CN111327295A - Piezoelectric filter, mass load realization method thereof and device comprising piezoelectric filter - Google Patents
Piezoelectric filter, mass load realization method thereof and device comprising piezoelectric filter Download PDFInfo
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Abstract
The invention provides a method for realizing mass load of a piezoelectric filter, the piezoelectric filter, a duplexer, a high-frequency front-end circuit and a communication device. In the method, the piezoelectric filter includes a series branch and a parallel branch, the series branch includes three or more bulk acoustic wave resonators connected in series between input and output terminals of the piezoelectric filter, a parallel circuit is provided between a connection point of adjacent resonators and a ground terminal, in the method, a temperature compensation layer of the resonators is used as a mass load, and: all the series resonators are the same resonators, and each series resonator has or does not have a temperature compensation layer; all parallel resonators have a temperature compensation layer and are thicker than the temperature compensation layer of the series resonator. By adopting the technical scheme of the invention, the left side roll-off of the filter and the better selection of the passband insertion loss performance are considered.
Description
Technical Field
The present invention relates to the field of microelectronics, and more particularly, to a method for implementing a mass load of a piezoelectric filter, a duplexer, a high-frequency front-end circuit, and a communication device.
Background
At present, a small-sized filtering device capable of meeting the use requirement of a communication terminal is mainly a piezoelectric acoustic wave filter, and resonators constituting the acoustic wave filter mainly include: FBAR (Film Bulk Acoustic Resonator), SMR (solid Mounted Resonator), and SAW (Surface Acoustic wave). Among them, filters manufactured based on the bulk acoustic wave principle FBAR and SMR (collectively referred to as BAW, bulk acoustic wave resonator) have advantages of lower insertion loss, faster roll-off characteristics, and the like, compared to filters manufactured based on the surface acoustic wave principle SAW.
The piezoelectric material and the metal material which form the acoustic wave resonator have the characteristic of negative temperature coefficient, namely, when the temperature is increased, the resonance frequency of the resonator moves towards the low frequency direction (temperature drift) in a certain proportion. Generally, the temperature coefficient of SAW is-35 ppm/DEG C to-50 ppm/DEG C, and the temperature coefficient of BAW is-25 ppm/DEG C to-30 ppm/DEG C. Although BAW has a significant performance advantage in temperature drift compared to SAW, in some special application scenarios, such a temperature coefficient still has an adverse effect on the performance of the rf transceiver system to which the filter is applied, for example, a filter defines a frequency variable range from the passband edge to the out-of-band rejection, and then the existence of the temperature coefficient makes the variable range smaller after considering the temperature drift frequency, thereby greatly increasing the design difficulty of the filter.
In order to solve the temperature drift problem commonly existing in the filter, a common solution is to add a material capable of achieving a temperature compensation effect into the resonator. For acoustic wave resonators, this temperature compensation material is often chosen to be silicon dioxide, mainly because silicon dioxide has a positive temperature coefficient that is exactly opposite to that of most materials, can be manufactured by common process, and is cheap at the same time, suitable for application in mass production of products. Such temperature compensated material resonators, also called TCF resonators, are components of temperature compensated filters.
However, the introduction of a temperature compensation layer in the resonator is not without cost, and it deteriorates the characteristics of the resonator, mainly due to the increase in the loss of the resonator and the decrease in the electromechanical coupling coefficient. The loss of the resonator increases and the insertion loss of the filter increases, thereby increasing the loss in the radio frequency link and deteriorating the transceiving performance of the radio frequency front end. The electromechanical coupling coefficient is reduced, the distance between the series resonance frequency and the parallel resonance frequency of the resonator is reduced, the roll-off characteristic of the filter is possibly improved, but the bandwidth of the filter is narrowed at the same time, in most communication systems, the bandwidth of the filter is provided according to the system requirements, and the bandwidth cannot be narrowed without limitation.
Therefore, how to realize the high roll-off requirement and the temperature characteristic of the BAW filter under the condition of a certain bandwidth requirement becomes a problem to be solved by filter design engineers.
Disclosure of Invention
In view of the above, the present invention provides a method for implementing a mass load of a piezoelectric filter, a duplexer, a high-frequency front-end circuit, and a communication device, so as to solve the technical problems in the prior art.
To achieve the above object, according to one aspect of the present invention, there is provided a method of implementing a mass load of a piezoelectric filter.
In the method of the present invention for realizing a mass load of a piezoelectric filter, the piezoelectric filter includes a series branch and a parallel branch, the series branch includes three or more bulk acoustic wave resonators connected in series between input and output terminals of the piezoelectric filter, and a parallel circuit is provided between a connection point of adjacent resonators and a ground terminal, in the method, a temperature compensation layer of the resonator is used as the mass load, and: all the series resonators are the same resonators, and each series resonator has or does not have a temperature compensation layer; all parallel resonators have a temperature compensation layer and are thicker than the temperature compensation layer of the series resonator.
