CN114513188A - Trapezoidal surface acoustic wave filter - Google Patents
Trapezoidal surface acoustic wave filter Download PDFInfo
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- CN114513188A CN114513188A CN202210140391.1A CN202210140391A CN114513188A CN 114513188 A CN114513188 A CN 114513188A CN 202210140391 A CN202210140391 A CN 202210140391A CN 114513188 A CN114513188 A CN 114513188A
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Classifications
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- H—ELECTRICITY
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- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/64—Filters using surface acoustic waves
- H03H9/6423—Means for obtaining a particular transfer characteristic
- H03H9/6433—Coupled resonator filters
- H03H9/6483—Ladder SAW filters
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02535—Details of surface acoustic wave devices
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- H—ELECTRICITY
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- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02535—Details of surface acoustic wave devices
- H03H9/02818—Means for compensation or elimination of undesirable effects
- H03H9/02834—Means for compensation or elimination of undesirable effects of temperature influence
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- H—ELECTRICITY
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- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/05—Holders; Supports
- H03H9/058—Holders; Supports for surface acoustic wave devices
- H03H9/059—Holders; Supports for surface acoustic wave devices consisting of mounting pads or bumps
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/125—Driving means, e.g. electrodes, coils
- H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/64—Filters using surface acoustic waves
- H03H9/6489—Compensation of undesirable effects
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
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- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
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- Physics & Mathematics (AREA)
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- Chemical & Material Sciences (AREA)
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Abstract
The invention provides a trapezoidal surface acoustic wave filter, which comprises a substrate, a series arm and a parallel arm, wherein the series arm and the parallel arm are formed on the same substrate, the series arm comprises a plurality of series resonator groups, each series resonator group comprises a plurality of series resonators, the series arm is connected with an input terminal and an output terminal, the parallel arm comprises a plurality of parallel resonator groups, the parallel arm is connected with the series arm and a grounding terminal, and a packaging structure for accommodating a surface acoustic wave filter element is arranged, and the packaging structure is connected with the surface acoustic wave filter element through a bump. Therefore, the surface acoustic wave device has improved power resistance, is miniaturized, can meet the requirements of high-frequency and high-power surface acoustic wave devices on comprehensive performances such as good heat dissipation, low insertion loss and the like, and is easy to manufacture.
Description
Technical Field
The present invention relates to a ladder-type surface wave filter, and more particularly, to a high power tolerant miniaturized ladder-type surface wave filter.
Background
Ladder type surface acoustic wave filters are widely used in mobile phones and the like, and radio frequency circuits having similar frequency bands are often used in the same mobile phone. With the rapid development of radio frequency circuits, the requirements on the frequency indexes of radio frequency modules such as surface acoustic wave filters, duplexers and the like are increasingly strict, filters with larger bandwidth, higher frequency and higher power are required, the steepness is provided on the low-frequency side and the high-frequency side so as to meet the requirements on larger and larger information transmission quantity and wide frequency bandwidth, but simultaneously, the requirements on the volume are also more and more strict, and the volume must be developed towards miniaturization.
In the prior art, the steepness, high frequency, power tolerance and miniaturization of the ladder-shaped surface acoustic wave filter are improved, a plurality of resonators are required to be connected in series, the width of an interdigital electrode in each resonator is reduced, high electrical stress and mechanical stress are generated on each resonator, and then characteristic degradation of the ladder-shaped surface acoustic wave filter or damage of the interdigital electrode are generated.
Disclosure of Invention
To the deficiency among the prior art, an object of this application lies in providing a trapezoidal surface acoustic wave filter, improves electric power resistance, and is miniaturized, can satisfy the requirement of high frequency high power surface acoustic wave device to comprehensive properties such as good heat dissipation, low insertion loss, and easily makes.
The purpose of the invention is mainly realized by the following technical scheme:
the invention provides a trapezoidal surface acoustic wave filter, which is characterized by comprising:
a surface acoustic filter element including a substrate, a series arm and a parallel arm, the series arm and the parallel arm being formed on the same substrate;
the series arm includes a plurality of series resonator groups including a plurality of series resonators, the series arm connecting an input terminal and an output terminal;
the parallel arm includes a plurality of parallel resonator groups including a plurality of parallel resonators connecting the series arm and a ground terminal;
and a package structure accommodating the SAW element, the package structure and the SAW element being connected by bumps.
Further, the number of the series resonator groups is the same as the number of the parallel resonator groups, and the number of the series resonators is greater than the number of the parallel resonators.
Further, the series resonator group is provided with a first series resonator group, a second series resonator group, a third series resonator group and a fourth series resonator group in sequence from the input terminal to the output terminal; the parallel resonator group comprises a first parallel resonator group, a second parallel resonator group, a third parallel resonator group and a fourth parallel resonator group; the first parallel resonator group is connected between a connection point formed by the first series resonator group and the second series resonator group and the ground terminal.
Further, the package structure and/or the substrate provide at least one inductive component connected to the set of parallel resonators.
Further, the parallel resonator group includes a first parallel resonator including a first IDT electrode and first reflectors disposed on both sides of the first IDT electrode, and a second parallel resonator including a second IDT electrode and second reflectors disposed on both sides of the second IDT electrode; the first IDT electrode and the second IDT electrode are connected in series by a common bus bar; the first IDT electrode includes a first bus bar and the common bus bar that are disposed opposite each other, and the second IDT electrode includes a second bus bar and the common bus bar that are disposed opposite each other.
