阅读说明：本技术 具有反谐振频率校正的滤波器 (Filter with anti-resonant frequency correction ) 是由 金显俊 朴润锡 金性泰 于 2019-05-23 设计创作，主要内容包括：本公开提供一种具有反谐振频率校正的滤波器,所述滤波器包括：串联单元,包括多个串联谐振器；分路单元,包括多个分路谐振器,所述分路单元连接在所述多个串联谐振器与地之间；以及校正单元,包括电感器单元和阻抗单元,所述电感器单元连接在所述多个串联谐振器中的一组串联谐振器与所述多个分路谐振器中的一组分路谐振器中的至少一者的两端之间,所述阻抗单元连接在所述电感器单元与地之间。(The present disclosure provides a filter with anti-resonant frequency correction, the filter comprising: a series unit including a plurality of series resonators; a shunt unit including a plurality of shunt resonators, the shunt unit being connected between the plurality of series resonators and ground; and a correction unit including an inductor unit connected between both ends of at least one of a set of series resonators of the plurality of series resonators and a set of shunt resonators of the plurality of shunt resonators, and an impedance unit connected between the inductor unit and ground.)

1. A filter, the filter comprising:

a series unit including a plurality of series resonators;

a shunt unit including a plurality of shunt resonators, the shunt unit being disposed between the plurality of series resonators and ground; and

a correction unit comprising:

an inductor unit disposed between both ends of at least one of a set of series resonators of the plurality of series resonators and a set of shunt resonators of the plurality of shunt resonators; and

an impedance unit disposed between the inductor unit and ground.

2. The filter of claim 1, wherein the set of series resonators are connected in series and the set of shunt resonators are connected in parallel.

3. The filter of claim 1, wherein the inductor unit comprises at least one inductor disposed between both ends of at least one series resonator of the set of series resonators and the ground or between both ends of at least one shunt resonator of the set of shunt resonators and the ground in a configuration of three nodes connected in a Y-connection.

4. The filter of claim 3, wherein the inductor unit comprises three inductors disposed at different ones of the three nodes.

5. The filter of claim 3, wherein the inductor unit comprises two inductors disposed at different ones of the three nodes.

6. The filter of claim 5, wherein the two inductors are coupled to each other and their mutual inductances are formed in the remaining nodes of the three nodes.

7. The filter of claim 6, wherein the coupling coefficients of the two inductors have positive signs.

8. The filter of claim 1, wherein the inductor unit comprises at least two inductors connected in series between a first end of one of the set of series resonators and the set of shunt resonators and the impedance unit, and a connection node of the at least two inductors is connected to a second end of the set of series resonators or a second end of the set of shunt resonators.

9. The filter of claim 8, wherein the at least two inductors are coupled to each other and a mutual inductance of the at least two inductors is formed between the connection node of the at least two inductors and the second end of the set of series resonators.

10. The filter of claim 8, wherein the coupling coefficients of the at least two inductors have a negative sign.

11. The filter of claim 1, wherein the impedance unit comprises a first capacitor disposed between the inductor unit and the ground.

12. The filter of claim 11, wherein the impedance unit further comprises a first inductor connected in parallel with the first capacitor.

13. The filter of claim 12, wherein the impedance unit further comprises a second capacitor and a second inductor connected in series with each other, and the second capacitor and the second inductor are connected in parallel with the first capacitor and the first inductor connected in parallel.

14. The filter according to claim 1, wherein the correction unit further includes a correction resonator connected in parallel with the impedance unit, and the correction resonator has a frequency characteristic identical to that of one of the series resonator and the shunt resonator.

15. The filter of claim 1, wherein the set of series resonators corresponds to one or more than one series resonator and the set of shunt resonators corresponds to one or more than one shunt resonator.

16. A filter, the filter comprising:

a series resonator provided between the signal input terminal and the signal output terminal;

a shunt resonator disposed between one end of the series resonator and ground; and

a correction unit comprising:

a series correction unit including at least two inductors connected in series and coupled to each other between both ends of the series resonator, and a capacitor provided between a connection node of the at least two inductors and ground; and

a shunt correction unit including at least two inductors connected in series and coupled to each other between both ends of the shunt resonator, and a capacitor disposed between a connection node of the at least two inductors and the ground.

17. A filter, the filter comprising:

a series resonator provided between the signal input terminal and the signal output terminal;

a shunt resonator disposed between one end of the series resonator and ground; and

a correction unit comprising:

a series correction unit including a capacitor connected to ground and at least two series-connected inductors coupled to each other between one end of the series resonator and the capacitor; and

a shunt correction unit including at least two series-connected inductors coupled to each other between both ends of the shunt resonator, and a capacitor disposed between a connection node of the at least two inductors and the ground.

Technical Field

The present disclosure relates to a filter.