Compared with the common piezoelectric filter without the temperature compensation layer, the filter only adding the temperature compensation layer on the parallel resonator has the following advantages: the parallel resonator adopts zero temperature drift and small Kt2A temperature compensated resonator ofThe roll-off characteristic on the left side of the filter is effectively improved. Meanwhile, compared with a temperature compensation filter with the series resonators and the parallel resonators all made of temperature compensation resonators, the temperature compensation filter has the following advantages: 1) the temperature compensation layer is used as the mass load, so that the additional process step of manufacturing the mass load is omitted; 2) the series resonator adopts a common resonator instead of a temperature compensation resonator, and the loss of the resonator is relatively good, so that the insertion loss characteristic of the filter is improved; 3) the series resonator adopts a common resonator instead of a temperature compensation resonator, and properly reduces the Kt of the temperature compensation resonator2The reduction in filter bandwidth is reduced.
Optionally, the thickness of the temperature compensation layer of the parallel resonator satisfies the following condition: the positive temperature drift effect generated by the temperature compensation layer counteracts the negative temperature drift effect of other layers of the parallel resonator, so that the temperature coefficient of the parallel resonator is in the neighborhood of a specified range of 0 ppm/DEG C.
Optionally, the thickness of the temperature compensation layer of the parallel resonator further satisfies the following condition: the mass load effect generated by the thickness of the temperature compensation layer of the parallel resonator enables the difference value between the series resonance frequency of the series resonator and the parallel resonance frequency of the parallel resonator after the temperature compensation layer is added to be within a preset range.
Optionally, the method further comprises: adjusting the thickness of one or more of the upper electrode, the lower electrode, the piezoelectric layer, and the temperature compensation layer of the shunt resonator to bring the temperature coefficient of the shunt resonator within the neighborhood of a preset range of 0 ppm/DEG C, and adjusting the thickness of one or more of the upper electrode, the lower electrode, the piezoelectric layer, and the temperature compensation layer of the series resonator to bring the temperature coefficient of the series resonator within the neighborhood of a preset range of a specified value less than 0 ppm/DEG C to adjust the roll-off performance of the filter.
According to another aspect of the present invention, a piezoelectric filter is provided.
The piezoelectric filter comprises a series branch and a parallel branch, wherein the series branch comprises more than three bulk acoustic wave resonators connected in series between the input end and the output end of the piezoelectric filter, a parallel circuit is arranged between the connecting point of adjacent resonators and a grounding end, all the series resonators are the same resonators, and each series resonator is provided with or does not have a temperature compensation layer; all parallel resonators have a temperature compensation layer and are thicker than the temperature compensation layer of the series resonator.
Optionally, the thickness of the temperature compensation layer of the parallel resonator satisfies the following condition: the positive temperature drift effect generated by the temperature compensation layer counteracts the negative temperature drift effect of other layers of the parallel resonator, so that the temperature coefficient of the parallel resonator is in the neighborhood of a specified range of 0 ppm/DEG C.
Optionally, the thickness of the temperature compensation layer of the parallel resonator further satisfies the following condition: the mass load effect generated by the thickness of the temperature compensation layer of the parallel resonator enables the difference value between the series resonance frequency of the series resonator and the parallel resonance frequency of the parallel resonator after the temperature compensation layer is added to be within a preset range.
According to still another aspect of the present invention, there is provided a duplexer including the piezoelectric filter according to the present invention.
According to still another aspect of the present invention, a high-frequency front-end circuit includes the piezoelectric filter according to the present invention.
According to still another aspect of the present invention, there is provided a communication apparatus including the piezoelectric filter of the present invention.