Further, the thickness of the first bus bar is smaller than the thickness of the common bus bar.
Further, the common bus bar is connected to any one of reflectors provided on the side of the first IDT electrode or the second IDT electrode.
Further, the first bus bar includes a plurality of first electrode fingers and a plurality of first dummy finger electrodes, the first electrode fingers being alternately arranged with the first dummy finger electrodes; the second bus bar includes a plurality of second electrode fingers and a plurality of second dummy finger electrodes, the second electrode fingers being alternately arranged with the second dummy finger electrodes; the common bus bar includes a plurality of electrode fingers in which a plurality of the first dummy finger electrodes and a plurality of the second dummy finger electrodes are disposed correspondingly.
Further, the second series resonator group includes a first series resonator including a first IDT electrode and first reflectors disposed on both sides of the first IDT electrode, a second series resonator including a second IDT electrode and second reflectors disposed on both sides of the second IDT electrode, and a third series resonator including a third IDT electrode and third reflectors disposed on both sides of the third IDT electrode; the first reflector and the second reflector are connected in series by a first common bus bar, and the second reflector are connected in series by a second common bus bar.
Further, the surface of the substrate in contact with the series arm is single-crystal lithium niobate or lithium tantalate having an Euler angle of (0, theta, phi), 30 DEG-128 DEG, 0 DEG-90 deg.
Further, the substrate comprises a piezoelectric single crystal substrate, a junction layer and a support layer, the junction layer is located between the piezoelectric single crystal substrate and the support layer, the series arms and the parallel arms are located on the surface of one side, away from the support layer, of the piezoelectric single crystal substrate, the packaging structure comprises a first packaging structure and a second packaging structure, the first packaging structure and the second packaging structure enclose a hollow structure, the first packaging structure is in contact with the bump, and the support layer is in contact with the second packaging structure.
Further, the package structure includes a plurality of external electrodes, at least one of which is connected to the ground terminal through the bump.
Further, the series arm includes at least three series arm resonator groups, resonance frequencies of the series arm resonator groups are different, and when a product of an electrode finger intersection width and a logarithm of an electrode finger in the series arm resonator group is set as a series cross product, the series arm resonator group having the smallest series cross product is located on the input terminal side or the output terminal side.
Further, the parallel arm includes at least three parallel arm resonator groups, and when a product of an intersection width of the electrode fingers in the parallel arm resonator group and a logarithm of the electrode fingers is set as a parallel longitudinal and lateral product, the parallel arm resonator group with the largest parallel longitudinal and lateral product is located on one side of the input terminal or the output terminal.
The invention has the following beneficial effects:
(1) the trapezoidal surface acoustic wave filter can meet the design of power resistance and miniaturization of the trapezoidal surface acoustic wave filter through the design of the multistage series resonator group and the parallel resonator group;
(2) according to the trapezoidal surface acoustic wave filter, the power resistance of the trapezoidal surface acoustic wave filter can be further improved by carrying out partition design on the series resonator group and the parallel resonator group, and the requirement for miniaturization of the trapezoidal surface acoustic wave filter is met;
(3) according to the trapezoidal surface acoustic wave filter, the common bus bar is arranged in the series resonator group and the parallel resonator group, so that the heat dissipation performance of the trapezoidal surface acoustic wave filter is improved;
(4) the invention provides a ladder type surface acoustic wave filter which can realize wide frequency while inhibiting the deterioration of insertion loss.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
fig. 1 is an equivalent circuit diagram for explaining a saw filter device according to an embodiment of the present invention;
FIG. 2 is a schematic top view for explaining a SAW device according to an embodiment of the present invention;
FIG. 3 is a schematic cross-sectional view of an SAW device in accordance with an embodiment of the present invention;
fig. 4 is an equivalent circuit diagram for explaining a saw filter device according to a second embodiment of the present invention;
fig. 5 is a schematic top view for explaining a surface acoustic wave filter device according to a second embodiment of the present invention;
fig. 6 is a schematic cross-sectional view for explaining a surface acoustic wave filter device according to a second embodiment of the present invention;
fig. 7 is a schematic diagram illustrating a structure of a parallel resonator group P1 in a saw surface filter device according to a third embodiment of the present invention;
fig. 8 is a schematic view for explaining still another structure of a parallel resonator group P1 in the saw filter device according to the third embodiment of the present invention;
fig. 9 is a schematic structural diagram for explaining the series resonator group S2 in the saw filter device according to the fourth embodiment of the present invention.
Fig. 10 is an equivalent circuit diagram for explaining the saw filter device according to the fifth embodiment of the present invention.
Fig. 11 is a graph showing the pass characteristics of the filter devices of the fifth embodiment and the first comparative example.
Detailed Description
So that the manner in which the above recited objects, features and advantages of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and therefore the scope of the present invention is not limited by the specific embodiments disclosed below.
Example one
A surface acoustic wave filter device according to a first embodiment will be described with reference to the drawings of fig. 1 to 3.
Fig. 1 is an equivalent circuit diagram of a surface acoustic wave filter device according to embodiment 1. Fig. 2 is a schematic plan view for explaining the surface acoustic wave filter device according to embodiment 1 of the present invention.
