CN115955212B - SAW filter with enlarged bandwidth - Google Patents
SAW filter with enlarged bandwidth Download PDFInfo
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- CN115955212B CN115955212B CN202310239456.2A CN202310239456A CN115955212B CN 115955212 B CN115955212 B CN 115955212B CN 202310239456 A CN202310239456 A CN 202310239456A CN 115955212 B CN115955212 B CN 115955212B
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- 230000008878 coupling Effects 0.000 claims abstract description 27
- 238000010168 coupling process Methods 0.000 claims abstract description 27
- 238000005859 coupling reaction Methods 0.000 claims abstract description 27
- 239000000758 substrate Substances 0.000 claims abstract description 11
- WSMQKESQZFQMFW-UHFFFAOYSA-N 5-methyl-pyrazole-3-carboxylic acid Chemical compound CC1=CC(C(O)=O)=NN1 WSMQKESQZFQMFW-UHFFFAOYSA-N 0.000 claims abstract description 9
- 238000004519 manufacturing process Methods 0.000 abstract description 5
- 238000010897 surface acoustic wave method Methods 0.000 description 27
- 238000000034 method Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 4
- 238000003780 insertion Methods 0.000 description 4
- 230000037431 insertion Effects 0.000 description 4
- 230000001629 suppression Effects 0.000 description 4
- 230000007704 transition Effects 0.000 description 3
- 238000004891 communication Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 2
- 230000009977 dual effect Effects 0.000 description 1
- 238000010295 mobile communication Methods 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
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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
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
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Abstract
The invention relates to the technical field of filters, in particular to a SAW filter with enlarged bandwidth, which is manufactured on a lithium tantalate substrate and comprises an input port and an output port; the first filter unit and the second filter unit are arranged in parallel and are coupled between the input port and the output port. The first filter unit adopts the combination of the acoustic coupling filter and the impedance element resonator to improve the rectangular coefficient at the left side of the passband frequency band; the second filter unit adopts a combination of series and parallel impedance element resonators to improve the rectangular coefficient on the right side of the passband frequency band; meanwhile, the combined design of the first filter unit and the second filter unit can also realize ultra-wide bandwidth and effective out-of-band rejection, and can be used for frequency band designs with very high requirements on bandwidth and rectangular coefficients, such as B20+28, so that the production cost of products is greatly reduced, and after an integrated inductor is additionally arranged at the grounding front end, the out-of-band rejection can be further greatly improved.
Description
Technical Field
The invention relates to the technical field of filters, in particular to a SAW filter with an enlarged bandwidth.
Background
The Surface Acoustic Wave (SAW) filter is widely applied to mobile communication equipment and has the advantages of low insertion loss, wide bandwidth, small volume, low cost, mass production and the like.
The two most important performance indexes of the filter are passband interpolation loss and out-of-band rejection, the steeper degree of a transition zone between passband frequency and out-of-band rejection frequency is rectangular coefficient, the steeper the transition zone is, the higher the rectangular coefficient is, the larger the space reserved by the filter for process deviation and temperature drift is, and the better the performance is.
SAW filters can be generally classified into a general SAW, TCSAW, TFSAW according to a fabrication process, in which a general SAW refers to a process of fabricating a circuit directly on a LT (lithium tantalate) substrate, and TCSAW and TFSAW are special processes evolved from the general SAW process, so that the cost is far higher than that of the general SAW.
The bandwidth of SAW devices is limited by the type of substrate, e.g., common SAW substrates have coupling coefficients of about 8-10% and are typically used to design filters having a relative bandwidth of no more than 5%. While there are tens of communication bands, each of which has a different bandwidth, although most of the bands have a bandwidth of not more than 4%, some bands have very wide bandwidths, such as B41F (7.5% relative bandwidth) and b20+28 (8% relative bandwidth). The former is realized by using CRF+IEF structure, while B20+28 is wider in bandwidth, and rectangular coefficients on the left and right sides are higher (each side has a transition band space of only 10 MHz), and the former is realized by using IEF design of a special cut LN (lithium niobate) substrate with particularly high coupling coefficient, so that TCSAW technology is needed, and the technology cost of TCSAW is more than twice that of ordinary SAW; the present invention thus developed an extended bandwidth SAW filter to solve the problems of the prior art.
Disclosure of Invention
The invention aims at: the SAW filter with the bandwidth enlarged is provided to solve the problem that the requirements on rectangular coefficients at two ends of a passband cannot be met due to the fact that the bandwidth of a communication frequency band is very wide in the prior art.