Drawings
The drawings are included to provide a better understanding of the invention and are not to be construed as unduly limiting the invention. Wherein:
FIG. 1A is an electrical symbol of BAW, and FIG. 1B is an equivalent electrical model diagram of BAW;
FIG. 2 is a diagram of resonator impedance versus fs, fp;
FIG. 3 is a schematic diagram of a conventional generic resonator;
FIG. 4 is a schematic diagram of a temperature compensated resonator;
FIG. 5 is a graph comparing the performance of a resonator before and after heating a temperature compensation layer;
fig. 6 is a circuit diagram of the piezoelectric filter 100 of the embodiment of the present invention;
fig. 7 is a circuit diagram of the first proportional piezoelectric filter 001;
fig. 8A is a schematic diagram of the series-parallel resonator impedance-frequency relationship of the piezoelectric filter 001, and fig. 8B is a schematic diagram of the series-parallel resonator impedance-frequency relationship of the piezoelectric filter 100;
fig. 9A is a schematic diagram comparing amplitude-frequency curves of the piezoelectric filter 100 and the piezoelectric filter 001, and fig. 9B is a partially enlarged view of fig. 9A;
fig. 10A is a schematic diagram of three temperature curves of the piezoelectric filter 001 at low temperature, normal temperature, and high temperature, and fig. 10B is a partial enlarged view of fig. 10A;
fig. 11A is a schematic diagram of three temperature curves of the piezoelectric filter 100 at low temperature, normal temperature, and high temperature, and fig. 11B is a partial enlarged view of fig. 11A;
fig. 12 is a circuit diagram of the second comparative piezoelectric filter 002;
fig. 13A is a schematic diagram of the series-parallel resonator impedance-frequency relationship of the piezoelectric filter 002, and fig. 13B is a schematic diagram of the series-parallel resonator impedance-frequency relationship of the piezoelectric filter 100;
fig. 14A is a schematic diagram comparing amplitude-frequency curves of the piezoelectric filter 100 and the piezoelectric filter 002, and fig. 14B is a partially enlarged view of fig. 14A;
fig. 15 is a schematic diagram of the structure of a filter in which both the series filter and the parallel filter have temperature-compensated layers according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
In order to make the content of the present invention better known to those skilled in the art, the inventor first briefly introduces the basic structure and performance of the temperature compensated resonator.
FIG. 1A is an electrical notation of a piezoelectric acoustic wave resonatorFIG. 1B is a diagram of an equivalent electrical model thereof, which is simplified to L without considering a loss termm、CmAnd C0To form a resonant circuit. According to the resonance condition, the resonance circuit has two resonance frequency points: one is f when the impedance value of the resonant circuit reaches a minimum valuesA 1 is to fsDefining the resonance frequency point of the resonator in series; the other is f when the impedance value of the resonance circuit reaches a maximum valuepA 1 is to fpDefined as the parallel resonance frequency point of the resonator. Wherein the content of the first and second substances,
and, fsRatio fpIs small. At the same time, the electromechanical coupling coefficient Kt of the resonator is defined2 eff(hereinafter abbreviated as Kt)2) It may be used with fsAnd fpTo show that:
FIG. 2 shows resonator impedance vs. fsAnd fpThe relationship between them. At a particular frequency, the greater the effective electromechanical coupling coefficient, the greater fsAnd fpThe larger the frequency difference, i.e. the further apart the two resonance frequency points are. At the same time, the resonator is at fsThe magnitude of the impedance is defined as RsIt is the minimum value in the resonator impedance curve; bringing the resonator at fpThe magnitude of the impedance is defined as RpWhich is the maximum in the resonator impedance curve. RsAnd RpIs an important parameter for describing the resonance loss characteristics when RsThe smaller RpThe larger the loss of the resonator, the smaller the Q value, and the better the insertion loss characteristics of the filter.
Fig. 3 is a schematic diagram of a conventional general resonator. As shown in fig. 3, the resonator is fabricated on a substrate 104, and the bottom electrode 102 and the top electrode 101 are metal electrodes, typically several hundred nanometers thick. The piezoelectric material film 103 generally uses a zinc oxide or aluminum nitride material, and has a thickness of several hundred nanometers to several micrometers. In order to enable resonance of the acoustic wave generated therein, it is necessary to cause the acoustic wave to be reflected at the top and bottom electrode surfaces. Above the top electrode 101 is air capable of forming acoustic wave reflections, and in order to make the acoustic wave also reflect on the bottom surface of the bottom electrode, an air cavity 100 is formed below the bottom electrode 102. When an alternating voltage is applied to the top electrode 101 and the bottom electrode 102, the piezoelectric material film 103 is excited to generate a piezoelectric effect to generate a mechanical acoustic wave. The acoustic wave propagates and reflects between the top and bottom electrodes, forming a standing wave resonance that in turn forms a resonance in the electrical response. Such resonators are called cavity reflection bulk acoustic wave resonators, since the use of a cavity forms the reflection.
