Surface acoustic wave band-pass filter, design method thereof and electronic equipment

Abstract

The invention discloses a surface acoustic wave band-pass filter, a design method thereof and electronic equipment, and the method comprises the steps: determining a first structure parameter of a resonator, and determining a second structure parameter which comprises the piezoelectric material and thickness of a piezoelectric film; extracting a first relation and a second relation related to the in-plane transmission directions of the resonators; building a target filter based on the first relation and the second relation; the target filter comprises a basic resonator group and a compensation resonator group, the frequency temperature coefficient of the basic resonator group at the center frequency of the filter is zero, and the frequency temperature coefficient of the compensation resonator group at the transmission zero point is zero; and if the frequency temperature coefficient of the detected target filter is not zero, returning to the step of determining the second structure parameter until the frequency temperature coefficient of the detected target filter is zero. Through interaction of the resonators, it is guaranteed that the passband range of the filter does not change along with temperature change, and the band-pass filter with the frequency temperature coefficient being zero is achieved.

Description

Technical Field

[0001] The present application relates to the field of communication technology, and in particular to a surface acoustic wave bandpass filter, a design method thereof, and an electronic device. Background Art

[0002] Temperature Coefficient of Frequency (TCF) is a key indicator for measuring filter performance, especially in radio frequency (RF) systems, where it indicates the degree to which the filter characteristic frequency changes with temperature. The characteristic frequency points are generally the center frequency point, the frequency point at which the high-band edge of the S21 parameter is attenuated by 3dB, and the frequency point at which the low-band edge is attenuated by 3dB. In frequency bands below 3G, due to the tight spectrum resources, operators need more efficient spectrum utilization and more stable RF performance to maintain network quality, which requires a lower TCF value to ensure the stability of the filter at different temperatures, thereby ensuring the reliability and consistency of communication systems or electronic equipment in temperature fluctuation environments.

[0003] Traditional bandpass filters are composed of cascaded resonator units arranged in a specific topological structure. In related technologies, filters mainly reduce the TCF of the resonator as much as possible by changing the substrate structure, so as to achieve the purpose of reducing the TCF of the filter. However, the TCF of the resonant frequency and anti-resonant frequency of the resonator cannot be zero at the same time, and the TCF of the resonator will also change with the change of wavelength. Therefore, even if the TCF of the resonator is reduced as much as possible by changing the substrate structure, it is difficult to achieve a passband that does not change with temperature. Summary of the invention

[0004] In view of at least one technical problem in the prior art, the purpose of the present application is to provide a surface acoustic wave bandpass filter, a preparation method thereof, and an electronic device.

[0005] In order to solve the above technical problems, on the one hand, the present application provides a design method of a surface acoustic wave bandpass filter, wherein the surface acoustic wave bandpass filter is composed of a plurality of resonators, wherein the resonator includes an electrode layer, a piezoelectric film and a supporting substrate, and the method includes:

[0006] Determining first structural parameters, wherein the first structural parameters include a substrate material of the support substrate, an electrode material and a thickness of the electrode layer;

[0007] Determining second structural parameters, wherein the second structural parameters include piezoelectric material and thickness of the piezoelectric film;

[0008] Based on the first structural parameter and the second structural parameter, forming a plurality of resonators;

[0009] Extract the first relationship and the second relationship related to the in-plane transmission direction of each resonator, the first relationship is used to characterize the relationship between the in-plane transmission direction of the resonator and the temperature coefficient of frequency TCF, and the second relationship is used to characterize the in-plane transmission direction of the resonator and the resonant frequency and electromechanical coupling coefficient K of the resonator 2 the relationship between;

[0010] Based on the first relationship and the second relationship, a target filter is constructed; the target filter includes a basic resonator group and a compensation resonator group, the frequency temperature coefficient of the basic resonator group at the center frequency of the filter is zero, and the frequency temperature coefficient of the compensation resonator group at the transmission zero point is zero;

[0011] If the frequency temperature coefficient of the target filter is detected to be zero, the target filter is determined as the surface acoustic wave bandpass filter of the final design;

[0012] If the frequency temperature coefficient of the target filter is not zero, return to the step of determining the second structural parameter until the frequency temperature coefficient of the target filter is zero, and determine the filter with a frequency temperature coefficient of zero as the final designed surface acoustic wave bandpass filter.

[0013] In some embodiments, the basic resonator group includes a first series resonator and a first parallel resonator;

[0014] The first series resonator is a resonator selected from the plurality of resonators and having a resonance frequency point of zero, and the first parallel resonator is a resonator selected from the plurality of resonators and having an anti-resonance frequency point of zero.

