CN212695970U - Surface acoustic wave filter - Google Patents
Surface acoustic wave filter Download PDFInfo
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- CN212695970U CN212695970U CN202021543985.XU CN202021543985U CN212695970U CN 212695970 U CN212695970 U CN 212695970U CN 202021543985 U CN202021543985 U CN 202021543985U CN 212695970 U CN212695970 U CN 212695970U
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Abstract
The application discloses a surface acoustic wave filter. The method comprises the following steps: the piezoelectric transducer comprises a piezoelectric substrate, and an input transducer and an output transducer which are arranged on the piezoelectric substrate; the input transducer and the output transducer adopt collinear structures, and the fingertips of the input transducer and the output transducer are respectively subjected to weighting processing. This application designs input transducer and output transducer specifically on the piezoelectric substrate, with input transducer and output transducer on traditional collinear structure's basis, carries out weighting to input transducer and output transducer respectively, and input transducer adopts the finger length to overlap the weighting processing mode, and output transducer adopts the finger-out weighting processing mode, and the length that the weighted transducer of finger-out overlaps the weighted transducer is shorter than the finger length to realize improving the rectangle degree of this filter and the miniaturized purpose of device.
Description
Technical Field
The present disclosure relates generally to the field of filtering devices, and more particularly to a surface acoustic wave filter.
Background
The surface acoustic wave filter mainly utilizes the piezoelectric property of piezoelectric materials, utilizes an input transducer and an output transducer to convert input signals of electric waves into mechanical energy, and converts the mechanical energy into electric signals after processing, so as to achieve the aims of filtering unnecessary signals and noises and improving the receiving quality.
At present, in the surface acoustic wave filter in the prior art, the steeper the edge of the surface acoustic wave filter is, the higher the squareness is, the desired squareness is 1, that is, the filter edge is perpendicular to the horizontal plane, but it is technically impossible to realize; in addition, when the squareness of the filter is desired to be high, the squareness cannot be unilaterally sought in consideration of the requirements of the application circuit for other indexes of the filter, such as insertion loss and chip size.
Therefore, we propose a surface acoustic wave filter to solve the above-mentioned problem of low filter squareness.
Disclosure of Invention
In view of the above-mentioned drawbacks or shortcomings in the prior art, it is desirable to provide a surface acoustic wave filter having a high degree of squareness, being miniaturized, and being easy to implement.
In a first aspect, the present application provides a surface acoustic wave filter comprising: the piezoelectric transducer comprises a piezoelectric substrate, and an input transducer and an output transducer which are arranged on the piezoelectric substrate;
the input transducer and the output transducer adopt collinear structures, and the fingertips of the input transducer and the output transducer are respectively subjected to weighting processing.
According to the technical scheme provided by the embodiment of the application, the input transducer and the output transducer are interdigital transducers.
According to the technical scheme provided by the embodiment of the application, the finger strips of the input transducers adopt a finger length overlapping weighting processing mode.
According to the technical scheme provided by the embodiment of the application, the finger length overlapping weighting processing mode is that finger strips of the input transducers are overlapped to form an envelope.
According to the technical scheme provided by the embodiment of the application, the finger strips of the output transducers adopt a finger-drawing weighting processing mode.
According to the technical scheme provided by the embodiment of the application, the finger extraction weighting processing mode is to extract a certain number of fingers on one side of the output transducer to form homopolar fingers.
According to the technical scheme provided by the embodiment of the application, the piezoelectric substrate is further provided with a shielding strip, and the shielding strip is positioned between the input transducer and the output transducer.
In summary, the present technical solution specifically discloses a specific structure of a surface acoustic wave filter. The method specifically comprises the steps that an input transducer and an output transducer are designed on a piezoelectric substrate, the input transducer and the output transducer are weighted respectively on the basis of a traditional collinear structure, the input transducer adopts a finger length overlapping weighting processing mode, the output transducer adopts a finger drawing weighting processing mode, and the finger drawing weighting transducer is shorter than the finger length overlapping weighting transducer, so that the purposes of improving the rectangularity of the filter and miniaturizing the device are achieved;
in the technical scheme, a shielding strip is further arranged on the piezoelectric substrate and is positioned between the input transducer and the output transducer, so that grounding is increased, through signals are shielded and reduced, and out-of-band rejection of the filter is guaranteed.
Drawings
Other features, objects and advantages of the present application will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, made with reference to the accompanying drawings in which:
fig. 1 is a schematic diagram of a structure of a surface acoustic wave filter.
Fig. 2 is a schematic diagram of a structure in which input transducers are repeatedly weighted.
FIG. 3 is a schematic diagram of the structure of output transducer finger weighting.
Fig. 4 and 5 are graphs comparing frequency response of the surface acoustic wave filter.
