CN106877838B - Surface acoustic wave filter - Google Patents
Surface acoustic wave filter Download PDFInfo
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- CN106877838B CN106877838B CN201710029506.9A CN201710029506A CN106877838B CN 106877838 B CN106877838 B CN 106877838B CN 201710029506 A CN201710029506 A CN 201710029506A CN 106877838 B CN106877838 B CN 106877838B
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- surface acoustic
- interdigital transducers
- acoustic wave
- wave filter
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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
- H03H9/6486—Coupled resonator filters having crossing or intersecting acoustic tracks, e.g. intersection in a perpendicular or diagonal orientation
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Abstract
The invention relates to a surface acoustic wave filter, which comprises two interdigital transducers and two reflecting gratings, wherein the two interdigital transducers are arranged on a piezoelectric substrate side by side, two pairs of bus bars of the two interdigital transducers extend out of two pairs of conductive terminals respectively, the two conductive terminals on the same side of the two interdigital transducers are differential input ends or differential output ends, and the two reflecting gratings are arranged on two sides of the two interdigital transducers respectively and are used for reflecting the surface acoustic waves generated by the two interdigital transducers; the two interdigital transducers are arranged side by side, conductive terminals extend out of respective bus bars, the two conductive terminals on the same side of the two interdigital transducers are used as differential input ends or differential output ends, and reflection grids are arranged on two sides of the two interdigital transducers respectively to form a differential structure; the common mode interference of the surface acoustic wave filter can be inhibited, the signal to noise ratio is enhanced, the occupied area is small, and the cost is low.
Description
Technical Field
The invention relates to the field of filtering, in particular to a surface acoustic wave filter.
Background
The differential structure has the advantages of common-mode interference suppression, high signal-to-noise ratio and the like, so that the differential structure is widely applied to differential filters, differential amplifiers and the like.
In the field of surface acoustic filters, differential structures are generally implemented by a plurality of resonators. As shown in fig. 1, the surface acoustic wave filter with the simplest differential structure includes two series resonators X and one parallel resonator Y, and the surface acoustic wave filter obtained by this method has a large occupied area and high cost.
Disclosure of Invention
Therefore, it is necessary to provide a surface acoustic wave filter, which can realize a differential structure, suppress common mode interference of the surface acoustic wave filter, enhance signal-to-noise ratio, occupy a small area, and have low cost.
In one aspect, the present invention provides a surface acoustic wave filter, including:
the two interdigital transducers are arranged on the piezoelectric substrate side by side, two pairs of conductive terminals extend out of two pairs of bus bars of the two interdigital transducers respectively, and the two conductive terminals on the same side of the two interdigital transducers are differential input ends or differential output ends;
and the two reflecting gratings are respectively arranged on two sides of the two interdigital transducers and used for reflecting the surface acoustic waves generated by the two interdigital transducers.
In the surface acoustic wave filter, the two interdigital transducers are arranged side by side, the conductive terminals extend out of the respective bus bars, the two conductive terminals on the same side of the two interdigital transducers are used as differential input ends or differential output ends, and the two sides of the two interdigital transducers are respectively provided with the reflection gates to form a differential structure; the common mode interference of the surface acoustic wave filter can be inhibited, the signal to noise ratio is enhanced, the occupied area is small, and the cost is low.
In one embodiment, the distance between centers of two adjacent electrode bars on two interdigital transducers of the differential input end is (1.5+ n) P (n is 1, 2, 3 …), and the distance between centers of two adjacent electrode bars on two interdigital transducers of the differential output end is (0.5+ n) P (n is 1, 2, 3 …);
wherein P is the period of the interdigital transducer.
In one embodiment, the center distance between two adjacent electrode strips on two interdigital transducers of the differential input end is 1.5P, and the center distance between two adjacent electrode strips on two interdigital transducers of the differential output end is 0.5P;
wherein P is the period of the interdigital transducer.
In one embodiment, the differential input and/or the differential output is connected to a balun.
In one embodiment, the differential input end and/or the differential output end are connected with a balanced bridge filter.
In one embodiment, one end of the reflection grating is electrically connected with the bus bar on the same side of the adjacent interdigital transducer.
In one embodiment, the thickness of the bus bar is greater than the thickness of the electrode bars of the interdigital transducer and the thickness of the electrode bars of the reflective grating.
In one embodiment, the half wavelength of the reflective grating is the same as the half wavelength of the interdigital transducer.