The surface acoustic wave filter element 1 includes a substrate 2, and a series arm 3 and a parallel arm 4 formed on the same substrate 2. The series arm 3 connects the input terminal 5 and the output terminal 6. The series arm 3 sequentially arranges series resonator groups S1, S2, S3, S4 in a direction from the input terminal 5 to the output terminal 6, wherein the series resonator group S2 includes two series resonators S201 and S202, and the series resonator group S3 includes two series resonators S301 and S302. The series resonators S201, S202, S301, S302 may be single-port resonators or longitudinally-coupled resonators, preferably single-port resonators.
The parallel arm 4 includes parallel resonator groups P1, P2, P3, P4 connected in parallel between the series arm 3 and the ground terminal 7, respectively, each parallel resonator group defining one parallel arm, and parallel resonator groups P1, P2, P3, P4 connected between the first ground terminal 701, the second ground terminal 702, the third ground terminal 703 and the fourth ground terminal 704, respectively. The series resonator groups S1, S2, S3, S4 and the parallel resonator groups P1, P2, P3, P4 are alternately connected to each other. The parallel resonator group P2 includes two parallel resonators P201 and P202 connected in series, and the parallel resonator group P3 includes two parallel resonators P301 and P302 connected in series. The parallel resonator group P1 is connected between the first ground terminal 701 and a connection point D101 formed by the series resonator group S1 and the series resonator group S2. The parallel resonator group P2 is connected between the second ground terminal 702 and a connection point D102 formed by the series resonator group S2 and the series resonator group S3. The parallel resonator group P3 is connected between the third ground terminal 703 and a connection point D103 formed by the series resonator group S3 and the series resonator group S4. The parallel resonator group P4 is connected between the connection point D104 formed by the series resonator group S4 and the output terminal 6 and the third ground terminal 704.
At least 1 of the series resonator groups S1, S2, S3, S4 has a different structure or frequency characteristic from the other series resonator groups. The resonance frequencies of at least 1 of the series resonator groups S1, S2, S3, S4 are located outside the pass band of the ladder type surface acoustic wave filter. At least 1 of the parallel resonator groups P1, P2, P3, P4 has a different structure or frequency characteristic from the other parallel resonator groups. At least 1 antiresonance frequency in the parallel resonator groups P1, P2, P3 and P4 is positioned outside the passband of the trapezoidal surface acoustic wave filter, so that the passband width of the trapezoidal surface acoustic wave filter can be increased, and the electric power resistance of the trapezoidal surface acoustic wave filter is improved.
The substrate 2 is preferably made of, for example, single crystal lithium tantalate having an euler angle of (0, 42 °, 0 °) in the present preferred embodiment. The substrate 2 is not limited to the single crystal lithium tantalate having the euler angle of (0, 42 °, 0 °), and may be made of another piezoelectric single crystal such as single crystal lithium niobate or lithium hexafluoroborate having the euler angle of (0, 30 °, 90 °), or may be made of, for example, a piezoelectric ceramic. Also, as will be described later, the base plate 2 is not limited to a material made of only a piezoelectric material, and a piezoelectric body in which a piezoelectric film is laminated on a support substrate may also be used. The series arm 3 and the parallel arm 4 are formed on the same substrate 2. The surface acoustic wave filter element can be made compact and easy to manufacture, compared to a design form in which the series arm and the parallel arm are formed on different substrates, respectively.
Fig. 3 shows a schematic cross-sectional view illustrating a surface acoustic wave filter device according to embodiment 1 of the present invention. And a packaging structure 8 for accommodating the surface acoustic wave filter element 1, wherein the packaging structure 8 is connected with the surface acoustic wave filter element 1 through a bump 9. The package structure 8 includes a first package structure 801 and a second package structure 802, the first package structure 801 and the second package structure 802 enclose a hollow structure, and the saw filter element 1 is located in the hollow structure.
The bump 9 may be plural. In order to improve the connection strength between the bump 9 and the package structure 8 and the surface acoustic wave filter element 1, the bump 9 has a three-layer composite bump structure. Each bump 9 includes a base electrode 901, an intermediate bump electrode 902, and a package electrode 903, wherein the base electrode 901 is provided on the surface of the substrate 2 forming the series arm 3 and the parallel arm 4, the base electrode 901 is made of NiCr alloy and has a thickness of 10nm, the intermediate bump electrode 902 is connected to the base electrode 901 by a ball bonding method, the intermediate bump electrode 902 is a spherical or ellipsoidal structure made of Au or an alloy containing Au, and the package electrode 903 is connected to the intermediate bump electrode 902 by an ultrasonic pressure welding process. By adopting the three-layer composite bump, the stress applied to the surface of the surface acoustic wave filter element 1 can be reduced, the mechanical strength and the reliability of the packaging structure are improved, and the device failure caused by the fracture of the substrate 2 is reduced.
Example two
Different from the first embodiment, the resonant frequency of the series resonator group, the inductance component of the package structure, and the multilayer substrate are further designed, so that the saw filter element 1 is further miniaturized, and the power resistance is further enhanced.
A surface acoustic wave filter device according to a second embodiment will be described with reference to the drawings of fig. 4 to 6.
