CN112737544B - Surface acoustic wave filter - Google Patents
Surface acoustic wave filter Download PDFInfo
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- CN112737544B CN112737544B CN202011597117.4A CN202011597117A CN112737544B CN 112737544 B CN112737544 B CN 112737544B CN 202011597117 A CN202011597117 A CN 202011597117A CN 112737544 B CN112737544 B CN 112737544B
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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
- H03H9/6423—Means for obtaining a particular transfer characteristic
- H03H9/6433—Coupled resonator filters
Abstract
The invention discloses a surface acoustic wave filter, comprising: the series component is connected between the input port and the output port in series; the series component at least comprises one or more of a coupling capacitor and a resonator; at least one branch connected between a connection node of the series assembly and ground potential, different branches connecting different connection nodes of the series assembly; and the inductor is bridged between two non-adjacent connection nodes of the series assembly. The series connection component, the branch and the inductor form the surface acoustic wave filter to realize the function of the filter, the inductor is bridged between any two connection nodes of the filter series connection component to increase the number of zero points, the out-of-band rejection capability is improved, and when the series connection component is a coupling capacitor, the series connection loss can be reduced.
Description
Technical Field
The embodiment of the invention relates to the technical field of band-pass filters, in particular to a surface acoustic wave filter.
Background
The surface acoustic wave filter is widely applied to mobile communication terminals as a frequency selection device. The surface acoustic wave filter comprises resonators, the resonators are interdigital electrode structures manufactured on a piezoelectric substrate, and the resonators are connected in series or in parallel to form the surface acoustic wave filter to complete the function of the filter.
The existing filter generally only comprises series resonators and parallel resonators, the number of zeros of the existing filter is limited, the improvement of out-of-band rejection is limited, and the selection of specific frequencies cannot be well completed.
Disclosure of Invention
The invention provides a surface acoustic wave filter, which aims to increase the number of zero points and improve the out-of-band rejection capability.
An embodiment of the present invention provides a surface acoustic wave filter, including:
the series component is connected between the input port and the output port in series; the series component at least comprises one or more of a coupling capacitor and a resonator;
at least one branch connected between a connection node of the series assembly and ground potential, different ones of the branches connecting different connection nodes of the series assembly;
an inductor connected across two non-adjacent connection nodes of the series assembly.
Optionally, the resonator includes an interdigital electrode and a reflective grating.
Optionally, each branch comprises a parallel component, and the parallel component at least comprises one resonator;
one end of the resonator is connected with the connecting node, and the other end of the resonator is connected with the ground potential or connected with the ground potential through at least one grounding inductor.
Optionally, at least two series components and one branch circuit are included between the two non-adjacent connection nodes of the inductor cross-connection.
Optionally, the saw filter includes one or more first series units including at least one of the series modules connected in series.
Optionally, the saw filter includes one or more second series units, and the second series unit includes at least two of the series modules connected in parallel.
Optionally, part of the branches includes one or more first parallel units, and the first parallel units include at least one of the resonators connected in series.
Optionally, a part of the branches includes a second parallel unit, and the second parallel unit includes at least two resonators connected in parallel.
Optionally, the branches include at least a first branch and a second branch; each branch comprises at least one resonator;
and the first end of the resonator is connected with the connecting node, the second end of the resonator is connected with the second ends of the rest branch resonators to form a common port, and the common port is connected with the ground potential through a grounding inductor.
Optionally, the inductor is integrated on the piezoelectric substrate or in the package substrate.
Optionally, the piezoelectric substrate is a piezoelectric single crystal or piezoelectric ceramic.
Optionally, the interdigital electrode is made of at least one elemental metal of aluminum, copper, titanium, tungsten, platinum and gold, or an alloy electrode material with the elemental metal as a main component.
The embodiment of the invention provides a surface acoustic wave filter, which comprises a series component, at least one branch and an inductor, wherein the series component is connected between an input port and an output port in series, the at least one branch is connected between a connection node of the series component and the ground potential, the inductor is bridged between any two non-adjacent connection nodes of the series component, and the series component, the parallel branch and the inductor form the surface acoustic wave filter to realize the function of the filter. The number of zero points is increased by bridging the inductors between any two non-adjacent connecting nodes of the filter series assembly, the out-of-band rejection capability is improved, and when the series assembly is a coupling capacitor, the series loss can be reduced.
Drawings
Fig. 1 is a circuit diagram of a surface acoustic wave filter according to an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of a resonator according to an embodiment of the present invention.