Background

With the rapid development of mobile communication devices, chemical and biological testing devices, and the like, the demand for small and lightweight filters, oscillators, resonant elements, acoustic wave resonant mass sensors, and the like for use in such devices has also increased.

Film Bulk Acoustic Resonators (FBARs) are commonly used to implement such small and lightweight filters, oscillators, resonating elements, and acoustic wave resonant mass transducers and similar components. The FBAR can be mass-produced at a minimum cost and can be realized to have a subminiature size. In addition, the FBAR may have a high quality factor (Q) value, which is a main feature of a filter, and may be used even in a microwave band, especially a frequency band in which a Personal Communication System (PCS) and a frequency band in which a digital radio system (DCS) may be implemented.

Generally, such an FBAR has a structure including a resonance unit realized by sequentially stacking a first electrode, a piezoelectric layer, and a second electrode on a substrate. The operational principle of the FBAR will be described below. First, an electric field is induced in the piezoelectric layer by electric energy applied to the first and second electrodes, and a piezoelectric phenomenon may be generated in the piezoelectric layer by the induced electric field, thereby vibrating the resonance unit in a predetermined direction. As a result, bulk acoustic waves are generated in the same direction as the direction in which the resonance unit vibrates, thereby generating resonance.

Disclosure of Invention

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In one general aspect, a filter includes: a series unit including a plurality of series resonators; a shunt unit including a plurality of shunt resonators, the shunt unit being disposed between the plurality of series resonators and ground; and a correction unit including an inductor unit disposed between both ends of at least one of a set of series resonators of the plurality of series resonators and a set of shunt resonators of the plurality of shunt resonators, and an impedance unit disposed between the inductor unit and a ground.

The set of series resonators may be connected in series and the set of shunt resonators connected in parallel.

The inductor unit includes at least one inductor disposed between both ends of at least one series resonator of the set of series resonators and the ground or between both ends of at least one shunt resonator of the set of shunt resonators and the ground in a configuration of three nodes connected in a Y-connection.

The inductor unit includes three inductors disposed at different nodes of the three nodes.

The inductor unit includes two inductors disposed at different nodes of the three nodes.

The two inductors may be coupled to each other, and mutual inductances of the two inductors may be formed in remaining nodes of the three nodes.

The coupling coefficients of the two inductors may have positive signs.

The inductor unit may include at least two inductors connected in series between a first end of one of the set of series resonators and the set of shunt resonators and the impedance unit, and a connection node of the at least two inductors may be connected to a second end of the set of series resonators or a second end of the set of shunt resonators.

The at least two inductors may be coupled to each other, and mutual inductances of the at least two inductors may be formed between the connection nodes of the at least two inductors and the second ends of the set of series resonators.

The coupling coefficient of the at least two inductors may have a negative sign.

The impedance unit may include a first capacitor disposed between the inductor unit and the ground.

The impedance unit may further include a first inductor connected in parallel with the first capacitor.

The impedance unit may further include a second capacitor and a second inductor connected in series with each other, and the second capacitor and the second inductor may be connected in parallel with the first capacitor and the first inductor connected in parallel.

The correction unit may further include a correction resonator connected in parallel with the impedance unit, and the correction resonator has a frequency characteristic identical to a frequency characteristic of one of the series resonator and the shunt resonator.

In one general aspect, a filter includes: a series resonator provided between the signal input terminal and the signal output terminal; a shunt resonator disposed between one end of the series resonator and ground; and a correction unit including a series correction unit including at least two inductors connected in series and coupled to each other between both ends of the series resonator and a capacitor connected between a connection node of the at least two inductors and a ground, and a shunt correction unit including at least two inductors connected in series and coupled to each other between both ends of the shunt resonator and a capacitor connected between a connection node of the at least two inductors and the ground.

In another general aspect, a filter includes: a series resonator connected between the signal input terminal and the signal output terminal; a shunt resonator connected between one end of the series resonator and ground; and a correction unit including a series correction unit including a capacitor connected to a ground and at least two series-connected inductors coupled to each other between one end of the series resonator and the capacitor, and a shunt correction unit including at least two series-connected inductors coupled to each other between both ends of the shunt resonator and a capacitor connected between a connection node of the at least two inductors and the ground.

The set of series resonators may correspond to one or more than one series resonator and the set of shunt resonators may correspond to one or more than one shunt resonator.

Other features and aspects will be apparent from the following detailed description, the accompanying drawings, and the claims.

Drawings

Fig. 1 is a sectional view showing an example of a filter;

FIG. 2 is an example of a block diagram of a filter;

fig. 3 shows an example of a circuit diagram of a filter;

FIG. 4 shows an example of the frequency response of the filter of FIG. 3;

fig. 5A is an example of a circuit diagram of a filter;

fig. 5B is another example of a circuit diagram of a filter;

fig. 6 is an example of a circuit diagram of a correction unit;

FIG. 7 is an example of a modified circuit diagram of the correction unit of FIG. 6;

fig. 8A, 8B, and 8C are examples of circuit diagrams of the impedance unit;

fig. 9 is another example of a circuit diagram of a correction unit;

fig. 10 is another example of a circuit diagram of a correction unit;

fig. 11 shows an example of a frequency response of a filter to which the correction unit of fig. 10 is applied; and

fig. 12 is a circuit diagram of another example of the correction unit.