The technical scheme of the invention is as follows: an extended bandwidth SAW filter fabricated on a lithium tantalate substrate, comprising:
an input port and an output port;
the first filter unit and the second filter unit are arranged in parallel, are coupled between the input port and the output port, and respectively improve rectangular coefficients on the left side and the right side of the passband frequency band; wherein,,
the first filter unit comprises at least one acoustic coupling filter connected in series between the input port and the output port, and at least one first impedance element resonator connected in parallel to ground; and/or the number of the groups of groups,
the second filter unit comprises at least one second impedance element resonator connected in series between the input port and the output port, and at least one third impedance element resonator connected in parallel to ground.
Preferably, the front ends of the grounding ends corresponding to the acoustic coupling filter, the first impedance element resonator and the third impedance element resonator are all provided with integrated inductors.
Preferably, the acoustic coupling filter is composed of interdigital transducers with multiple variation periods and reflecting grids arranged at two ends;
the first impedance element resonator, the second impedance element resonator and the third impedance element resonator have the same structure and are composed of interdigital transducers and reflecting grids arranged at two ends.
Preferably, the acoustic coupling filter is configured on a first serial path, and the first impedance element resonator is configured on a first parallel path and has a connection node with the first serial path;
the second impedance element resonator is configured on a second serial path, and the third impedance element resonator is configured on a second parallel path and is provided with a connection node with the second serial path;
the first series path and the second series path are arranged in parallel and connected between the input port and the output port.
Preferably, two acoustic coupling filters are configured on the first serial path, two first impedance element resonators are configured on the two first parallel paths, and two corresponding connecting nodes are respectively positioned at one side, close to an input port and an output port, of the two acoustic coupling filters;
the second impedance element resonators are arranged in three on the second series path, the third impedance element resonators are arranged in two in total and are positioned on the two second parallel paths, and two corresponding connecting nodes are respectively positioned between two adjacent second impedance element resonators.
Compared with the prior art, the invention has the advantages that:
(1) The SAW filter with the bandwidth expanded is divided into two parts to be designed and manufactured on the lithium tantalate substrate, so that the ultra wide bandwidth and high rectangular coefficients at the left end and the right end of a passband can be simultaneously realized on the common SAW process, the SAW filter can be used for the frequency band design with very high requirements on the bandwidth and the rectangular coefficients, such as B20+28, and the production cost of products is greatly reduced.
(2) The first filter unit adopts the combination of an acoustic coupling filter and an impedance element resonator to improve the rectangular coefficient at the left side of the passband frequency band; the second filter unit adopts a combination of series and parallel impedance element resonators to improve the rectangular coefficient on the right side of the passband frequency band; based on the parallel connection of the first filter unit and the second filter unit, ultra wide bandwidth can be realized, effective out-of-band suppression can be realized, and the out-of-band suppression can be further and greatly improved after the integrated inductor is additionally arranged at the grounding front end.
Drawings
The invention is further described below with reference to the accompanying drawings and examples:
fig. 1 is a circuit diagram of a SAW filter with an enlarged bandwidth according to embodiment 1 of the present invention;
fig. 2 is a structural diagram of the acoustic coupling filter according to the embodiment 1 and embodiment 2 of the present invention;
fig. 3 is a structural diagram of the first, second and third impedance resonators according to embodiment 1 and embodiment 2 of the present invention;
FIG. 4 is a plot of the insertion loss of an extended bandwidth SAW filter of the present invention in accordance with example 1;
fig. 5 is a circuit diagram of a SAW filter with an enlarged bandwidth according to embodiment 2 of the present invention;
fig. 6 is a plot of the insertion loss of an extended bandwidth SAW filter according to the present invention in example 2.
Wherein: 1. an input port;
2. an output port;
3. a first filter unit 31, an acoustic coupling filter 32, a first impedance element resonator;
4. a second filter unit 41, a second impedance element resonator 42, and a third impedance element resonator;
5. and integrating the inductor.
Detailed Description
The following describes the present invention in further detail with reference to specific examples:
[ example 1 ]
As shown in fig. 1, a SAW filter with an enlarged bandwidth is fabricated on a lithium tantalate substrate, and includes an input port 1, an output port 2, a first filter unit 3, and a second filter unit 4; the first filter unit 3 and the second filter unit 4 are arranged in parallel, are coupled between the input port 1 and the output port 2, and respectively improve rectangular coefficients on the left side and the right side of the passband frequency band.
