CN104796108A - Ultra-narrow-band surface acoustic wave filter - Google Patents
Ultra-narrow-band surface acoustic wave filter Download PDFInfo
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- CN104796108A CN104796108A CN201510206322.6A CN201510206322A CN104796108A CN 104796108 A CN104796108 A CN 104796108A CN 201510206322 A CN201510206322 A CN 201510206322A CN 104796108 A CN104796108 A CN 104796108A
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- interdigital transducer
- wave filter
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Abstract
The invention relates to a surface wave filter, in particular to an ultra-narrow-band surface acoustic wave filter comprising a piezoelectric substrate and an interdigital transducer. The interdigital transducer is disposed on the piezoelectric substrate and is in a split-digital structure or tri-digital structure. The interdigital transducer comprises a first interdigital transducer and a second interdigital transducer arranged in adjacency, forming a first input port, a second input port, a first output port and a second output port. The ultra-narrow-band surface acoustic wave filter is in the transverse filter design, optimal withdraw-weighted design and diffraction analysis and correction are adopted, and waveguide effect is suppressed effectively by taking measures. The ultra-narrow-band surface acoustic wave filter has the advantages of ultra-narrow bandwidth, high rectangularity and high out-of-band rejection.
Description
Technical field
The present invention relates to surface wave filter, particularly a kind of pole narrow-band sound surface wave filter.
Background technology
Surface wave filter with the piezoelectric crystal such as quartz, lithium niobate or pricker lead titanates for substrate, layer of metal film is evaporated thereon after surface finish, make by photoetching process the metal electrode that two groups have the interdigital of power conversion function, be called input interdigital transducer and output interdigital transducer.When inputting interdigital transducer and connecting ac voltage signal, the surface of piezoelectric crystal substrate just produces vibration, and inspire the sound wave with external signal same frequency, this sound wave is mainly propagated along the direction of rising with interdigital electrode on the surface of substrate, therefore be called sound surface filtering, the sound wave dividend sound-absorbing material in one of them direction absorbs, and the sound wave in an other direction is then sent to output interdigital transducer, is converted into the signal of telecommunication and exports.
Surface Acoustic Wave Filter has the features such as operating frequency is high, pass band, selecting frequency characteristic are good, volume is little and lightweight, and the production technology identical with integrated circuit can be adopted, manufacture simple, cost is low, the consistency of frequency characteristic is good, therefore be widely used in various electronic equipment, as being widely used in, in satellite, radar, communication, target simulation and electronic countermeasures isoelectronic series system, becoming the first-selected device of radio frequency, the selection of the Mid Frequency signal of telecommunication.
Surface acoustic wave SAW (Surface Acoustic Wave) produces on piezoelectric substrate materials surface and propagates and the degree of depth that amplitude gos deep into substrate material increases and the elastic wave that reduces rapidly.The basic structure of SAW filter makes two acoustic-electrical transducers---interdigital transducer (IDT) on the substrate material burnishing surface with piezoelectric property.It adopts the planar technique of semiconductor integrated circuit, at the certain thickness aluminium film of piezoelectric substrate surface evaporation, the mask pattern of two IDT designed, utilizes photoetching method to be deposited on substrate surface, respectively as input transducer and output transducer.Its operation principle is that the signal of telecommunication is become acoustical signal by input transducer, and propagate along plane of crystal, the acoustical signal received is become the signal of telecommunication and exports by output transducer again.
Now, for meeting each side's demand, the electromagnetic environment that reply is day by day complicated, Surface Acoustic Wave Filter develops towards small-sized chip type, and in order to adapt to complete electronic set high frequency, broadband requirement, Surface Acoustic Wave Filter also must improve operating frequency and expand bandwidth, farthest reduces insertion loss.Existing Surface Acoustic Wave Filter is difficult to meet extremely narrow signal behavior.
Summary of the invention
The present invention mainly solves the deficiency existing for prior art, there is provided a kind of pole narrow-band sound surface wave filter, described pole narrow-band sound surface wave filter adopts transversal filter method for designing, by optimizing withdraw-weighted design, diffraction analysis and correction, take measures effectively to suppress waveguiding effect simultaneously.Surface Acoustic Wave Filter of the present invention has the advantage of very narrow bandwidth, high rectangle degree, high out-of-side rejection.
