Transducer structure and surface acoustic wave resonator

Abstract

The invention discloses a transducer structure and a surface acoustic wave resonator, the transducer structure comprises at least two bus bars which are oppositely arranged, and each bus bar is connected with a plurality of finger bars; the finger strips connected with different bus bars are distributed in a staggered manner at intervals; the tail ends of only part of the fingers connected with one bus bar are connected with the other bus bar in a phase inversion mode, and the number and the phase inversion amplitude of the phase inversion fingers can be adjusted. The number of the phase inversion finger strips and the phase inversion amplitude of the transducer structure can be flexibly adjusted, the coupling characteristic can be optimized, the boundary of a pass band is steeper, the rectangularity of a filter is improved, and the out-of-band rejection performance of the filter is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of surface acoustic wave devices, and in particular to a transducer structure and a surface acoustic wave resonator having the structure. Background Art

[0002] The basic structure of the surface acoustic wave (SAW) filter is to make an acoustic-electric transducer on a piezoelectric substrate material. It has the advantages of low electro-acoustic conversion loss, flexible design, and easy large-scale production using semiconductor technology. It has been widely used in modern communication systems.

[0003] Surface acoustic wave (SAW) devices are widely used in signal processing and filtering in modern electronic systems such as wireless communications and sensors. The performance of SAW resonators directly affects the stability of the system and the quality of signal transmission. However, there are many challenges in the design of traditional SAW resonator structures, especially in the control of resonator rectangularity, out-of-band suppression, and coupling coefficient.

[0004] Existing surface acoustic wave resonators usually use interdigital transducers (IDTs) to achieve the conversion between electrical signals and acoustic signals. It consists of metal electrodes and piezoelectric substrates. The traditional IDT structure has a fixed material coupling coefficient, and the filter produced has a limited relative bandwidth range, which cannot be too wide or too narrow, making it difficult to achieve good frequency selectivity. These shortcomings limit the application of filters and make it difficult for existing filters to be developed in modern communication systems that have stricter requirements for high-frequency signals. Summary of the invention

[0005] The present invention aims to at least solve the technical problems existing in the prior art, and in particular innovatively proposes a transducer structure and a surface acoustic wave resonator having the structure.

[0006] In order to achieve the above-mentioned purpose of the present invention, according to the first aspect of the present invention, the present invention provides a transducer structure, including: at least two bus bars arranged relatively to each other, each bus bar being connected to a plurality of fingers; fingers connected to different bus bars are staggered and spaced apart; among the fingers connected to a certain bus bar, only the end portions of some of the fingers are inverted and connected to another bus bar, and the number and inversion amplitude of the inverted fingers are adjustable.

[0007] In the transducer structure of the present invention, the ends of some fingers are partially inverted (ie, a partially inverted electrode is formed), and the number and amplitude of the inverted fingers are adjustable, thereby achieving fine control of the coupling coefficient to effectively improve the rectangularity.

[0008] According to a preferred embodiment of the present invention, the transducer coupling coefficient is related to the total length of the inverted phase part. By adjusting the total length of the inverted phase part, the coupling characteristics are optimized, the rectangularity is flexibly adjusted, and the out-of-band suppression performance of the filter is effectively improved. The present invention can achieve more accurate frequency response control, so that the resonator has better electrical performance in practical applications.

[0009] According to a preferred embodiment of the present invention, the number of the phase inversion fingers is one for every 5 to 50 fingers in the transducer.

[0010] The number of phase inversion fingers can be flexibly adjusted according to specific transducer performance requirements.

[0011] According to yet another preferred embodiment of the present invention, the inversion amplitude (the ratio of the length of the inversion part to the length of a single finger) is 10% to 90%.

[0012] The inversion amplitude can be flexibly adjusted according to the specific transducer performance requirements.

[0013] According to a preferred embodiment of the present invention, the inversion amplitudes of the plurality of inversion fingers are equal, or not completely equal, or are all unequal.

[0014] Thereby achieving structural diversity and ensuring the mediation effect on the coupling characteristics.

[0015] According to yet another preferred embodiment of the present invention, the following structure is also included: a portion of the connected fingers of a certain bus bar are connected to another bus bar in reverse phase in its entirety.

[0016] Further optimize the coupling characteristics, flexibly adjust the rectangularity, and effectively improve the out-of-band suppression performance of the filter.