In another aspect, the present invention provides an application of a surface acoustic wave filter to processing a leaky acoustic wave, wherein the surface acoustic wave filter is the above surface acoustic wave filter.
Drawings
Fig. 1 is a schematic structural diagram of a conventional surface acoustic wave filter with a differential structure;
fig. 2 is a schematic structural view of a surface acoustic wave filter in the first embodiment;
fig. 3 is a schematic structural view of a surface acoustic wave filter in a second embodiment;
fig. 4 is a schematic structural view of a surface acoustic wave filter in a third embodiment;
fig. 5 is a schematic structural view of a surface acoustic wave filter in a fourth embodiment;
fig. 6 is a schematic structural view of a surface acoustic wave filter in a fifth embodiment;
fig. 7 is a schematic diagram of the structure of a surface acoustic wave filter in the sixth embodiment.
Detailed Description
Referring to fig. 2, fig. 2 is a schematic diagram of the structure of the surface acoustic wave filter in the first embodiment.
In the present embodiment, the surface acoustic wave filter includes two interdigital transducers (IDTs) and two reflection gratings (REF) 20.
Two interdigital transducers set up side by side on the piezoelectric substrate, two pairs of conducting terminals are extended respectively to two pairs of busbar of two interdigital transducers, two conducting terminals of two interdigital transducers homonymies are differential input or difference output.
The interdigital transducer comprises two bus bars and a plurality of electrode bars, wherein the electrode bars are arranged in a crossed mode and are electrically connected with the bus bars arranged on two sides. The two interdigital transducers include an interdigital transducer 10 and an interdigital transducer 11, the interdigital transducer 10 includes a bus bar 101, a bus bar 102, and a plurality of electrode bars 103, the interdigital transducer 11 includes a bus bar 111, a bus bar 112, and a plurality of electrode bars 113, and the two interdigital transducers are disposed on a piezoelectric substrate and are located on a propagation channel of an acoustic wave.
The conductive terminal 1 is led out from the bus bar 101 of the interdigital transducer 10, the conductive terminal 3 is led out from the bus bar 102, the conductive terminal 2 is led out from the bus bar 111 of the interdigital transducer 11, the conductive terminal 4 is led out from the bus bar 112, the conductive terminal 1 and the conductive terminal 2 are used as differential input ends, and the conductive terminal 3 and the conductive terminal 4 are used as differential output ends. The power is input from the differential input end, and the signal is output from the differential output end, so that the surface acoustic wave filter with the differential structure is formed, and the functions of inhibiting common mode interference and enhancing the signal-to-noise ratio can be achieved.
Two reflection bars 20 are respectively arranged on two sides of the two interdigital transducers and used for reflecting surface acoustic waves generated by the two interdigital transducers.
The power supply is loaded on the two interdigital transducers, so that the piezoelectric substrate excites the bidirectional surface acoustic wave, and the reflection grating 20 reflects the surface acoustic wave after receiving the surface acoustic wave, thereby realizing the transmission of the surface acoustic wave. The power supply is an alternating voltage signal, and the interdigital transducer is very sensitive to frequency, converts the alternating voltage signal into mechanical vibration of the piezoelectric substrate, further forms surface acoustic waves, and reflects the surface acoustic waves back through the reflecting grating 20.
In the prior art, the surface acoustic wave filter of the differential structure shown in fig. 1 needs two series resonators X and one parallel resonator Y to be implemented. The structure of one series resonator X is REF + IDT + REF, and only two series resonators just need occupy two spaces and areas of this structure, and the REF + IDT + IDT + REF difference structure area occupied of comparing this embodiment is big, and the space is big, and the cost is corresponding to increase.
In addition, the surface acoustic wave filter can also have other using methods, such as only one interdigital transducer 10 or 11 is connected into a circuit and is used as a resonator, and the surface acoustic wave filter can be flexibly selected according to the circuit requirements.
In one embodiment, the distance between the centers of two adjacent electrode bars on two interdigital transducers of the differential input end is (1.5+ n) P (n is 1, 2, 3 …), and the distance between the centers of two adjacent electrode bars on two interdigital transducers of the differential output end is (0.5+ n) P (n is 1, 2, 3 …), where P is the period of the interdigital transducers, and specifically the distance between the centers of two adjacent electrode bars connected to the same bus bar.
When the distance between the two interdigital transducers meets the condition, the structures of the two interdigital transducers are synchronous, the coupling degree of the two interdigital transducers is high, the resonance intensity is high, and the filtering effect is good.