Like reference numerals refer to like elements throughout the drawings and the detailed description. The figures may not be drawn to scale and the relative sizes, proportions and depictions of the elements in the figures may be exaggerated for clarity, illustration and convenience.

Detailed Description

The following detailed description is provided to assist the reader in obtaining a thorough understanding of the methods, devices, and/or systems described herein. However, various changes, modifications, and equivalents of the methods, apparatus, and/or systems described herein will be apparent to those skilled in the art upon review of the disclosure of this application. For example, the order of operations described herein is merely an example, and is not limited to the order set forth herein, but rather, variations may be made, as will be apparent upon an understanding of the present disclosure, in addition to the operations which must occur in a particular order. Moreover, descriptions of features known in the art may be omitted for greater clarity and conciseness.

The features described herein may be embodied in different forms and should not be construed as limited to the examples described herein. Rather, the examples described herein have been provided merely to illustrate some of the many possible ways to implement the methods, devices, and/or systems described herein that will be apparent upon understanding the disclosure of the present application.

Throughout the specification, when an element such as a layer, region or substrate is described as being "on," connected to "or" coupled to "another element, it may be directly on," connected to or directly coupled to the other element or one or more other elements may be present therebetween. In contrast, when an element is referred to as being "directly on," "directly connected to" or "directly coupled to" another element, there may be no intervening elements present.

As used herein, the term "and/or" includes any one of the associated listed items and any combination of any two or more.

Although terms such as "first," "second," "third," and the like may be used herein to describe various elements, components, regions, layers or sections, these elements, components, regions, layers or sections should not be limited by these terms. Rather, these terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed in connection with the examples described herein could be termed a second element, component, region, layer or section without departing from the teachings of the examples.

Spatially relative terms, such as "above," "upper," "lower," and "below," may be used herein for ease of description to describe one element's relationship to another element as illustrated in the figures. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "upper" relative to another element would then be "below" or "lower" relative to the other element. Thus, the term "above" includes both an orientation of "above" and "below" depending on the spatial orientation of the device. The device may also be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative terms used herein should be interpreted accordingly.

The terminology used herein is for the purpose of describing various examples only and is not intended to be limiting of the disclosure. The singular is intended to include the plural unless the context clearly indicates otherwise. The terms "comprises," "comprising," and "having" specify the presence of stated features, quantities, operations, elements, components, and/or combinations thereof, but do not preclude the presence or addition of one or more other features, quantities, operations, components, elements, and/or combinations thereof.

The shapes of the illustrations as a result of manufacturing techniques and/or tolerances may vary. Accordingly, the examples described herein are not limited to the particular shapes shown in the drawings, but include changes in shapes that occur during manufacturing.

The features of the examples described herein may be combined in various ways as will be apparent after understanding the disclosure of the present application. Further, while the examples described herein have a variety of configurations, other configurations are possible as will be apparent upon understanding the disclosure of the present application.

Fig. 1 is a cross-sectional view illustrating a filter according to an example.

Referring to fig. 1, a filter 10 according to an example may include at least one bulk acoustic wave resonator 100 and a cover 200. In fig. 1, the filter 10 is shown as including two bulk acoustic wave resonators 100. However, the filter 10 may include one bulk acoustic wave resonator 100, two bulk acoustic wave resonators 100, or three or more bulk acoustic wave resonators 100. The bulk acoustic wave resonator 100 may be a Film Bulk Acoustic Resonator (FBAR).

The bulk acoustic wave resonator 100 may be configured by a laminated structure composed of a plurality of films. The stacked structure constituting the bulk acoustic wave resonator 100 may include a substrate 110, an insulating layer 115, an air cavity 133, a support unit 134, an auxiliary support unit 135, and a resonance unit 155, and may further include a protective layer 170 and a metal layer 180, wherein the resonance unit 155 includes a first electrode 140, a piezoelectric layer 150, and a second electrode 160.

According to the manufacturing process of the example bulk acoustic wave resonator 100, a sacrificial layer may be formed on the insulating layer 115, and then a portion of the sacrificial layer may be removed to form a pattern in which the supporting unit 134 is disposed. Here, the auxiliary support unit 135 may be formed of the remaining sacrificial layer. The upper surface of the pattern formed on the sacrificial layer may have a width wider than that of the lower surface, and a side surface connecting the upper surface and the lower surface may be inclined. After forming a pattern on the sacrificial layer, a film 130 may be formed on the insulating layer 115 exposed to the outside through the sacrificial layer and the pattern.

