CN115498976A

CN115498976A - Filter, method for improving performance of filter and electronic equipment

Info

Publication number: CN115498976A
Application number: CN202110673412.1A
Authority: CN
Inventors: 李娜; 庞慰; 蔡华林
Original assignee: ROFS Microsystem Tianjin Co Ltd
Current assignee: ROFS Microsystem Tianjin Co Ltd
Priority date: 2021-06-17
Filing date: 2021-06-17
Publication date: 2022-12-20

Abstract

The embodiment of the invention discloses a filter, which comprises an LC filter circuit consisting of a capacitor and an inductor, wherein the LC filter circuit comprises a plurality of resonance structures, at least one resonance structure is configured to be a hybrid resonance structure, the hybrid resonance structure is realized by replacing the capacitor of the resonance structure at a specified position in the LC filter circuit with an acoustic resonator, so that the hybrid resonance structure can improve the roll-off of the left side or the right side of the filter, the specified position is determined by the inductance value of the inductor and the capacitance value of the capacitor of each resonance structure in the LC filter circuit, and the acoustic resonator has a predetermined resonance frequency. The embodiment of the invention also discloses a method for improving the performance of the filter. The invention can improve the design efficiency and the roll-off of the filter for a flexible and changeable LC filter framework.

Description

Filter, method for improving performance of filter and electronic equipment

Technical Field

The invention relates to the technical field of semiconductors, in particular to a filter, a method for improving the performance of the filter and electronic equipment.

Background

With the rapid development of communication technology, communication systems become increasingly complex, the requirements of filters are increased, and the design difficulty of the filters is also increased. The filters required by the conventional systems require a sharp roll-off in order to prevent the signals in adjacent and closer pass bands from interfering with each other while requiring low insertion loss and large bandwidth. Although a conventional LC filter can achieve a large bandwidth, many stages of filtering are required to suppress the high potential, which increases insertion loss. If a separate acoustic filter is used, the bandwidth is limited, although a sharp roll-off can be provided.

The hybrid filter adopting the LC filter and the acoustic resonator has the advantages of the LC filter and the acoustic resonator, and can realize high roll-off performance while realizing a wide frequency band. In the correlation technique, when combining the design acoustics syntonizer in the LC wave filter, because the structure of LC wave filter is various nimble, especially the LC wave filter of complex structure, can't simple efficient confirm the position of acoustics syntonizer in the design process, lead to the design process efficiency lower, and can't realize the good matching of acoustics syntonizer and LC wave filter.

Disclosure of Invention

In order to solve the above problems, an object of the present invention is to provide a filter, a method for improving the performance of the filter, and an electronic device, which can determine the optimal matching between an LC filter and an acoustic resonator in a complicated LC filter architecture.

The embodiment of the invention provides a filter, which comprises an LC filter circuit consisting of a capacitor and an inductor, wherein the LC filter circuit comprises a plurality of resonance structures,

at least one resonant structure is configured as a hybrid resonant structure implemented by replacing a capacitor of the resonant structure at a designated location in the LC filter circuit with an acoustic resonator, such that the hybrid resonant structure can increase the filter roll-off on the left or right side,

wherein the specified position is determined by inductance values of inductors and capacitance values of capacitors of respective resonance structures in the LC filter circuit, and the acoustic resonator has a predetermined resonance frequency.

As a further improvement of the invention, the inductance value of the inductor and the capacitance value of the capacitor of the resonance structure at the specified position meet the preset condition,

the meeting of the preset condition comprises one of the following steps:

the inductance value of the inductor and the capacitance value of the capacitor satisfy

Wherein C represents a capacitance value of the capacitor, L represents an inductance value of the inductor, fp _left Representing the frequency point, fp, of the left edge of the filter passband _right And representing the frequency point of the edge on the right side of the passband of the filter.

As a further improvement of the invention, the inductance value of the inductor and the capacitance value of the capacitor are satisfied

Is located at a first specified position in said LC filter circuit,

after the hybrid resonance structure is configured at the first designated position, the hybrid resonance structure is used for improving the roll-off of the left side of the filter.

As a further improvement of the invention, the inductance value of the inductor and the capacitance value of the capacitor satisfy

Is located at a second specified position in said LC filter circuit,

and after the second appointed position is configured with the hybrid resonance structure, the hybrid resonance structure is used for improving the roll-off of the right side of the filter.

As a further improvement of the present invention, the hybrid resonance structure is a series resonance structure in which the acoustic resonator and the inductor are connected in series, or

The acoustic resonator and the inductor are connected in parallel to form a parallel resonant structure.

As a further improvement of the present invention, the filter is one of a low-pass filter, a high-pass filter and a band-pass filter.

As a further improvement of the invention, the acoustic resonator is a BAW resonator or a SAW resonator.

As a further improvement of the present invention, the resonant frequency of the acoustic resonator is determined by the frequency point at the position where the filter roll-off is to be increased.

The embodiment of the invention also provides a method for improving the performance of a filter, wherein the filter comprises an LC filter circuit consisting of a capacitor and an inductor, the LC filter circuit comprises a plurality of resonance structures, and the method comprises the following steps:

determining at least one designated location in the LC filter circuit by the inductance of the inductor and the capacitance of the capacitor of each resonant structure in the LC filter circuit,

replacing the capacitors of the resonant structure at the designated location with acoustic resonators configured to form a hybrid resonant structure such that the hybrid resonant structure increases roll-off on the left or right side of the filter after the hybrid resonant structure is configured at the designated location,

wherein the acoustic resonator has a predetermined resonant frequency.

As a further improvement of the present invention, the determining at least one designated position in the LC filter circuit by the inductance value of the inductor and the capacitance value of the capacitor of each resonant structure in the LC filter circuit includes one of:

when the inductance value of the inductor and the capacitance value of the capacitor of the resonant structure satisfy

Determining the position of the resonance structure in the LC filter circuit as the designated position;

Is located at a first specified position in said LC filter circuit,

the method further comprises the following steps: after the hybrid resonant structure is configured at the first designated position, the hybrid resonant structure is used for improving the roll-off on the left side of the filter.