Reference numbers in the figures: 1. an input transducer; 2. an output transducer; 3. a shielding strip; 4. enveloping; 5. like polarity finger.
Detailed Description
The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
Example one
Please refer to fig. 1, which illustrates a schematic structural diagram of a first embodiment of a saw filter provided by the present application, including: the piezoelectric transducer comprises a piezoelectric substrate, and an input transducer 1 and an output transducer 2 which are arranged on the piezoelectric substrate;
the input transducer 1 and the output transducer 2 adopt a collinear structure, and the finger strips of the input transducer 1 and the finger strips of the output transducer 2 are respectively subjected to weighting processing.
In this embodiment, an input transducer 1 and an output transducer 2 are designed on a piezoelectric substrate, where the input transducer 1 and the output transducer 2 are both interdigital transducers, and the input transducer 1 and the output transducer 2 are respectively weighted on the basis of a traditional collinear structure, so as to achieve the purposes of improving the rectangularity of the filter and miniaturizing the device.
In any preferred embodiment, the finger of the input transducer 1 adopts a finger length overlapping weighting processing mode.
In the present embodiment, the finger of the input transducer 1 adopts a finger length overlapping weighting processing mode, specifically, each finger of the input transducer 1 is subjected to overlapping processing, so that the finger of the input transducer 1 forms an envelope 4.
In any preferred embodiment, the output transducer 2 is finger-weighted.
In the present embodiment, the fingering of the output transducer 2 adopts a finger-extracting weighting processing manner, specifically, for example, three or ten finger-extracting paths are extracted from the fingering on one side of the output transducer 2, so that the fingering on the other side of the output transducer 2 are all homopolar fingering 5; here, the number of the decimation fingers can be set according to the specific specification requirement of the filter.
In any preferred embodiment, a shielding strip 3 is further disposed on the piezoelectric substrate and is located between the input transducer 1 and the output transducer 2.
In this embodiment, the shielding strip 3 is disposed on the piezoelectric substrate and located between the input transducer 1 and the output transducer 2, and is used for increasing grounding, shielding and reducing through signals to ensure out-of-band rejection of the filter.
As shown in fig. 4, curve a is the case where the input transducers adopt the weighted overlap of the fingers, the output transducers adopt the unweighted structure, as shown in fig. 5, curve B is the case where the input transducers adopt the weighted overlap of the fingers, and the output transducers adopt the weighted structure of the fingers;
the squareness is the ratio of 40dB bandwidth to 1dB bandwidth or 3dB bandwidth, the steeper the edge of the filter is, the higher the squareness is, and the squareness in an ideal state is 1;
comparing curve a with curve B, the edge of the filter using the finger weighting is steeper, and therefore, the squareness is higher.
The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of the invention as referred to in the present application is not limited to the embodiments with a specific combination of the above-mentioned features, but also covers other embodiments with any combination of the above-mentioned features or their equivalents without departing from the inventive concept. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.
Claims (7)
1. A surface acoustic wave filter, comprising: the piezoelectric transducer comprises a piezoelectric substrate, and an input transducer (1) and an output transducer (2) which are arranged on the piezoelectric substrate;
the input transducer (1) and the output transducer (2) adopt collinear structures, and finger strips of the input transducer (1) and the output transducer (2) are respectively subjected to weighting processing.
2. A surface acoustic wave filter as claimed in claim 1, characterized in that the input transducer (1) and the output transducer (2) are interdigital transducers.
3. A surface acoustic wave filter as claimed in claim 1, characterized in that the fingers of the input transducer (1) are weighted by means of finger length overlap.
4. A surface acoustic wave filter as claimed in claim 3, characterized in that the finger length overlap weighting is performed in such a way that the overlapping arrangement of the fingers of the input transducer (1) forms an envelope (4).
5. A surface acoustic wave filter as claimed in claim 1, characterized in that the fingers of the output transducer (2) are finger weighted.
6. A surface acoustic wave filter as claimed in claim 5, characterized in that the finger weighting is performed by extracting a number of fingers on one side of the output transducer (2) to form like-polarity fingers (5).
7. A surface acoustic wave filter as claimed in claim 1, characterized in that a shielding strip (3) is arranged on the piezoelectric substrate and is located between the input transducer (1) and the output transducer (2).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202021543985.XU CN212695970U (en) | 2020-07-30 | 2020-07-30 | Surface acoustic wave filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202021543985.XU CN212695970U (en) | 2020-07-30 | 2020-07-30 | Surface acoustic wave filter |
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| Publication Number | Publication Date |
|---|---|
| CN212695970U true CN212695970U (en) | 2021-03-12 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202021543985.XU Active CN212695970U (en) | 2020-07-30 | 2020-07-30 | Surface acoustic wave filter |
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| CN (1) | CN212695970U (en) |
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2020
- 2020-07-30 CN CN202021543985.XU patent/CN212695970U/en active Active
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