[0017] According to yet another preferred embodiment of the present invention, the total number of fingers NF of the transducer is:

[0018]

[0019] Among them, i is the serial number of the inversion amplitude sorted by size, I is the total serial number of the inversion amplitude sorted by size, is the number of inversion fingers with inversion amplitude i, is the inversion amplitude of each finger with inversion amplitude i, N Idt is the number of fingers of an IDT without phase inversion fingers with the same capacitance.

[0020] According to yet another preferred embodiment of the present invention, the transducer finger aperture WF is:

[0021]

[0022] in, is the number of inversion fingers with inversion amplitude i, is the inversion amplitude of each finger with inversion amplitude i, W0 is the finger aperture of the IDT without inversion finger with the same capacitance, N Idt is the number of fingers of an IDT without phase inversion fingers with the same capacitance.

[0023] This ensures that the capacitance of the transducer remains unchanged and does not affect the performance of the resonator.

[0024] According to yet another preferred embodiment of the present invention, the inverted portion of the finger is integrally connected with the adjacent in-phase finger after the inversion.

[0025] Since adjacent electrodes are connected to the same side bus bar, there is no potential difference and no sound-to-electric conversion, thereby reducing the overall coupling coefficient in the resonator and increasing the steepness of the edge in the filter.

[0026] According to yet another preferred embodiment of the present invention, a suspended portion is provided on the remaining portion of the phase-inverting finger except the phase-inverting portion, and the suspended portion is not connected to any bus bar.

[0027] By setting the suspended part, a specific electric field distribution is formed, which improves the uniformity of acoustic wave excitation, thereby optimizing the coupling characteristics, improving the out-of-band suppression performance of the filter, and achieving more precise frequency response control.

[0028] The suspended part is not connected to the bus bar, which helps to reduce signal interference and crosstalk inside the transducer, reduce the impact of parasitic capacitance on IDT performance, and improve the signal transmission quality of the transducer.

[0029] In order to achieve the above-mentioned purpose of the present invention, according to the second aspect of the present invention, the present invention provides a surface acoustic wave resonator, which includes a common SAW filter, or a surface acoustic wave filter of a composite stacked wafer (such as TC-SAW), or a surface acoustic wave filter with a bonding wafer as a substrate, or a surface acoustic wave filter with an IHP / POI wafer as a substrate; at least one transducer structure of the present invention is arranged in the above-mentioned structure.

[0030] The present invention can be used for common SAW filters, TC-SAW filters, or surface acoustic wave filters with bonding wafer as substrate, or surface acoustic wave filters with IHP / POI wafer as substrate, and has a wide range of applications and strong applicability. Various structures can significantly reduce the coupling coefficient of the resonator, improve the rectangularity of the filter, and significantly improve the out-of-band noise suppression.

[0031] The transducer structure of the present invention has a large degree of design freedom, can more flexibly adjust the coupling coefficient, optimize the coupling characteristics, and make the passband boundary steeper; the introduction of partial inverted electrodes has a significant effect in reducing parasitic modes and improving resonator performance, which can not only improve the rectangularity of the filter, but also effectively improve the out-of-band suppression performance of the filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic structural diagram of a transducer in a preferred embodiment of the present invention;

[0033] Figure 2 is a schematic structural diagram of a transducer in another preferred embodiment of the present invention;

[0034] Figure 3 is a schematic structural diagram of a transducer in another preferred embodiment of the present invention;

[0035] Figure 4 is a schematic structural diagram of a transducer in yet another preferred embodiment of the present invention;

[0036] Figure 5a is a schematic structural diagram of a transducer in yet another preferred embodiment of the present invention;

[0037] Figure 5b is a schematic structural diagram of a transducer in yet another preferred embodiment of the present invention;

[0038] Figure 6a is a schematic structural diagram of a transducer in yet another preferred embodiment of the present invention;

[0039] Figure 6b is a schematic structural diagram of a transducer in yet another preferred embodiment of the present invention;

[0040] Figure 7a is a schematic structural diagram of a transducer in yet another preferred embodiment of the present invention;

[0041] Figure 7b is a schematic structural diagram of a transducer in yet another preferred embodiment of the present invention;

[0042] Figure 8 It is a comparison diagram of the admittance amplitude values ​​of a common IDT (without an inverting electrode) and the transducer structure of the present invention in a preferred embodiment of the present invention;

[0043] Fig. 9 It is a comparison diagram of the real part of the admittance of a fully withdrawn finger structure (withdrawing the entire finger and fully inverting) in a preferred embodiment of the present invention and the transducer structure of the present invention;

[0044] Fig.10It is a comparison diagram of the out-of-band of a common IDT (without an inverting electrode) in a preferred embodiment of the present invention and the transducer structure of the present invention;

[0045] Fig.11 It is a comparison diagram of the right transition band of the passband of a common IDT (without an inverting electrode) in a preferred embodiment of the present invention and the transducer structure of the present invention.