The first filter unit 3 comprises at least one acoustic coupling filter 31 connected in series between the input port 1 and the output port 2, and at least one first impedance element resonator 32 connected in parallel; as shown in fig. 1, the acoustic coupling filter 31 is disposed on a first series path, and the first impedance element resonator 32 is disposed on a first parallel path with a connection node therebetween; in this embodiment, two acoustic coupling filters 31 are disposed on the first series path, two first impedance resonators 32 are disposed on the two first parallel paths, and two corresponding connection nodes are disposed on one side of the two acoustic coupling filters 31 close to the input port 1 and the output port 2, respectively.
The second filter unit 4 comprises at least one second impedance element resonator 41 connected in series between the input port 1 and the output port 2, and at least one third impedance element resonator 42 connected in parallel to ground; as shown in fig. 2, the second impedance element resonator 41 is disposed on the second series path, and the third impedance element resonator 42 is disposed on the second parallel path and has a connection node with the second series path; the first and second series paths are arranged in parallel and connected between the input port 1 and the output port 2. In this embodiment, three second impedance resonators 41 are disposed on the second serial path, two third impedance resonators 42 are disposed on the two second parallel paths, and two corresponding connection nodes are respectively located between two adjacent second impedance resonators 41.
As shown in fig. 2, the acoustic coupling filter 31 is composed of interdigital transducers of a plurality of variation periods and reflective gratings provided at both ends; acoustic coupling filter 31 (CRF), also commonly referred to as a dual mode filter (DMS), is a filter composed of a plurality of periodic IDTs and reflective gratings, which can achieve a wider bandwidth than Impedance Element Filters (IEFs), and thus is typically collocated with impedance element resonators (IEs) to form a filter; however, the rectangular coefficients of the CRF-containing filter on the right side of the passband are difficult to achieve left-side levels.
As shown in fig. 3, the first, second and third impedance resonators 32, 41 and 42 have the same structure and each consist of an interdigital transducer (IDT) and reflective gratings provided at both ends, the interdigital transducer (IDT) is a basic device for producing a surface acoustic wave filter, and the filters each consisting of the impedance resonators (IE) are called impedance filters (IEFs) in general, the IDT and the reflective gratings have the same structural period.
Referring to fig. 4, which shows an actually measured insertion loss curve of the SAW filter with bandwidth expanded in the present embodiment, where a line segment a is an index requirement of bandwidth, and a line segment B is an index requirement of out-of-band rejection, it can be seen that, in conjunction with the drawing, the first filter unit 3 and the second filter unit 4 that are arranged in parallel can achieve ultra-wide bandwidth, and can achieve effective out-of-band rejection; in the invention, the first filter unit 3 adopts the combination of the acoustic coupling filter 31 and the impedance element resonator to improve the rectangular coefficient at the left side of the passband frequency band; since the rectangular coefficient of the filter with CRF on the right side of the passband frequency band is difficult to achieve the left side level, the second filter unit 4 is set, and a combination of series and parallel impedance element resonators is adopted to improve the rectangular coefficient on the right side of the passband frequency band.
In summary, the invention is manufactured on the lithium tantalate substrate, thereby realizing the ultra wide bandwidth and high rectangular coefficients at the left end and the right end of the passband on the process of the common SAW, being applicable to the frequency band design with very high requirements on the bandwidth and the rectangular coefficients, such as B20+28, and further greatly reducing the production cost of the product.
[ example 2 ]
As shown in fig. 5, a SAW filter with an enlarged bandwidth is fabricated on a lithium tantalate substrate, and includes an input port 1, an output port 2, a first filter unit 3, a second filter unit 4, and an integrated inductor 5; the first filter unit 3 and the second filter unit 4 are arranged in parallel, are coupled between the input port 1 and the output port 2, and respectively improve rectangular coefficients on the left side and the right side of the passband frequency band.
The acoustic coupling filter 31 is disposed on the first series path, and the first impedance element resonator 32 is disposed on the first parallel path; the second impedance element resonator 41 is arranged on the second series path, and the third impedance element resonator 42 is arranged on the second parallel path; the first and second series paths are arranged in parallel and connected between the input port 1 and the output port 2. In this embodiment, the front ends of the grounding ends corresponding to the acoustic coupling filter 31, the first impedance element resonator 32 and the third impedance element resonator 42 are all provided with the integrated inductor 5; in combination with the illustration of fig. 6, where the line segment a is the index requirement of bandwidth and the line segment B is the index requirement of out-of-band suppression, it can be seen that both the bandwidth and the rectangular coefficient can reach the requirements, and the out-of-band suppression can be further improved substantially.