FIG. 3 is a circuit diagram of another SAW filter according to an embodiment of the present invention
Fig. 4 is a circuit diagram of another saw filter according to an embodiment of the present invention.
Fig. 5 is a frequency response graph of a surface acoustic wave filter according to an embodiment of the present invention.
Fig. 6 is an enlarged view of the passband of the frequency response curve of the saw filter according to the embodiment of the present invention.
Fig. 7 is a circuit diagram of another saw filter according to an embodiment of the present invention.
Fig. 8 is a circuit diagram of another saw filter according to an embodiment of the present invention.
Fig. 9 is a circuit diagram of another saw filter according to an embodiment of the present invention.
Fig. 10 is a circuit diagram of another surface acoustic wave filter according to an embodiment of the present invention.
Fig. 11 is a circuit diagram of another saw filter according to an embodiment of the present invention.
Fig. 12 is a circuit diagram of another saw filter according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
Fig. 1 is a circuit diagram of a surface acoustic wave filter according to an embodiment of the present invention, and referring to fig. 1, optionally, the surface acoustic wave filter includes:
a series assembly 100 connected IN series between an input port IN and an output port OUT; the series assembly 100 includes at least one or more of a coupling capacitor 110, a resonator 120;
at least one branch connected between the connection node of the series assembly 100 and ground potential GND, different branches connecting different connection nodes of the series assembly 100;
and an inductor 200, wherein the inductor 200 is connected between two connection nodes of the series assembly 100 in a bridge.
The series elements 100 may be all the coupling capacitors 110, as shown in fig. 1, or in other embodiments, the series elements 100 may be all the resonators 120 or include both the coupling capacitors 110 and the resonators 120, and the number of the series elements 100 may be set according to the requirement, and the resonant frequency of each resonator 120 or the capacitance of each coupling capacitor 110 may be set according to the requirement. The coupling capacitor 110 may be an interdigital electrode, or may be a stacked structure of a metal layer, a dielectric layer, and a metal layer. The series components 100 are connected IN series between the input port IN and the output port OUT, a connection node exists between the input port IN and the series component 100 connected to the input port IN, a connection node exists between two adjacent series components 100 connected IN series, and a connection node exists between the output port OUT and the series component 100 connected to the output port OUT. There may be a branch on each connection node, each branch including at least one resonator 120.
The surface acoustic wave filter exemplarily shown IN fig. 1 includes five coupling capacitors 110, the five coupling capacitors 110 are sequentially connected IN series between the input port IN and the output port OUT, a capacitance value of each coupling capacitor 110 can be set as required, the surface acoustic wave filter further includes four branches, and a branch exists at a connection node between every two adjacent coupling capacitors 110 connected IN series. Each branch comprises a resonator 120, one end of the resonator 120 is connected to the connection node, the other end of the resonator 120 is connected to the ground potential GND, and the frequency of each resonator 120 in the branch can be set according to requirements. The saw filter further includes an inductor 200, one end of the inductor 200 is connected to the connection node connected to the first branch 310, and the other end of the inductor 200 is connected to the connection node connected to the third branch 320. The number and type of the series elements 100, the number of branches, the number and resonant frequency of the resonators 120 on each branch, the structure of the branches, and the number of the inductors 200 can be set according to the requirement, and the embodiment is not limited specifically herein.
As shown IN fig. 1, the frequencies of the resonators 120, the coupling capacitors 110, and the inductors 200 together determine the selection capability of the filter for signals with different frequencies, so that signals with specific frequencies are transmitted from the input port IN to the output port OUT, while signals with other frequencies are suppressed, thereby implementing the filtering function. In the process of signal transmission, the inductor 200 connected between the connection nodes, the series assembly 100 and the resonator 120 on the branch circuit jointly complete the filtering function, and a plurality of zero points can be added out of the band by adding the inductor 200, so that the out-of-band part frequency band suppression is improved, and the design flexibility is increased.
The surface acoustic wave filter provided by the embodiment comprises series components connected in series between an input port and an output port, at least one branch connected between a connection node of the series components and the ground potential, and an inductor bridged between any two connection nodes of the series components, wherein the two connection nodes at least comprise two series components, the connection node between the two series components is connected with the branch, and the series components, the branch and the inductor form the surface acoustic wave filter to realize a filtering function. The inductors are bridged between any two connecting nodes of the filter series assembly, so that a plurality of zero points can be added out of the band, the out-of-band part frequency band suppression is improved, and the design flexibility is improved.
Fig. 2 is a schematic structural diagram of a resonator according to an embodiment of the present invention, and referring to fig. 2, the resonator optionally includes an interdigital electrode 121 and a reflective grating 122.
