WO2022042463A1

WO2022042463A1 - Method for optimising out-of-band suppression of filter, and filter, multiplexer, and communication device

Info

Publication number: WO2022042463A1
Application number: PCT/CN2021/114004
Authority: WO
Inventors: 徐利军; 庞慰
Original assignee: 诺思(天津)微系统有限责任公司
Priority date: 2020-08-24
Filing date: 2021-08-23
Publication date: 2022-03-03
Also published as: CN112073028B; CN112073028A

Abstract

The present invention relates to the technical field of filters, and relates in particular to a method for optimising the out-of-band suppression of a filter, and a filter, a multiplexer, and a communication device. In the present method, the effective electromechanical coupling coefficients of a series resonator and a parallel resonator can be flexibly adjusted, not only keeping filter passband coverage unchanged, but also solving the problem of the poor harmonic suppression of low-frequency bulk acoustic wave filters, and also ensuring the suppression balance of harmonic suppression areas.

Description

Filter out-of-band suppression optimization method and filter, multiplexer, communication equipment

technical field

The present invention relates to the technical field of filters, and in particular, to a filter out-of-band suppression optimization method, a filter, a multiplexer, and a communication device.

Background technique

With the rapid development of wireless communication technology in the direction of multi-band and multi-mode, filters, duplexers and multiplexers, which are key components of RF front-end, have received extensive attention, especially in the fastest growing field of personal mobile communications. application. At present, filters and duplexers that are widely used in the field of personal mobile communications are mostly made of surface acoustic wave resonators or bulk acoustic wave resonators. Compared with surface acoustic wave resonators, BAW resonators have better performance. BAW resonators have the characteristics of high Q value, wide frequency coverage, and good heat dissipation performance, which are more suitable for the development needs of 5G communication. The resonance of BAW resonators is generated by mechanical waves, not electromagnetic waves. The wavelength of mechanical waves is shorter than that of electromagnetic waves. Therefore, the volume of BAW resonators and the filters they consist of is greatly reduced compared to traditional electromagnetic filters. In addition, due to The crystal growth of piezoelectric crystals can be well controlled, the loss of the resonator is extremely small, and the quality factor is high, which can cope with complex design requirements such as steep transition band and low insertion loss.

In general, BAW resonators are suitable for frequency bands above 1.2GHz, but not suitable for frequency bands below 1.2GHz. There are two main reasons. The first reason is that when the frequency is low, the piezoelectric layer is thicker. , resulting in a large resonator area, which is not conducive to miniaturization. However, with the emergence of scandium-doped aluminum nitride technology and technology, this problem has been solved. The second reason is that when the frequency is low, the high order of the resonator The resonance amplitude is very strong. When such resonators form a ladder-type filter, in addition to forming a fundamental frequency passband, a filter passband with poor insertion loss will also be formed near the high frequency band, so it will cause the filter to have poor performance. Out-of-band rejection, especially the deterioration of high-frequency out-of-band rejection, affects the normal use of the filter.

Therefore, in order to enable BAW resonators to be applied in low-frequency filters, how to use BAW resonator technology to reduce the impact of high-order harmonics on out-of-band suppression of filters is still a technical problem to be solved.

SUMMARY OF THE INVENTION

The invention provides an optimization method for out-of-band suppression of a filter, a filter, a multiplexer, and a communication device, which can not only keep the passband coverage of the filter unchanged, but also solve the problem of poor harmonic suppression of the low-frequency bulk acoustic wave filter. At the same time, it can also ensure the suppression balance in the harmonic suppression region.