The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement the same according to the content of the present invention, and are not intended to limit the scope of the present invention. It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore desired that the present invention be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (4)
1. A bandwidth-extended SAW filter fabricated on a lithium tantalate substrate, comprising:
an input port and an output port;
the first filter unit and the second filter unit are arranged in parallel, are coupled between the input port and the output port, and respectively improve rectangular coefficients on the left side and the right side of the passband frequency band; wherein,,
the first filter unit comprises at least one acoustic coupling filter connected in series between the input port and the output port, and at least one first impedance element resonator connected in parallel to ground;
the second filter unit comprises at least one second impedance element resonator connected in series between the input port and the output port, and at least one third impedance element resonator connected in parallel with ground;
the acoustic coupling filter consists of interdigital transducers with a plurality of changing periods and reflecting grids arranged at two ends;
the first impedance element resonator, the second impedance element resonator and the third impedance element resonator have the same structure and are composed of interdigital transducers and reflecting grids arranged at two ends.
2. An extended bandwidth SAW filter as defined in claim 1, wherein: the front ends of the grounding ends corresponding to the acoustic coupling filter, the first impedance element resonator and the third impedance element resonator are respectively provided with an integrated inductor.
3. An extended bandwidth SAW filter as defined in claim 1, wherein: the acoustic coupling filter is configured on a first serial path, and the first impedance element resonator is configured on a first parallel path and is provided with a connection node with the first serial path;
the second impedance element resonator is configured on a second serial path, and the third impedance element resonator is configured on a second parallel path and is provided with a connection node with the second serial path;
the first series path and the second series path are arranged in parallel and connected between the input port and the output port.
4. A bandwidth extended SAW filter as claimed in claim 3, wherein: the two acoustic coupling filters are configured on the first serial path, the two first impedance element resonators are configured on the two first parallel paths, and the two corresponding connecting nodes are respectively positioned at one side of the two acoustic coupling filters, which is close to the input port and the output port;
the second impedance element resonators are arranged in three on the second series path, the third impedance element resonators are arranged in two in total and are positioned on the two second parallel paths, and two corresponding connecting nodes are respectively positioned between two adjacent second impedance element resonators.
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| CN202310239456.2A CN115955212B (en) | 2023-03-14 | 2023-03-14 | SAW filter with enlarged bandwidth |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3424971B2 (en) * | 1994-01-20 | 2003-07-07 | 松下電器産業株式会社 | Surface acoustic wave filter |
| JP3873802B2 (en) * | 2001-06-12 | 2007-01-31 | 株式会社村田製作所 | Surface acoustic wave filter |
| JP3928534B2 (en) * | 2002-02-28 | 2007-06-13 | 株式会社村田製作所 | Surface acoustic wave filter |
| JP4230347B2 (en) * | 2003-12-19 | 2009-02-25 | 富士通メディアデバイス株式会社 | Surface acoustic wave filter |
| CN100502239C (en) * | 2004-07-13 | 2009-06-17 | 中国科学院声学研究所 | An acoustic surface wave duplexer |
| CN101882920B (en) * | 2006-04-06 | 2012-07-04 | 株式会社村田制作所 | Duplexer |
| JP4177389B2 (en) * | 2006-05-18 | 2008-11-05 | 富士通メディアデバイス株式会社 | Filters and duplexers |
| CN103117727A (en) * | 2013-02-06 | 2013-05-22 | 中国电子科技集团公司第二十六研究所 | High-impedance sound surface wave resonator |
| JP6589824B2 (en) * | 2016-11-04 | 2019-10-16 | 株式会社村田製作所 | Multiplexer |
| DE102018102891A1 (en) * | 2017-02-13 | 2018-08-16 | Murata Manufacturing Co., Ltd. | Multiplexer, transmission device and receiving device |
| CN112134541B (en) * | 2020-09-24 | 2024-06-04 | 成都频岢微电子有限公司 | Novel broadband sound table filter |
| CN115622529A (en) * | 2021-11-17 | 2023-01-17 | 北京中科汉天下电子技术有限公司 | Filter and multiplexer including same |
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