An alternating current signal is input into the input port IN, the signal generates a variable electromagnetic field between the fingers through the bus electrode, the fingers manufactured on the piezoelectric substrate emit elastic vibration on the substrate through inverse piezoelectric effect, the elastic vibration generates bulk acoustic waves IN the substrate, surface acoustic waves are generated on the surface of the substrate, and acoustic-electric conversion is realized. The surface acoustic wave reaches an output end after being transmitted on the substrate with certain time delay, and is converted into an electric signal through a piezoelectric effect, so that the acoustic-electric conversion is realized. The reflection grating 122 reflects the surface acoustic waves which are diffused outwards in the transmission process, so that the loss of the surface acoustic waves is reduced. The selectivity of the saw filter for different frequency electrical signals is affected by the internal parameters of the resonator 120, the coupling capacitor 110 and the inductor 200, and the internal parameters of the resonator 120 include the interdigital pair period, number, aperture, duty ratio, film thickness, etc.
Optionally, each branch comprises a parallel component 1201; the parallel assembly 1201 includes at least one resonator 120;
one end of the resonator 120 is connected to the connection node, and the other end of the resonator 120 is connected to the ground potential GND, or connected to the ground potential GND through at least one ground inductor 400.
Optionally, the inductor 200 includes at least two series components 100 and a branch between two non-adjacent connection nodes.
Fig. 3 is a circuit diagram of another saw filter according to an embodiment of the present invention, referring to fig. 3, optionally, the saw filter includes at least two inductors 200, where two connection nodes bridged by each inductor 200 are different from two connection nodes bridged by another inductor 200;
each branch comprises at least two resonators 120 and at least one grounding inductor 400, the at least two resonators 120 are connected in series to form a parallel component 1201, one end of the parallel component 1201 is connected with a connection node of the series component 100, the other end of the parallel component 1201 is connected with one end of the grounding inductor 400, and the other end of the grounding inductor 400 is connected with a ground potential GND.
Illustratively, the surface acoustic wave filter of the present embodiment includes seven series components 100, two inductors 200, six branches, and six grounding inductors 400, where the seven series components 100 are all coupling capacitors 110, the seven coupling capacitors 110 are sequentially connected IN series between the input port IN and the output port OUT, a capacitance value of each coupling capacitor 110 is set according to requirements, one end of one inductor 200 is connected to a connection node connected to the first branch 310, and the other end is connected to a connection node connected to the second branch 320. One end of another inductor 200 is connected to the connection node connected to the third branch 330, the other end of the another inductor 200 is connected to the connection node connected to the fourth branch 340, and the inductance of each inductor 200 is set as required, in this embodiment, the connection nodes connected across the two inductors 200 are different, and the two inductors 200 are connected across the two series components 100. Each branch of the surface acoustic wave filter includes a parallel component 1201 and a grounding inductor 400, each parallel component 1201 includes a first resonator 11 and a second resonator 12, one end of the first resonator 11 is connected to a corresponding connection node, the other end of the first resonator 11 is connected to one end of the second resonator 12, the other end of the second resonator 12 is connected to one end of the grounding inductor 400, and the other end of the grounding inductor 400 is connected to a ground potential GND. The frequency of each resonator in the branch and the inductance of each grounding inductor 400 are set as desired. In this embodiment, the resonators 120 are all connected to the ground potential GND through the grounding inductor 400, and in other embodiments, the branches may only include the resonators 120, and the resonators 120 are connected between the connection node and the ground potential GND.
The frequency of the resonator 120, the coupling capacitor 110, the inductor 200, and the grounding inductor 400 jointly determine the selection capability of the filter for signals with different frequencies, so that signals with specific frequencies are transmitted from the input port IN to the output port OUT, while signals with other frequencies are suppressed, and thus the filtering function is realized. The inductor 200 and the grounding inductor 400 bridged between the connection nodes can be added with a plurality of zero points outside the band, so that the frequency band suppression of the out-of-band part is improved, and the design flexibility is increased. In addition, when no grounding inductor exists, the resonators on the branches are connected to the ground through the gold balls, the gold balls introduce a small parasitic inductor under high frequency, the size of the parasitic inductor is influenced by the shape and the position of the gold balls, the performance of the filter is influenced, the influence of the size and the position of the gold balls on the performance of the filter is weakened by the increase of the grounding inductor 400, and the bandwidth of the filter is widened.
Fig. 4 is a circuit diagram of another saw filter according to an embodiment of the present invention, where fig. 4 does not include the inductor 200 in fig. 3, and the rest of the structure is the same as that of the saw filter shown in fig. 3.