[0046] Reference numerals:

[0047] 1 first bus bar; 2 first finger bar; 3 second bus bar; 4 second finger bar; 5 third bus bar;

[0048] 6 third finger; 7 fourth finger; 8 piezoelectric substrate; 9 metal electrode reflection grid; 10 partial phase inversion electrode;

[0049] 11 suspended part. DETAILED DESCRIPTION

[0050] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0051] In the description of the present invention, it is necessary to understand that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0052] In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection between two components. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0053] The present invention provides a transducer structure, such as Figure 1 and Figure 5a As shown, it includes at least two bus bars arranged opposite to each other on the piezoelectric substrate 8, each bus bar is connected to a plurality of fingers, and the fingers connected to different bus bars are staggered and spaced. In a preferred embodiment of the present invention, as Figure 1As shown, two bus bars may be provided, namely a first bus bar 1 and a second bus bar 3, the first bus bar 1 is connected to a plurality of first fingers 2, and the second bus bar 3 is connected to a plurality of second fingers 4. In another preferred embodiment, as Figure 5a As shown, three bus bars may be provided, namely a first bus bar 1, a second bus bar 3 and a third bus bar 5, the first bus bar 1 being connected to a plurality of first fingers 2, the second bus bar 3 being connected to a plurality of second fingers 4, and the third bus bar 5 being connected to a plurality of third fingers 6 and a fourth finger 7.

[0054] The busbars on both sides of the three busbars (the first busbar 1 and the second busbar 3) are in phase, and the central busbar (the third busbar 5) is out of phase with the busbars on both sides. In addition, metal electrode reflective grids 9 can be set at both ends of the transducer.

[0055] In a preferred embodiment of the present invention, only some of the fingers connected to a bus bar have their ends partially inverted (i.e., partially inverted electrodes 10) connected to another bus bar with a different phase. Figure 1 As shown, there are two busbars arranged opposite to each other, the two busbars are the first busbar 1 (the upper busbar) and the second busbar 2 (the lower busbar), wherein the first busbar 1 is connected to a plurality of first fingers 2, the second busbar 3 is connected to a plurality of second fingers 4, and the second fingers 4 are staggered and spaced from the first fingers 2. The end portions of the two first fingers 2 connected to the first busbar 1 are connected to the second busbar 3 in an inverted manner, and the inverted amplitudes of the two fingers at the end portions can be the same, as shown in FIG. Figure 1 In another embodiment, as shown. Figure 2 As shown, the end portions of the two first fingers 2 connected to the first bus bar 1 are connected to the second bus bar 3 in an inverted manner, and the inverted amplitudes of the ends of the two fingers are different.

[0056] The number of inverted fingers and the inverted amplitude of the present invention are adjustable, and the transducer coupling coefficient is related to the total length of the inverted part. The partially inverted fingers will weaken the coupling, and the longer the total length of the inverted part is, the weaker the coupling is. By controlling the length of the inverted part, the out-of-band suppression distortion problem caused by the full-finger inverted structure is improved. Figure 1 The sum of the lengths of the two finger inversion parts is equal to Figure 2 The sum of the lengths of the two finger inversion parts is equal, and the same transducer coupling coefficient can be obtained.

[0057] Among the fingers connected to the first bus bar 1, only the end portions of some of the fingers are connected to the second bus bar 3 in an inverted manner. In order to ensure the uniformity of the electric and acoustic fields in the IDT, in a preferred embodiment, the inverted amplitudes of the multiple inverted fingers are equal, and the sum of the number of inverted fingers and the length of the inverted amplitude is constant. In another preferred embodiment, the inverted amplitudes of the multiple inverted fingers are not all equal, and the sum of the lengths of the inverted parts of the inverted fingers is constant. For example, the inverted amplitude can be reduced and the number of inverted fingers can be increased.

[0058] In this embodiment, the number of inverted fingers is one for every 5 to 50 fingers. In another preferred embodiment of the present invention, the inverted amplitude (the ratio of the length of the inverted portion to the length of a single finger) is 10% to 90%.