After the film 130 is formed, an etching stopper material constituting a basis of the formation of the supporting unit 134 may be formed to cover the film 130. After the etch stop material is formed, one surface of the etch stop material may be planarized so that the film 130 formed on the upper surface of the sacrificial layer may be exposed to the outside. In the process of planarizing one surface of the etch stop material, a portion of the etch stop material may be removed, and the support unit 134 may be formed by the etch stop material remaining in the pattern after removing the portion of the etch stop material. As a result of the process of planarizing the etch stop material, one surface of the support unit 134 and the sacrificial layer may be substantially flat. Here, the film 130 may be used as a stop layer for a planarization process of an etch stop material.

Thereafter, the air cavity 130 may be formed by an etching process of etching and removing the sacrificial layer after stacking the first electrode 140, the piezoelectric layer 150, the second electrode 160, and the like. For example, the sacrificial layer may include polysilicon (Poly-Si). The air chamber 133 may be located at a lower portion of the resonance unit 155 so that the resonance unit 155 composed of the first electrode 140, the piezoelectric layer 150, and the second electrode 160 may vibrate in a predetermined direction.

The substrate 110 may be composed of a silicon substrate, and the insulating layer 115 may be disposed to electrically isolate the resonance unit 155 from the substrate 110. The insulating layer 115 may use silicon dioxide (SiO)₂) Silicon nitride (Si)₃N₄) Alumina (Al)₂O₃) And aluminum nitride (AlN), but not limited thereto, and the insulating layer 115 may be formed on the substrate 110 by chemical vapor deposition, RF magnetron sputtering, or evaporation.

An etch stop layer may be additionally formed on the insulating layer 115. The etch stop layer may protect the substrate 110 and the insulating layer 115 from the etching process and may serve as a base for depositing other layers on the etch stop layer.

The air cavity 133 and the supporting unit 135 may be formed on the insulating layer 115. As described above, after the pattern is formed in which the sacrificial layer is formed on the insulating layer and the support unit 134 is disposed on the sacrificial layer, the air cavity 133 may be formed through an etching process of etching and removing the sacrificial layer, and then the first electrode 140, the piezoelectric layer 150, and the second electrode 160 are formed and laminated.

The air chamber 133 may be located at a lower portion of the resonance unit 155 so that the resonance unit 155 composed of the first electrode 140, the piezoelectric layer 150, and the second electrode 160 may vibrate in a predetermined direction. The supporting unit 134 may be disposed on one side of the air chamber 133.

The thickness of the supporting unit 134 may be the same as that of the air cavity 133, but is not limited thereto. Therefore, the upper surface provided by the air chamber 133 and the support unit 134 may be substantially flat. According to an example, the resonance unit 155 may be disposed on the planarized surface where the steps are removed, so that the attenuation characteristics of the bulk acoustic wave resonator may be improved.

Cross section of the supporting unit 134May have a substantially trapezoidal shape. Specifically, the width of the upper surface of the supporting unit 134 may be wider than that of the lower surface, and the side surface connecting the upper and lower surfaces may be inclined. The support unit 134 may be formed using a material that is not etched in an etching process for removing the sacrificial layer. For example, the support unit 134 may be formed using the same material as that of the insulating layer 115, and in particular, the support unit 134 may be formed using silicon dioxide (SiO)₂) And silicon nitride (Si)₃N₄) Or a combination thereof.

According to an example, the side surface of the supporting unit 134 may be formed to be inclined to prevent a steep step (abrupt step) from occurring at the boundary between the supporting unit 134 and the sacrificial layer, and the width of the lower surface of the supporting unit 134 may be formed to be narrow to prevent the occurrence of the dishing phenomenon. For example, an angle between the lower surface of the support unit 134 and the side surface may be 110 ° to 160 °, and the width of the lower surface of the support unit 134 may be 2 μm to 30 μm.

The auxiliary support unit 135 may be disposed outside the support unit 134. The auxiliary supporting unit 135 may be formed using the same material as that of the supporting unit 134, and may be formed using a material different from that of the supporting unit 134. For example, when the auxiliary support unit 135 is formed using a material different from that of the support unit 134, the auxiliary support unit 135 may correspond to a portion of a sacrificial layer formed on the insulating layer 115 remaining after the etching process.