Fig. 5 is a frequency response curve diagram of a surface acoustic wave filter according to an embodiment of the present invention, and fig. 6 is an enlarged view of a pass band of a frequency response curve of the surface acoustic wave filter according to the embodiment of the present invention. The solid line in fig. 5 is a frequency response curve of a surface acoustic wave filter designed according to the structure of the surface acoustic wave filter of fig. 3, the center frequency of the filter is 2426MHz, the relative bandwidth of 1dB is 5%, and the minimum loss is less than 0.5dB, the dotted line in fig. 5 is a frequency response curve of a surface acoustic wave filter designed according to the structure of the surface acoustic wave filter of fig. 4, the center frequency of the filter is 2426MHz, the relative bandwidth of 1dB is 5%, and the minimum loss is less than 0.5 dB. Fig. 5 shows frequency on the abscissa, in GHz, Attenuation on the ordinate, i.e., Attenuation suppression of an unnecessary frequency signal after an input signal passes through a filter, and fig. 6 shows Insertion Loss representing Loss of a signal in a pass band frequency range after an input signal passes through a filter, and fig. 6 is a partially enlarged view of fig. 5 in the vicinity of a pass band N.
Referring to fig. 3-6, after the inductor 200 is added, the low-end zero points a and b are formed, which effectively improves out-of-band rejection. When the series components are all the coupling capacitors 110, the (m2, m3) form the passband of the filter, the attenuation at the m1 point is-0.487 dB, the attenuation at the m2 point is-1.578 dB, and the attenuation at the m3 point is-1.516 dB, namely when the structure that the coupling capacitors 110 are connected in series as shown in the figure 3 is adopted, the minimum loss of the passband of the filter is only-0.487 dB.
Fig. 7 is a circuit diagram of another saw filter according to an embodiment of the present invention, and referring to fig. 7, optionally, the saw filter includes at least two inductors 200, and one end of each of the at least two inductors 200 is connected to the same connection node;
each branch comprises at least one resonator 120 and at least one grounding inductor 400, one end of the resonator 120 is connected to the connection node, the other end of the resonator 120 is connected to one end of the grounding inductor 400, and the other end of the grounding inductor 400 is connected to the ground potential GND.
The surface acoustic wave filter of the present embodiment includes seven series components 100, two inductors 200, and six branches, each of which includes one resonator 120 and one grounding inductor 400, the seven series components 100 are sequentially connected IN series between the input port IN and the output port OUT, and the series components 100 may be one or more of a coupling capacitor and a resonator. One end of an inductor 200 is connected to the connection node connected to the first branch 310, and the other end is connected to the connection node connected to the second branch 320; one end of another inductor 200 is connected to the connection node to which the first branch 310 is connected, and the other end of another inductor 200 is connected to the connection node to which the third branch 330 is connected. In the present embodiment, the inductance values of each inductor 200 and each grounding inductor 400 and the resonant frequency of each resonator 120 can be set according to requirements, and when the series assembly 100 includes a coupling capacitor, the capacitance value of each coupling capacitor can also be set according to requirements.
When the series assembly 100 includes the coupling capacitor 110, the frequency of the resonator 120, the coupling capacitor 110, the inductor 200, and the grounding inductor 400 together determine the selection capability of the filter for signals with different frequencies, so that signals with specific frequencies are transmitted from the input port IN to the output port OUT, and signals with other frequencies are suppressed, thereby implementing a filtering function. The inductor 200 and the grounding inductor 400 bridged between the connection nodes can be added with a plurality of zero points outside the band, so that the out-of-band part frequency band suppression is improved, the design flexibility is increased, the influence of the size and the position change of the gold ball on the performance of the filter is weakened by adding the grounding inductor 400, and the bandwidth of the filter is widened.
Fig. 8 is a circuit diagram of another saw filter according to an embodiment of the present invention, and referring to fig. 8, optionally, the series assembly 100 includes at least one coupling capacitor 110 or at least one resonator 120, and the coupling capacitor 110 or the resonator 120 is connected IN series and then connected between the input port IN and the output port OUT;
each branch comprises at least two resonators 120 and at least one grounding inductor 400, the at least two resonators 120 are connected in series to form a parallel component 1201, one end of the parallel component 1201 is connected with the connection node, the other end of the parallel component 1201 is connected with one end of the grounding inductor 400, and the other end of the grounding inductor 400 is connected with the ground potential GND.