For solving the problem, the invention provides a kind of pole narrow-band sound surface wave filter, comprise piezoelectric substrate and interdigital transducer, described interdigital transducer is arranged on piezoelectric substrate,
Described interdigital transducer is that division refers to that structure or three refers to structure, described interdigital transducer comprises the first interdigital transducer, second interdigital transducer, described first interdigital transducer layout adjacent with the second interdigital transducer, form the first input port, second input port, first delivery outlet and the second delivery outlet be totally four ports, wherein, first input port and the first delivery outlet divide and are listed in the relative both sides of described first interdigital transducer, described second input port and the second delivery outlet divide and are listed in the relative both sides of described second interdigital transducer, and, described first input port and described second input port homonymy, described second delivery outlet and described first delivery outlet homonymy.
When adding an alternating signal on described first interdigital transducer, by inverse piezoelectric effect, piezoelectric substrate motivates the surface acoustic wave equal with the described first interdigital transducers electrodes cycle, and propagate to both sides, when through described second interdigital transducer, by direct piezoelectric effect, described second interdigital transducer converts the acoustical signal of cycle synchronisation interdigital with it to signal of telecommunication, and the described signal of telecommunication takes out by load.
Particularly, described first interdigital transducer and the second interdigital transducer are made up of multiple independently delay tap, described delay tap is corresponding with the position of interdigital transducer finger on piezoelectric substrate, and signal is by the delay of some and these inhibit signals are carried out superposition realize filtering.
Further, each described tap is weighted by coefficient An, and coefficient An correspond to the weight coefficient that interdigital transducer provides, and described interdigital transducer frequency response H (f) is provided by discrete Fourier transform, when frequency is f, is expressed as
In formula, Tn is the accumulative time delay of the n-th tap.
Particularly, described first interdigital transducer and/or the second interdigital transducer are that division refers to structure; Described first interdigital transducer and/or the second interdigital transducer are three finger structures.
Further, adopt division to refer to that the finger width of the interdigital transducer of structure is 1.44 microns, the finger width adopting the interdigital transducer of three finger structures is 1.526 microns.
Further, the material model of described piezoelectric substrate is 40 ° of Y-X STQz.
Due to technique scheme, beneficial effect of the present invention is:
Pole of the present invention narrow-band sound surface wave filter adopts transversal filter method for designing, and by optimizing withdraw-weighted design, diffraction analysis and correction, take measures effectively to suppress waveguiding effect simultaneously.Surface Acoustic Wave Filter of the present invention has the advantage of very narrow bandwidth, high rectangle degree, high out-of-side rejection.Insertion loss about-21dB, the 1dB relative bandwidth about 1 ‰ of described pole narrow-band sound surface wave filter, Out-of-band rejection is greater than 5OdB, passband ripple 0.3dB, whole synthesis excellent performance, can meet completely in very narrow bandwidth signal behavior function.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.
Fig. 1 is the operation principle schematic diagram of SAW (Surface Acoustic Wave) filter;
Fig. 2 is the schematic diagram of signal by filter;
Fig. 3 is the corresponding figure of diffraction analysis frequency;
Fig. 4 is the waveguiding effect in interdigital transducer;
Fig. 5 is the long array pole narrowband device frequency response chart under waveguiding effect impact.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, the every other embodiment that those of ordinary skill in the art obtain under the prerequisite of not making creative work, all belongs to the scope of protection of the invention.
As shown in Figure 1, Surface Acoustic Wave Filter of the present invention, comprises piezoelectric substrate 1 and interdigital transducer, and described interdigital transducer is arranged on piezoelectric substrate 1,
Described interdigital transducer is that division refers to that structure or three refers to structure, described interdigital transducer comprises the first interdigital transducer, second interdigital transducer, described first interdigital transducer layout adjacent with the second interdigital transducer, form the first input port 3, second input port 4, first delivery outlet 5 and the second delivery outlet 6 totally four ports, wherein, first input port 3 and the first delivery outlet 5 points are listed in the relative both sides of described first interdigital transducer, described second input port 4 and the second delivery outlet 6 points are listed in the relative both sides of described second interdigital transducer, and, described first input port 3 and described second input port 4 homonymy, described second delivery outlet 5 and described first delivery outlet 6 homonymy.