In one aspect of the present invention, there is provided a method for optimizing out-of-band suppression of a filter, the filter includes a plurality of series resonators and a plurality of parallel resonators, the method includes: adjusting the piezoelectricity of the series resonators and the parallel resonators The thickness of the layer, so that the effective electromechanical coupling coefficient of the parallel resonator is larger than the initial value of the effective electromechanical coupling coefficient of the series resonator, and the sum of the two said initial values is a fixed value, and the series resonance of the harmonics of the parallel resonator The frequency point is located between the series resonance frequency point and the parallel resonance frequency point of the harmonics of the series resonator; when the fundamental frequency of the filter meets the requirements of the index and the low frequency suppression amplitude and high frequency suppression amplitude of the filter harmonic region are not equal , perform the following steps A or B until the low frequency suppression amplitude and high frequency suppression amplitude in the harmonic region of the filter are equal and greater than the specified value, wherein: Step A: If the low frequency suppression amplitude in the harmonic region of the filter is greater than the high frequency suppression amplitude , then reduce the initial value of the effective electromechanical coupling coefficient of the parallel resonator, increase the initial value of the effective electromechanical coupling coefficient of the series resonator, and keep the sum of the two initial values as a fixed value; Step B: If the filter If the low frequency suppression amplitude in the harmonic region is smaller than the high frequency suppression amplitude, the initial value of the effective electromechanical coupling coefficient of the parallel resonator is increased, the initial value of the effective electromechanical coupling coefficient of the series resonator is decreased, and the two initial values are maintained. The sum is a fixed value.

Optionally, in the filter, each parallel resonator is connected with a grounding inductor, and the inductance value of the grounding inductor is smaller than a preset value.

Optionally, the step of adjusting the thicknesses of the piezoelectric layers of the series resonators and the parallel resonators includes: fabricating the series resonators and the parallel resonators on different wafers, and adjusting the thicknesses of the piezoelectric layers on the two wafers respectively. , so that the thicknesses of the piezoelectric layers of the series and parallel resonators are different.

Optionally, the initial value of the effective electromechanical coupling coefficient of the parallel resonator is 1% to 2% larger than the initial value of the effective electromechanical coupling coefficient of the series resonator, and the sum of the two is 4-5 times the relative bandwidth of the filter.

Optionally, the specified value is 30dB.

Optionally, in step A or step B, the initial value of the effective electromechanical coupling coefficient of the parallel resonator and the initial value of the effective electromechanical coupling coefficient of the series resonator are increased or decreased by 0.5%.

Optionally, the preset value is 0.5nH.

In another aspect of the present invention, a filter is also provided, comprising an upper wafer, a lower wafer, multiple series resonators and multiple parallel resonators, all parallel resonators are arranged on the first surface of the upper wafer, and all are connected in series The resonator is arranged on the first surface of the lower wafer; the upper wafer and the lower wafer are superimposed to form a package structure; inside the package structure, the first surface of the upper wafer and the first surface of the lower wafer are arranged in parallel and opposite to each other , the series resonator and the parallel resonator are bonded by butt pins to form a multi-stage series-parallel filter circuit; wherein the thickness of the piezoelectric layer of the multiple series resonators is different from the thickness of the piezoelectric layer of the parallel resonator, and , the effective electromechanical coupling coefficient of the parallel resonator is greater than the effective electromechanical coupling coefficient of the series resonator, and the low frequency and high frequency suppression amplitudes of the filter in the harmonic region are equal and greater than the specified value.

Optionally, the filter circuit further includes a grounding inductor, the first end of the grounding inductor is connected to the parallel resonator, and the second end is grounded; the inductance value of the grounding inductor is less than a preset value.

In yet another aspect of the present invention, there is also provided a duplexer including the above filter.

In yet another aspect of the present invention, there is also provided a communication device including the above filter.