Fig. 4 is a schematic diagram of a temperature compensated resonator. The temperature compensated resonator may include: the top electrode 201, the bottom electrode 202, the piezoelectric layer 203, the substrate 204, the temperature compensation layer 205 inside the bottom electrode 202, and the air cavity 200 can be regarded as an FBAR resonator with the temperature compensation layer added on the basis of fig. 3. The material of the temperature compensation layer 205 is typically silicon dioxide and has a pattern that is less than or equal to the pattern of the bottom electrode, i.e., the compensation layer and bottom electrode appear as a sandwich biscuit or sandwich. Preferably, the temperature compensation layer 205 is completely encapsulated in the bottom electrode material, which is advantageous in that it can be effectively protected from other manufacturing processes. In addition, because the electrode materials above and below the temperature compensation layer are connected together at the edge, the formation of parasitic capacitance formed by the three is avoided, thereby greatly deteriorating the Kt of the resonator2And loss characteristics. Optionally, the ratio of the layout area of the temperature compensation layer to the layout area of the top layer or the bottom layer of the bottom electrode is 0.5-1.
Fig. 5 is a comparison of the resonator impedance curves before and after the temperature compensation layer is added to the resonator. Kt of resonator after adding temperature compensation layer2The original 6.5 percent is reduced to 3.4 percent, RsThe temperature coefficient of the resonator is changed from-25 ppm/DEG C to-30 ppm/DEG C to about 0 ppm/DEG C. As can be seen, the addition of the temperature compensation layer,Kt2will become about half of the original, RsWill increase to about 2 times the original, RpThe loss is reduced to about half of the original loss and the loss of the resonator is increased to some extent resulting in a reduction in the Q value.
The first aspect of the present invention provides a method for realizing a mass load of a piezoelectric filter, the piezoelectric filter including a series branch and a parallel branch, the series branch including three or more bulk acoustic wave resonators connected in series between output terminals of the piezoelectric filter, a parallel circuit being provided between a connection point of adjacent resonators and a ground terminal, in which method a temperature compensation layer of the resonators is used as the mass load, and: all the series resonators are the same resonators, and each series resonator has or does not have a temperature compensation layer; all the parallel resonators have a temperature compensation layer and are thicker than the temperature compensation layer of the series resonators.
It should be noted that, when the series resonators are the same common resonators, the series resonators have the advantages of simple structure and easy processing. In this embodiment, the thickness of the temperature compensation layer in the series resonator is zero, and therefore the difference in the thickness of the temperature compensation layer in the series-parallel resonator is equal to the thickness of the temperature compensation layer in the parallel resonator. It should be further noted that, when the series resonators are the same temperature compensation resonators, and the thickness of the temperature compensation layer of the series resonators is smaller than that of the temperature compensation layer of the parallel resonators, the thickness difference of the temperature compensation layers exists in the series resonators, so as to ensure that the series-parallel frequency difference is realized, that is, the load effect is realized.
Further, the temperature coefficient of the series resonator is zero. This means that the positive temperature drift effect produced by the temperature compensation layer can exactly cancel the negative temperature drift effect of all other layers, making the parallel resonator a temperature compensated resonator with a temperature coefficient equal to 0 ppm/c. In this embodiment, the temperature coefficient is zero, which means that the temperature drift effect of the temperature compensation layer exactly offsets the temperature drift effect of other layers, so that the piezoelectric filter has stable electrical performance under different environmental temperatures.
Further, the thickness of the temperature compensation layer of the parallel resonator is equivalent to the mass load effect, so that the parallel resonance frequency of the parallel resonator after the temperature compensation layer is added is equal to the series resonance frequency of the series resonator. It means that the thickness of the temperature compensation layer is exactly equal to the mass loading effect, so that the parallel resonance frequency of the parallel resonator after the temperature compensation layer is added is not nearly equal to the series resonance frequency of the series resonator without the temperature compensation layer, thereby forming the characteristic curve of the filter.
The method for realizing the mass load of the piezoelectric filter has obvious advantages in performance no matter compared with the situation that the series-parallel resonators are all provided with the common FBAR resonators or compared with the situation that the series-parallel resonators are all provided with the temperature compensation resonators, and gives consideration to the better choices of the left-side roll-off and the passband insertion loss performance.
A second aspect of the present invention provides a piezoelectric filter, including a series branch and a parallel branch, the series branch including three or more bulk acoustic wave resonators connected in series between output terminals of the piezoelectric filter, and a parallel circuit provided between a connection point of adjacent resonators and a ground terminal, characterized in that all the series resonators are identical resonators, and each series resonator has or does not have a temperature compensation layer; all the parallel resonators have a temperature compensation layer and are thicker than the temperature compensation layer of the series resonators.
Further, the temperature coefficient of the series resonator is zero.
Further, the thickness of the temperature compensation layer of the parallel resonator is equivalent to the mass load effect, so that the parallel resonance frequency of the parallel resonator after the temperature compensation layer is added is equal to the series resonance frequency of the series resonator.