[0015] In some embodiments, building a target filter based on the first relationship and the second relationship includes:

[0016] Based on the first relationship and the second relationship, adjusting the resonator parameters of each of the resonators to obtain an adjusted resonator;

[0017] Select the basic resonator group from the adjusted resonators to build an initial filter; calculate the anti-resonance frequency f of the first series resonator within the operating temperature range of the initial filter. p1 The maximum offset Δ p1 ; and the resonant frequency f of the first parallel resonator s2 The maximum offset Δ s2 ;

[0018] Based on the maximum offset Δ p1 and the maximum offset Δ s2 , determining the compensating resonator group from the adjusted resonators;

[0019] The initial filter is adjusted based on the compensating resonator group to construct the target filter.

[0020] In some embodiments, the compensation resonator group includes a second series resonator and a second parallel resonator;

[0021] The second series resonator is a resonator selected from the plurality of resonators and having an anti-resonance frequency point of zero, and the anti-resonance frequency f of the second series resonator is p3 is less than or equal to the anti-resonance frequency f of the first series resonator p1 With the maximum offset Δ p1 The anti-resonance frequency f of the second series resonator p3 is less than the anti-resonance frequency f of the first series resonator p1；

[0022] The second parallel resonator is a resonator selected from the plurality of resonators and having a resonance frequency point of zero, and the resonance frequency f of the second parallel resonator is s4 is greater than the resonant frequency f of the second series resonator s2 and the maximum offset Δ s2 sum.

[0023] In some embodiments, the compensating resonator group further satisfies:

[0024] The anti-resonance frequency f of the first parallel resonator p2 <The resonant frequency f of the second parallel resonator s3 <The anti-resonance frequency f of the second series resonator p3 ;

[0025] The resonant frequency f of the first series resonator s1 >The anti-resonance frequency f of the second parallel resonator p4 >The resonant frequency f of the second parallel resonator s4 .

[0026] In some embodiments, the number of the second series resonators is one or more, and the number of the second parallel resonators is one or more;

[0027] The number of the second series resonators is the same as or different from the number of the second parallel resonators.

[0028] In some embodiments, the resonator satisfies at least one of the following:

[0029] The piezoelectric material of the piezoelectric film is lithium tantalate or lithium niobate;

[0030] The thickness of the piezoelectric film ranges from 150 nm to 1.5 μm;

[0031] The crystal cut of the piezoelectric film is X-cut, and the corresponding Euler angle is (90°, 90°, γ), where 150°<γ<180° or 20°<γ<60°; or rotated Y-cut, and the corresponding Euler angle is (0, β, 0), where β ranges from 30° to 90°; or Z-cut, and the corresponding Euler angle is (α, 0, 0), where α is an arbitrary angle;

[0032] The support substrate is a high acoustic velocity support substrate, and the material of the support substrate includes one of silicon, quartz, silicon carbide, sapphire, and diamond;

[0033] The electrode layer material includes at least one metal material selected from the group consisting of aluminum, tungsten, chromium, titanium, copper, silver and gold;

[0034] The electrode layer is composed of a parallel arranged interdigital electrode array and a reflective grating array on the left and right sides. The in-plane transmission direction θ of the interdigital electrode array ranges from -90° to 90°.

[0035] In some embodiments, the resonator further includes a dielectric layer, wherein the dielectric layer is located between the piezoelectric film and the supporting substrate, and / or the dielectric layer covers the piezoelectric film and the electrode layer.

[0036] On the other hand, the present application also provides a surface acoustic wave bandpass filter, which is prepared by any of the methods described above.

[0037] On the other hand, the present application also provides an electronic device, which includes the surface acoustic wave bandpass filter described above.

[0038] A surface acoustic wave bandpass filter, a design method thereof, and an electronic device of the present application have at least the following beneficial effects:

[0039] The filter design method of the embodiment of the present application utilizes the change characteristics of the frequency temperature coefficient TCF of the resonator with the film thickness, wavelength, and in-plane transmission direction, selects appropriate parameters, and allows the resonators to interact with each other on the same substrate to ensure that the passband range of the filter does not change with temperature changes, thereby realizing a bandpass filter with a frequency temperature coefficient TCF = 0. In addition, the present invention does not require additional process steps, and retains the advantages of small size and easy integration of the surface acoustic wave filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1a is a schematic structural diagram of a surface acoustic wave bandpass filter provided in an embodiment of the present application;