Description of drawings

For purposes of illustration and not limitation, the present invention will now be described in accordance with preferred embodiments thereof, particularly with reference to the accompanying drawings, wherein:

Fig. 1 is the impedance curve schematic diagram of the low frequency resonator in the filter;

Fig. 2 is the impedance curve schematic diagram of two resonators in the filter;

3 is a schematic diagram of a passband curve of a filter;

Figure 4 is a schematic diagram of the comparison of resonator impedance curves;

5 is a schematic diagram of a passband curve of a filter;

6 is a schematic diagram of a passband curve of a filter;

Figure 7 is a schematic diagram showing the comparison of passband curves of parallel resonators with different piezoelectric layer thicknesses;

8 is a schematic flowchart of a filter out-of-band suppression optimization method provided by an embodiment of the present invention;

Fig. 9 is the topology structure schematic diagram of filter;

10 is a schematic diagram of a passband curve of a simulated filter;

Figure 11 is a schematic diagram of the passband curve after filter optimization;

Figure 12 is a schematic diagram showing the comparison of the change curve of the series resonance frequency point after the parallel resonator in the filter is connected to the ground inductance;

Figure 13 is a schematic diagram showing the comparison of the pass-band curves after the parallel resonator is connected to the ground inductance;

14 is a cross-sectional view of a filter package structure according to an embodiment of the present invention;

15 is a front view of an upper wafer in a filter package structure provided by an embodiment of the present invention;

FIG. 16 is a front view of the lower wafer in the filter package structure provided by the embodiment of the present invention.

detailed description

The technical solutions in the embodiments of the present invention can keep the passband coverage of the filter unchanged, and can solve the problem of poor harmonic suppression of low-frequency bulk acoustic wave filters. At the same time, it can also ensure the suppression balance in the harmonic suppression region. Explain in detail.

Figure 1 is a schematic diagram of the impedance curve of the low frequency resonator in the filter. The resonator is a typical resonator structure, which includes superimposed upper electrode, piezoelectric layer and lower electrode. The curve has two resonance regions, namely the fundamental frequency resonance region and the harmonic resonance region. The fundamental frequency resonance region has a lower frequency. , the resonance is about 900MHz, including the series resonance frequency and the parallel resonance frequency. Among them, the impedance Rp of the parallel resonance frequency is about 6500 ohms, while the frequency of the harmonic resonance region is higher, and the resonance is about 3000MHz, including the series resonance frequency. and the parallel resonance frequency point, wherein the Rp of the parallel resonance frequency point is 800 ohms, which has a higher impedance value.

FIG. 2 is a schematic diagram of impedance curves of two resonators in the filter. As shown in Figure 2, the solid line in the figure is the impedance curve of the series resonator, which is exactly the same as the impedance curve shown in Figure 1, and the dotted line is the impedance curve of the parallel resonator, which adopts the mass-loaded parallel resonator. The method realizes frequency shifting. This curve is similar to the impedance curve of the series resonator. It also includes two resonance regions, namely the fundamental frequency resonance region and the harmonic resonance region. The fundamental frequency resonance region has a lower frequency, and the resonance is around 865MHz. The area includes the series resonance frequency point and the parallel resonance frequency point. Among them, the impedance Rp of the parallel resonance frequency point is about 6500 ohms, while the frequency of the harmonic resonance area is higher, and the resonance is about 2900MHz. The harmonic resonance area includes the series resonance frequency point and The parallel resonance frequency point, wherein the Rp of the parallel resonance frequency point is 800 ohms, which has a higher impedance value. Comparing the two curves, it can be seen that the parallel resonance frequency of the fundamental frequency of the parallel resonator is located near the series resonance frequency of the fundamental frequency of the series resonator. form a passband. FIG. 3 is a schematic diagram of the passband curve of the filter. As shown in Figure 3, in this curve, a passband is formed near 900MHz, and a pseudo passband is formed near 2900MHz. The existence of the pseudo passband deteriorates the out-of-band rejection near this frequency. The frequency of the parallel resonator is similar, that is, the series and parallel resonators have the same stack, and only when the mass load is loaded on the parallel resonator, the parallel resonance frequency of the harmonic of the parallel resonator will be located near the series resonance frequency of the harmonic of the series resonator. , thus forming a pseudo-passband, the existence of the pseudo-passband deteriorates the out-of-band suppression of the frequency band, and seriously affects the promotion and use of the BAW filter in the low frequency band. Therefore, it needs to be improved.