Is located at a second specified position in said LC filter circuit,

the method further comprises the following steps: and after the hybrid resonance structure is configured at the second appointed position, the hybrid resonance structure is used for improving the roll-off on the right side of the filter.

As a further improvement of the present invention, the method further comprises:

and determining the resonant frequency of the acoustic resonator through the frequency point at the position where the filter rolls off to be lifted.

The embodiment of the invention also provides electronic equipment comprising the filter.

The invention has the beneficial effects that:

for a flexible and changeable LC filter framework, the inductance value of an inductor and the capacitance value range of a capacitor of an LC series resonance structure or a parallel resonance structure in the LC filter are defined, and the capacitance of a proper resonance structure is selected from the LC filter to replace an acoustic resonator, so that the roll-off of the filter is improved under the condition of not reducing in-band insertion loss and even improving the insertion loss of the edge of a pass band. The optimal matching of the acoustic resonator is determined through the inductance value of the inductor and the capacitance value of the capacitor, so that the design efficiency of the filter can be improved, and the filter can reach better performance indexes.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.

FIG. 1 is a schematic diagram of a related art filter circuit having a separate capacitor in the series branch of the LC filter circuit, in which 101-the LC filter circuit, C101-the capacitor, R101-the acoustic resonator;

FIG. 2 is a schematic diagram of a filter circuit in which the separately provided capacitors of FIG. 1 are replaced with acoustic filters, in this case 102-LC filter circuits;

FIG. 3 is a diagram illustrating the effect of the filter circuit shown in FIG. 2;

FIG. 4 is a schematic diagram of impedance comparison of an acoustic resonator alone and an acoustic resonator in series with an inductor;

FIG. 5 is a schematic diagram showing the roll-off improvement of different sides of the filter for different inductance values of the inductor and capacitance values of the capacitor when the equivalent resonant frequency of the acoustic resonator is 5240MHz after the acoustic resonator is connected with the inductor in series;

FIG. 6 is a schematic diagram of impedance comparison of an acoustic resonator alone and an acoustic resonator in parallel with an inductor;

FIG. 7 is a schematic diagram showing the roll-off improvement of different sides of the filter for different inductance values of the inductor and capacitance values of the capacitor when the equivalent resonant frequency of the acoustic resonator is 1960MHz after the inductor is connected in parallel with the acoustic resonator;

fig. 8 is a schematic diagram of a filter circuit in which the capacitors of the LC series resonant structure in the series branches of the LC filter circuit are replaced with acoustic resonators, according to the first exemplary embodiment of the present invention, in which 210-the LC filter circuit, L210-the inductor, R210-the BAW resonator;

FIG. 9 is a diagram illustrating the effect of the filter circuit shown in FIG. 8;

fig. 10 is a schematic diagram of a filter circuit in which the capacitors of the LC series resonant structure in the series arms of the LC filter circuit are replaced by acoustic resonators, as described in a comparative example of the first exemplary embodiment of the present invention, in which 220-the LC filter circuit, the L220-inductor, and the R220-the BAW resonator;

FIG. 11 is a schematic diagram of the effect of the filter circuit shown in FIG. 10, wherein the effect of the filter circuit not satisfying the scope of the present invention is shown;

fig. 12 is a schematic diagram of a filter circuit in which the capacitors of the LC series resonant structure in the series arms of the LC filter circuit are replaced by acoustic resonators, in accordance with a second exemplary embodiment of the present invention, in which 230-LC filter circuit, L230-inductor, R230-BAW resonator;

FIG. 13 is a diagram illustrating the effect of the filter circuit shown in FIG. 12;

fig. 14 is a schematic diagram of a filter circuit in which capacitors of an LC series resonant structure in the series arm of an LC filter circuit are replaced with acoustic resonators, according to a comparative example of a second exemplary embodiment of the present invention, in which 240-LC filter circuit, L240-inductor, R240-BAW resonator;

FIG. 15 is a schematic diagram of the effect of the filter circuit shown in FIG. 14, wherein the effect of the filter circuit not satisfying the scope of the present invention is shown;

fig. 16 is a schematic diagram of a filter circuit in which capacitors of an LC parallel resonant structure in parallel branches of an LC filter circuit are replaced with acoustic resonators, according to a third exemplary embodiment of the present invention, in which 250-LC filter circuit, L250-inductor, R250-BAW resonator;

FIG. 17 is a diagram illustrating the effect of the filter circuit shown in FIG. 16;

fig. 18 is a schematic diagram of a filter circuit in which capacitors of an LC parallel resonant structure in parallel branches of an LC filter circuit are replaced with acoustic resonators, according to a fourth exemplary embodiment of the present invention, in which 260-LC filter circuit, L260-inductor, R260-BAW resonator;

fig. 19 is a schematic diagram illustrating an effect of the filter circuit shown in fig. 18.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that, if directional indications (such as up, down, left, right, front, and back … …) are involved in the embodiment of the present invention, the directional indications are only used to explain the relative position relationship between the components, the motion situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indications are changed accordingly.

In addition, in the description of the present invention, the terms used are only for illustrative purposes, and are not intended to limit the scope of the present invention. The terms "comprises" and/or "comprising" are used to specify the presence of stated elements, steps, operations, and/or components, but do not preclude the presence or addition of one or more other elements, steps, operations, and/or components. The terms "first," "second," and the like may be used to describe various elements, not necessarily order, and not necessarily limit the elements. In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified. These terms are only used to distinguish one element from another. These and/or other aspects will become apparent to those of ordinary skill in the art in view of the following drawings, and the description of the embodiments of the present invention will be more readily understood by those of ordinary skill in the art. The drawings are only for purposes of illustrating the described embodiments of the invention. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated in the present application may be employed without departing from the principles described in the present application.

In the related art, in a simpler LC filtering architecture, a capacitor is separately disposed in a series or parallel branch of a filtering circuit, and at this time, the capacitor may be directly replaced by an acoustic resonator to enhance the roll-off of the filter. The maximum impedance of the acoustic resonator is at the roll-off and the minimum impedance is in the pass-band, so that when the acoustic resonator is substituted for the capacitor, the roll-off is strengthened, and the insertion loss at the edge of the pass-band is improved, which is the optimal matching condition when the capacitor is independently arranged on the series branch or the parallel branch.