Compared with a filter which is totally an ordinary FBAR resonator or a filter which is totally a temperature compensation resonator, the piezoelectric filter provided by the embodiment of the invention has obvious advantages in performance, and gives consideration to the better choices of the left-side roll-off and the passband insertion loss performance.
The piezoelectric filter of the embodiment of the present invention is listed below as a performance comparison with two other piezoelectric filters.
A piezoelectric filter 100 according to an embodiment of the present invention, whose circuit diagram is shown in fig. 6, includes 5 series resonators and 4 parallel resonators. All parallel resonators are temperature compensated resonators as in fig. 4, and all series resonators are common FBAR resonators as in fig. 3. The passband frequency range of the filter is 2565 MHz-2595 MHz, the passband bandwidth is 30MHz, and the out-of-band rejection of more than 45dB at 2540MHz is required.
A first comparative example, a piezoelectric filter 001, whose circuit diagram is shown in fig. 7, is provided, including 5 series common resonators and 4 parallel common resonators. The piezoelectric filter 001 is in a ladder-shaped cascade structure formed by a series resonator and a parallel resonator, a mass load layer is added on the parallel resonator, the material is the same as the electrode material for manufacturing a BAW device, and the parallel resonance frequency of the piezoelectric filter is basically the same as the resonance frequency of the series resonator, so that the curve characteristic of the filter is formed.
Fig. 8A is a schematic diagram of the series-parallel resonator impedance-frequency relationship of the piezoelectric filter 001, and fig. 8B is a schematic diagram of the series-parallel resonator impedance-frequency relationship of the piezoelectric filter 100. As can be seen from comparison of the two figures, the filter requires out-of-band rejection greater than 45dB at 2540MHz, and the series resonant frequency of the parallel resonator in the piezoelectric filter 100 of the embodiment and the first comparative piezoelectric filter 001 is set around 2530MHz, but since the parallel resonator in the embodiment is a temperature compensation resonator with relatively small Kt2 and the distance between fs and fp is smaller, the series resonant frequency of the series resonator in the embodiment is significantly lower than that of the first comparative resonator, which is to ensure the impedance matching characteristic of the filter in the passband.
Fig. 9A is a schematic diagram comparing amplitude-frequency curves of the piezoelectric filter 100 (solid line) and the piezoelectric filter 001 (broken line), and fig. 9B is a partially enlarged view of fig. 9A. Since the piezoelectric filter 001 uses common FBAR resonators, Kt2 is about 6.5%, and the bandwidth of the filter is wide. In order to ensure the out-of-band rejection at 2540MHz, the insertion loss of the filter at 2565MHz is about 3.2dB, meanwhile, because the passband is wider, the insertion loss at the right side of the passband can reach nearly 1.0dB, and the fluctuation value in the 30MHz passband range is larger. The parallel resonator of the embodiment adopts a temperature compensation resonator, the Kt2 of the parallel resonator is about 3.4%, and the frequency range of transition from the impedance minimum value to the impedance maximum value is smaller, so that better left-side roll-off characteristics can be realized. Meanwhile, due to the zero temperature drift characteristic of the parallel resonators, the roll-off edge on the left side of the filter is slightly changed along with the change of the temperature, and the roll-off margin of the filter is further increased.
Fig. 10A is a schematic diagram of three temperature curves of the piezoelectric filter 001 at low temperature, normal temperature, and high temperature, and fig. 10B is a partially enlarged view of fig. 10A. Wherein the black solid line is a curve at the normal temperature, since all resonators used have a temperature coefficient of-25 ppm/c to-30 ppm/c, the filter has a high insertion loss while the amplitude-frequency curve moves in the high frequency direction at a low temperature, and a low insertion loss while the amplitude-frequency curve moves in the low frequency direction at a high temperature, as compared with the normal temperature curve.
Fig. 11A is a schematic diagram of three temperature curves of the piezoelectric filter 100 at low temperature, normal temperature, and high temperature, and fig. 11B is a partially enlarged view of fig. 11A. The black solid line is a curve at normal temperature, because the series resonator is a common resonator and has a temperature coefficient of-25 ppm/DEG C to-30 ppm/DEG C, and the parallel resonator is a temperature compensation resonator and has a temperature coefficient of 0 ppm/DEG C, compared with the normal temperature curve, the filter moves towards the high frequency direction at the right side of the amplitude-frequency curve at low temperature, the insertion loss is good, and moves towards the low frequency direction at high temperature, and the insertion loss is poor. The right edge of the filter is anchored by the zero temperature drift characteristic of the temperature compensation resonator, and the change of the face frequency position is small, so that the roll-off characteristic of the full-eye wave filter at the corresponding position is improved.