In order to solve the above problems, the following method can be adopted: the series resonator and the parallel resonator of the filter are respectively used with different piezoelectric layer thicknesses, and the thickness of the piezoelectric layer of the parallel resonator is larger than that of the series resonator. thickness (that is, the effective electromechanical coupling coefficient of the parallel resonator is greater than the effective electromechanical coupling coefficient of the series resonator), so that in the fundamental frequency band, the parallel resonance frequency of the fundamental frequency of the parallel resonator is located at the series resonance frequency of the fundamental frequency of the series resonator. The thickness of the piezoelectric layer of the parallel resonator is larger than that of the series resonator, so in the harmonic frequency band, the harmonic resonance region of the parallel resonator is higher than that of the series resonator. wave resonance region. FIG. 4 is a schematic diagram showing the comparison of the impedance curves of the resonators. As shown in Figure 4, the solid line is the impedance curve of the series resonator, which includes two resonance regions, namely the fundamental frequency resonance region and the harmonic resonance region, while the dotted line is the impedance curve of the parallel resonator. The stack is different from the series resonator, and the piezoelectric layer thickness of the parallel resonator is larger than that of the series resonator, that is, the frequency shift is realized by using the piezoelectric layer as a loading mass load. This curve is similar to the impedance curve of the series resonator. , also includes two resonance regions, namely the fundamental frequency resonance region and the harmonic resonance region, the parallel resonance frequency of the fundamental frequency of the parallel resonator is located near the series resonance frequency of the fundamental frequency of the series resonator, and a plurality of the above series and parallel resonators are composed of filter ladder topology, which creates a passband at the fundamental frequency. As shown in Figure 5, in the harmonic region, if the series resonance frequency of the harmonic of the parallel resonator is just near the parallel resonance frequency of the harmonic of the series resonator, a region similar to a stop band will be formed in the harmonic region, Improve out-of-band rejection in this region.

In the above method, the piezoelectric layers of the series resonator and the parallel resonator are set as follows: first, the thickness of the piezoelectric layer of the series resonator is set to a certain value (that is, the effective electromechanical coupling coefficient of the series resonator is a constant value), and then the thickness of the piezoelectric layer of the series resonator is set to a certain value. Optimize the thickness of the piezoelectric layer of the parallel resonator (ie, the effective electromechanical coupling coefficient of the parallel resonator), so as to achieve the purpose of improving the suppression of the harmonic region. Since this method limits the thickness of the piezoelectric layer of the series resonator, it can no longer take into account the fundamental frequency passband insertion loss, the suppression of the adjacent band and the suppression of the harmonic region, that is, if the thickness of the piezoelectric layer of the parallel resonator is small, parallel resonance will occur The series resonance frequency of the harmonics of the series resonator deviates from the parallel resonance frequency of the harmonics of the series resonator, and is close to the series resonance frequency of the harmonics of the series resonator, which will lead to the deterioration of the low-frequency suppression in the harmonic region, circle 1 in Figure 5 The suppression of the indicated position is only 22dB, and the suppression of the position indicated by circle 2 can reach 37dB. The suppression difference between the two positions is 16dB, and the suppression amplitude of the two positions is unbalanced; The series resonance frequency of the harmonic deviates from the parallel resonance frequency of the harmonic of the series resonator, and is larger than the parallel resonance frequency of the harmonic of the series resonator, which will lead to the deterioration of high frequency suppression in the harmonic region, indicated by circle 1 in Figure 6. The position suppression can reach 41dB, and the position indicated by circle 2 has only 21dB suppression. The suppression difference between these two positions is 20dB, and the two sides are unbalanced.

FIG. 7 is a schematic diagram showing the comparison of passband curves of parallel resonators with different piezoelectric layer thicknesses. As shown in Figure 7, the dotted line is the curve when the piezoelectric layer of the parallel resonator is thin, and the solid line is the curve when the piezoelectric layer of the parallel resonator is thick. The range of the filter varies. If there is suppression on the left and right sides of the passband, during the optimization process, the passband coverage of the filter changes, and the filter will cause the adjacent band suppression to become worse because the passband becomes wider, or because the passband becomes narrower. , resulting in worse sideband insertion loss.