[0059] In order to ensure that the IDT capacitance remains unchanged, the finger aperture WF of the IDT or the total number of fingers NF can be adjusted. The total number of fingers NF of the transducer can be adjusted as follows:

[0060]

[0061] Among them, i is the serial number of the inversion amplitude sorted by size, I is the total serial number of the inversion amplitude sorted by size, is the number of inversion fingers with inversion amplitude i, is the inversion amplitude of each finger with inversion amplitude i, N Idt is the number of fingers of an IDT without phase inversion fingers with the same capacitance.

[0062] The transducer finger aperture (the length of the intersection of the positive and negative electrodes of the full length) WF can be adjusted to:

[0063]

[0064] in, is the number of inversion fingers with inversion amplitude i, is the inversion amplitude of each finger with inversion amplitude i, W0 is the finger aperture of the IDT without inversion finger with the same capacitance, N Idt is the number of fingers of an IDT without phase inversion fingers with the same capacitance.

[0065] In this embodiment, W0 and N Idt It can be a common SAW filter, or a surface acoustic wave filter of a composite laminated wafer, or a surface acoustic wave filter with a bonding wafer as a substrate, or a surface acoustic wave filter with an IHP / POI wafer as a substrate. The finger aperture and finger number of any transducer can be used. W0 can be, but is not limited to, tens of microns to several millimeters. N IdtSpecifically, it can be but not limited to dozens to hundreds of lines. In a more preferred embodiment, W0 can be 20 surface acoustic wave wavelengths (surface acoustic wave wavelength is generally tens of microns to hundreds of microns), N Idt The value can be 200.

[0066] For example: Assume that the original number of fingers of the transducer without inverting electrode is N Idt is 100, N invert There are 3 lines, and the inversion amplitude is L invert 10%, it can be obtained that to ensure that the IDT capacitance remains unchanged, the NF is 103. Similarly, the WF transducer aperture can also be adjusted. In the actual implementation process, under the premise of ensuring that the transducer capacitance after partial phase inversion is the same as the capacitance of the original transducer without phase inversion electrode, only the total number of fingers NF after phase inversion can be adjusted, or only the transducer aperture WF can be adjusted, or the total number of fingers NF after phase inversion and the transducer aperture WF can be adjusted at the same time.

[0067] like Figure 3 As shown, in another preferred embodiment, the end portion of the first finger connected to the first bus bar 1 is inverted and connected to the second finger 4 in the same direction connected to the adjacent second bus bar 3 after the inversion. Since the adjacent electrodes are connected to the same side bus bar, there is no potential difference and no sound-to-electric conversion, thereby reducing the overall coupling coefficient in the resonator and improving the steepness of the edge in the filter.

[0068] like Figure 4 As shown, in the inverted finger, there is a suspended portion 11 on the rest of the inverted portion, and the suspended portion 11 is not connected to the bus bar. By setting the suspended portion 11, a specific electric field distribution is formed, and the uniformity of the acoustic wave excitation is improved, thereby optimizing the coupling characteristics, improving the out-of-band suppression performance of the filter, and achieving more precise frequency response control. The suspended portion 11 is not connected to the bus bar, which helps to reduce the interference and crosstalk of the signal inside the transducer, reduce the influence of parasitic capacitance on the performance of the IDT, and improve the signal transmission quality of the transducer.

[0069] like Figure 5aAs shown, in another preferred embodiment, two or more IDTs can be cascaded to form multiple sound channels. For example, three bus bars are arranged opposite to each other, namely, a first bus bar 1, a second bus bar 3 and a third bus bar 5, wherein the first bus bar 1 is connected to a plurality of first fingers 2, the second bus bar 3 is connected to a plurality of second fingers 4, the third bus bar 5 is connected to a plurality of third fingers 6 on a side opposite to the first bus bar 1, and the third bus bar 5 is connected to a plurality of fourth fingers 7 on a side opposite to the second bus bar 3, wherein the plurality of third fingers 6 and the plurality of fourth fingers 7 are symmetrically connected along the third bus bar 5, so that the plurality of first fingers 2 and the plurality of third fingers 6 are staggered and spaced; the plurality of second fingers 4 and the plurality of fourth fingers 7 are staggered and spaced, and at the same time, the finger end portion of the second bus bar 3 is invertedly connected to the oppositely arranged third bus bar 5, for example Figure 5a In a more preferred embodiment, as Figure 5b As shown, the part of the fingers connected to the second bus bar 3 in the lower sound channel is connected to the third bus bar 5 in reverse phase.