[0042] Figure 1b It is a schematic structural diagram of an electrode layer in a surface acoustic wave bandpass filter provided in an embodiment of the present application;

[0043] Figure 1c is a schematic structural diagram of another surface acoustic wave bandpass filter provided in an embodiment of the present application;

[0044] Figure 1d is a schematic structural diagram of another surface acoustic wave bandpass filter provided in an embodiment of the present application;

[0045] Figure 2 It is a flow chart of a design method of a surface acoustic wave bandpass filter provided in an embodiment of the present application;

[0046] Figure 3a A schematic diagram of a topological structure of a seventh-order surface acoustic wave ladder filter in the related art;

[0047] Figure 3b yes Figure 3a Schematic diagram of the relationship between the S-parameter response of the surface acoustic wave ladder filter and the resonator;

[0048] Figure 4 It is a schematic diagram of the structure of an 11th-order surface acoustic wave filter designed in an embodiment of the present application;

[0049] Figure 5a is the temperature coefficient TCF of the resonator wavelength λ and the anti-resonance frequency measured in the embodiment of the present application p relationship;

[0050] Figure 5b is the relationship between the measured in-plane rotation direction θ of the resonator and the temperature coefficient of frequency TCF of the resonator provided in the embodiment of the present application;

[0051] Figure 5c The measured in-plane rotation direction θ of the resonator provided in the embodiment of the present application and the resonant frequency and electromechanical coupling coefficient K of the resonator are 2 the relationship between;

[0052] Figure 6It is a schematic diagram of the process of the design method of the surface acoustic wave bandpass filter provided in an embodiment of the present application;

[0053] Figure 7a is the S parameter response of the surface acoustic wave bandpass filter provided in the embodiment of the present application and its corresponding resonator admittance response;

[0054] Figure 7b It is the S21 response of the surface acoustic wave bandpass filter under different temperature offsets ΔT provided in the embodiments of the present application. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0056] The "one embodiment" or "embodiment" referred to below refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. In the description of the present invention, unless otherwise clearly specified and limited, the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "top", "bottom", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Moreover, the terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein.

[0057] It should be understood that when describing the structure of a component, when a layer or a region is referred to as being located "on" or "above" another layer or another region, it may mean that it is directly located on the other layer or another region, or that other layers or regions are included between it and the other layer or another region. Moreover, if the component is turned over, the layer or a region will be located "below" or "beneath" another layer or another region.

[0058] First, in order to facilitate understanding, some terms involved in the present invention are explained.

[0059] TCF: Temperature coefficient of frequency, T0 is the base (reference) temperature point, generally room temperature.

[0060] Resonance frequency f s : The maximum point of the admittance curve. Wherein, admittance is the reciprocal of impedance.

[0061] Anti-resonance frequency f p : The minimum point of the admittance curve, the frequency is higher than the resonance point.

[0062] Electromechanical coupling coefficient K 2 : Used to describe the anti-resonance frequency f p With the resonant frequency f s The relative spacing between the two. The electromechanical coupling coefficient is expressed as: k t 2 =((f p / f s )^2-1)*π^2 / 8.

[0063] Traditional bandpass filters are composed of cascaded resonator units arranged in a specific topological structure. In related technologies, filters mainly reduce the TCF of the resonator as much as possible by changing the substrate structure, so as to achieve the purpose of reducing the TCF of the filter. However, the TCF of the resonant frequency and anti-resonant frequency of the resonator cannot be zero at the same time, and the TCF of the resonator will also change with the change of wavelength. Therefore, even if the TCF of the resonator is reduced as much as possible by changing the substrate structure, it is difficult to achieve a passband that does not change with temperature.

[0064] The present invention proposes a surface acoustic wave bandpass filter and a design method and electronic device thereof, wherein the design method utilizes the change characteristics of the resonator TCF with the film thickness, wavelength, and in-plane transmission direction, selects appropriate parameters, and allows the resonators to interact with each other on the same substrate to ensure that the passband range of the filter does not change with temperature changes, thereby realizing a bandpass filter with a frequency temperature coefficient TCF = 0. In addition, the present invention does not require additional process steps, and retains the advantages of the surface acoustic wave filter of small size and easy integration.

[0065] The present application provides a design method for a surface acoustic wave bandpass filter, wherein the surface acoustic wave bandpass filter is composed of a plurality of resonators. Figure 1a As shown, the resonator includes an electrode layer 100, a piezoelectric film 200 and a supporting substrate 300 from top to bottom. Figure 1b As shown, the electrode layer 100 is composed of a parallel arranged interdigital electrode array 110 (IDT electrode array) and a reflective grating array 120 on the left and right sides. The in-plane transmission direction θ of the interdigital electrode array 110 ranges from -90° to 90°.