The resonance unit 155 may include a first electrode 140, a piezoelectric layer 150, and a second electrode 160. A common region where the first electrode 140, the piezoelectric layer 150, and the second electrode 160 are stacked in the vertical direction may be located at an upper portion of the air cavity 133. The first and second electrodes 140 and 160 may be formed using one of gold (Au), titanium (Ti), tantalum (Ta), molybdenum (Mo), ruthenium (Ru), platinum (Pt), tungsten (W), aluminum (Al), iridium (Ir), and nickel (Ni), or an alloy thereof. The piezoelectric layer 150 is a layer of piezoelectric effect that converts electrical energy into mechanical energy in the form of an elastic wave. In the piezoelectric layer 150, zinc oxide (ZnO), aluminum nitride (AlN), doped aluminum nitride, lead zirconate titanate, quartz, and the like can be selectively used. In the case of doped aluminum nitride, it may also include rare earth metals, transition metals, or alkaline earth metals. For example, the rare earth metal may include at least one of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La), and the content of the rare earth metal may be 1 to 20 at% based on the total content of the doped aluminum nitride. The transition metal may include at least one of hafnium (Hf), titanium (Ti), zirconium (Zr), tantalum (Ta), and niobium (Nb). Further, the alkaline earth metal may include magnesium (Mg).

The film 130 may be formed using a material that cannot be easily removed in the process of forming the air cavity 133. For example, when a portion of the sacrificial layer is removed using a halide-based etching gas, such as fluorine (F), chlorine (Cl), or the like, to form the cavity 133, the film 130 may be formed using a material having low reactivity with the etching gas. In this example, the film 130 may include silicon dioxide (SiO)₂) And silicon nitride (Si)₃N₄) At least one of (1). In addition, the film 130 may include magnesium oxide (MgO) and zirconium oxide (ZrO)₂) Aluminum nitride (AlN), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO)₂) Alumina (Al)₂O₃) Titanium oxide (TiO)₂) And zinc oxide (ZnO), or may be formed using a metal layer including at least one material of aluminum (Al), nickel (Ni), chromium (Cr), platinum (Pt), gallium (Ga), and hafnium (Hf).

According to an example, a seed layer made of aluminum nitride (AlN) may be formed on the film 130. In particular, the seed layer may be disposed between the film 130 and the first electrode 140. The seed layer may be formed using a metal or a dielectric having an HCP structure, in addition to aluminum nitride (AlN). In an example of forming the seed layer using a metal, the seed layer may be formed using titanium (Ti).

A protective layer 170 may be disposed on the second electrode 160 to prevent the second electrode 160 from being exposed to external conditions. The protective layer 170 may be formed using an insulating material of one of silicon oxide series, silicon nitride series, aluminum nitride series, and aluminum oxide series. The metal layer 180 may be formed on the first and second electrodes 140 and 160 exposed to an external condition.

The resonance unit 155 may be divided into an active area and an inactive area. The effective area of the resonance unit 155 is an area that vibrates and resonates in a predetermined direction by a piezoelectric phenomenon generated in the piezoelectric layer 150 when electric energy (such as a radio frequency signal) is applied to the first electrode 140 and the second electrode 160, and corresponds to an area where the first electrode 140, the piezoelectric layer 150, and the second electrode 160 at the upper portion of the air cavity 133 are stacked in the vertical direction. The inactive area of the resonance unit 155 is an area that does not resonate due to a piezoelectric phenomenon even if power is applied to the first and second electrodes 140 and 160, and corresponds to an area outside the active area.

The resonance unit 155 outputs a radio frequency signal having a specific frequency based on a piezoelectric phenomenon. Specifically, the resonance unit 155 may output a radio frequency signal having a resonance frequency corresponding to vibration according to a piezoelectric phenomenon of the piezoelectric layer 150.

The cover 200 may be coupled to a stacked structure forming a plurality of bulk acoustic wave resonators 100. The cover 200 may be formed to have a cover shape having an inner space in which the plurality of bulk acoustic wave resonators 100 are accommodated. The cover 200 may be formed in a hexahedral shape having an open bottom surface, and may include an upper portion and a plurality of side portions connected to the upper portion. However, the shape of the cover is not limited thereto.

The cover 220 may be formed with a receiving unit at the center to receive the resonance units 155 of the plurality of bulk acoustic wave resonators 100. The laminated structure may be bonded to the plurality of side portions in the bonding regions, and the bonding regions of the laminated structure may correspond to sides of the laminated structure. The cover 220 may be coupled to the substrate 110. In addition, the cover 200 may be bonded to at least one of the protective layer 170, the film 130, the insulating layer 115, the first electrode 140, the piezoelectric layer 150, the second electrode 160, and the metal layer 180.

Fig. 2 is an example of a block diagram of a filter. Referring to fig. 2, the filter 10 may include at least one series unit 11 and at least one shunt unit 12, the at least one shunt unit 12 being disposed between the at least one series unit 11 and ground. The filter 10 as shown in fig. 2 may be formed using a ladder-type filter structure, or may be formed using a lattice-type filter structure.

At least one series unit 11 may be disposed between a signal input terminal (RFin) to which an input signal is input and a signal output terminal (RFout) to which an output signal is output, and the shunt unit 12 may be disposed between the series unit 11 and ground. Each of the at least one series unit 11 and the at least one shunt unit 12 may have at least one of the bulk acoustic wave resonators shown in fig. 1.