The surface acoustic wave filter of the present embodiment includes 4 series components 100, an inductor 200, three branches, and three grounding inductors 400, wherein four series components 100 include three coupling capacitors 110 and one resonator 120, the three coupling capacitors 110 are connected IN series and then connected IN series with the resonator 120 to form a series circuit 130, one end of the series circuit 130 is connected to the input port IN, and the other end of the series circuit 130 is connected to the output port OUT. Each branch comprises a first resonator 11, a second resonator 12 and a grounding inductor 400, one end of the first resonator 11 is connected with a corresponding connection node, the other end of the first resonator 11 is connected with one end of the second resonator 12, the other end of the second resonator 12 is connected with one end of the grounding inductor 400, and the other end of the grounding inductor 400 is connected with a ground potential GND. The inductor 200 is connected across a connection node connected to the first branch 310 and a connection node connected to the output port OUT. In the present embodiment, the inductance values of the inductor 200 and each grounding inductor 400, the resonant frequency of each resonator 120, and the capacitance value of each coupling capacitor 110 can be set according to the requirement.
The frequency of the resonator 120, the coupling capacitor 110, the inductor 200, and the grounding inductor 400 jointly determine the selection capability of the filter for signals with different frequencies, so that signals with specific frequencies are transmitted from the input port IN to the output port OUT, while signals with other frequencies are suppressed, and thus the filtering function is realized. The inductor 200 and the grounding inductor 400 bridged between the connection nodes can be added with a plurality of zero points outside the band, so that the out-of-band part frequency band suppression is improved, the design flexibility is increased, the influence of the size and the position change of the gold ball on the performance of the filter is weakened by adding the grounding inductor 400, and the bandwidth of the filter is widened.
Optionally, the saw filter includes one or more first series units 101, and the first series unit 101 includes at least one series module 100 connected in series.
Optionally, the saw filter includes one or more second series units 102, and the second series unit 102 includes at least two series modules 100 connected in parallel.
Optionally, part of the branches comprises one or more first parallel units comprising at least one resonator 120 connected in series.
Optionally, part of the branches comprises a second parallel unit comprising at least two resonators 120 connected in parallel.
Fig. 9 is a circuit diagram of another surface acoustic wave filter according to an embodiment of the present invention, and referring to fig. 9, optionally, the surface acoustic wave filter further includes a first series unit 101 and a second series unit 102, where the first series unit 101 includes two series modules 100 connected IN series, the second series unit 102 includes two series modules 100 connected IN parallel, and the first series unit 101 and the second series unit 101 are connected IN series with other series modules and then connected between the input port IN and the output port OUT.
The surface acoustic wave filter of the present embodiment includes a first coupling capacitor 111, one end of the first coupling capacitor 111 is connected to the input port IN, the other end of the first coupling capacitor 111 is connected to one end of the first resonator 11, the other end of the first resonator 11 is connected to one end of the first series unit 101, the other end of the first series unit 101 is connected to one end of the second series unit 102, the other end of the second series unit 102 is connected to one end of the second resonator 12, the other end of the second resonator 12 is connected to one end of the second coupling capacitor 112, and the other end of the second coupling capacitor 112 is connected to the output port OUT. The first series unit 101 includes two resonators 120 connected in series, and the second series unit 102 includes two resonators 120 connected in parallel. In other embodiments, the series components 100 of the first series unit 101 may be all coupling capacitors 110, and the series components 100 of the second series unit 102 may also be all coupling capacitors, and the number of the series components 100 in the first series unit 101 and the number of the series components in the second series unit may be set as required.
The surface acoustic wave filter further includes a first arm 310, a second arm 320, a third arm 330, a fourth arm 340, and a fifth arm 350, the first arm 310 is connected to a connection node between the first coupling capacitor 111 and the first resonator 11, the second arm 320 is connected to a connection node between the first resonator 11 and the first series unit 101, the third arm 330 is connected to a connection node between the first series unit 101 and the second series unit 102, the fourth arm 340 is connected to a connection node between the second series unit 102 and the second resonator 12, and the fifth arm 350 is connected to a connection node between the second resonator 12 and the second coupling capacitor 112. The first branch 310 includes a resonator 120 and a grounding inductor 400, one end of the resonator 120 is connected to the connection node, the other end of the resonator 120 is connected to one end of the grounding inductor 400, the other end of the grounding inductor 400 is connected to the ground potential GND, and the fourth branch 340 and the fifth branch 350 are the same as the first branch 310. The second branch comprises a first parallel unit and a grounding inductor 400, the first parallel unit comprises a third resonator 13 and a fourth resonator 14, one end of the third resonator 13 is connected with the connection node, the other end of the third resonator 13 is connected with one end of the fourth resonator 14, the other end of the fourth resonator 14 is connected with one end of the grounding inductor 400, and the other end of the grounding inductor 400 is connected with the ground potential GND. The third branch 330 includes a second parallel unit and a grounding inductor 400, the second parallel unit includes a fifth resonator 15 and a sixth resonator 16, one end of the fifth resonator 15 is connected to one end of the sixth resonator 16, the connected common end is connected to the connection node, the other end of the fifth resonator 15 is connected to the other end of the sixth resonator 16, the connected common end is connected to one end of the grounding inductor 400, and the other end of the grounding inductor 400 is connected to the ground GND. In other embodiments, the number of the first parallel units on the branch circuit can be set according to requirements, and the inductance values of each inductor 200 and each grounding inductor 400, the resonant frequency of each resonator 120, and the capacitance value of each coupling capacitor can be set according to requirements.