[0066] Figure 2 is a flow chart of a method for designing a surface acoustic wave bandpass filter provided in an embodiment of the present application, Figure 6 Schematic diagram of the process of designing a surface acoustic wave bandpass filter provided in an embodiment of the present application. Figure 2 and Figure 6 As shown, the design method of the surface acoustic wave bandpass filter includes:

[0067] Step S202, determining first structural parameters, where the first structural parameters include the substrate material of the support substrate, and the electrode material and thickness of the electrode layer.

[0068] Optionally, before determining the first structural parameters, the target of the surface acoustic wave bandpass filter can be determined first, and the target is the design index requirement of the filter, for example, including but not limited to the center frequency, the use bandwidth, the insertion loss, etc. Then, based on the target of the filter, the first structural parameters of each resonator are determined. The first structural parameters include the substrate material of the support substrate 300, the electrode material and thickness of the electrode layer 100.

[0069] As an example only, the material of the support substrate 300 may include one of silicon, quartz, silicon carbide, sapphire, and diamond. Preferably, in the embodiment of the present application, a high acoustic velocity support substrate is selected as the support substrate of the resonator, and the acoustic velocity of the high acoustic velocity support substrate needs to be higher than the acoustic velocity of the target acoustic wave mode in the pressure point film, so as to constrain the acoustic field energy in the piezoelectric film acoustic waveguide.

[0070] As an example only, the electrode layer material includes at least one metal material selected from aluminum, tungsten, chromium, titanium, copper, silver and gold. The thickness of the electrode layer may include but is not limited to any value in the range of 80-150 nm. Specifically, the electrode layer may be aluminum with a thickness of 120 nm.

[0071] In practical applications, according to the goal of the filter, the substrate material of the supporting substrate, the electrode material and thickness of the electrode layer can be selected as a set of first structural parameters of the resonator, and the number of the first structural parameters can be multiple groups. In subsequent operations, multiple groups of first structural parameters can be selected to respectively make multiple resonators, so as to facilitate the subsequent selection of appropriate resonators to cascade to form a filter.

[0072] Of course, in some embodiments, such as Figure 1cAs shown, the resonator further includes a dielectric layer 400, the dielectric layer 400 is located between the piezoelectric film 200 and the supporting substrate 300, and / or the dielectric layer 400 covers the piezoelectric film 200 and the electrode layer 100. In this case, the first structural parameter may also include the material of the dielectric layer. As an example only, the material of the dielectric layer 400 may include SiO x 、SiN x At least one of the high resistivity materials such as , Al2O3, etc.

[0073] Of course, in some embodiments, such as Figure 1d As shown, the pressure point film at the location of the resonator is suspended, that is, a suspended resonator is formed. At this time, the suspended support substrate is used as a support and does not limit the energy of the sound field, so there is no need to deliberately select a material with a high sound velocity as the support substrate. The support substrate may include but is not limited to one of silicon, quartz, silicon carbide, sapphire, and diamond. For the convenience of the process, silicon can be used as the support substrate.

[0074] Step S204: determining second structural parameters, where the second structural parameters include the piezoelectric material and thickness of the piezoelectric film.

[0075] Optionally, after determining the first structural parameters, the second structural parameters of each resonator are determined according to the target of the filter. The second structural parameters may include the piezoelectric material and thickness of the piezoelectric film. Similar to the first structural parameters, the number of the second structural parameters may be multiple groups. In subsequent operations, multiple groups of second structural parameters may be selected to respectively manufacture multiple resonators, so as to facilitate the subsequent selection of suitable resonators to cascade to form a filter.

[0076] As an example only, the piezoelectric material of the piezoelectric film 200 is lithium tantalate (LiTaO 3 ) or lithium niobate (LiNbO 3 ).

[0077] As an example only, the thickness of the piezoelectric film 200 is in the range of 150 nm to 1.5 μm.

[0078] Of course, in some embodiments, the second structural parameter may also include the crystal cut of the piezoelectric film. As an example only, the crystal cut of the piezoelectric film is an X cut, and the corresponding Euler angle is (90°, 90°, γ), where 150°<γ<180° or 20°<γ<60°; or a rotated Y cut, and the corresponding Euler angle is (0, β, 0), where β ranges from 30° to 90°; or a Z cut, and the corresponding Euler angle is (α, 0, 0), where α is an arbitrary angle.