As is clear from the comparison between the piezoelectric filter 100 and the piezoelectric filter 001, the filter in which the temperature compensation layer is added only to the parallel resonators has the following advantages over the ordinary piezoelectric filter without the temperature compensation layer: the parallel resonator adopts zero temperature drift and small Kt2The temperature compensation resonator can effectively improve the roll-off characteristic of the left side of the filter.
A second comparative example, a piezoelectric filter 002, whose circuit diagram is shown in fig. 12, includes 5 series temperature compensation resonators and 4 parallel temperature compensation resonators, is provided.
Fig. 13A is a schematic diagram showing the impedance-frequency relationship of the series-parallel resonators of the piezoelectric filter 002, and fig. 13B is a schematic diagram showing the impedance-frequency relationship of the series-parallel resonators of the piezoelectric filter 100, and it can be seen that the piezoelectric filter 002 has Kt2Small size, high loss and zero temp drift.
Fig. 14A is a comparison of amplitude-frequency curves of the piezoelectric filter 100 (solid line) and the piezoelectric filter 002 (broken line), and fig. 14B is a partially enlarged view of fig. 14A. Since the piezoelectric filter 002 is a temperature compensation resonator, Kt is2About 3.4% and the loss is large, so the bandwidth of the filter is narrow, the insertion loss at 2565MHz is about 3.6dB, the insertion loss at 2595MHz is about 2.6dB, and the overall in-band insertion loss in the passband is about 0.35dB worse than in the example. Although the piezoelectric filter 002 has good temperature drift characteristics of the roll-off edges on the left and right sides because of all the temperature compensation resonators, the loss in the bandwidth and insertion loss is large, and the application requirements of the filter cannot be met.
As can be seen from the comparison between the piezoelectric filter 100 and the piezoelectric filter 002, the piezoelectric filter according to the embodiment of the present invention has the following advantages compared to a piezoelectric filter in which all the series and parallel resonators are made of temperature compensation resonators: (1) the temperature compensation layer is used as the mass load, so that the process step of manufacturing the mass load is omitted; (2) the series resonator adopts a common resonator instead of a temperature compensation resonator, and the loss of the resonator is relatively good, so that the insertion loss characteristic of the filter is improved; (3) the series resonator adopts a common resonator instead of a temperature compensation resonator, and properly reduces the Kt of the temperature compensation resonator2The reduction in filter bandwidth is reduced.
Fig. 15 is a schematic diagram of the structure of a filter according to an embodiment of the present invention. The FBAR filter 300 shown in fig. 15 has the same circuit diagram as that of fig. 11, and both series and parallel resonators are temperature-compensated resonators. The figure shows a cavity, a lower electrode, a piezoelectric layer, an upper electrode, and a temperature compensation layer wrapped around the lower electrode and located in the resonance region. It should be noted that, in order to protect the resonator from oxidation due to environmental influences, a passivation layer is usually formed above the upper electrode, and the passivation layer may be made of a non-metallic material with relatively stable properties, such as silicon dioxide, or even the same material as the piezoelectric layer, such as aluminum nitride. The resonators on the left side in fig. 15 are series resonators, the resonators on the right side are parallel resonators, and the resonators in the other filters are not shown. The thickness of the temperature compensation layer of the series resonator is t1, the thickness of the temperature compensation layer of the parallel resonator is t2, t1 and t2 satisfy the relation, t2 is greater than t1, and the thickness difference between the t2 and the t1 forms the frequency difference between the parallel resonator and the series resonator, namely the mass load effect required by the design of the filter. The thickness of other layers of the series resonator and the parallel resonator are the same, and in order to better show the thickness relation of each layer, the figure shows the boundary oblique angle formed in the thin film deposition manufacturing process of each layer due to different thicknesses of the temperature compensation layers in more detail compared with the previous resonator. In this embodiment, since the thickness of the temperature compensation layers of the series and parallel resonators is different, and the other layers are the same, the temperature coefficients of the two resonators must be different. In the design process, a proper lamination can be selected according to the characteristics of the electrical performance of the filter, so that the temperature coefficient of the corresponding position is closer to 0 ppm/DEG C. For example: for roll-off requirements on the left side of the filter passband, the thickness of each layer may be designed such that the temperature coefficient of the shunt resonators is around 0 ppm/deg.C, while the temperature coefficient of the series resonators may differ a little more than 0 ppm/deg.C, e.g., -10 ppm. The filter formed in this way can obtain better left side roll-off, and meanwhile, the right side roll-off is also improved to a certain extent compared with the filter without a temperature compensation resonator.