The frequency of the resonator 120, the coupling capacitor 110, the inductor 200, and the grounding inductor 400 jointly determine the selection capability of the filter for signals with different frequencies, so that signals with specific frequencies are transmitted from the input port IN to the output port OUT, while signals with other frequencies are suppressed, and thus the filtering function is realized. The inductor 200 and the grounding inductor 400 bridged between the connection nodes can be added with a plurality of zero points outside the band, so that the out-of-band part frequency band suppression is improved, the design flexibility is increased, the influence of the size and the position change of the gold ball on the performance of the filter is weakened by adding the grounding inductor 400, and the bandwidth of the filter is widened.
Optionally, the branches include at least a first branch 310 and a second branch 320; each branch comprises at least one resonator 120;
the first end of the resonator 120 is connected to the connection node, and the second end of the resonator is connected to the second ends of the remaining resonators 120 to form a common end, and the common end is connected to a ground potential GND through a grounding inductor 400.
Fig. 10 is a circuit diagram of another saw filter according to an embodiment of the present invention, and referring to fig. 10, the branches optionally include a first branch 310, a second branch 320, a third branch 330, a fourth branch 340, a fifth branch 350, and a sixth branch 360. The third branch 330 includes at least one resonator 120, one end of the resonator 120 is connected to the connection node, and the other end of the resonator 120 is connected to the ground potential GND;
the first branch 310 includes at least one resonator 120 and at least one ground inductor 400, one end of the resonator 120 is connected to the connection node, and the other end of the resonator 120 is connected to the first end a1 of the ground inductor 400;
the second branch 320 includes at least one resonator 120 and at least one ground inductor 400, one end of the resonator 120 is connected to the connection node, and the other end of the resonator 120 is connected to the first end a2 of the ground inductor 400;
the second terminal A3 of the grounding inductor 400 of the first branch 310 is connected to the second terminal a4 of the grounding inductor 400 of the second branch 320, and the common terminal of the first branch 310 and the second branch 320 is connected to the ground potential GND via the grounding inductor 400.
The surface acoustic wave filter of the present embodiment includes seven series components 100, one inductor 200, six branches, and two grounding inductors 400, the series components 100 are one or more of coupling capacitors and resonators 120, and the seven series components 100 are connected IN series IN this order between an input port IN and an output port OUT. The third branch 330 comprises a resonator 120 connected between the connection node and the ground potential GND, the first branch 310 comprises a resonator 120 and a ground inductor 400, one end of the resonator 120 is connected to the connection node, the other end of the resonator 120 is connected to the first end a1 of the ground inductor 400 of the first branch 310, the second branch 320 comprises a resonator 120 and a ground inductor 400, one end of the resonator 120 is connected to the connection node, the other end of the resonator 120 is connected to the first end a2 of the ground inductor 400 of the second branch 320, the second end A3 of the ground inductor 400 of the first branch 310 is connected to the second end a4 of the ground inductor 400 of the second branch 320, and the common end of the second branch 320 and the first branch 310 is connected to the ground potential GND via the ground inductor 400. The fourth branch 340 is the same as the second branch 320 or the first branch 310, the fifth branch 350 is the same as the second branch 320, the first branch 310 or the fourth branch 340, the connection relationship between the fourth branch 340 and the fifth branch 350 is the same as the connection relationship between the second branch 320 and the first branch 310, the common terminal of the fourth branch 340 and the fifth branch 350 is connected with the ground potential GND through the grounding inductor 400, and the sixth branch 360 is the same as the third branch 330. In the present embodiment, the inductance values of the inductor 200 and each grounding inductor 400 and the resonant frequency of each resonator 120 can be set according to requirements, and when the series assembly 100 includes a coupling capacitor, the capacitance value of each coupling capacitor can also be set according to requirements.