Fig. 4 is an equivalent circuit diagram of the surface acoustic wave filter device according to embodiment 2. Fig. 5 is a schematic plan view for explaining a surface acoustic wave filter device according to embodiment 2 of the present invention. Fig. 6 is a schematic cross-sectional view of a surface acoustic wave filter device according to embodiment 2 of the present invention.
The surface acoustic wave filter element 1 includes a substrate 2, and a series arm 3 and a parallel arm 4 formed on the same substrate 2. The series arm 3 connects the input terminal 5 and the output terminal 6. The series arm 3 sequentially arranges series resonator groups S1, S2, S3, S4 in a direction from the input terminal 5 to the output terminal 6, wherein the series resonator group S1 includes two series resonators S101 and S102, the series resonator group S2 includes three series resonators S201, S202, and S203, the series resonator group S3 includes two series resonators S301 and S302, and the series resonator group S4 includes two series resonators S401 and S402. The series resonators S101, S102, S201, S202, S203, S301, S302, S401, and S402 may be single-port resonators or longitudinally-coupled resonators, and are preferably single-port resonators.
The resonant frequencies of the series arm resonator groups are different. The resonance frequency and the anti-resonance frequency of at least 1 of the series resonator groups S1, S2, S3, S4 are located outside the pass band of the surface acoustic wave filter element 1, and the resonance frequency and the anti-resonance frequency of the remaining series resonator groups are located within the pass band of the surface acoustic wave filter element 1, whereby it is possible to make the loss in the pass band of the ladder-shaped surface acoustic wave filter low and the sharpness on the high frequency side of the pass band improved.
The parallel arm 4 includes parallel resonator groups P1, P2, P3, P4 connected in parallel between the series arm 3 and the ground terminal 7, respectively, each parallel resonator group defining one parallel arm. The parallel resonator group P1 includes two parallel resonators P101 and P102 connected in series, the parallel resonator group P2 includes two parallel resonators P201 and P202 connected in series, the parallel resonator group P3 includes two parallel resonators P301 and P302 connected in series, and the parallel resonator group P4 includes two parallel resonators P401 and P402 connected in series.
The resonance frequency and anti-resonance frequency of at least 1 of the groups of parallel resonators P1, P2, P3, P4 are located outside the pass band of the surface acoustic filter element 1, and the resonance frequency and anti-resonance frequency of the remaining groups of parallel resonators are located within the pass band of the surface acoustic filter element 1.
In the surface acoustic filter element 1, the number of the series resonator group is the same as the number of the parallel resonator group, and the number of the series resonator group is greater than the number of the parallel resonator group, so that the area of the series resonator group is larger than the area of the parallel resonator group, and the series resonator group has a larger capacitance than the parallel resonator group, so that the stop band attenuation of the surface acoustic filter element 1 is larger, the length of the welding wire forming the series arm 3 and the parallel arm 4 is shorter, and the surface acoustic filter element 1 can be greatly miniaturized.
The ladder type surface acoustic wave filter having the above arrangement preferably further includes a package structure 8, and the parallel inductance component is arranged in this package structure 8. The parallel inductance component includes a first inductance component L1 and a second inductance component L2, wherein the first inductance component L1 is provided in the package structure, connected in parallel with the parallel resonator groups P1, P2 and then connected to the common ground terminal 705 through bonding wires, and the second inductance component L2 is provided in the package structure, connected in parallel with the parallel resonator groups P3, P4 and then connected to the common ground terminal 706 through bonding wires. The package structure 8 includes a plurality of external electrodes, for example, the package structure 8 includes a first external electrode W1, a second external electrode W2, and a third external electrode W3, and the first external electrode W1 is connected to the bump 9 through a first inductance component L1. The size of the surface acoustic filter device is reduced relative to a discrete ground terminal.
The substrate 2 includes a piezoelectric single crystal substrate 201, a bonding layer 202, and a support layer 203, the bonding layer 202 is located between the piezoelectric single crystal substrate 201 and the support layer 203, and the series arms 3 and the parallel arms 4 are located on a surface of the piezoelectric single crystal substrate 201 on a side away from the support layer 203. The piezoelectric single crystal substrate 201 may be lithium tantalate or lithium niobate, and the material, cutting angle, and thickness of the piezoelectric single crystal may be appropriately selected according to the required specification. The bulk acoustic wave velocity propagated through the bonding layer 202 is lower than the bulk acoustic wave velocity propagated through the piezoelectric single crystal substrate 201, and various materials such as silicon dioxide, glass, silicon oxynitride, tantalum oxide, and the like can be used. The support layer 203 is a structure that supports the bonding layer 202 and the piezoelectric single crystal substrate 201. As the support layer 203, a piezoelectric body such as lithium tantalate, lithium niobate, or quartz, alumina, magnesia, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, steatite, or forsterite, a dielectric such as sapphire or glass, or a semiconductor such as silicon or gallium nitride can be used. Here, the support layer 203 is, for example, a silicon substrate having excellent heat dissipation properties. In this structure, the support layer 203 can enclose the surface acoustic wave in the laminated piezoelectric single crystal substrate 201 and the bonding layer 202, and the leakage of the surface acoustic wave energy to the series resonator group or the parallel resonator group is suppressed, thereby reducing the insertion loss of the surface acoustic wave filter.