In summary, the piezoelectric filter of the embodiment of the present invention has obvious advantages in performance, and gives consideration to both the left-side roll-off and the pass-band insertion loss performance, compared with a filter that is entirely a common FBAR resonator and a filter that is entirely a temperature compensation resonator.
The above-described embodiments should not be construed as limiting the scope of the invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions can occur, depending on design requirements and other factors. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method of realizing a mass load of a piezoelectric filter including a series arm and a parallel arm, the series arm including three or more bulk acoustic wave resonators connected in series between input and output terminals of the piezoelectric filter, a parallel circuit being provided between a connection point of adjacent resonators and a ground terminal, characterized in that in the method, a temperature compensation layer of a resonator is taken as a mass load, and:
all the series resonators are the same resonators, and each series resonator has or does not have a temperature compensation layer;
all parallel resonators have a temperature compensation layer and are thicker than the temperature compensation layer of the series resonator.
2. The method of claim 1, wherein the thickness of the temperature compensation layer of the parallel resonator satisfies the following condition: the positive temperature drift effect generated by the temperature compensation layer counteracts the negative temperature drift effect of other layers of the parallel resonator, so that the temperature coefficient of the parallel resonator is in the neighborhood of a specified range of 0 ppm/DEG C.
3. The method of claim 2, wherein the thickness of the temperature compensation layer of the parallel resonator further satisfies the following condition: the mass load effect generated by the thickness of the temperature compensation layer of the parallel resonator enables the difference value between the series resonance frequency of the series resonator and the parallel resonance frequency of the parallel resonator after the temperature compensation layer is added to be within a preset range.
4. The method of claim 1, further comprising:
adjusting the thickness of one or more of the upper electrode, the lower electrode, the piezoelectric layer, and the temperature compensation layer of the shunt resonator to bring the temperature coefficient of the shunt resonator within the neighborhood of a preset range of 0 ppm/DEG C, and adjusting the thickness of one or more of the upper electrode, the lower electrode, the piezoelectric layer, and the temperature compensation layer of the series resonator to bring the temperature coefficient of the series resonator within the neighborhood of a preset range of a specified value less than 0 ppm/DEG C to adjust the roll-off performance of the filter.
5. A piezoelectric filter includes a series branch and a parallel branch, the series branch includes more than three bulk acoustic wave resonators connected in series between the input and output terminals of the piezoelectric filter, a parallel circuit is provided between the connection point of the adjacent resonators and the ground terminal,
all the series resonators are the same resonators, and each series resonator has or does not have a temperature compensation layer;
all parallel resonators have a temperature compensation layer and are thicker than the temperature compensation layer of the series resonator.
6. The piezoelectric filter according to claim 5, wherein the thickness of the temperature compensation layer of the parallel resonator satisfies the following condition: the positive temperature drift effect generated by the temperature compensation layer counteracts the negative temperature drift effect of other layers of the parallel resonator, so that the temperature coefficient of the parallel resonator is in the neighborhood of a specified range of 0 ppm/DEG C.
7. The piezoelectric filter according to claim 6, wherein the thickness of the temperature compensation layer of the parallel resonator further satisfies the following condition: the mass load effect generated by the thickness of the temperature compensation layer of the parallel resonator enables the difference value between the series resonance frequency of the series resonator and the parallel resonance frequency of the parallel resonator after the temperature compensation layer is added to be within a preset range.