It can be seen that the above methods have poor flexibility in adjusting the thickness of the piezoelectric layers of the series resonators and parallel resonators, and cannot take into account the fundamental frequency passband insertion loss, adjacent band suppression, and harmonic region suppression.

The embodiments of the present invention provide an optimization method for filter out-of-band suppression, which can not only maintain the filter passband coverage almost constant during the optimization process, but also solve the problem of poor harmonic suppression of low-frequency bulk acoustic wave filters problem, as well as ensuring the suppression balance in the harmonic suppression region.

FIG. 8 is a schematic flowchart of a method for optimizing out-of-band suppression of a filter provided by an embodiment of the present invention. As shown in FIG. 8 , step S81 : adjust the thicknesses of the piezoelectric layers of the series resonator and the parallel resonator, so that the thicknesses of the piezoelectric layers of the two are different, so that the initial values of the effective electromechanical coupling coefficients of the two are different, wherein, The two initial values should meet the following two conditions: 1. The initial value of the effective electromechanical coupling coefficient of the parallel resonator is greater than the initial value of the effective electromechanical coupling coefficient of the series resonator; 2. The sum of the two is a fixed value; under normal circumstances , the initial value of the effective electromechanical coupling coefficient of the parallel resonator is 1% to 2% larger than the initial value of the effective electromechanical coupling coefficient of the series resonator, and the sum of the two is 4 to 5 times the relative bandwidth of the filter; Step S82: determine Whether the series resonance frequency of the harmonics of the parallel resonator is located between the series resonance frequency and the parallel resonance frequency of the harmonics of the series resonator, if so, go to step S83, otherwise return to step S81; step S83: check the filter topology Perform simulation to determine whether the fundamental frequency of the filter meets the index requirements, if so, go to step S84, otherwise return to step S81; Step S84: determine whether the low-frequency suppression amplitude and high-frequency suppression amplitude in the harmonic region are equal, and greater than the specified value, specify The value is generally 30dB; if so, the optimization is over, otherwise, go to step S85; step S85: determine whether the low frequency suppression amplitude in the harmonic region is greater than the high frequency suppression amplitude; if so, reduce the initial value of the effective electromechanical coupling coefficient of the parallel resonator m%, and after increasing the initial value of the effective electromechanical coupling coefficient of the series resonator by m%, return to step S83; otherwise, increase the initial value of the effective electromechanical coupling coefficient of the parallel resonator by n%, and increase the initial value of the effective electromechanical coupling coefficient of the series resonator by n% After the initial value of the effective electromechanical coupling coefficient is reduced by n%, the process returns to step S83. So many cycles of optimization design, until both the index requirements of the fundamental frequency and the harmonic suppression requirements are met, the balance of the harmonic region suppression must be ensured, and the low frequency and high frequency suppression amplitudes in the harmonic region are basically equal. Design is complete.

The effectiveness of the above method is verified by specific examples below. A low-frequency filter is designed using a bulk acoustic wave resonator, whose frequency range covers 880-915MHz, and the harmonic suppression is greater than 35dB. FIG. 9 is a schematic diagram of the topology structure of the filter. As shown in Figure 9, the topology is a 5-4 structure (of course not limited to the 5-4 structure, it can be an MN structure, M and N are natural numbers, here only the 5-4 structure is used as an example), the topology includes 1 series branch and 4 parallel branches. The series branch is composed of series resonators S11, S12, S13, S14 and S15 connected in series between port 1 and port 2. The parallel branch includes parallel resonators and For the grounding inductor, one end of the parallel resonator is connected to the node between two adjacent series resonators, and the other end is connected to the grounding inductor. The first parallel branch includes a parallel resonator P11 and a grounded inductor L11, the second parallel branch includes a parallel resonator P12 and a grounded inductor L12, the third parallel branch includes a parallel resonator P13 and a grounded inductor L13, and the fourth parallel branch includes a parallel resonator P13 and a grounded inductor L13. The branch includes a parallel resonator P14 and a grounded inductor L14.