The package structure 8 includes a first package structure 801 and a second package structure 802, the first package structure 801 and the second package structure 802 form a hollow structure, and the first package structure 801 is in contact with the bump 9. The second package structure 802 is a double-layer structure, and includes a first layer 802-1 and a second layer 802-2, the second layer 802-2 is embedded in the inner surface of the first layer 802-1, the thickness of the second layer 802-2 is smaller than that of the first layer 802-1, and the support layer 203 is in contact with the second layer 802-2, so that the saw filter element 1 has good heat dissipation and sealing properties.
EXAMPLE III
Different from the first embodiment and the second embodiment, the parallel resonator group is further designed, so that the saw filter element 1 is further miniaturized, and the electric power resistance is further enhanced.
A surface acoustic wave filter device according to a third embodiment will be described with reference to the drawings of fig. 7 to 9.
The surface acoustic wave filter element 1 includes a substrate 2, and a series arm 3 and a parallel arm 4 formed on the same substrate 2. The series arm 3 connects the input terminal 5 and the output terminal 6. The series arm 3 is provided with series resonator groups S1, S2, S3, S4 in this order in the direction from the input terminal 5 to the output terminal 6. The parallel arm 5 includes parallel resonator groups P1, P2, P3, P4 connected in parallel between the series arm 3 and the ground terminal 7, respectively, each parallel resonator group defining one parallel arm. The equivalent circuit structure of the surface acoustic wave filter element 1 is substantially the same as that of the second embodiment, and is not described herein again.
Fig. 7 is a schematic structural diagram of a parallel resonator group P1 in the third embodiment. The parallel resonator group P1 includes a first parallel resonator P101 and a second parallel resonator P102, the first parallel resonator P101 including a first IDT electrode X1 and a first reflector F1 disposed on both sides of the first IDT electrode, the second parallel resonator P102 including a second IDT electrode X2 and a second reflector F2 disposed on both sides of the second IDT electrode, the first IDT electrode X1 and the second IDT electrode X2 being connected in series by a common bus bar H0, the first IDT electrode X1 including a first bus bar H1 and a common bus bar H0 disposed oppositely, and the second IDT electrode X2 including a second bus bar H2 and a common bus bar H0 disposed oppositely. The common bus bar H0 is a member that generates the largest amount of heat when the parallel resonator group P1 operates, and the thickness of the common bus bar H0 is larger than the thickness of the first bus bar H1, and the heat is dissipated to the outside via the common bus bar, and this structure can suppress temperature rise, suppress metal migration in the IDT electrode to the substrate, improve the power resistance of the acoustic surface filter element 1, and promote miniaturization of the device.
Fig. 8 shows still another embodiment of the parallel resonator group P1 in the third embodiment. The parallel resonator group P1 includes a first parallel resonator P101 and a second parallel resonator P102, the first parallel resonator P101 including a first IDT electrode X1 and a first reflector F1 disposed on both sides of the first IDT electrode, the second parallel resonator P102 including a second IDT electrode X2 and a second reflector F2 disposed on both sides of the second IDT electrode, the first IDT electrode X1 and the second IDT electrode X2 being connected in series by a common bus bar H0, the first IDT electrode X1 including a first bus bar H1 and a common bus bar H0 disposed oppositely, and the second IDT electrode X2 including a second bus bar H2 and a common bus bar H0 disposed oppositely. The common bus bar H0 is connected to any one of the reflectors provided on the first IDT electrode X1 or the second IDT electrode X2 side.
In the ladder-type surface acoustic wave filter, when power is applied, the temperature of the IDT electrode located at the center tends to rise, and particularly, the common bus bar H0 has the highest temperature and heat is not easily diffused, which causes a problem that the power resistance of the entire ladder-type surface acoustic wave filter is lowered. By connecting the common bus bar to any one of the reflectors provided on the first IDT electrode X1 or the second IDT electrode X2, the heat of the common bus bar is conducted to the reflector on one side, so that the heat radiation area of the common bus bar can be increased, and the power durability of the entire ladder type surface acoustic wave filter can be improved.
Example four
Different from the first to third embodiments, the form of the series resonator group is further designed, so that the saw filter element 1 is further miniaturized and the power resistance is further enhanced.
The surface acoustic wave filter element 1 includes a substrate 2, and a series arm 3 and a parallel arm 4 formed on the same substrate 2. The series arm 3 connects the input terminal 5 and the output terminal 6. The series arm 3 is provided with series resonator groups S1, S2, S3, S4 in this order in the direction from the input terminal 5 to the output terminal 6. The parallel arm 5 includes parallel resonator groups P1, P2, P3, P4 connected in parallel between the series arm 3 and the ground terminal 7, respectively, each parallel resonator group defining one parallel arm. The equivalent circuit structure of the surface acoustic wave filter element 1 is substantially the same as that of the second embodiment, and is not described herein again.
The series resonator group S1 includes two series resonators S101 and S102, and the series resonator group S1 has the same structure as the parallel resonator group P1 in the third embodiment, so that the series resonator group S1 and the parallel resonator group P1 respond to different frequencies by designing the thickness of the IDT electrodes and the pitch between the interdigital electrodes.
Fig. 9 is a schematic structural diagram of a series resonator group S2 in the fourth embodiment.