For example, when the series unit 11 includes a plurality of bulk acoustic wave resonators and the shunt unit 12 includes a plurality of bulk acoustic wave resonators, the plurality of bulk acoustic wave resonators provided in the series unit 11 may be connected in series, and a part of the bulk acoustic wave resonators may be connected in parallel according to an example. Further, the plurality of bulk acoustic wave resonators provided in the shunt unit 12 may be provided between one node of the plurality of bulk acoustic wave resonators provided in the series unit 11 and the ground.

Fig. 3 shows an exemplary circuit diagram of a filter, and fig. 4 shows a frequency response of the filter of fig. 3.

Referring to fig. 3, the filter may include a series resonator (SE) disposed between a signal input terminal (RFin) and a signal output terminal (RFout) and a shunt resonator (Sh) disposed between the series resonator (SE) and ground.

Referring to fig. 4, a first curve (curve 1) represents the frequency response of the series resonator (SE), a second curve (curve 2) represents the frequency response of the shunt resonator (Sh), and a third curve (curve 3) represents the frequency response of a filter including the series resonator (SE) and the shunt resonator (Sh).

The frequency response of the series resonator (SE) has a resonance frequency (fr _ SE) and an antiresonance frequency (fa _ SE), and the frequency response of the shunt resonator (Sh) has a resonance frequency (fr _ Sh) and an antiresonance frequency (fa _ Sh).

With reference to the frequency response of the filter, the bandwidth of the filter may be determined in proportion to the interval between the resonance frequency (fr) and the anti-resonance frequency (fa) of the resonator.

In order to realize the filter as a band pass filter, the resonance frequency (fr _ SE) of the series resonator (SE) should be higher than the resonance frequency (fr _ Sh) of the shunt resonator (Sh), and the anti-resonance frequency (fa _ SE) of the series resonator (SE) should be higher than the anti-resonance frequency (fa _ Sh) of the shunt resonator (Sh). For example, the piezoelectric layer of the shunt resonator (Sh) may be realized to be thicker than the piezoelectric layer of the series resonator (SE), so that the relationship between the resonance frequency and the anti-resonance frequency as described above may be set.

On the other hand, the bandwidth and the effective electromechanical coupling coefficient Kt can be defined according to the following equations 1 and 2²。

Formula 1:

formula 2:

on the other hand, the bandwidth of the filter can be adjusted by connecting passive elements to the series resonator (SE) and the shunt resonator (Sh). Specifically, in order to adjust the bandwidth by changing only the anti-resonance frequency (fa) in a state where the resonance frequency (fr) of the resonator is fixed, the passive element may be connected in parallel to the series resonator. For example, when a capacitor is connected in parallel with the series resonator (SE), the anti-resonance frequency (fa _ SE) can be adjusted low. However, when the bandwidth of the filter becomes narrower with reference to equation 1, it may not be used for the purpose of increasing the bandwidth. As another example, when an inductor is connected in parallel with the series resonator (SE), the anti-resonance frequency (fa _ SE) of the series resonator (SE) may be adjusted to be high, so that the bandwidth may be increased.

However, when an inductor is connected in parallel with the series resonator (SE), harmonics of the anti-resonance frequency may be generated, so that the attenuation characteristic is deteriorated, and an inductor having a sufficiently high inductance may be required to increase the bandwidth, so that the quality factor Q and the insertion loss characteristic may be deteriorated.

Fig. 5A is a circuit diagram of an example of a filter.

Referring to fig. 5A, the filter 10 according to an example may include a series resonator (SE) disposed between a signal input terminal (RFin) and a signal output terminal (RFout), a shunt resonator (Sh) disposed between the series resonator (SE) and ground, and a correction unit 1000. The series resonator (SE) corresponds to the configuration included in the series unit 11 of fig. 2, and the shunt resonator (Sh) corresponds to the configuration included in the shunt unit 12 of fig. 2.

The correction unit 1000 may include at least one of a series correction unit 1000a disposed at both ends of the series resonator (SE) and a shunt correction unit 1000b disposed at both ends of the shunt resonator (Sh). For example, the series correction unit 1000a may be disposed between both ends of the series resonator (SE) and the ground, and the shunt correction unit 1000b may be disposed between both ends of the shunt resonator (Sh) and the ground.

In fig. 5A, the filter 10 is shown as including one series resonator (SE) and one shunt resonator (Sh). However, a plurality of series resonators (SE) and a plurality of shunt resonators (Sh) may be provided. In this example, the series correction unit 1000a may be disposed between both ends of a series resonator (SE) of a part of a plurality of series resonators (SE) connected in series or in parallel, and the shunt correction unit 1000b may be disposed between both ends of a shunt resonator (Sh) of a part of a plurality of shunt resonators (Sh) connected in series or in parallel. More specifically, when the correction unit is applied to the resonators connected in parallel, the correction unit may be disposed in parallel with the resonators connected in parallel, and when the correction unit is applied to the resonators connected in series, the correction unit may be disposed in parallel with nodes at both ends of the entire circuit constituted by the resonators connected in series.

