, and verifying and optimizing the design according to the simulation result. As a further improvement of the technical scheme, the finite element simulation software is COMSOL Multiphysics. The method comprises the steps of taking a primary crystal axis Z as a rotation axis, rotating an X axis to an N axis, taking N as a rotation axis, rotating a Z axis to an X3 axis, taking X3 as a rotation axis, rotating the N axis to an X1 axis, enabling a Y axis to reach an X2 axis position at the moment, obtaining a new crystal coordinate system (X1, X2 and X3), carrying out parameterization scanning on Euler angles in a preset range i