The series resonator group S2 includes a first series resonator S201, a second series resonator S202, and a third series resonator S203. The first series resonator S201 includes a first IDT electrode X201 and first reflectors F201 disposed on both sides of the first IDT electrode, the second series resonator S202 includes a second IDT electrode X202 and second reflectors F202 disposed on both sides of the second IDT electrode, and the third series resonator S203 includes a third IDT electrode X203 and third reflectors F203 disposed on both sides of the third IDT electrode. The first reflector F201, the second reflector F202, and the third reflector F203 are connected by a common bus bar.
The first IDT electrode X201 and the second IDT electrode X202 are connected in series by a first common bus bar H01, and the second IDT electrode X202 and the third IDT electrode X203 are connected in series by a second common bus bar H02. The first IDT electrode X201 includes a first bus bar H1 and a first common bus bar H01 which are oppositely disposed, the second IDT electrode X202 includes a first common bus bar H01 and a second common bus bar H02 which are oppositely disposed, and the third IDT electrode X203 includes a second common bus bar H02 and a third bus bar H3 which are oppositely disposed.
The first bus bar H1 includes a plurality of first electrode fingers and a plurality of first dummy finger electrodes, the first electrode fingers being alternately arranged with the first dummy finger electrodes.
A plurality of second electrode fingers disposed corresponding to the first dummy finger electrodes are disposed on one side of the first common bus bar H01, and a plurality of third electrode fingers are disposed on the other side of the first common bus bar H01 to be spaced apart from the plurality of second electrode fingers.
A plurality of fourth electrode fingers are disposed on one side of the second common bus bar H02 to be spaced opposite the plurality of third electrode fingers, and a plurality of fifth electrode fingers are disposed on the other side of the second common bus bar H02 to be spaced apart from the plurality of fourth electrode fingers.
The third bus bar H3 includes a plurality of sixth electrode fingers and a plurality of sixth dummy finger electrodes, the sixth electrode fingers being alternately arranged with the sixth dummy finger electrodes.
By providing the dummy finger electrodes on the first common bus bar H01 and the second common bus bar H02, instead of providing the dummy finger electrodes on the first bus bars H1 and H3, it is possible to improve the power resistance of the surface acoustic filter element 1, suppress deterioration of the frequency characteristics of the surface acoustic filter element 1, and reduce the device size.
EXAMPLE five
Different from the first to fourth embodiments, the vertical and horizontal areas of the series resonator group or the parallel resonator group are further designed, so that the attenuation amount in the attenuation region in the vicinity of the pass band of the surface acoustic filter element 1 can be increased, and the deterioration of the sharpness of the filter characteristic on the low frequency side of the pass band can be suppressed, whereby the surface acoustic filter element 1 can be further downsized and the power resistance can be further enhanced.
The surface acoustic wave filter element 1 includes a substrate 2, and a series arm 3 and a parallel arm 4 formed on the same substrate 2. The series arm 3 connects the input terminal 5 and the output terminal 6. The series arm 3 is provided with series resonator groups S1, S2, S3, S4 in this order in the direction from the input terminal 5 to the output terminal 6. The parallel arm 5 includes parallel resonator groups P1, P2, P3, P4 connected in parallel between the series arm 3 and the ground terminal 7, respectively, each parallel resonator group defining one parallel arm. The equivalent circuit structure of the surface acoustic wave filter element 1 is substantially the same as that of the second embodiment, and is not described herein again.
In order to increase the amount of attenuation in the attenuation region near the pass band of the surface acoustic filter element 1 and suppress the deterioration of the sharpness of the filter characteristic in the low frequency side of the pass band, it is necessary to design the design parameters of the series resonator groups S1, S2, S3, S4 and the parallel resonator groups P1, P2, P3, P4. The design parameters generally include at least one of the crossover width of the electrode fingers, the number of pairs of interdigitated fingers, and the period length of the electrode fingers.
When the product of the electrode finger intersection width and the number of pairs of electrode fingers in the series arm resonator group is set to the series aspect, the series arm resonator group S1, S2, S3, S4 all have different series aspects, and the series arm resonator group having the smallest series aspect is located on the input terminal or the output terminal side. The amount of attenuation in the attenuation domain near the passband can be increased.
When the product of the intersection width of the electrode fingers and the logarithm of the electrode fingers in the parallel arm resonator group is set as a parallel longitudinal and transverse product, the parallel longitudinal and transverse products of the parallel arm resonator groups P1, P2, P3 and P4 are all different, and the parallel arm resonator group with the largest parallel longitudinal and transverse product is positioned on one side of the input terminal or the output terminal.
[ Filter characteristics ]
The pass band of the filter devices in example five and comparative example one were set to 1950-.
Fig. 10 shows an equivalent circuit diagram of the surface acoustic wave filter device according to the fifth embodiment. As design parameters of the series resonator groups S1, S2, S3, S4 and the parallel resonator groups P1, P2, P3, P4, the filter device in the fifth embodiment is shown in table 1 as the filter device 101, in which the minimum series resonator group S4 having the minimum series aspect ratio is located on the output terminal side, and the maximum parallel resonator group P1 having the maximum parallel aspect ratio is located on the input terminal side, as the electrode fingers.
[ Table 1]
As a further modification of the fifth embodiment, the filter device 102 shows the intersection width, the number of pairs of fingers, the cross product of the electrode fingers, and the period length of the electrode fingers in table 2 as design parameters of the series resonator groups S1, S2, S3, S4 and the parallel resonator groups P1, P2, P3, P4, where the series resonator group S1 with the smallest series cross product is located on the input terminal side, and the parallel resonator group P4 with the largest parallel cross product is located on the output terminal side.