[0079] Step S206: forming a plurality of resonators based on the first structural parameters and the second structural parameters.

[0080] Optionally, based on the above determined multiple groups of first structural parameters and second structural parameters, multiple resonators are prepared respectively. The first structural parameters and / or the second structural parameters in the multiple resonators are at least partially different.

[0081] Step S208, extracting a first relationship and a second relationship related to the in-plane transmission direction of each resonator, wherein the first relationship is used to characterize the relationship between the in-plane transmission direction of the resonator and the temperature coefficient of frequency TCF, and the second relationship is used to characterize the relationship between the in-plane transmission direction of the resonator and the resonant frequency and electromechanical coupling coefficient K of the resonator. 2 The relationship between.

[0082] Figure 3a It is a schematic diagram of the topological structure of a seventh-order surface acoustic wave ladder filter in the related art. Figure 3b yes Figure 3a Schematic diagram of the relationship between the S-parameter response of the surface acoustic wave ladder filter and the resonator. Figure 3a and Figure 3b It can be seen that the resonant frequency f of the series resonator Z1 s1 and the anti-resonance frequency f of the parallel resonator Z2 p2 They determine the upper and lower transmission zero positions of the filter respectively; the anti-resonance frequency f of the series resonator Z1 p1 and the resonant frequency f of the parallel resonator Z2 s2 Together they determine the center frequency of the filter.

[0083] Figure 5a is the relationship between the measured resonator wavelength λ and the temperature coefficient of frequency TCFp of the antiresonance frequency; Figure 5b is the measured relationship between the in-plane rotation direction θ of the resonator and the temperature coefficient of frequency TCF of the resonator (λ = 2.4 μm); Figure 5c is the measured in-plane rotation direction θ of the resonator and the resonant frequency and electromechanical coupling coefficient K of the resonator 2 In this embodiment, the supporting substrate is Y42°500nm LiTaO3 film / 500nm SiO2 / Si, and the IDT electrode is a 120nm Al electrode. Figure 5a and Figure 5b It can be seen that the in-plane transmission direction θ affects the TCF of the resonator, which has a great influence on the subsequent selection of resonators Z1, Z2, Z3 and Z4. Figure 5c It can be seen that when the resonator parameters such as wavelength remain unchanged, changing the in-plane transmission direction θ will also affect the resonant frequency and K of the resonator. 2 , which has an impact on the center frequency, bandwidth, etc. of the filter, so it needs to be extracted for conventional design.

[0084] In order to subsequently construct a filter that meets the design requirements, we first extract the first relationship and the second relationship related to the in-plane transmission direction of each resonator prepared in step S206. The first relationship is used to characterize the relationship between the in-plane transmission direction of the resonator and the frequency temperature coefficient TCF, and the second relationship is used to characterize the relationship between the in-plane transmission direction of the resonator and the resonant frequency and electromechanical coupling coefficient K of the resonator. 2 The relationship between.

[0085] Step S110, building a target filter based on the first relationship and the second relationship; the target filter includes a basic resonator group and a compensation resonator group, the frequency temperature coefficient of the basic resonator group at the center frequency of the filter is zero, and the frequency temperature coefficient of the compensation resonator group at the transmission zero point is zero.

[0086] In some embodiments, the basic resonator group includes a first series resonator and a first parallel resonator; the first series resonator is a resonator with a resonant frequency point of zero selected from the multiple resonators, and the first parallel resonator is a resonator with an anti-resonant frequency point of zero selected from the multiple resonators.

[0087] In some embodiments, building a target filter based on the first relationship and the second relationship includes:

[0088] Based on the first relationship and the second relationship, adjusting the resonator parameters of each of the resonators to obtain an adjusted resonator;

[0089] Selecting the basic resonator group from the adjusted resonators to build an initial filter;

[0090] Calculate the anti-resonance frequency f of the first series resonator within the initial filter operating temperature range. p1 The maximum offset Δ p1 ; and the resonant frequency f of the first parallel resonator s2 The maximum offset Δ s2 ;

[0091] Based on the maximum offset Δ p1 and the maximum offset Δ s2 , determining the compensating resonator group from the adjusted resonators;

[0092] The initial filter is adjusted based on the compensating resonator group to construct the target filter.