When the series assembly 100 includes the coupling capacitor 110, the frequency of the resonator 120, the coupling capacitor 110, the inductor 200, and the grounding inductor 400 together determine the selection capability of the filter for signals with different frequencies, so that signals with specific frequencies are transmitted from the input port IN to the output port OUT, and signals with other frequencies are suppressed, thereby implementing a filtering function. The inductor 200 and the grounding inductor 400 bridged between the connection nodes can be added with a plurality of zero points outside the band, so that the out-of-band part frequency band suppression is improved, the design flexibility is increased, the influence of the size and the position change of the gold ball on the performance of the filter is weakened by adding the grounding inductor 400, and the bandwidth of the filter is widened.
Fig. 11 is a circuit diagram of another saw filter according to an embodiment of the present invention, referring to fig. 11, optionally including at least two inductors 200 connected across any two connection nodes, and branches between two connection nodes connected across one inductor 200 are included in branches between two connection nodes connected across another inductor 200;
each branch comprises at least one resonator 120, one end of the resonator 120 is connected to the connection node, the other end of the resonator 120 is connected to one end of the resonator 120 of all other branches, the other ends of the resonators 120 of all other branches are connected to their respective corresponding connection nodes, and the common end of all branches is connected to ground potential GND via a grounding inductor 400.
The surface acoustic wave filter of the present embodiment includes seven series components 100, two inductors 200, six branches, and a grounding inductor 400, the seven series components 100 are connected IN series between the input port IN and the output port OUT, each series component 100 may be a coupling capacitor or a resonator 120, each branch includes one resonator 120 therein, one inductor 200 is bridged between a connection node connected to the first branch 310 and a connection node connected to the second branch 320, and the other inductor 200 is connected between a connection node connected to the third branch 330 and a connection node connected to the fourth branch 340. In the present embodiment, the inductance values of each inductor 200 and the grounding inductor 400 and the resonant frequency of each resonator 120 can be set according to requirements, and when the series assembly 100 includes a coupling capacitor, the capacitance value of each coupling capacitor can also be set according to requirements.
When the series assembly 100 includes the coupling capacitor 110, the frequency of the resonator 120, the coupling capacitor 110, the inductor 200, and the grounding inductor 400 together determine the selection capability of the filter for signals with different frequencies, so that signals with specific frequencies are transmitted from the input port IN to the output port OUT, and signals with other frequencies are suppressed, thereby implementing a filtering function. The inductor 200 and the grounding inductor 400 bridged between the connection nodes can be added with a plurality of zero points outside the band, so that the out-of-band part frequency band suppression is improved, the design flexibility is increased, the influence of the size and the position change of the gold ball on the performance of the filter is weakened by adding the grounding inductor 400, and the bandwidth of the filter is widened.
Fig. 12 is a circuit diagram of another saw filter according to an embodiment of the present invention, referring to fig. 12, the saw filter includes two inductors 200, and one end of each inductor 200 is connected to the same connection node;
the series assembly 100 includes a coupling capacitor 110 and a resonator 120 connected in series between an input port and an output port;
each branch comprises two resonators 120, and the resonators 120 of each branch are connected in series between the connection node and ground potential GND.
The surface acoustic wave filter comprises a first coupling capacitor 111, one end of the first coupling capacitor 111 is connected with an input port IN, the other end of the first coupling capacitor 111 is connected with one end of a second coupling capacitor 112, the other end of the second coupling capacitor 112 is connected with one end of a first resonator 11, the other end of the first resonator 11 is connected with one end of a third coupling capacitor 113, the other end of the third coupling capacitor 113 is connected with one end of a second resonator 12, the other end of the second resonator 12 is connected with one end of a third resonator 13, the other end of the third resonator 13 is connected with one end of a fourth resonator 14, and the other end of the fourth resonator 14 is connected with an output port OUT. The surface acoustic wave filter further includes a first branch 310, a second branch 320, a third branch 330, and a fourth branch 340, the first branch 310 is connected to a connection node between the first coupling capacitor 111 and the second coupling capacitor 112, the second branch 320 is connected to a connection node between the first resonator 11 and the third coupling capacitor 113, the third branch 330 is connected to a connection node between the third coupling capacitor 113 and the second resonator 12, the fourth branch 340 is connected to a connection node between the second resonator 12 and the third resonator 13, each branch includes two resonators 120 connected in series, and the two resonators 120 are connected in series between the connection node and the ground potential GND. The saw filter further includes two inductors 200, one end of one inductor 200 is connected to the connection node connected to the first branch 310, the other end is connected to the connection node connected to the third branch 330, one end of the other inductor 200 is connected to the connection node connected to the first branch 310, and the other end of the other inductor 200 is connected to the connection node between the third resonator 13 and the fourth resonator 14. In the present embodiment, the inductance of each inductor 200, the resonant frequency of each resonator 120, and the capacitance of each coupling capacitor 110 can be set according to the requirement.