In order to make the effective electromechanical coupling coefficients of series resonators and parallel resonators different, all series resonators are fabricated on one wafer, and all parallel resonators are fabricated on another wafer. According to the above optimization steps: First, select The initial value of the piezoelectric layer thickness of the series resonator is 0.65 microns, the initial value of the effective electromechanical coupling coefficient is 7%, the initial value of the piezoelectric layer thickness of the parallel resonator is 0.9 microns, and the initial value of the effective electromechanical coupling coefficient is 9.3%. The sum of the effective electromechanical coupling coefficients of the resonator and the parallel resonator is 16.3%; the series-parallel resonance frequency point analysis of the harmonics of the series-parallel resonator is carried out, and the thickness of the piezoelectric layer selected above is determined, so that the series-parallel resonance of the harmonics of the parallel resonator is determined. The resonance frequency is just between the series resonance frequency and the parallel resonance frequency of the harmonics of the series resonator; then the filter topology can be simulated and optimized. The above parameters show that the passband insertion loss of the entire filter is less than 1.8dB, which is basically If the fundamental frequency index requirements are met, the next step can be performed to analyze the harmonic suppression of the filter. FIG. 10 is a schematic diagram of the passband curve of the simulated filter. From the curve shown in Figure 10, it can be seen that the worst point of harmonic suppression is only 25dB, which does not meet the requirements. At the same time, it is found that the worst point of harmonic suppression is the high frequency part of the harmonic region, and the low frequency part of the harmonic region is better. up to 40dB. According to the above method, the effective electromechanical coupling coefficient of the parallel resonator is reduced by 0.5%, while the effective electromechanical coupling coefficient of the series resonator is increased by 0.5%, the effective electromechanical coupling coefficient of the parallel resonator is changed to 8.8%, and its piezoelectric layer is changed to 0.87 micron, the effective electromechanical coupling coefficient of the series resonator is changed to 7.5%, and its piezoelectric layer is 0.68 μm, keeping the sum of the effective electromechanical coupling coefficient of the series resonator and the parallel resonator unchanged at 16.3%. After updating the effective electromechanical coupling coefficient, re-substitute it into the original design, and then perform the simulation. Figure 11 is a schematic diagram of the passband curve after filter optimization. As shown in Figure 11, the insertion loss of the fundamental frequency meets the requirements of the index, the insertion loss of the entire passband is less than 1.8dB, and the entire out-of-band suppression of the filter is greater than 40dB, especially in the harmonic region, where the suppression is greater than 40dB, and the low-frequency suppression in the harmonic region Amplitude and high frequency rejection are more balanced.

The grounding inductance of the parallel branch in the filter also plays a key role in harmonic suppression. The main reason is that when a parallel resonator is connected in series with a grounding inductance, it will change the position of the fundamental frequency of the resonator and the series resonance frequency in the harmonic region. Generally speaking, the position of the series resonance frequency is generally moved to the low frequency, so when the inductance value of the parallel resonator series is large, the series resonance frequency of the harmonics of the parallel resonator may be smaller than the series resonance frequency of the harmonics of the series resonator. The resonant frequency no longer meets the requirement that it must be located between the series resonant frequency point and the parallel resonant frequency point of the harmonics of the series resonator, resulting in the deterioration of the suppression of the low-frequency part of the harmonic region. FIG. 12 is a schematic diagram showing the comparison of the change curve of the series resonance frequency point after the parallel resonator in the filter is connected to the grounding inductor. As shown in Figure 12, the harmonic resonance of the series resonator is marked with a thin solid line in the figure. The harmonic series resonance frequency is at 2.88GHz, and the parallel resonance frequency is at 2.93GHz. When the inductance connected to the parallel resonator is At 0.3nH, its harmonic series resonance frequency is at 2.925GHz, and its parallel resonance frequency is at 2.96GHz. At this time, the series resonance frequency of the parallel resonator harmonic is just at the series resonance frequency of the series resonator harmonic and the parallel resonance frequency. Between the frequency points, with the increase of the series inductance, the harmonic series resonance frequency point moves to the low frequency, that is, when the inductance increases to 0.5nH, the series resonance frequency point of the harmonics of the parallel resonator moves to 2.84GHz. It is located between the series resonance frequency and the parallel resonance frequency of the harmonics of the series resonator, so the suppression of the low frequency band in the harmonic region will be deteriorated. FIG. 13 is a schematic diagram showing the comparison of pass-band curves after the parallel resonator is connected to the grounded inductor. As shown in Figure 13, the solid line in the figure is the corresponding curve when the grounding inductance value is 0nH, the harmonic suppression in this curve is better, and the dotted line is the corresponding curve when the grounding inductance value is 0.5nH, the harmonics in the curve are Rejection deteriorated by 15dB.