[0093] In some embodiments, the compensation resonator group includes a second series resonator and a second parallel resonator;

[0094] The second series resonator is a resonator selected from the plurality of resonators and having an anti-resonance frequency point of zero, and the anti-resonance frequency f of the second series resonator is p3 is less than or equal to the anti-resonance frequency f of the first series resonator p1 With the maximum offset Δ p1 The anti-resonance frequency f of the second series resonator p3 is less than the anti-resonance frequency f of the first series resonator p1 ;

[0095] The second parallel resonator is a resonator selected from the plurality of resonators and having a resonance frequency point of zero, and the resonance frequency f of the second parallel resonator is s4 is greater than the resonant frequency f of the second series resonator s2 and the maximum offset Δ s2 sum.

[0096] Generally speaking, the maximum offset = TCF of the resonator * change in operating temperature. For example, if a resonator is measured with TCFs = 10ppm / K, TCFp = -5ppm / K, the resonant frequency measured at room temperature (20°C) is fs, the anti-resonant frequency is fp, and the operating temperature is 25°C ~ 85°C, then the resonator's Δs = TCFs / 1000000*fs*60 (positive number), Δp = TCFp / 1000000*fp*60 (negative number).

[0097] The above maximum offset Δ p1 and the maximum offset Δ s2 It can be positive or negative. The frequency point will be left / right deviated due to temperature (TCF<0 / TCF>0 of the resonator). Here, the second series resonator Z3 and the second parallel resonator Z4 ensure that the innermost transmission zero of the filter does not move. Therefore, when designing, it is necessary to ensure that the transmission zero provided by the first series resonator Z1 and the first parallel resonator Z2 is not closer to the filter passband than the transmission zero provided by the second series resonator Z3 and the second parallel resonator Z4.

[0098] The TCF of the resonator is related to the substrate material and the film thickness. When these structural parameters are determined by the first structural parameter and the second structural parameter, changing the in-plane transmission direction can also change the TCF. By adjusting the resonator parameters such as the in-plane transmission direction and the resonator wavelength, a resonator that meets the TCF and frequency requirements can be obtained, that is, the adjusted resonator. Subsequently, appropriate basic resonator groups and compensation resonator groups can be selected from the adjusted resonator to build the target filter.

[0099] In general, the center frequency of the filter is determined by the first series resonator Z1 and the first parallel resonator Z2, and the anti-resonance frequency f of the second parallel resonator is p4 and the resonant frequency f of the second parallel resonator s3 Generally, the performance within the passband is not greatly affected. However, for the sake of rigor, in some embodiments, the compensation resonator group also satisfies:

[0100] The anti-resonance frequency f of the first parallel resonator p2 <The resonant frequency f of the second parallel resonator s3 <The anti-resonance frequency f of the second series resonator p3 ;

[0101] The resonant frequency f of the first series resonator s1 >The anti-resonance frequency f of the second parallel resonator p4 >The resonant frequency f of the second parallel resonator s4 .

[0102] Step S112: if the frequency temperature coefficient of the target filter is detected to be zero, the target filter is determined as the finally designed surface acoustic wave bandpass filter.

[0103] Optionally, after constructing the target filter, it is detected whether the temperature coefficient of frequency TCF of the target filter is zero. If the detection result is yes, indicating that the designed target filter is a zero temperature drift filter, the target filter is determined as the final designed surface acoustic wave bandpass filter. If the detection result is no, the subsequent step S114 is executed.

[0104] Step S114, if the frequency temperature coefficient of the target filter is not zero, return to the step of determining the second structural parameter until the frequency temperature coefficient of the target filter is zero, and determine the filter with a frequency temperature coefficient of zero as the final designed surface acoustic wave bandpass filter.

[0105] Optionally, if the frequency temperature coefficient TCF of the target filter is not zero, which indicates that the designed target filter is not a zero temperature drift filter, the step of determining the second structural parameters is returned, that is, the second structural parameters need to be redetermined to redesign the filter, that is, step S204 and subsequent steps are repeated until the frequency temperature coefficient of the target filter is detected to be zero, and the filter with a frequency temperature coefficient of zero is determined as the final designed surface acoustic wave bandpass filter.

[0106] In practical applications, when the piezoelectric film and material selection are not good, it may be difficult to find a suitable resonator in the transmission direction of the rotating plane, and it is impossible to build a filter with a TCF of 0. At this time, it is necessary to reselect the material and thickness of the piezoelectric film 200, and it is necessary to return to the step of determining the second structural parameters to redesign the resonator to build a filter with a frequency temperature coefficient TCF of 0, that is, a filter with a frequency temperature coefficient of zero.

[0107] In some embodiments, the number of the second series resonators is one or more, and the number of the second parallel resonators is one or more. The number of the second series resonators is the same as or different from the number of the second parallel resonators.