The series correction unit 1000a can adjust the anti-resonance frequency (fa _ SE) of the series resonator (SE), and the shunt correction unit 1000b can adjust the anti-resonance frequency (fa _ Sh) of the shunt resonator (Sh).

In fig. 5A, the correction unit 1000 is shown to include both a series correction unit 1000a and a shunt correction unit 1000 b. However, according to an example, the correction unit 1000 may include at least one of the series correction unit 1000a and the shunt correction unit 1000b or both the series correction unit 1000a and the shunt correction unit 1000 b.

Hereinafter, for convenience of explanation, it is assumed that the correction unit 1000 includes only the series correction unit 1000a, and an example will be described in detail. However, the following description is applicable to the shunt correction unit 1000 b.

Fig. 5B is a circuit diagram of a filter according to an example.

Referring to fig. 5B, the filter 10 may include a plurality of series resonators (S1 to S5) and a plurality of shunt resonators (Sh1 to Sh 5). The plurality of series resonators (S1 to S5) may be connected in series between the signal input terminal (RFin) and the signal output terminal (RFout). For example, the first series resonator S1, the second series resonator S2, the third series resonator S3, the fourth series resonator S4, and the fifth series resonator S5 may be connected in series.

The plurality of shunt resonators (Sh1 to Sh5) may be individually disposed or connected between the plurality of series resonators S1 to S5 and the ground. For example, each of the plurality of shunt resonators (Sh1 to Sh5) may be disposed between a different series resonator (S1 to S5) and ground.

The first shunt resonator Sh1 may be disposed between a node between the first series resonator S1 and the second series resonator S2 and the ground, the second shunt resonator Sh2 may be disposed between a node between the second series resonator S2 and the third series resonator S3 and the ground, the third shunt resonator Sh3 may be disposed between a node between the third series resonator S3 and the fourth series resonator S4 and the ground, the fourth shunt resonator Sh4 may be disposed between a node between the fourth series resonator S4 and the fifth series resonator S5 and the ground, and the fifth shunt resonator Sh5 may be disposed between a node between the fifth series resonator S5 and the signal output terminal (RFout) and the ground.

Fig. 6 is a circuit diagram of a correction unit according to an example.

Referring to fig. 6, the correction unit 1000 may include an inductor unit 1100 and an impedance unit 1200, the inductor unit 1100 including a plurality of inductors, and the impedance unit 1200 including at least one capacitor.

The inductor unit 1100 may include at least one inductor. At least one inductor may be provided in a unit of three nodes connected in a Y-connection between both ends of the series resonator (SE) and ground.

Referring to fig. 6, the inductor unit 1100 may include: an inductor (La) and an inductor (Lc) provided in series at both ends of the series resonator (SE); and an inductor (Lb) provided at a node between the inductor (La) and the inductor (Lc). In fig. 6, an inductor unit 1100 is shown to include three inductors La, Lb, and Lc. However, this is merely an example, and the inductor unit 1100 may include at least one of the three inductors La, Lb, and Lc or include more than three inductors.

In an example, the inductor unit may be connected between both ends of at least one of a set of series resonators of the plurality of series resonators and a set of shunt resonators of the plurality of shunt resonators. In an example, a set of series resonators may be equivalent to one series resonator or more than one series resonator. Similarly, a set of shunt resonators may be equivalent to one shunt resonator or more than one shunt resonator.

Further, in fig. 6, the inductor unit 1100 is shown to include three inductors La, Lb, and Lc. However, this is merely an example. The inductor unit 1100 may include two inductors of the three inductors La, Lb, and Lc, and the remaining inductors may be formed by mutual impedances of the two inductors. The impedance unit 1200 may include an impedance Z disposed between the inductor (Lb) and ground.

Fig. 7 is an example of a circuit diagram of a modification of the correction unit of fig. 6.

Referring to fig. 7, according to the conversion of Y to D, the impedance Z of the impedance unit 1200 of fig. 6 may be converted into an impedance a × Z connected in series with the inductor (La), an impedance cx (-1/Z) connected in series with the inductor (Lb), and an impedance B × Z connected in series with the inductor (Lc).

Inductor La and total impedance Z of impedances a × Z_ARoll-off characteristics are improved by forming an additional pole outside the bandwidth in the frequency response of the filter, and the total impedance Z of inductor Lb and impedance Cx (-1/Z)_BConnected in parallel to the series resonator SE to change the anti-resonance frequency fa _ SE of the series resonator SE, the total impedance Z of the inductor Lc and the impedance B x Z_CConnected in parallel to the shunt resonator (Sh), the anti-resonance frequency (fa _ Sh) of the shunt resonator (Sh) can be changed.