For example, the band pass filter 101 shown in fig. 1 has a separate capacitor C101 in its series branch, and in this case, the capacitor C101 may be replaced with an acoustic resonator R101 to form a filter circuit 102 shown in fig. 2. The acoustic resonator R101 and the capacitor C101 have the same capacitance value in the range of the filter passband, the parallel resonance frequency Fp of the acoustic resonator R101 forms a zero point at the right roll-off edge of the filter passband to strengthen the roll-off index at the right side of the LC filter, and the series resonance frequency Fs of the acoustic resonator R101 is in the filter passband to reduce the passband insertion loss at the position. Fig. 3 shows the effect of replacing capacitor C101 with acoustic resonator R101, where LC represents the LC filter circuit in fig. 1 and LC + BAW represents the replaced filter circuit in fig. 2, and it can be seen that the new filter will enhance the right roll-off without reducing the insertion loss at the edges, and is an optimal match for the LC filter and the acoustic resonator.

However, for a more complex LC filter architecture, there is no separately arranged capacitor in the serial or parallel branch of the filter circuit, and the above method cannot satisfy the LC filter with a complex structure. Based on the structure, the invention provides the filter which can be applied to the LC filter framework with the complex structure so as to improve the roll-off performance of the complex LC filter while realizing the broadband.

The filter comprises an LC filter circuit consisting of a capacitor and an inductor, wherein the LC filter circuit comprises a plurality of resonance structures,

Due to the structural versatility and flexibility of LC filters, the effect of acoustic resonators on the overall filter performance, especially at the passband edge and near out-of-band rejection, is different instead of capacitors at different locations. The filter is a filter combining an LC filter and an acoustic resonator, and can be suitable for LC filters with complex structures. According to the difference of LC filter frameworks and the difference of inductance and capacitance values of each resonance structure in an LC filter circuit, through analyzing the value range of each inductance and capacitance, the most suitable resonance structure is selected from a plurality of resonance structures, and a capacitor in the most suitable resonance structure is replaced by an acoustic resonator, so that the performance of the filter can be improved, especially the roll-off of a filter sideband is enhanced, for example, the roll-off of the left side or the right side of the filter sideband is realized, the optimal matching of the LC filter and the acoustic resonator is further realized, and the roll-off of the acoustic resonator on the filter is improved to a great extent under the condition that the in-band insertion loss is not reduced and even the insertion loss of a passband edge can be improved. The acoustic resonator replaces a capacitor that has the same capacitance value as the replaced capacitor.

It is noted that the resonant structure in the LC filter circuit may be located in the series branch or may be located in the parallel branch. The resonance structure may be an LC series resonance structure in which an inductor and a capacitor are connected in series, or an LC parallel resonance structure in which an inductor and a capacitor are connected in parallel. Alternatively, the resonant structure is a composite resonant structure composed of one or more capacitors, inductors, resistors capable of producing at least one series resonant electrical response or at least one parallel resonant electrical response, which can be equivalent to a combination of one or more elementary LC series resonant structures and/or LC parallel resonant structures. It is to be understood that the plurality of resonant structures may be a plurality of LC series resonant structures, a plurality of LC parallel resonant structures, or a combination of an LC series resonant structure and an LC parallel resonant structure. The plurality of resonant structures may also comprise a composite resonant structure as described above that can be equivalent to one or more LC series resonant structures or LC parallel resonant structures. The number, location and constituent elements of the resonant structures in the LC filter circuit are not particularly limited by the present invention.

In an alternative embodiment, the hybrid resonant structure is a series resonant structure in which the acoustic resonator and the inductor are connected in series, or

In a more complicated LC filter structure, there is no separate capacitor in the LC filter branch, and in this case, the capacitor in the LC resonance structure (which may be an LC series resonance structure or an LC parallel resonance structure) in the LC filter circuit needs to be replaced by an acoustic resonator, so as to configure and form a hybrid resonance structure. The hybrid resonance structure may be a series resonance structure formed by replacing a capacitor in an LC series resonance structure with an acoustic resonator, or may be a parallel resonance structure formed by replacing a capacitor in an LC parallel resonance structure with an acoustic resonator.

In an alternative embodiment, the inductance value of the inductor and the capacitance value of the capacitor of the resonance structure at the specified position satisfy a preset condition,

the meeting of the preset condition comprises one of the following steps:

Wherein C represents a capacitance value of the capacitor, L represents an inductance value of the inductor, fp _left Representing the frequency point, fp, of the left edge of the filter passband _right And representing the right edge frequency point of the filter passband.

As described above, in a more complex LC filter structure, when there is no separate capacitor in the LC filter branch or the separate capacitor is not suitable, the optimal acoustic resonator needs to be selected to replace the capacitor by specifically analyzing the architecture of the LC filter circuit and the value range of L, C of each resonant structure (LC series resonant structure and/or LC parallel resonant structure) in the filter circuit, so as to configure a hybrid resonant structure, thereby achieving the best performance and the best matching of the filter circuit. When the value ranges of the capacitor and the inductor are analyzed, each resonance structure in the LC filter circuit is focused on, and when the values of the capacitor and the inductor in a certain resonance structure meet preset conditions, the capacitor in the resonance structure can be determined to be an optimal substitute, so that optimal matching is realized. It is understood that the preset conditions to be satisfied in determining the optimum substitution are consistent regardless of the LC series resonance structure or the LC parallel resonance structure as the resonance structure.

In an alternative embodiment, the resonant frequency of the acoustic resonator is determined by the frequency point where the filter roll-off is to be increased.

When the preset condition is judged, firstly, the suppression frequency point of the filter (namely, the frequency point at the position where the filter rolls down to be lifted) is determined, namely, the resonance frequency of the acoustic resonator is determined, and then based on the preset condition, the appropriate resonance structure in the LC filter circuit is selected to configure the hybrid resonance structure, so that the optimal replacement of the acoustic resonator is realized. The resonant frequency may be an equivalent parallel resonant frequency of the hybrid resonant structure, or an equivalent series resonant frequency of the hybrid resonant structure, and is determined according to whether the hybrid resonant structure is a parallel/series resonant structure, and whether the hybrid resonant structure is connected in parallel/series on a branch of the LC filter circuit.