In a further embodiment, n is 1, the distance between the centers of two adjacent electrode strips on two interdigital transducers of the differential input end is 1.5P, and the distance between the centers of two adjacent electrode strips on two interdigital transducers of the differential output end is 0.5P. The occupied area of the surface acoustic wave filter is minimized.
The center distance between two adjacent electrode strips on two interdigital transducers at the differential input end is 1.5P, which is greater than the center distance between two adjacent electrode strips on two interdigital transducers at the differential output end by 0.5P, the input interdigital transducer is very sensitive to input power, and the larger the distance between the adjacent electrode strips of the transducer is, the larger the input power can be born.
In one embodiment, referring to fig. 3 and 4, the differential inputs and/or the differential outputs are connected to a BALUN (BALUN) 30. The BALUN can realize the conversion from a differential port to a single port and can also realize impedance conversion, so that the surface acoustic wave filter with the differential structure is more flexible to use and has better filtering effect.
In one embodiment, referring to fig. 5 and 6, the differential input and/or the differential output is connected to a balanced Bridge Filter 40 (BBF) to Balance the input and output signals.
In one embodiment, referring to fig. 7, one end of the reflective grating 20 is electrically connected to the bus bar on the same side as the adjacent interdigital transducers.
Specifically, one end of the reflection grating adjacent to the interdigital transducer 10 is electrically connected to the bus bar 101 on the same side as the interdigital transducer 10, and one end of the reflection grating adjacent to the interdigital transducer 11 is electrically connected to the bus bar 111 on the same side as the interdigital transducer 11. By increasing the bond pad or bump connections of the pressure wire, the insertion loss can be minimized, enhancing the useful power of the saw filter.
In one embodiment, the thickness of the bus bar is greater than the thickness of the electrode bars of the interdigital transducer and the thickness of the electrode bars of the reflection grating 20, so that the resistance loss of the surface acoustic wave filter can be reduced. The electrode strips 201 of the reflective grating 20 are shown in fig. 2.
In one embodiment, the half wavelength of the reflective grating 20 is the same as the half wavelength of the interdigital transducer. The half wavelength of the reflection grating and the half wavelength of the interdigital transducer refer to the center distance of two adjacent electrode strips.
In one embodiment, the surface acoustic wave filter can realize filtering processing of various sound waves, including surface acoustic waves, leaky sound waves or sound waves in other forms, removes noise, obtains sound waves in a specific frequency band, and has a good filtering effect.
According to the surface wave filter, the two interdigital transducers are arranged on the piezoelectric substrate side by side to realize the surface wave filter with a differential structure, so that common-mode interference is suppressed, the signal-to-noise ratio is enhanced, the occupied area is small, and the cost is low. By reasonably setting the distance between the two interdigital transducers, the coupling degree of the interdigital transducers can be enhanced, so that the interdigital transducers have high resonance intensity and good filtering effect. The conversion from the differential port to the single port can be realized by accessing the BALUN at the differential input end and the differential output end, and simultaneously, the impedance conversion can be realized, or the BBF is accessed. By electrically connecting one end of the reflection grating 20 to the bus bar on the same side as the adjacent interdigital transducer, and increasing the connection of the bonding pad or the metal block, the insertion loss can be reduced, and at the same time, by setting the thickness of the bus bar to be greater than the thickness of the interdigital transducer and the electrode bar of the reflection grating 20, the resistance loss thereof can be reduced. The surface acoustic wave filter can realize the filtering processing of various sound waves, remove noise, obtain the sound waves of a specific frequency band and has good filtering effect.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (7)
1. A surface acoustic wave filter, comprising:
the two interdigital transducers are arranged on the piezoelectric substrate side by side, two pairs of conductive terminals extend out of two pairs of bus bars of the two interdigital transducers respectively, and the two conductive terminals on the same side of the two interdigital transducers are differential input ends or differential output ends;
the two reflection gratings are respectively arranged on two sides of the two interdigital transducers and are used for reflecting surface acoustic waves generated by the two interdigital transducers;
the center distance between two adjacent electrode bars on two interdigital transducers of the differential input end is (1.5+ n) P (n is 1, 2, 3 …), and the center distance between two adjacent electrode bars on two interdigital transducers of the differential output end is (0.5+ n) P (n is 1, 2, 3 …); or
The center distance between two adjacent electrode strips on two interdigital transducers at the differential input end is 1.5P, and the center distance between two adjacent electrode strips on two interdigital transducers at the differential output end is 0.5P;
wherein P is the period of the interdigital transducer.