FIG. 14 is a cross-sectional view of a filter package structure according to an embodiment of the present invention. As shown in FIG. 14 , in the package structure of the filter, all parallel resonators are fabricated on the upper wafer, and all series resonators are fabricated on the lower wafer. Fig. 15 is a front view of the upper wafer in the filter package structure provided by the embodiment of the present invention; Fig. 16 is the front view of the lower wafer in the filter package structure provided by the embodiment of the present invention. As shown in Figure 15 and Figure 16, the upper wafer includes parallel resonators P11, P12, P13 and P14, as well as ground pins G1, G2, G3, G4 and transfer bonding pins J1, J2, J3, J4; The lower wafer includes series resonators S11, S12, S13, S14 and S15, as well as ground pins G1, G2, G3, G4, transfer bonding pins J1, J2, J3, J4, input pins IN and output pins pin OUT. The upper wafer and the lower wafer are superimposed on top of each other, and the bonding pins J1, J2, J3, J4 are bonded, and the ground pins G1, G2, G3, and G4 are bonded; Through holes, the signal terminals and the ground terminals of the filters manufactured by the upper wafer and the lower wafer are connected to the pads under the lower wafer through vias, and the pads under the lower wafer can be connected to the package through metal solder balls substrate to form a package structure.

In this filter, the thicknesses of the piezoelectric layers of the plurality of series resonators are different from the thicknesses of the piezoelectric layers of the parallel resonators, and the effective electromechanical coupling coefficient of the parallel resonators is larger than the effective electromechanical coupling coefficient of the series resonators. The low frequency suppression amplitude and high frequency suppression amplitude of the harmonic region are equal to and greater than the specified value, such as greater than 30dB. Since the series resonator and the parallel resonator are separately provided on two wafers, the piezoelectric layer can be provided with different thicknesses, and the thickness can be easily adjusted. The filter can not only maintain the filter passband coverage unchanged, but also solve the problem of poor harmonic suppression of the low-frequency bulk acoustic wave filter, and at the same time, it can also ensure the suppression balance in the harmonic suppression region.

The embodiment of the present invention also provides a duplexer, which includes the above-mentioned filter. Therefore, the duplexer can also maintain the filter passband coverage unchanged, and can solve the harmonics of the low-frequency bulk acoustic wave filter. The problem of poor suppression and the effect of ensuring the balance of suppression in the harmonic suppression area.

Embodiments of the present invention also provide a communication device, which includes the above-mentioned filter. Therefore, the communication device can also maintain the filter passband coverage unchanged, and can solve the problem of poor harmonic suppression of the low-frequency bulk acoustic wave filter. problem, and the effect of ensuring the suppression balance of the harmonic suppression region.