In an alternative embodiment, the inductance of the inductor and the capacitance of the capacitor are such that

Is located at a first specified position in said LC filter circuit,

after the hybrid resonance structure is configured at the first designated position, the hybrid resonance structure is used for inhibiting roll-off on the left side of the filter.

Is located at a second specified position in said LC filter circuit,

and after the hybrid resonance structure is configured at the second appointed position, the hybrid resonance structure is used for inhibiting the roll-off on the right side of the filter.

The filter of the invention can be a low-pass filter, in which case, the inductance value of the capacitor of the resonance structure at the designated position and the capacitance value of the capacitor are satisfied

And the hybrid resonance structure is used for improving the roll-off on the right side of the filter.

The filter of the invention can be a high-pass filter, in which case, the inductance value of the capacitor of the resonance structure at the specified position and the capacitance value of the capacitor are satisfied

The hybrid resonant structure is used to increase the filter left roll-off.

The filter of the invention can be a band-pass filter, in which case, the inductance value of the capacitor of the resonance structure at the designated position and the capacitance value of the capacitor are satisfied

When the filter is used, the hybrid resonance structure is used for improving the roll-off of the right side of the filter, and the inductance value of the capacitor of the resonance structure at the specified position and the capacitance value of the capacitor meet the requirement

And the hybrid resonance structure is used for improving the roll-off of the left side of the filter.

As described above, when the hybrid resonant structure is configured, the LC series resonant structure or the LC parallel resonant structure in the LC filter circuit may be selected, and the predetermined conditions are determined to be the same. Accordingly, after the hybrid resonant structure is configured and formed, the formed hybrid resonant structure can be used for inhibiting roll-off on the left side or the right side of the filter so as to improve the roll-off performance of the filter. If the branch of the LC filter circuit has an LC series resonance structure, the requirement is met

The acoustic resonator is used for replacing the capacitor therein, so that the effective improvement of the roll-off at the left side of the sideband of the filter can be realized, and the requirement of

An effective improvement in roll-off on the right side of the filter sideband can be achieved by replacing the capacitors therein with acoustic resonators. If the branch of the LC filter circuit has an LC parallel resonance structure, the requirement is met

The acoustic resonator is used for replacing the capacitor therein, and the roll-off on the left side of the sideband of the filter can be realizedThe effect is improved and satisfied

An effective improvement in roll-off on the right side of the filter sideband can be achieved by replacing the capacitors therein with acoustic resonators.

When there is an LC series resonance structure in a filter circuit branch in which a capacitor is replaced with an acoustic resonator, attention needs to be paid to changes in the equivalent series resonance frequency and the equivalent parallel resonance frequency after the acoustic resonator series inductor. In fig. 4, an impedance comparison graph of an individual acoustic resonator and an acoustic resonator in series with an inductor is shown, wherein a gray dotted line is an impedance curve of the individual acoustic resonator, and a black solid line is an impedance curve of the acoustic resonator in series with the inductor, it can be seen that after the series inductance of the acoustic resonator forms a hybrid resonance structure, the series resonance frequency Fs of the acoustic resonator moves to a low frequency, which is Fs1, and the low impedance point Fs2 is added. If the hybrid resonant structure is connected in series with a branch of the LC filter circuit, fp is the frequency point that forms the high rejection zero, and one of Fs1 or Fs2 will fall within the filter passband. If the hybrid resonance structure is connected in parallel to a branch of an LC filter circuit, fs1 or Fs2 is a frequency point forming a high suppression zero, fp and another Fs2 or Fs1 generally fall outside a filter passband so as not to affect an in-band index, for example, fs1 may be a frequency point of a high suppression zero, fp and Fs2 may be outside a filter passband, or Fs2 may be a frequency point of a high suppression zero, fp and Fs1 may be outside a filter passband. In both cases of connecting the hybrid resonant structure in series or in parallel in the branches of the LC filter circuit, the value ranges of the inductor and the capacitor directly affect whether the alternative acoustic resonator is used to enhance the roll-off on the left or right side of the passband.

If the inductance value of the inductor and the capacitance value of the capacitor in the LC series resonance structure satisfy

Replacing the LC series resonant structure with an acoustic resonatorThe capacitor can realize effective improvement of roll-off on the left side of the filter sideband, and the parallel resonance frequency of the acoustic resonator in the hybrid resonance structure is on the left side of the filter passband. If the inductance of the inductor and the capacitance of the capacitor in the LC series resonance structure satisfy

An effective improvement in roll-off to the right of the filter sideband can be achieved by replacing the capacitors in the LC series resonant structure with acoustic resonators whose parallel resonant frequencies are to the right of the filter passband in the hybrid resonant structure.

As described above, after the rejection frequency point of the improved filter is determined, that is, the resonant frequency of the acoustic resonator is determined, and according to the preset conditions, a range of inductance and capacitance (corresponding to the area of the acoustic resonator if the acoustic resonator is a BAW resonator) can be obtained, and the capacitor in the LC series resonant structure in the LC filter circuit is selected to replace the acoustic resonator. As shown in fig. 5, when the resonant frequency Fp of the acoustic resonator is, for example, 5240MHz, and the numerical range of LC in the LC series resonant structure on the series branch of the LC filter circuit is on the upper right side of the curve, then this LC series resonant structure may be configured as a hybrid resonant structure, which is applied to roll-off improvement on the left side of the filter passband; similarly, if the LC ranges from the left to the bottom of the curve, then this LC series resonant structure can be configured as a hybrid resonant structure, which applies to roll-off improvement on the right side of the filter passband.