[0070] like Figure 6a As shown, in another preferred embodiment, the plurality of third fingers 6 and the plurality of fourth fingers 7 are asymmetrically arranged along the third bus bar 5, and the plurality of third fingers 6 and the plurality of fourth fingers 7 are alternately arranged along the third bus bar 5, so that the plurality of first fingers 2 and the plurality of third fingers 6 are staggered and spaced; the plurality of second fingers 4 and the plurality of fourth fingers 7 are staggered and spaced, and at the same time, the finger end portion of the second bus bar 3 is invertedly connected to the oppositely arranged third bus bar 5, for example Figure 6b In a more preferred embodiment, as Figure 6a As shown, some of the fingers connected to the second bus bar 3 in the lower sound channel are connected to the third bus bar 5 in an inverted manner. In another more preferred embodiment, some of the inverted fingers and the inverted fingers can be combined in one transducer (not shown).

[0071] like Figure 7a As shown, in another preferred embodiment, the end portion of the third bus bar 5 is connected to the first bus bar 1 disposed oppositely in reverse phase, and the end portion of the second bus bar 3 is connected to the third bus bar 3 disposed oppositely in reverse phase. Figure 7b As shown, the third bus bar 5 is connected to the first bus bar 1 in reverse phase, and the second bus bar 3 is connected to the third bus bar 5 in reverse phase. Figure 5a , Figure 6a and Figure 7aThe inversion amplitudes of the fingers may be the same or different, but in order to ensure that the IDT capacitance remains unchanged, the inversion amplitudes of the multiple inversion fingers may be equal or not all equal or not all equal, and the sum of the lengths of the inversion parts of the inversion fingers may be constant.

[0072] In some other embodiments, Figure 5b , Figure 6b and Figure 7b The inversion amplitude of the fingers can be full inversion, and the inversion amplitudes can be the same or different. However, in order to ensure that the IDT capacitance remains unchanged, the inversion amplitudes of multiple inversion fingers are equal, and the sum of the lengths of the inversion parts of the inversion fingers is constant.

[0073] The present invention also provides a surface acoustic wave resonator, which includes a common SAW structure, or a surface acoustic wave filter of a composite stacked wafer (such as TC-SAW), or a surface acoustic wave filter with a bonding wafer as a substrate, or a surface acoustic wave filter with an IHP wafer (high performance silicon on insulator wafer) or a POI wafer (partially depleted silicon on insulator wafer) as a substrate; at least one transducer structure of the present invention is arranged in the above structures.

[0074] In a preferred embodiment of the present invention, the specific implementation process is: select a suitable piezoelectric substrate 8 material according to the design requirements, which can be specifically but not limited to various cut types of LiTaO3 (lithium tantalate), LiNbO3 (lithium niobate), quartz and other piezoelectric base materials; deposit a metal film on the surface of the piezoelectric material by electron beam evaporation, plasma sputtering, magnetron sputtering, etc. to make interdigital transducer (IDT) fingers; the metal fingers of the interdigital transducer IDT can be but not limited to titanium, chromium, copper, silver, aluminum, platinum, tungsten, etc. or a combination thereof to make a common SAW filter device.

[0075] In a more preferred embodiment of the present invention, the piezoelectric substrate of the surface acoustic wave resonator is LiNbO3 or LiTaO3, or a composite multilayer structure based on them, especially a substrate with a relatively large coupling coefficient. The inverted electrode transducer uses aluminum electrodes, Cu or Pt electrodes, and the inverted length of some electrodes is controlled within the range of 1 / 4 to 1 / 2 of the finger length. Through comparative experiments, it was found that in a midband filter with an f0 of 2185MHz and a bandwidth of 30MHz, the introduction of the inverted electrode reduced the out-of-band suppression 20dB frequency of the overall filter from 2217MHz to 2215MHz, and the steepness of the transition band increased by about 1 to 2MHz.

[0076] like Figure 8As shown, a comparison chart of the admittance amplitude values ​​of an ordinary IDT and the transducer structure of the present invention is shown. The horizontal axis is frequency, the vertical axis is the amplitude of the frequency, the solid line represents the IDT structure of the present invention, and the dotted line represents the ordinary IDT. In an ordinary IDT, the electrode structure is single, the coupling coefficient is relatively high, and it is difficult to effectively control the out-of-band suppression performance. The present invention introduces a phase reversal design in some electrodes, so that the coupling coefficient of the resonator is significantly reduced, the admittance amplitude bandwidth is narrowed, and when it is applicable to a series resonator, the rectangularity of the transition band on the right side of the filter passband can be improved, and the out-of-band noise suppression performance is significantly improved.