The frequency of the resonator 120, the coupling capacitor 110 and the inductor 200 together determine the selection capability of the filter for signals with different frequencies, so that signals with specific frequencies are transmitted from the input port IN to the output port OUT, and signals with other frequencies are suppressed, thereby realizing a filtering function. The inductor 200 bridged between the connection nodes can be added with a plurality of zero points outside the band, thereby improving the frequency band suppression of the out-of-band part and increasing the design flexibility.
Optionally, the inductor is integrated on the piezoelectric substrate or in the package substrate.
The inductor bridged between the connection nodes is integrated in the piezoelectric substrate or the packaging substrate and connected with the filter circuit, so that the miniaturization of the filter is realized. For filters in which a grounding inductor is present, the grounding inductor may also be integrated into the piezoelectric substrate or package substrate.
Optionally, the piezoelectric substrate is made of piezoelectric single crystal or piezoelectric ceramic.
The piezoelectric substrate is made of piezoelectric single crystal such as quartz, lithium tantalate (LiTaO3) or lithium LiNbO3, or piezoelectric ceramic.
Optionally, the interdigital electrode is made of at least one elemental metal of aluminum, copper, titanium, tungsten, platinum and gold, or an alloy electrode material containing the elemental metal as a main component.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (11)
1. A surface acoustic wave filter, comprising:
the series component is connected between the input port and the output port in series; the series components are all coupling capacitors, and the coupling capacitors are of a laminated structure of a metal layer, a dielectric layer and a metal layer;
at least one branch connected between a connection node of the series assembly and ground potential, different ones of the branches connecting different connection nodes of the series assembly; each branch comprises a parallel component; the parallel component comprises at least one resonator; one end of the resonator is connected with the connecting node, and the other end of the resonator is connected with the ground potential through at least one grounding inductor;
the direction of the coupling capacitor is 90 degrees to the direction of the resonator;
an inductor connected across two non-adjacent connection nodes of the series assembly.
2. A surface acoustic wave filter as set forth in claim 1, wherein said resonators include interdigital electrodes and reflection gratings.
3. A surface acoustic wave filter as set forth in claim 1, wherein said inductance bridge includes at least two series components and one of said branches between said two non-adjacent connection nodes.
4. A surface acoustic wave filter as set forth in claim 1, characterized by comprising one or more first series units including at least one of said series components connected in series.
5. A surface acoustic wave filter as set forth in claim 1, characterized by comprising one or more second series units comprising at least two of said series components connected in parallel.
6. A surface acoustic wave filter as set forth in claim 1, wherein part of said arms include one or more first parallel units including at least one of said resonators connected in series.
7. A surface acoustic wave filter as set forth in claim 1, wherein part of said arms include a second parallel unit including at least two of said resonators connected in parallel.
8. A surface acoustic wave filter according to claim 1, wherein said arms include at least a first arm and a second arm; each branch comprises at least one resonator;
and the first end of the resonator is connected with the connecting node, the second end of the resonator is connected with the second ends of the rest branch resonators to form a common end, and the common end is connected with the ground potential through a grounding inductor.
9. A surface acoustic wave filter according to any of claims 1-8, characterized in that said inductance is integrated on a piezoelectric substrate or in a package substrate.
10. A surface acoustic wave filter as set forth in claim 9, wherein said piezoelectric substrate is a piezoelectric single crystal or a piezoelectric ceramic.
11. A surface acoustic wave filter as set forth in claim 2, wherein said interdigital electrode is made of at least one elemental metal of aluminum, copper, titanium, tungsten, platinum, gold, or an alloy electrode material having the elemental metal as a main component.
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Denomination of invention: SAW filter Effective date of registration: 20221025 Granted publication date: 20220329 Pledgee: Hangzhou United Rural Commercial Bank Co.,Ltd. Haining sub branch Pledgor: TIANTONG RUIHONG TECHNOLOGY Co.,Ltd. Registration number: Y2022980019519 |
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