When there is an LC parallel resonance structure in a filter circuit branch in which a capacitor is replaced with an acoustic resonator, attention needs to be paid to changes in the equivalent series resonance frequency and the equivalent parallel resonance frequency after the acoustic resonator parallel inductor. In fig. 6, an impedance comparison graph of an individual acoustic resonator and an acoustic resonator in parallel with an inductor is shown, wherein a gray dotted line is an impedance curve of the individual acoustic resonator, and a black solid line is an impedance curve of the acoustic resonator in parallel with the inductor, it can be seen that after the parallel inductor forms a hybrid resonance structure, the parallel resonance frequency Fp of the acoustic resonator shifts to a high frequency to become Fp2, and Fp1 is added to the high impedance point. If the hybrid resonant structure is connected in parallel to a branch of the LC filter circuit, fs is the frequency point that forms the rejection zero, and either Fp1 or Fp2 will fall within the filter passband. If the hybrid resonance structure is connected in series on a branch of an LC filter circuit, fp1 or Fp2 is a frequency point forming a high suppression zero point, and Fs and other Fp2 or Fp1 generally fall outside a filter passband so as not to affect an in-band index, for example, fp1 is a frequency point of the high suppression zero point, fs and Fp2 are outside the filter passband, or Fp2 is a frequency point of the high suppression zero point, and Fs and Fp1 are outside the filter passband. In both cases of connecting the hybrid resonant structure in series or in parallel in the branches of the LC filter circuit, the value ranges of the inductor and the capacitor directly affect whether the alternative acoustic resonator is used to enhance the roll-off on the left or right side of the passband.

If the inductance value of the inductor and the capacitance value of the capacitor in the LC parallel resonance structure satisfy

An effective improvement in roll-off to the left of the filter side-band can be achieved by replacing the capacitors in the LC series resonant structure with acoustic resonators whose parallel resonant frequencies are to the left of the filter passband in the hybrid resonant structure. If the inductance value of the inductor and the capacitance value of the capacitor in the LC parallel resonance structure satisfy

As described above, after the rejection frequency point of the improved filter is determined, that is, the resonant frequency of the acoustic resonator is determined, and according to the preset conditions, a certain range of inductance and capacitance (if the acoustic resonator is a BAW resonator, the area of the acoustic resonator corresponds to this time) can be obtained, and the capacitor in the LC parallel resonant structure in the LC filter circuit is selected to replace the acoustic resonator. As shown in fig. 7, when the resonant frequency Fp of the acoustic resonator is, for example, 1960MHz, and the numerical range of LC in the LC parallel resonant structure on the parallel branch of the LC filter circuit is on the upper right side of the curve, then this LC parallel resonant structure can be configured as a hybrid resonant structure, which is applied to roll-off improvement on the left side of the filter passband; similarly, if the LC ranges from the left to the bottom of the curve, then this LC parallel resonant structure can be configured as a hybrid resonant structure, which is applied for roll-off improvement on the right side of the filter passband.

In an alternative embodiment, the acoustic resonator is a BAW resonator or a SAW resonator.

It is to be understood that the acoustic resonator of the present invention may be a BAW resonator, i.e., a bulk acoustic wave resonator, or a SAW resonator, i.e., a surface acoustic wave resonator, and the present invention is not limited to the structure of the acoustic resonator.

The method for improving the performance of the filter comprises an LC filter circuit consisting of a capacitor and an inductor, wherein the LC filter circuit comprises a plurality of resonance structures, and the method comprises the following steps:

wherein the acoustic resonator has a predetermined resonant frequency.

Due to the structural versatility and flexibility of LC filters, the effect of acoustic resonators on the overall filter performance, especially at the passband edge and near out-of-band rejection, is different instead of capacitors at different locations. According to the difference of LC filter frameworks and the difference of inductance and capacitance values of each resonance structure in an LC filter circuit, the optimum resonance structure is selected from a plurality of resonance structures through analyzing the value range of each inductance and capacitance, and the capacitor in the resonance structure is replaced by the acoustic resonator, so that the performance of the filter can be improved, particularly the roll-off of the sideband of the filter is enhanced, for example, the roll-off of the left side or the right side of the sideband of the filter, the optimal matching of the LC filter and the acoustic resonator is realized, and the roll-off of the acoustic resonator on the filter is improved to a great extent under the condition that the in-band insertion loss is not reduced and even the insertion loss of the edge of a pass band can be improved. The acoustic resonator replaces a capacitor that has the same capacitance value as the replaced capacitor.

It is noted that the resonant structure in the LC filter circuit may be located in the series branch or may be located in the parallel branch. The resonance structure may be an LC series resonance structure in which an inductor and a capacitor are connected in series, or an LC parallel resonance structure in which an inductor and a capacitor are connected in parallel. Alternatively, the resonant structure is a composite resonant structure of one or more capacitors, inductors, resistors capable of producing at least one series resonant electrical response or at least one parallel resonant electrical response, which composite resonant structure can be equivalent to a combination of one or more basic LC series resonant structures and/or LC parallel resonant structures. It is to be understood that the plurality of resonant structures may be a plurality of LC series resonant structures, a plurality of LC parallel resonant structures, or a combination of an LC series resonant structure and an LC parallel resonant structure. The plurality of resonant structures may also comprise a composite resonant structure as described above that can be equivalent to one or more LC series resonant structures or LC parallel resonant structures. The number, position and constituent elements of the resonant structures in the LC filter circuit are not particularly limited in the present invention.

As mentioned above, in a more complex LC filter structure, there is no separate capacitor in the LC filter branch, and in this case, it is necessary to replace the capacitor in the LC resonance structure (which may be an LC series resonance structure or an LC parallel resonance structure) in the LC filter circuit with an acoustic resonator, so as to configure and form a hybrid resonance structure. The hybrid resonance structure may be a series resonance structure formed by replacing a capacitor in an LC series resonance structure with an acoustic resonator, or may be a parallel resonance structure formed by replacing a capacitor in an LC parallel resonance structure with an acoustic resonator.