[0108] In the embodiment of the present application, the structure of the surface acoustic wave bandpass filter finally designed is as follows: Figure 4 As shown, Figure 4 1 is a schematic diagram of the structure of an 11th-order surface acoustic wave filter designed in the embodiment of the present application. Figure 3a The filter shown, Figure 4 The filter in the embodiment of the present invention additionally adds two second series resonators Z3 and two second parallel resonators Z4 as compensation resonators. In the filter designed in the present application, the temperature coefficient TCF of a part of the resonators (such as the first series resonator Z1 and the first parallel resonator Z2) at the center frequency of the filter is 0, and the TCF of a part of the resonators (the second series resonator Z3 and the second parallel resonator Z4) at the transmission zero point is 0, thereby ensuring that the overall temperature coefficient TCF of the filter is 0.

[0109] Of course, in the actual design process, the second series resonator Z3 and the second parallel resonator Z4 may not be limited to Figure 4 The number and distribution shown. For example, the second series resonator and the second parallel resonator can be 1, or even 3, 4, etc. It can be based on the actual design requirements, but both the second series resonator Z3 and the second parallel resonator Z4 must be present, because one of them has an upper sideband and the other has a lower sideband, and they can also be asymmetric, such as two second series resonators Z3 and one second parallel resonator Z4. The core purpose of the design is that, under the trapezoidal topology filter structure, a part of the resonators limit the center passband and does not change with temperature, and a part of the resonators limit the transmission zero point (that is, limit the sideband to remain unchanged) to achieve the overall passband position of the filter unchanged.

[0110] In order to reflect the design method of the present application, a zero temperature drift surface acoustic wave bandpass filter is designed by the above design method, and its simulation results are as follows Figure 7a and Figure 7b shown. Figure 7a is the S-parameter response of the SAW bandpass filter and its corresponding resonator admittance response; Figure 7b : is the S21 response of the surface acoustic wave bandpass filter under different temperature offsets ΔT. In this embodiment, the substrate is Y42° 500nm LiTaO3 film / 500nm SiO2 / Si, and the IDT electrode is a 120nm Al electrode. Figure 7b It can be seen that the TCF of this surface acoustic wave bandpass filter is ≈ 0, that is, a surface acoustic wave bandpass filter with zero temperature drift can be successfully designed through the above design method.

[0111] The present invention proposes a method for designing a surface acoustic wave bandpass filter with zero temperature drift, which utilizes the change characteristics of the resonator TCF with film thickness, wavelength, and in-plane transmission direction, selects appropriate parameters, and allows the resonators to interact with each other on the same substrate to ensure that the passband range of the filter does not change with temperature changes, thereby realizing a bandpass filter with a frequency temperature coefficient TCF = 0. In addition, the present invention does not require additional process steps, and retains the advantages of small size and easy integration of the surface acoustic wave filter.

[0112] The embodiment of the present application also provides a surface acoustic wave bandpass filter, which is prepared by using any of the above methods.

[0113] It should be noted that the details and beneficial effects not elaborated in the above structural embodiments can be found in the above method embodiments, and will not be described in detail again.

[0114] The present application also provides an electronic device, which includes the surface acoustic wave bandpass filter described above.

[0115] It should be noted that the specific details and beneficial effects of the above electronic device embodiments can be found in the above structural embodiments or method embodiments, which will not be repeated here.

[0116] The above description has fully disclosed the specific implementation methods of the present application. It should be pointed out that any changes made by technicians familiar with the field to the specific implementation methods of the present application do not deviate from the scope of the claims of the present application. Accordingly, the scope of the claims of the present application is not limited to the above specific implementation methods.

Claims

1. A method for designing a surface acoustic wave bandpass filter, characterized in that: The surface acoustic wave bandpass filter is based on a plurality of resonators, wherein the resonators include an electrode layer, a piezoelectric film and a supporting substrate, and the method includes: Determining first structural parameters, wherein the first structural parameters include a substrate material of the support substrate, an electrode material and a thickness of the electrode layer; Determining second structural parameters, wherein the second structural parameters include piezoelectric material and thickness of the piezoelectric film; Based on the first structural parameter and the second structural parameter, forming a plurality of resonators; Extract the first relationship and the second relationship related to the in-plane transmission direction of each resonator, the first relationship is used to characterize the relationship between the in-plane transmission direction of the resonator and the temperature coefficient of frequency TCF, and the second relationship is used to characterize the in-plane transmission direction of the resonator and the resonant frequency and electromechanical coupling coefficient K of the resonator 2 the relationship between; Based on the first relationship and the second relationship, a target filter is constructed; the target filter includes a basic resonator group and a compensation resonator group, the frequency temperature coefficient of the basic resonator group at the center frequency of the filter is zero, and the frequency temperature coefficient of the compensation resonator group at the transmission zero point is zero; If the frequency temperature coefficient of the target filter is detected to be zero, the target filter is determined as the surface acoustic wave bandpass filter of the final design; If the frequency temperature coefficient of the target filter is not zero, return to the step of determining the second structural parameter until the frequency temperature coefficient of the target filter is zero, and determine the filter with a frequency temperature coefficient of zero as the final designed surface acoustic wave bandpass filter.