[ Table 2]
| Filter arrangement 102 | S1 | S2 | S3 | S4 | P1 | P2 | P3 | P4 |
| Width of cross | 21 | 35.2 | 26.8 | 35.8 | 28 | 33.8 | 33.78 | 34.34 |
| Number of pairs of insertion fingers | 73.5 | 100.5 | 71.5 | 95.5 | 69.5 | 80.5 | 62.5 | 94.5 |
| Longitudinal and transverse product | 1543.5 | 3537.6 | 1916.2 | 3418.9 | 1946 | 2720.9 | 2111.25 | 3245.13 |
The circuit configuration of the filter device 1011 in the first comparative example is the same as that of the filter device in the fifth embodiment shown in fig. 10. The filter apparatus 1011 differs from the filter apparatus 101 in that the series longitudinal and transverse products of the series resonator group S2 are minimum, the series resonator group S2 is located between the connection points D102 and D103, the parallel longitudinal and transverse products of the series and parallel resonator group P3 are maximum, and the parallel resonator group S3 is located between the connection point D103 and the ground terminal. The design parameters of the series resonator groups S1, S2, S3, and S4 and the parallel resonator groups P1, P2, P3, and P4 in the filter device 1011 are shown in table 3 as the intersection width, the number of pairs of fingers, the vertical and horizontal product, and the period length of the electrode fingers.
[ Table 3]
| Filter device 1011 | S1 | S2 | S3 | S4 | P1 | P2 | P3 | P4 |
| Width of intersection | 35.2 | 21 | 35.8 | 26.8 | 33.8 | 28 | 34.34 | 33.78 |
| Number of pairs of insertion fingers | 100.5 | 73.5 | 95.5 | 71.5 | 80.5 | 69.5 | 94.5 | 62.5 |
| Longitudinal and transverse product | 3537.6 | 1543.5 | 3418.9 | 1916.2 | 2720.9 | 1946 | 3245.13 | 2111.25 |
The pass characteristics of the filter devices of the fifth embodiment and the first comparative embodiment are compared. Fig. 11 is a graph showing the pass characteristics of the filter devices of the fifth embodiment, the fifth modification, and the first comparative example. The solid line shows the pass characteristics of the filter devices 101 and 102 in the fifth embodiment, and the broken line shows the pass characteristics of the filter device 1011 in the first comparative example.
As shown in fig. 11, at the frequency 1955MHz, the maximum insertion loss of the filter device 101 is 1.582dB, the maximum insertion loss of the filter device 102 is 1.582dB, and the maximum insertion loss of the filter device 1011 is 1.713 dB. At a frequency of 2020MHz, the maximum insertion loss of the filter device 101 is 1.989dB, the maximum insertion loss of the filter device 102 is 1.989dB, and the maximum insertion loss of the filter device 1011 is 2.125 dB. The insertion loss of the filter devices 101 and 102 in the fifth embodiment is suppressed from being deteriorated as compared with the insertion loss of the filter device 1011 in the first comparative example.
The filter device 1011 in the first comparative example has the smallest series aspect ratio of the series resonator group S2, the series resonator group S2 is located between the connection points D102 and D103, the maximum parallel aspect ratio of the series-parallel resonator group P3, and the parallel resonator group S3 is located between the connection point D103 and the ground terminal, and significant stop band ripple is generated on the high-frequency side of the pass band, resulting in degradation of insertion loss in the pass band, particularly on the high-frequency side. On the premise of not greatly changing the passing characteristic of the filter device, the cascade relation of the series resonator group and the parallel resonator group needs to be designed, so that the frequency of the stop band ripple is far away from the pass band of the filter device.
In the filter device 101 according to the fifth embodiment, the series resonator group S4 having the smallest series aspect ratio is located on the output terminal side, and the parallel resonator group P1 having the largest parallel aspect ratio is located on the input terminal side, so that the capacitance of the series resonator group S4 is reduced, the capacitance of the parallel resonator group P1 is increased, and the anti-resonance frequency can be lowered. Compared with the first comparative example, the frequency of the stop band ripple can be kept the same, the return resonance frequency can be reduced, the interval between the frequency of the stop band ripple and the pass band of the filter device is enlarged, and the insertion loss of the filter device is reduced.
Similarly, the filter device 102 in the fifth embodiment has the series resonator group S1 with the smallest series aspect ratio located on the input terminal side and the parallel resonator group P4 with the largest parallel aspect ratio located on the output terminal side, so that the electrostatic capacitance of the series resonator group S1 decreases and the electrostatic capacitance of the parallel resonator group P4 increases, and the anti-resonance frequency can be lowered. Compared with the first comparative example, the frequency of the stop band ripple can be kept the same, the return resonance frequency can be reduced, the interval between the frequency of the stop band ripple and the pass band of the filter device is enlarged, and the insertion loss of the filter device is reduced.
In the present invention, the terms "first", "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; the term "plurality" means two or more. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (13)
1. A ladder type surface acoustic wave filter, comprising:
a surface acoustic filter element including a substrate, a series arm and a parallel arm, the series arm and the parallel arm being formed on the same substrate;
the series arm includes a plurality of series resonator groups including a plurality of series resonators, the series arm connecting an input terminal and an output terminal;
the parallel arm includes a plurality of parallel resonator groups including a plurality of parallel resonators connecting the series arm and a ground terminal;
and a package structure accommodating the SAW element, the package structure being connected to the SAW element by a bump.