In an alternative embodiment, the determining at least one designated position in the LC filter circuit by the inductance value of the inductor and the capacitance value of the capacitor of each resonant structure in the LC filter circuit includes one of:

As described above, in a more complicated LC filter structure, when no separate capacitor is available or the separate capacitor is not suitable in the LC filter branch, the optimal acoustic resonator is selected to replace the capacitor by specifically analyzing the architecture of the LC filter circuit and the value range of L, C of each resonant structure (LC series resonant structure and/or LC parallel resonant structure) in the filter circuit, so as to configure a hybrid resonant structure, thereby achieving the best performance and the best matching of the filter circuit. When the value ranges of the capacitor and the inductor are analyzed, each resonance structure in the LC filter circuit is focused on, and when the values of the capacitor and the inductor in a certain resonance structure meet preset conditions, the capacitor in the resonance structure can be determined to be an optimal substitute, so that optimal matching is realized. It is understood that the preset conditions to be satisfied in determining the optimum substitution are consistent regardless of the LC series resonance structure or the LC parallel resonance structure as the resonance structure.

In an alternative embodiment, the method further comprises:

When the preset condition is judged, the suppression frequency point of the improved filter is firstly determined, namely the resonant frequency of the acoustic resonator is firstly determined, and then the appropriate resonant structure in the LC filter circuit is selected to configure the hybrid resonant structure based on the preset condition, so that the optimal replacement of the acoustic resonator is realized. The resonant frequency may be an equivalent parallel resonant frequency of an acoustic resonator in the hybrid resonant structure, or an equivalent series resonant frequency of an acoustic resonator in the hybrid resonant structure, and is determined according to whether the hybrid resonant structure is a parallel/series resonant structure, and whether the hybrid resonant structure is connected in parallel/in series on a branch of the LC filter circuit.

Is located at a first specified position in said LC filter circuit,

Is located at a second specified position in said LC filter circuit,

the method further comprises the following steps: and after the hybrid resonant structure is configured at the second appointed position, the hybrid resonant structure is used for improving the roll-off on the right side of the filter.

The method of the invention can be used for improving the roll-off of a low-pass filter, a high-pass filter or a band-pass filter.

For the low-pass filter, when the inductance value of the capacitor of the resonant structure at the specified position and the capacitance value of the capacitor are satisfied

And when the filter is used, the hybrid resonance structure is used for improving the roll-off of the right side of the filter.

For the high-pass filter, when the inductance value of the capacitor of the resonant structure at the specified position and the capacitance value of the capacitor are satisfied

And when the filter is used, the hybrid resonance structure is used for improving the roll-off of the left side of the filter.

For the band-pass filter, when the inductance value of the capacitor of the resonant structure at the specified position and the capacitance value of the capacitor are satisfied

When the mixed resonance structure is used for improving the roll-off of the right side of the filter, when the inductance value of the capacitor of the resonance structure at the specified position and the capacitance value of the capacitor meet the requirement

And on the other hand, the hybrid resonance structure is used for improving the roll-off of the left side of the filter.

As described above, when the hybrid resonant structure is configured, the LC series resonant structure or the LC parallel resonant structure in the LC filter circuit may be selected, and the predetermined conditions are determined to be the same. Accordingly, after the hybrid resonant structure is configured and formed, the formed hybrid resonant structure can be used for improving roll-off on the left side or the right side of the filter so as to improve the roll-off performance of the filterCan be used. If the branch of the LC filter circuit has an LC series resonance structure, the requirement is met

The acoustic resonator is used for replacing the capacitor therein, so that the effective improvement of the roll-off at the left side of the sideband of the filter can be realized, and the requirements

When there is an LC series resonance structure in a filter circuit branch in which a capacitor is replaced with an acoustic resonator, attention needs to be paid to changes in the equivalent series resonance frequency and the equivalent parallel resonance frequency after the acoustic resonator series inductor. In fig. 4, an impedance comparison graph of an individual acoustic resonator and an acoustic resonator in series with an inductor is shown, wherein a gray dotted line is an impedance curve of the individual acoustic resonator, and a black solid line is an impedance curve of the acoustic resonator in series with the inductor, it can be seen that after the series inductance of the acoustic resonator forms a hybrid resonance structure, the series resonance frequency Fs of the acoustic resonator moves to a low frequency, which is Fs1, and the low impedance point Fs2 is added. If the hybrid resonant structure is connected in series with the branches of the LC filter circuit, fp is the frequency point that forms the high rejection zero, and Fs1 or Fs2 will fall within the filter passband. If the hybrid resonance structure is connected in parallel to a branch of an LC filter circuit, fs1 or Fs2 is a frequency point forming a high suppression zero, fp and another Fs2 or Fs1 generally fall outside a filter passband so as not to affect an in-band index, for example, fs1 may be a frequency point of a high suppression zero, fp and Fs2 may be outside a filter passband, or Fs2 may be a frequency point of a high suppression zero, fp and Fs1 may be outside a filter passband. In both cases of connecting the hybrid resonant structure in series or in parallel in the branches of the LC filter circuit, the value ranges of the inductor and the capacitor directly affect whether the alternative acoustic resonator is used to enhance the roll-off on the left or right side of the passband.

An effective improvement in roll-off to the left of the filter side-band can be achieved by replacing the capacitors in the LC series resonant structure with acoustic resonators whose parallel resonant frequencies are to the left of the filter passband in the hybrid resonant structure. If the inductance value of the inductor and the capacitance value of the capacitor in the LC series resonance structure satisfy

When there is an LC parallel resonance structure in a filter circuit branch in which a capacitor is replaced with an acoustic resonator, attention needs to be paid to changes in the equivalent series resonance frequency and the equivalent parallel resonance frequency after the acoustic resonator parallel inductor. In fig. 6, an impedance comparison graph of an individual acoustic resonator and an acoustic resonator in parallel with an inductor is shown, wherein a gray dotted line is an impedance curve of the individual acoustic resonator, and a black solid line is an impedance curve of the acoustic resonator in parallel with the inductor, it can be seen that after the parallel inductor forms a hybrid resonance structure, the parallel resonance frequency Fp of the acoustic resonator shifts to a high frequency to become Fp2, and Fp1 is added to the high impedance point. If the hybrid resonant structure is connected in parallel to a branch of the LC filter circuit, fs is the frequency point that forms the rejection zero, and either Fp1 or Fp2 will fall within the filter passband. If the hybrid resonance structure is connected in series on a branch of an LC filter circuit, fp1 or Fp2 is a frequency point forming a high suppression zero point, and Fs and other Fp2 or Fp1 generally fall outside a filter passband so as not to affect an in-band index, for example, fp1 is a frequency point of the high suppression zero point, fs and Fp2 are outside the filter passband, or Fp2 is a frequency point of the high suppression zero point, and Fs and Fp1 are outside the filter passband. In both cases where the hybrid resonant structure is connected in series or in parallel with a branch of an LC filter circuit, the range of values of the inductor and capacitor directly affects whether the alternative acoustic resonator is used to enhance roll-off on the left or right side of the passband.