8. A duplexer comprising the piezoelectric filter according to any one of claims 5 to 7.
9. A high-frequency front-end circuit comprising the piezoelectric filter according to any one of claims 5 to 7.
10. A communication apparatus comprising the piezoelectric filter according to any one of claims 5 to 7.
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| CN202010088342.9A CN111327295B (en) | 2020-02-12 | 2020-02-12 | Piezoelectric filter, mass load realization method thereof and device comprising piezoelectric filter |
| PCT/CN2020/141269 WO2021159882A1 (en) | 2020-02-12 | 2020-12-30 | Piezoelectric filter and mass loading implementation method therefor, and apparatus comprising piezoelectric filter |
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| CN202010088342.9A CN111327295B (en) | 2020-02-12 | 2020-02-12 | Piezoelectric filter, mass load realization method thereof and device comprising piezoelectric filter |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111988013A (en) * | 2020-08-31 | 2020-11-24 | 诺思(天津)微系统有限责任公司 | Temperature compensation filter optimization method, temperature compensation filter, multiplexer and communication equipment |
| WO2021159882A1 (en) * | 2020-02-12 | 2021-08-19 | 诺思(天津)微系统有限责任公司 | Piezoelectric filter and mass loading implementation method therefor, and apparatus comprising piezoelectric filter |
| WO2021227941A1 (en) * | 2020-05-09 | 2021-11-18 | 诺思(天津)微系统有限责任公司 | Bulk acoustic wave resonance assembly and manufacturing method, filter and electronic device |
| WO2022135252A1 (en) * | 2020-12-24 | 2022-06-30 | 诺思(天津)微系统有限责任公司 | Bulk acoustic resonator having temperature compensation layer, and filter and electronic device |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1174452A (en) * | 1996-07-10 | 1998-02-25 | 松下电器产业株式会社 | Energy trapping piezoelectric device and producing method thereof |
| CN1507152A (en) * | 2002-12-11 | 2004-06-23 | Tdk��ʽ���� | Piezoelectric resonance wave filter and duplexer |
| CN1929303A (en) * | 2005-09-09 | 2007-03-14 | 安华高科技无线Ip（新加坡）私人有限公司 | Adjusted frequency temperature coefficient resonator |
| CN102916674A (en) * | 2011-08-03 | 2013-02-06 | 太阳诱电株式会社 | Acoustic wave filter |
| US20130207515A1 (en) * | 2012-02-14 | 2013-08-15 | Taiyo Yuden Co., Ltd. | Acoustic wave device |
| CN109831176A (en) * | 2018-12-05 | 2019-05-31 | 天津大学 | A kind of piezoelectric acoustic-wave filter and duplexer |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10784840B2 (en) * | 2018-06-25 | 2020-09-22 | Ishiang Shih | Tunable film bulk acoustic resonators and FBAR filters with digital to analog converters |
| CN111327295B (en) * | 2020-02-12 | 2020-11-27 | 诺思(天津)微系统有限责任公司 | Piezoelectric filter, mass load realization method thereof and device comprising piezoelectric filter |
-
2020
- 2020-02-12 CN CN202010088342.9A patent/CN111327295B/en active Active
- 2020-12-30 WO PCT/CN2020/141269 patent/WO2021159882A1/en active Application Filing
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1174452A (en) * | 1996-07-10 | 1998-02-25 | 松下电器产业株式会社 | Energy trapping piezoelectric device and producing method thereof |
| CN1507152A (en) * | 2002-12-11 | 2004-06-23 | Tdk��ʽ���� | Piezoelectric resonance wave filter and duplexer |
| CN1929303A (en) * | 2005-09-09 | 2007-03-14 | 安华高科技无线Ip（新加坡）私人有限公司 | Adjusted frequency temperature coefficient resonator |
| CN102916674A (en) * | 2011-08-03 | 2013-02-06 | 太阳诱电株式会社 | Acoustic wave filter |
| US20130207515A1 (en) * | 2012-02-14 | 2013-08-15 | Taiyo Yuden Co., Ltd. | Acoustic wave device |
| CN109831176A (en) * | 2018-12-05 | 2019-05-31 | 天津大学 | A kind of piezoelectric acoustic-wave filter and duplexer |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2021159882A1 (en) * | 2020-02-12 | 2021-08-19 | 诺思(天津)微系统有限责任公司 | Piezoelectric filter and mass loading implementation method therefor, and apparatus comprising piezoelectric filter |
| WO2021227941A1 (en) * | 2020-05-09 | 2021-11-18 | 诺思(天津)微系统有限责任公司 | Bulk acoustic wave resonance assembly and manufacturing method, filter and electronic device |
| CN111988013A (en) * | 2020-08-31 | 2020-11-24 | 诺思(天津)微系统有限责任公司 | Temperature compensation filter optimization method, temperature compensation filter, multiplexer and communication equipment |
| CN111988013B (en) * | 2020-08-31 | 2021-06-01 | 诺思(天津)微系统有限责任公司 | Temperature compensation filter optimization method, temperature compensation filter, multiplexer and communication equipment |
| WO2022042464A1 (en) * | 2020-08-31 | 2022-03-03 | 诺思(天津)微系统有限责任公司 | Temperature compensating filter optimization method and temperature compensating filter, multiplexer, and communications device |
| WO2022135252A1 (en) * | 2020-12-24 | 2022-06-30 | 诺思(天津)微系统有限责任公司 | Bulk acoustic resonator having temperature compensation layer, and filter and electronic device |
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| WO2021159882A1 (en) | 2021-08-19 |
| CN111327295B (en) | 2020-11-27 |
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Denomination of invention: Piezoelectric filter and its mass load implementation method and device containing piezoelectric filter Effective date of registration: 20210908 Granted publication date: 20201127 Pledgee: Tianjin TEDA Haihe intelligent manufacturing industry development fund partnership (L.P.) Pledgor: ROFS MICROSYSTEM(TIANJIN) Co.,Ltd. Registration number: Y2021980009022 |
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