When adding an alternating signal on described first interdigital transducer, by inverse piezoelectric effect, piezoelectric substrate motivates the surface acoustic wave equal with the described first interdigital transducers electrodes cycle, and propagate to both sides, when through described second interdigital transducer, by direct piezoelectric effect, described second interdigital transducer converts the acoustical signal of cycle synchronisation interdigital with it to signal of telecommunication, and the described signal of telecommunication takes out by load.Often pair of finger of interdigital transducer is all one and postpones tap, by the physical size of appropriate change interdigital transducer interdigital electrode, or suitably controls on propagation path, can obtain required frequency, reach the object to Electric signal processing.
Fig. 2 is the interdigital transducer schematic diagram of signal by transversal filter.Interdigital transducer is made up of multiple independently delay (Dn) tap (metal finger).Each tap is weighted by coefficient An.Signal is by the delay of some and these inhibit signals are carried out superposition realize filtering.These postpone the position of interdigital transducer finger on the corresponding substrate of tap, and An correspond to the weight coefficient provided by interdigital transducer finger.Interdigital transducer frequency response H (f) of filter is provided by discrete Fourier transform, when frequency is f, is expressed as
In formula, Tn is the accumulative time delay of the n-th tap.
Particularly, described first interdigital transducer and/or the second interdigital transducer are that division refers to structure; Described first interdigital transducer and/or the second interdigital transducer are three finger structures.
Further, adopt division to refer to that the finger width of the interdigital transducer of structure is 1.44 microns, the finger width adopting the interdigital transducer of three finger structures is 1.526 microns.
Further, based on pole narrow-band technologies index request, need to select the substrate material that coupling coefficient is low, humidity stability is good, therefore select 40 ° of Y-X STQz, its principal character is as shown in table 1.
| Cut type | The velocity of sound/(m/s) | Coupling coefficient/% | Temperature coefficient/u DEG C -1 |
| 40°Y-X | 3144 | 0.14 | 0 |
According to the requirement of Out-of-band rejection and rectangular degree, withdraw-weighted mode all used by 2 interdigital transducers, to avoid a large amount of little tap, can realize the index of high out-of-side rejection, high rectangle degree.
The design parameter of adjustment filter, carries out circuit compensation factors, then carries out diffraction analysis to filter, compensates and revises.Fig. 3 is diffraction analysis frequency response chart.
The condition that waveguiding effect produces: transducer aperture square be less than transducer length; The inhomogeneities of surface acoustic wave longitudinal velocity.
Waveguiding effect in Fig. 4 interdigital transducer.As can be seen from Figure, will waveguiding effect be produced because the interdigital transducer array of this design is very long, high-end, outside proximal band, affect performance of filter.The present invention utilizes vacation to refer to and the optimal design in aperture, and adopts special process technology, effectively suppresses waveguiding effect, as shown in Figure 5.
Due to technique scheme, beneficial effect of the present invention is:
Pole of the present invention narrow-band sound surface wave filter adopts transversal filter method for designing, and by optimizing withdraw-weighted design, diffraction analysis and correction, take measures effectively to suppress waveguiding effect simultaneously.Surface Acoustic Wave Filter of the present invention has the advantage of very narrow bandwidth, high rectangle degree, high out-of-side rejection.Insertion loss about-21dB, the 1dB relative bandwidth about 1 ‰ of described pole narrow-band sound surface wave filter, Out-of-band rejection is greater than 5OdB, passband ripple 0.3dB, whole synthesis excellent performance, can meet completely in very narrow bandwidth signal behavior function.
Above disclosedly be only a kind of preferred embodiment of the present invention, certainly can not limit the interest field of the present invention with this, therefore according to the equivalent variations that the claims in the present invention are done, still belong to the scope that the present invention is contained.