The roll-off on the left side of the filter sideband can be achieved by replacing the capacitor in the LC series resonant structure with an acoustic resonatorEffective improvement is achieved when the parallel resonant frequency of the acoustic resonator in the hybrid resonant structure is to the left of the filter passband. If the inductance value of the inductor and the capacitance value of the capacitor in the LC parallel resonance structure satisfy

As described above, after the rejection frequency point of the improved filter is determined, that is, the resonant frequency of the acoustic resonator is determined, and according to the preset conditions, a range of inductance and capacitance (corresponding to the area of the acoustic resonator if the acoustic resonator is a BAW resonator) can be obtained, and the capacitor in the LC parallel resonant structure in the LC filter circuit is selected to replace the acoustic resonator. As shown in fig. 7, when the resonant frequency Fp of the acoustic resonator is, for example, 1960MHz, and the numerical range of LC in the LC parallel resonant structure on the parallel branch of the LC filter circuit is on the upper right side of the curve, then the LC parallel resonant structure can be configured as a hybrid resonant structure, which is applied to roll-off improvement on the left side of the filter passband; similarly, if the LC ranges from the left to the bottom of the curve, then this LC parallel resonant structure can be configured as a hybrid resonant structure, which is applied for roll-off improvement on the right side of the filter passband.

As described above, the acoustic resonator of the present invention may be a BAW resonator, that is, a bulk acoustic wave resonator, or a SAW resonator, that is, a surface acoustic wave resonator.

The present disclosure also relates to an electronic device including the filter in the foregoing embodiments.

The invention will now be described in terms of several specific embodiments.

Example 1

In this embodiment, LC filter circuitAn LC series resonant structure exists on the series branch, a capacitor in the LC series resonant structure is replaced by a BAW resonator, and a filter circuit after the replacement is shown in fig. 8. In the LC filter circuit 210, R210 is a BAW resonator having a capacitance of 0.5pF instead of a capacitor, and L210 is an inductor connected in series thereto and having an inductance of 0.66nH, which is calculated

The passband of the filter is 3.2-5.8GHz, the resonance frequency Fp of the alternative BAW resonator is 6GHz,

therefore, the mixed resonance structure formed by the BAW resonator R210 and the inductor L210 in series is suitable for improving the roll-off on the right side of the filter. Fig. 9 shows an impedance curve of the BAW resonator R210 after being connected in series with the inductor L210, and an insertion loss ratio chart of the BAW resonator R210 before and after replacing the capacitor, wherein a black solid line is a schematic diagram of an original LC series resonance structure, and a gray dotted line is a schematic diagram of a hybrid resonance structure. As can be seen from fig. 9, when the BAW resonator R210 is replaced, not only is the roll-off on the right side of the filter improved, but also the insertion loss index of the right side sideband is improved, and the result shows that the BAW resonator and the LC filter circuit achieve good matching.

Comparative example 1

In the present comparative embodiment, an LC series resonant structure exists in the series branch of the LC filter circuit, the capacitor in the LC series resonant structure is replaced with a BAW resonator, and the filter circuit after the replacement is as shown in fig. 10. In the LC filter circuit 220, R220 is a BAW resonator with a capacitance of 0.51pF, L220 is an inductor connected in series with the capacitor and has an inductance of 2.76nH, and the filter has a passband of 3.2-5.8GHz, which is not satisfied

Fig. 11 shows an impedance curve of the BAW resonator R220 after being connected in series with the inductor 220, and an insertion loss ratio graph of the BAW resonator R220 before and after replacing the capacitor, wherein a black solid line is a schematic diagram of an original LC series resonance structure,the dashed gray line is a schematic of the hybrid resonant structure. It can be seen from fig. 11 that when the BAW resonator R220 is replaced, the filter has a poor side band suppression effect on the right side, a high protrusion, and a corresponding deterioration in the insertion loss in the pass band.

Example 2

In this embodiment, an LC series resonant structure exists in a series branch of an LC filter circuit, a capacitor in the LC series resonant structure is replaced with a BAW resonator, and the filter circuit after replacement is as shown in fig. 12. In the LC filter circuit 230, R230 is a BAW resonator having a capacitance of 0.86pF instead of a capacitor, and L230 is an inductor connected in series thereto and having an inductance of 11.3nH, which is calculated

The passband of the filter is 2-2.8GHz, the resonance frequency Fp of the alternative BAW resonator is 1.92GHz,

therefore, the mixed resonance structure formed by the BAW resonator R230 and the inductor L230 in series is suitable for improving the roll-off on the left side of the filter. Fig. 13 shows an impedance curve of the BAW resonator R230 after being connected in series with the inductor L230, and an insertion loss ratio chart of the BAW resonator R230 before and after replacing the capacitor, wherein a black solid line is a schematic diagram of an original LC series resonance structure, and a gray dotted line is a schematic diagram of a hybrid resonance structure. As can be seen from fig. 13, when the BAW resonator R230 is replaced, not only is the roll-off on the left side of the filter improved, but also the insertion loss index of the left side sideband is improved, and the result shows that the BAW resonator and the LC filter circuit achieve good matching.

Comparative example 2

In the present comparative embodiment, an LC series resonant structure exists in the series branch of the LC filter circuit, the capacitor in the LC series resonant structure is replaced with a BAW resonator, and the filter circuit after the replacement is as shown in fig. 14. In the LC filter circuit 240, R240 is a BAW resonator with a capacitance of 0.83pF, L240 is an inductor connected in series with the resonator, an inductance of 3.5nH, and the passband of the filter is 2-2.8GHz, which is not satisfied

Fig. 15 shows an impedance curve of the BAW resonator R240 after being connected in series with the inductor 240, and an insertion loss ratio graph of the BAW resonator R240 before and after replacing the capacitor, in which a black solid line is a schematic diagram of an original LC series resonance structure, and a gray dotted line is a schematic diagram of a hybrid resonance structure. As can be seen from fig. 15, when the BAW resonator R240 is replaced, the filter has a poor left side sideband suppression effect and the insertion loss in the pass band is also deteriorated.