2. A surface acoustic wave filter as set forth in claim 1, wherein said differential input terminal and/or said differential output terminal are connected to a balun.
3. A surface acoustic wave filter as set forth in claim 1, wherein said differential input terminal and/or said differential output terminal is connected to a balanced bridge filter.
4. A surface acoustic wave filter as set forth in claim 1, wherein one end of said reflection grating is electrically connected to a bus bar on the same side as said adjacent interdigital transducers.
5. The surface acoustic wave filter as set forth in claim 1, wherein the thickness of said bus bar is larger than the thickness of the electrode bars of said interdigital transducer and the thickness of the electrode bars of said reflection grating.
6. A surface acoustic wave filter as set forth in claim 1, wherein a half wavelength of said reflection grating is the same as a half wavelength of said interdigital transducer.
7. Use of a surface acoustic wave filter for processing a leaky acoustic wave, wherein the surface acoustic wave filter is the surface acoustic wave filter according to any one of claims 1 to 6.
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| CN201710029506.9A CN106877838B (en) | 2017-01-16 | 2017-01-16 | Surface acoustic wave filter |
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| CN201710029506.9A CN106877838B (en) | 2017-01-16 | 2017-01-16 | Surface acoustic wave filter |
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| CN106877838A CN106877838A (en) | 2017-06-20 |
| CN106877838B true CN106877838B (en) | 2020-06-09 |
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| CN106911317B (en) * | 2017-02-07 | 2020-01-21 | 深圳华远微电科技有限公司 | Surface acoustic wave resonator |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001077654A (en) * | 1999-08-31 | 2001-03-23 | Mitsubishi Materials Corp | Surface acoustic wave element |
| JP2006261964A (en) * | 2005-03-16 | 2006-09-28 | Epson Toyocom Corp | Surface acoustic wave filter |
| CN101079609A (en) * | 2006-05-22 | 2007-11-28 | 富士通媒体部品株式会社 | Balanced filter and duplexer |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2762458B1 (en) * | 1997-04-18 | 1999-07-09 | Thomson Csf | SURFACE ACOUSTIC WAVE DEVICE HAVING PROXIMITY COUPLING WITH DIFFERENTIAL INPUTS / OUTPUTS |
| DE10007178A1 (en) * | 2000-02-17 | 2001-08-23 | Epcos Ag | Surface wave filter on piezoelectric substrate is configured as balanced/balanced e.g. for GSM mobile telephones, has symmetrical inputs/outputs, is electrically symmetrical, has 4- or 2-pole reactance series elements |
| JP2002176333A (en) * | 2000-12-07 | 2002-06-21 | Fujitsu Media Device Kk | Surface acoustic wave filter |
| JP4055651B2 (en) * | 2002-06-13 | 2008-03-05 | 株式会社村田製作所 | Surface wave device |
| JP4290199B2 (en) * | 2007-01-11 | 2009-07-01 | 富士通メディアデバイス株式会社 | filter |
| CN203027218U (en) * | 2013-02-06 | 2013-06-26 | 中国电子科技集团公司第二十六研究所 | Surface acoustic wave filter |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001077654A (en) * | 1999-08-31 | 2001-03-23 | Mitsubishi Materials Corp | Surface acoustic wave element |
| JP2006261964A (en) * | 2005-03-16 | 2006-09-28 | Epson Toyocom Corp | Surface acoustic wave filter |
| CN101079609A (en) * | 2006-05-22 | 2007-11-28 | 富士通媒体部品株式会社 | Balanced filter and duplexer |
Non-Patent Citations (2)
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| Unidirectional SAW transducer for GHz frequencies;Saku Lehtonen;《Proceedings of the IEEE Ultrasonics Symposium》;20031231;817-820 * |
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Address after: No. 101, 201, 301, 401, building 2, phase I, intelligent manufacturing industrial park, high tech Zone, Wuxing District, Huzhou City, Zhejiang Province, 313000 Patentee after: Zhejiang Huayuan Micro Electronics Technology Co.,Ltd. Address before: 518000 Building D and E, No.5 Zhuangcun Road, xiner community, Shajing street, Bao'an District, Shenzhen City, Guangdong Province Patentee before: SHENZHEN HUAYUAN MICRO ELECTRONIC TECHNOLOGY Co.,Ltd. |