Claims (7)
1. a pole narrow-band sound surface wave filter, comprises piezoelectric substrate and interdigital transducer, and described interdigital transducer is arranged on piezoelectric substrate, it is characterized in that,
Described interdigital transducer is that division refers to that structure or three refers to structure, described interdigital transducer comprises the first interdigital transducer, second interdigital transducer, described first interdigital transducer layout adjacent with the second interdigital transducer, form the first input port, second input port, first delivery outlet and the second delivery outlet be totally four ports, wherein, first input port and the first delivery outlet divide and are listed in the relative both sides of described first interdigital transducer, described second input port and the second delivery outlet divide and are listed in the relative both sides of described second interdigital transducer, and, described first input port and described second input port homonymy, described second delivery outlet and described first delivery outlet homonymy.
2. pole according to claim 1 narrow-band sound surface wave filter, it is characterized in that, when adding an alternating signal on described first interdigital transducer, by inverse piezoelectric effect, piezoelectric substrate motivates the surface acoustic wave equal with the described first interdigital transducers electrodes cycle, and propagate to both sides, when through described second interdigital transducer, by direct piezoelectric effect, described second interdigital transducer converts the acoustical signal of cycle synchronisation interdigital with it to signal of telecommunication, and the described signal of telecommunication takes out by load.
3. require the pole narrow-band sound surface wave filter described in 1 or 2 according to profit, it is characterized in that, described first interdigital transducer and the second interdigital transducer are made up of multiple independently delay tap, described delay tap is corresponding with the position of interdigital transducer finger on piezoelectric substrate, and signal is by the delay of some and these inhibit signals are carried out superposition realize filtering.
4. require the pole narrow-band sound surface wave filter described in 3 according to profit, it is characterized in that, each described tap is weighted by coefficient An, coefficient An correspond to the weight coefficient that interdigital transducer provides, described interdigital transducer frequency response H (f) is provided by discrete Fourier transform, when frequency is f, be expressed as
In formula, Tn is the accumulative time delay of the n-th tap.
5. require the pole narrow-band sound surface wave filter described in 1,2 or 4 according to profit, it is characterized in that, described first interdigital transducer and/or the second interdigital transducer are that division refers to structure; Described first interdigital transducer and/or the second interdigital transducer are three finger structures.
6. require the pole narrow-band sound surface wave filter described in 5 according to profit, it is characterized in that, adopt division to refer to that the finger width of the interdigital transducer of structure is 1.44 microns, the finger width adopting the interdigital transducer of three finger structures is 1.526 microns.
7. require the pole narrow-band sound surface wave filter described in 6 according to profit, it is characterized in that, the material model of described piezoelectric substrate is 40 ° of Y-X STQz.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107785643A (en) * | 2017-09-20 | 2018-03-09 | 戴承萍 | Resonator and the wave filter with resonator |
| CN109462384A (en) * | 2018-12-28 | 2019-03-12 | 河北时硕微芯科技有限公司 | A kind of SAW filter and production method |
| CN112532196A (en) * | 2020-11-26 | 2021-03-19 | 北京航天微电科技有限公司 | Surface acoustic wave filter, manufacturing method thereof and electronic equipment |
| CN116405006A (en) * | 2023-03-15 | 2023-07-07 | 北京航天微电科技有限公司 | Interdigital transducer parameter determination method, interdigital transducer parameter determination device, interdigital transducer parameter determination equipment and surface acoustic wave filter |
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| CN201008151Y (en) * | 2007-01-11 | 2008-01-16 | 中国科学院声学研究所 | Acoustic surface wave IF filter for SCDMA base station |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107785643A (en) * | 2017-09-20 | 2018-03-09 | 戴承萍 | Resonator and the wave filter with resonator |
| CN109462384A (en) * | 2018-12-28 | 2019-03-12 | 河北时硕微芯科技有限公司 | A kind of SAW filter and production method |
| CN112532196A (en) * | 2020-11-26 | 2021-03-19 | 北京航天微电科技有限公司 | Surface acoustic wave filter, manufacturing method thereof and electronic equipment |
| CN116405006A (en) * | 2023-03-15 | 2023-07-07 | 北京航天微电科技有限公司 | Interdigital transducer parameter determination method, interdigital transducer parameter determination device, interdigital transducer parameter determination equipment and surface acoustic wave filter |
| CN116405006B (en) * | 2023-03-15 | 2024-03-26 | 北京航天微电科技有限公司 | Interdigital transducer parameter determination method, interdigital transducer parameter determination device, interdigital transducer parameter determination equipment and surface acoustic wave filter |
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Application publication date: 20150722 |