2. The method according to claim 1, characterized in that The basic resonator group includes a first series resonator and a first parallel resonator; The first series resonator is a resonator selected to have a resonance frequency point of zero, and the first parallel resonator is a resonator selected to have an anti-resonance frequency point of zero.

3. The method according to claim 2, characterized in that The constructing a target filter based on the first relationship and the second relationship comprises: Based on the first relationship and the second relationship, adjusting the resonator parameters of each of the resonators to obtain an adjusted resonator; Selecting the basic resonator group from the adjusted resonators to build an initial filter; Calculate the anti-resonance frequency f of the first series resonator within the initial filter operating temperature range. p1 The maximum offset Δ p1 ; and the resonant frequency f of the first parallel resonator s2 The maximum offset Δ s2 ; Based on the maximum offset Δ p1 and the maximum offset Δ s2 , determining the compensating resonator group from the adjusted resonators; The initial filter is adjusted based on the compensating resonator group to construct the target filter.

4. The method according to claim 3, characterized in that The compensation resonator group includes a second series resonator and a second parallel resonator; The second series resonator is a resonator selected from the adjusted resonator, the anti-resonance frequency point of which is zero, and the anti-resonance frequency f of the second series resonator is p3 is less than or equal to the anti-resonance frequency f of the first series resonator p1 With the maximum offset Δ p1 The anti-resonance frequency f of the second series resonator p3 is less than the anti-resonance frequency f of the first series resonator p1； The second parallel resonator is a resonator with a resonance frequency point of zero selected from the adjusted resonator, and the resonance frequency f of the second parallel resonator is s4 is greater than the resonant frequency f of the second series resonator s2 and the maximum offset Δ s2 sum.

5. The method according to claim 4, characterized in that The compensation resonator group also satisfies: The anti-resonance frequency f of the first parallel resonator p2 <The resonant frequency f of the second parallel resonator s3 <The anti-resonance frequency f of the second series resonator p3 ; The resonant frequency f of the first series resonator s1 >The anti-resonance frequency f of the second parallel resonator p4 >The resonant frequency f of the second parallel resonator s4 .

6. The method according to claim 4, characterized in that The number of the second series resonators is one or more, and the number of the second parallel resonators is one or more; The number of the second series resonators is the same as or different from the number of the second parallel resonators.

7. The method according to claim 1, characterized in that The resonator satisfies at least one of the following: The piezoelectric material of the piezoelectric film is lithium tantalate or lithium niobate; The thickness of the piezoelectric film ranges from 150 nm to 1.5 μm; The crystal cut of the piezoelectric film is X-cut, and the corresponding Euler angle is (90°, 90°, γ), where 150°<γ<180° or 20°<γ<60°; or rotated Y-cut, and the corresponding Euler angle is (0, β, 0), where β ranges from 30° to 90°; or Z-cut, and the corresponding Euler angle is (α, 0, 0), where α is an arbitrary angle; The support substrate is a high acoustic velocity support substrate, and the material of the support substrate includes one of silicon, quartz, silicon carbide, sapphire, and diamond; The electrode layer material includes at least one metal material selected from the group consisting of aluminum, tungsten, chromium, titanium, copper, silver and gold; The electrode layer is composed of a parallel arranged interdigital electrode array and a reflective grating array on the left and right sides. The in-plane transmission direction θ of the interdigital electrode array ranges from -90° to 90°.

8. The method according to claim 1, characterized in that The resonator further comprises a dielectric layer, wherein the dielectric layer is located between the piezoelectric film and the supporting substrate, and / or the dielectric layer covers the piezoelectric film and the electrode layer.

9. A surface acoustic wave bandpass filter, characterized in that: The surface acoustic wave bandpass filter is prepared by the method described in any one of claims 1-8.

10. An electronic device, characterized in that: The electronic device comprises the surface acoustic wave bandpass filter according to claim 9.

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