Here, the impedance Z_AImpedance Z_BAnd impedance Z_CCan be determined according to equation 3 below. Formula 3:

fig. 8A, 8B, and 8C are circuit diagrams of an impedance unit according to an example.

Referring to fig. 8A, the impedance unit 1200 may include a capacitor C1, and referring to fig. 8B, the impedance unit 1200 may further include an inductor L1 connected in parallel with the capacitor C1 of fig. 8A. Further, referring to fig. 8C, the impedance unit 1200 may further include a circuit of a capacitor C2 and an inductor L2 connected in parallel with the capacitor C1 and the inductor L1.

The impedance unit 1200 according to an example may include one capacitor, or at least one capacitor and at least one inductor, to change the frequency response of the filter.

Fig. 9 is a circuit diagram of a correction unit according to another example.

Since the correction unit according to the example of fig. 9 is similar to the correction unit according to the example of fig. 6, a repetitive description will be omitted and differences will be mainly described.

Referring to fig. 9, the correction unit 1000 may include an inductor unit 1100, an impedance unit 1200, and a correction resonator 1300. The correction resonator 1300 may be connected in parallel to the impedance unit 1200. The correction resonator 1300 may have the same frequency characteristic as that of one of the series resonator (SE) and the shunt resonator (Sh) of the filter 10. For example, the correction resonator 1300 may have the same resonance frequency as the resonance frequency of the series resonator (SE) and the same anti-resonance frequency as the anti-resonance frequency of the series resonator (SE), or may have the same resonance frequency as the resonance frequency of the shunt resonator (Sh) and the same anti-resonance frequency as the anti-resonance frequency of the shunt resonator (Sh).

Fig. 10 is a circuit diagram of a correction unit according to another example.

Referring to fig. 10, the inductor unit 1100 may include an inductor Lx and an inductor Ly disposed in series at both ends of a series resonator (SE). The impedance unit 1200 may include a capacitor C disposed between a connection node of the inductor Lx and the inductor Ly and the ground. The inductor Lx and the inductor Ly of the inductor unit 1100 may be connected to each other, and the coupling coefficients of the inductor Lx and the inductor Ly may have positive signs. In other words, the inductor Lx and the inductor Ly may be connected by a direct coupling manner.

Fig. 11 is a diagram showing a frequency response of a filter to which the correction unit according to the example of fig. 10 is applied.

In fig. 11, a first curve (curve 1) represents the frequency response of a filter to which the correction unit according to the example of fig. 10 is applied to the series resonator (SE), and a second curve (curve 2) represents the frequency response of a filter corresponding to a comparative example to which the correction unit is not applied.

Referring to the first curve (curve 1) and the second curve (curve 2) of fig. 11, it can be seen that the filter according to the example of fig. 10 has a wider bandwidth and significantly improved insertion loss characteristics, compared to the filter according to the comparative example.

Fig. 12 is a circuit diagram of a correction unit according to another example.

Referring to fig. 12, the inductor unit 1100 may include an inductor Lx and an inductor Ly disposed at one end of a series resonator (SE) in series. Specifically, the inductor unit 1100 may include an inductor Ly connected to one end of the series resonator (SE) and an inductor Lx connected to the inductor Ly. A connection node of the inductor Lx and the inductor Ly may be connected to the other end of the series resonator (SE). The impedance unit 1200 may include a capacitor C disposed between the inductor Lx and the ground. The inductor Lx and the inductor Ly of the inductor unit 1100 may be connected to each other, and the coupling coefficients of the inductor Lx and the inductor Ly may have negative signs. In other words, the inductor Lx and the inductor Ly may be coupled in a reverse coupling manner.

The respective examples of the correction unit described above may be applied to the series correction unit and the shunt correction unit in the same form or in different forms. For example, the correction unit of the example of fig. 10 may be applied to a series correction unit and a shunt correction unit, and as another example, the correction unit of the example of fig. 12 may be applied to a series correction unit, and the correction unit of the example of fig. 10 may be applied to a shunt correction unit.

As set forth above, in the filter according to the example, deterioration of the attenuation characteristic, the quality factor Q, and the insertion loss according to the anti-resonance frequency generated when the inductor having a sufficiently high inductance is connected to the series resonator to increase the bandwidth can be prevented.

Although the present disclosure includes specific examples, it will be apparent upon an understanding of the present disclosure that various changes in form and detail may be made to these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein are to be considered in a descriptive sense only and not for purposes of limitation. The description of features or aspects in each example should be considered applicable to similar features or aspects in other examples. Suitable results may be achieved if the described techniques were performed in a different order and/or if components in the described systems, architectures, devices, or circuits were combined in a different manner and/or replaced or added by other components or their equivalents. Therefore, the scope of the present disclosure is defined not by the detailed description but by the claims and their equivalents, and all modifications within the scope of the claims and their equivalents will be understood to be included in the present disclosure.