Example 3

In this embodiment, an LC parallel resonance structure exists in a parallel branch of an LC filter circuit, a capacitor in the LC parallel resonance structure is replaced with a BAW resonator, and the filter circuit after replacement is as shown in fig. 16. In the LC filter circuit 250, R250 is a BAW resonator with a capacitor replaced, and the capacitance value is 0.29pF, and L250 is an inductor connected in parallel with the capacitor, and the inductance value is 1.5nH, and the calculation result is obtained

The pass band of the filter is 4.7-5.3GHz, the resonance frequency Fs of the alternative BAW resonator is 5.57GHz,

the BAW resonator R250 in parallel with the inductor L250 thus forms a specified resonant mechanism suitable for application in the roll-off improvement on the right side of the filter. Fig. 17 shows an impedance curve of the BAW resonator R250 after being connected in parallel with the inductor L250, and an insertion loss ratio chart of the BAW resonator R250 before and after replacing the capacitor, wherein a black solid line is a schematic diagram of an original LC series resonance structure, and a gray dotted line is a schematic diagram of a hybrid resonance structure. As can be seen from fig. 17, the replacement of the BAW resonator R250 significantly improves the roll-off on the right side of the filter, and the result shows that the BAW resonator achieves good matching with the LC filter circuit.

Example 4

In this embodiment, an LC parallel resonance structure exists on a parallel branch of the LC filter circuit, and a capacitor in the LC parallel resonance structure is connected to the parallel branchThe device is replaced by a BAW resonator and the filter circuit after replacement is shown in fig. 18. In the LC filter circuit 260, R260 is a BAW resonator with a capacitor replaced, the capacitance value is 0.3pF, L260 is an inductor connected in parallel with the capacitor, the inductance value is 4nH, and the calculation result is obtained

The pass band of the filter is 4.7-5.4GHz, the resonance frequency Fs of the alternative BAW resonator is 4.6GHz,

the BAW resonator R260 in parallel with the inductor L260 thus forms a specified resonant structure suitable for application in the improvement of roll-off on the left side of the filter. Fig. 19 shows an impedance curve of the BAW resonator R260 after being connected in parallel with the inductor L260, and an insertion loss ratio chart of the BAW resonator R260 before and after replacing the capacitor, wherein a black solid line is a schematic diagram of an original LC series resonance structure, and a gray dotted line is a schematic diagram of a hybrid resonance structure. As can be seen from fig. 19, when the BAW resonator R260 is replaced, not only is the roll-off on the left side of the filter improved, but also the insertion loss index of the left side sideband is improved, and the result shows that the BAW resonator and the LC filter circuit achieve good matching.

In the description provided herein, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Furthermore, those of ordinary skill in the art will appreciate that while some embodiments described herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments may be used in any combination.

It will be understood by those skilled in the art that while the present invention has been described with reference to exemplary embodiments, various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A filter, characterized in that it comprises an LC filter circuit consisting of capacitors and inductors, said LC filter circuit comprising a plurality of resonant structures,

2. The filter of claim 1, wherein an inductance value of the inductor and a capacitance value of the capacitor of the resonance structure at the designated position satisfy a preset condition,

the meeting of the preset condition comprises one of the following steps:

Wherein C represents a capacitance value of the capacitor, L represents an inductance value of the inductor, fp _left RepresentLeft side edge frequency point, fp, of filter passband _right And representing the right edge frequency point of the filter passband.

3. The filter of claim 2, wherein an inductance value of the inductor and a capacitance value of the capacitor satisfy

Is located at a first specified position in said LC filter circuit,

4. The filter of claim 2, wherein an inductance value of the inductor and a capacitance value of the capacitor satisfy

Is located at a second specified position in said LC filter circuit,

and after the hybrid resonance structure is configured at the second appointed position, the hybrid resonance structure is used for improving the roll-off of the right side of the filter.

5. A filter as claimed in any one of claims 1 to 4, wherein the hybrid resonant structure is a series resonant structure in which the acoustic resonator and inductor are connected in series, or

6. The filter of any one of claims 1-4, wherein the filter is one of a low pass filter, a high pass filter, and a band pass filter.

7. The filter of claim 1, wherein the acoustic resonator is a BAW resonator or a SAW resonator.

8. The filter of claim 1, wherein the resonant frequency of the acoustic resonator is determined by the frequency point at which the roll-off of the filter is to be increased.

9. A method of improving the performance of a filter comprising an LC filter circuit comprising a capacitor and an inductor, the LC filter circuit comprising a plurality of resonant structures, the method comprising:

wherein the acoustic resonator has a predetermined resonant frequency.

10. The method of claim 9, wherein said determining at least one specified location in the LC filter circuit by inductance values of inductors and capacitance values of capacitors of respective resonant structures in the LC filter circuit comprises one of:

11. The method of claim 10, wherein an inductance value of the inductor and a capacitance value of the capacitor satisfy

Is located at a first specified position in said LC filter circuit,

the method further comprises the following steps: after the hybrid resonant structure is configured at the first designated location, the hybrid resonant structure is used to increase the filter left roll-off.

12. The method of claim 10, wherein an inductance value of the inductor and a capacitance value of the capacitor satisfy

Is located at a second specified position in said LC filter circuit,

13. The method of any one of claims 9-12, wherein the hybrid resonant structure is a series resonant structure in which the acoustic resonator and inductor are connected in series, or

14. The method of any one of claims 9-12, wherein the filter is one of a low pass filter, a high pass filter, and a band pass filter.

15. The method of claim 9, wherein the acoustic resonator is a BAW resonator or a SAW resonator.

16. The method of claim 9, wherein the method further comprises:

17. An electronic device comprising a filter as claimed in any one of claims 1 to 8.