The above-mentioned specific embodiments do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may occur depending on design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

A method for optimizing out-of-band suppression of a filter, the filter comprising a plurality of series resonators and a plurality of parallel resonators, characterized in that the method comprises:

Adjust the thickness of the series resonator and the piezoelectric layer of the parallel resonator so that the effective electromechanical coupling coefficient of the parallel resonator is greater than the initial value of the effective electromechanical coupling coefficient of the series resonator, and the sum of the two initial values is a fixed value , and the series resonance frequency of the harmonics of the parallel resonator is located between the series resonance frequency of the harmonics of the series resonator and the parallel resonance frequency of the harmonics of the series resonator;

When the fundamental frequency of the filter meets the index requirements and the low frequency suppression amplitude and high frequency suppression amplitude in the harmonic region of the filter are not equal, perform the following steps A or B until the low frequency suppression amplitude and high frequency suppression amplitude in the harmonic region of the filter are not equal. The magnitude of the frequency rejection is equal and greater than the specified value, where:

Step A: If the low frequency suppression amplitude of the harmonic region of the filter is greater than the high frequency suppression amplitude, reduce the initial value of the effective electromechanical coupling coefficient of the parallel resonator, increase the initial value of the effective electromechanical coupling coefficient of the series resonator, and keep The sum of the two initial values is a fixed value;

Step B: If the low frequency suppression amplitude in the harmonic region of the filter is smaller than the high frequency suppression amplitude, increase the initial value of the effective electromechanical coupling coefficient of the parallel resonator, decrease the initial value of the effective electromechanical coupling coefficient of the series resonator, and keep The sum of the two initial values is a fixed value.
The method according to claim 1, wherein, in the filter, each parallel resonator is connected with a grounding inductor, and the inductance value of the grounding inductor is smaller than a preset value.
The method of claim 1, wherein the step of adjusting the thickness of the piezoelectric layers of the series resonator and the parallel resonator comprises:

The series resonator and the parallel resonator are fabricated on different wafers, and the thicknesses of the piezoelectric layers on the two wafers are adjusted respectively, so that the thicknesses of the piezoelectric layers of the series resonator and the parallel resonator are different.
The method according to claim 1, wherein the initial value of the effective electromechanical coupling coefficient of the parallel resonator is 1% to 2% larger than the initial value of the effective electromechanical coupling coefficient of the series resonator, and the sum of the two is the filter 4-5 times the relative bandwidth.
The method according to claim 1, wherein the specified value is 30dB.
The method according to claim 1, wherein in step A or step B, the initial value of the effective electromechanical coupling coefficient of the parallel resonator and the initial value of the effective electromechanical coupling coefficient of the series resonator are increased or decreased 0.5%.
The method according to claim 2, wherein the preset value is 0.5nH.
A filter is characterized in that it includes an upper wafer, a lower wafer, a plurality of series resonators and a plurality of parallel resonators, all the parallel resonators are arranged on the first surface of the upper wafer, and all the series resonators are arranged on the lower wafer the first surface of the wafer; the upper wafer and the lower wafer are stacked to form a package structure;

Inside the package structure, the first surface of the upper wafer and the first surface of the lower wafer are arranged in parallel and opposite to each other, and the series resonator and the parallel resonator are bonded by butt pins to form a multi-stage series-parallel filter circuit;

Wherein, the thicknesses of the piezoelectric layers of the plurality of series resonators are different from the thicknesses of the piezoelectric layers of the parallel resonators, and the thicknesses of the piezoelectric layers of the series resonators and the piezoelectric layers of the parallel resonators are the same as those of claim 1. The method described in any one of to 7 is adjusted to obtain, and the effective electromechanical coupling coefficient of the parallel resonator is greater than the effective electromechanical coupling coefficient of the series resonator, and the low frequency suppression amplitude and high frequency suppression amplitude of the harmonic region of the filter are equal and greater than Specify the value.
The filter according to claim 8, wherein the filter circuit further comprises a grounding inductor, the first end of the grounding inductor is connected to the parallel resonator, and the second end is grounded;

The inductance value of the grounding inductor is smaller than the preset value.
A duplexer, characterized by comprising the filter according to claim 8 or 9.
A communication device, characterized by comprising the filter according to claim 8 or 9.