2. The ladder surface acoustic wave filter as set forth in claim 1, wherein the number of said series resonator groups is the same as the number of said parallel resonator groups, and the number of said series resonators is greater than the number of said parallel resonators.
3. The ladder surface acoustic wave filter according to claim 1 or 2,
the series resonator group is provided with a first series resonator group, a second series resonator group, a third series resonator group and a fourth series resonator group in sequence from the input terminal to the output terminal;
the parallel resonator group comprises a first parallel resonator group, a second parallel resonator group, a third parallel resonator group and a fourth parallel resonator group;
the first parallel resonator group is connected between a connection point formed by the first series resonator group and the second series resonator group and the ground terminal.
4. The ladder surface acoustic wave filter as set forth in claim 1, wherein said package structure and/or said substrate provides at least one inductive component connected to said group of parallel resonators.
5. The ladder surface acoustic wave filter according to claim 3, wherein the first parallel resonator group includes a first parallel resonator including a first IDT electrode and first reflectors disposed on both sides of the first IDT electrode, and a second parallel resonator including a second IDT electrode and second reflectors disposed on both sides of the second IDT electrode;
the first IDT electrode and the second IDT electrode are connected in series by a common bus bar;
the first IDT electrode includes a first bus bar and the common bus bar that are disposed opposite each other, and the second IDT electrode includes a second bus bar and the common bus bar that are disposed opposite each other.
6. The ladder surface acoustic wave filter according to claim 5, wherein the common bus bar is connected to any one of reflectors provided on one side of the first IDT electrode or the second IDT electrode.
7. The ladder surface acoustic wave filter according to claim 5, wherein said first bus bar includes a plurality of first electrode fingers and a plurality of first dummy finger electrodes, said first electrode fingers being arranged alternately with said first dummy finger electrodes;
the second bus bar includes a plurality of second electrode fingers and a plurality of second dummy finger electrodes, the second electrode fingers being alternately arranged with the second dummy finger electrodes;
the common bus bar includes a plurality of electrode fingers in which a plurality of the first dummy finger electrodes and a plurality of the second dummy finger electrodes are disposed correspondingly.
8. The ladder surface acoustic wave filter according to claim 3, wherein the second series resonator group includes a first series resonator including the first IDT electrode and first reflectors disposed on both sides of the first IDT electrode, a second series resonator including the second IDT electrode and second reflectors disposed on both sides of the second IDT electrode, and a third series resonator including the third IDT electrode and third reflectors disposed on both sides of the third IDT electrode;
the first reflector and the second reflector are connected in series by a first common bus bar, and the second reflector are connected in series by a second common bus bar.
9. The ladder surface acoustic wave filter according to claim 1, wherein the substrate surface in contact with said series arms is single crystal lithium niobate or lithium tantalate having an euler angle of (0, θ, Φ), 30 ° ≦ θ ≦ 128 °, 0 ° ≦ Φ ≦ 90 °.
10. The ladder surface acoustic wave filter according to claim 4, wherein the substrate includes a piezoelectric single crystal substrate, a bonding layer and a support layer, the bonding layer is located between the piezoelectric single crystal substrate and the support layer, the series arms and the parallel arms are located on a surface of the piezoelectric single crystal substrate on a side away from the support layer, the package structure includes a first package structure and a second package structure, the first package structure and the second package structure enclose a hollow structure, the first package structure is in contact with the bump, and the support layer is in contact with the second package structure.
11. A ladder type surface acoustic wave filter as set forth in claim 10, wherein said package structure includes a first external electrode connected to said bump through said inductance component.
12. A ladder type surface acoustic wave filter according to claim 1, wherein said series arms include at least three series arm resonator groups, resonance frequencies of said series arm resonator groups are different, and when a product of a crossing width of an electrode finger and a number of pairs of electrode fingers in said series arm resonator groups is set as a series vertical and horizontal product, a series arm resonator group whose series vertical and horizontal product is smallest is located on said input terminal or said output terminal side.
13. The ladder surface acoustic wave filter according to claim 12, wherein said parallel arm includes at least three parallel arm resonator groups, and when a product of a cross width of an electrode finger and a logarithm of the electrode finger in said parallel arm resonator group is set to a parallel aspect, the parallel arm resonator group having the largest parallel aspect is located on the input terminal or the output terminal side.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20230008248A1 (en) * | 2021-07-06 | 2023-01-12 | Skyworks Solutions, Inc. | Multimode longitudinally coupled surface acoustic wave resonator with modulated pitch |
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| CN113872557A (en) * | 2021-09-29 | 2021-12-31 | 北京超材信息科技有限公司 | Composite substrate for surface acoustic wave device, manufacturing method thereof and surface acoustic wave device |
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| JPH08204501A (en) * | 1994-11-22 | 1996-08-09 | Tdk Corp | Surface acoustic wave filter |
| US20110128092A1 (en) * | 2009-11-30 | 2011-06-02 | Avago Technologies Wireless Ip (Singapore) Pte. Ltd. | Duplexer with negative phase shifting circuit |
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