[0077] In terms of admittance amplitude value, the transducer structure of the present invention improves rectangularity by narrowing the bandwidth, thereby achieving higher filtering performance in series resonator applications.

[0078] like Fig. 9 As shown, the real part of the admittance comparison diagram of other full-withdrawn finger structures and the transducer structure of the present invention, the horizontal axis is frequency, the vertical axis is the amplitude of frequency, the solid line represents the IDT structure of the present invention, and the dotted line represents other full-withdrawn finger structures. In other full-withdrawn finger structures, the introduction of the full-inverted electrode, generally one full-inverted electrode is added to 20 to 30 fingers, the IDT structure changes too drastically, causing a large change in the electric field, and easily generating spikes outside the band, resulting in unstable out-of-band suppression performance. The transducer structure of the present invention can add more partial inverted electrodes 10 to the IDT by finely adjusting the length of the inverted part, and one partial inverted electrode 10 can be added to 10 to 15 fingers, so that the field distribution in the IDT structure is more uniform. Finally, the real part curve of the resonator admittance will be smoother, avoiding the out-of-band suppression spike phenomenon, and significantly improving the out-of-band characteristics of the filter.

[0079] like Fig.10 As shown in FIG. 1 , a comparison diagram of the out-of-band of a common IDT and the transducer structure of the present invention is shown, where the horizontal axis is the frequency and the vertical axis is the frequency amplitude. The solid line represents the IDT structure of the present invention, and the dotted line represents the common IDT. Fig.10 As shown, compared with the filter of the ordinary IDT without partial inversion electrode transducer structure, the filter using the structure of the present invention has a better suppression effect in the out-of-band area, reducing the influence of out-of-band noise. In the comparison of the transition band on the right side of the passband, the transducer structure of the present invention significantly improves the performance of the transition band, making the boundary of the passband steeper and improving the rectangularity of the filter. In the actual filter prepared in the above embodiment, the transition band on the right side of the passband is increased by about 1 to 2 MHz.

[0080] like Fig.11 As shown in FIG. 1 , a comparison diagram of the right transition band of the passband of a common IDT and the transducer structure of the present invention is shown, where the horizontal axis is the frequency and the vertical axis is the amplitude of the frequency. The solid line represents the IDT structure of the present invention, and the dotted line represents the common IDT. Fig.11As shown, compared with the filter of the common IDT non-partial inversion electrode transducer structure, the filter using the structure of the present invention significantly improves the performance of the transition band, makes the boundary of the passband steeper, and improves the rectangularity of the filter.

[0081] The present invention can also be used in resonators of specific substrates, and the specific specific substrate can be 36LT (LiTaO3 is abbreviated as LT), SiO2, polycrystalline Si, one of the piezoelectric single crystal thin film structure materials on insulators (POI) structures, or other piezoelectric materials with relatively large coupling coefficients. The present invention is used in resonators of the above specific substrates to suppress the generation of parasitic modes and improve the stability of the resonator. In this structure, by adjusting the proportion of the inverted part, the coupling between different modes can be effectively suppressed. The present invention can also be applied to some other TC-SAW structures with thick film covering layers, such as TC-SAW covered with SiO2.

[0082] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0083] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A transducer structure, characterized in that: include: At least two bus bars are arranged opposite to each other, each bus bar is connected to a plurality of fingers; The fingers connecting different bus bars are staggered and spaced apart; The end portions of only some of the fingers connected to a bus bar are connected to another bus bar in reverse phase; The number of inversion fingers and the inversion amplitude are adjustable.

2. The transducer structure according to claim 1, characterized in that: The transducer coupling coefficient is related to the total length of the inverting part.

3. The transducer structure according to claim 1, characterized in that: The number of the phase inversion fingers is one for every 5 to 50 fingers in the transducer.

4. The transducer structure according to claim 1, characterized in that: The phase inversion amplitude is 10% to 90%.

5. The transducer structure according to any one of claims 1 to 4, characterized in that: The inversion amplitudes of the plurality of inversion fingers are equal, or not all equal, or all unequal.

6. The transducer structure according to claim 1, characterized in that: It also includes the following structure: a part of the fingers connected to a certain bus bar are connected to another bus bar in reverse phase.

7. The transducer structure according to claim 1, characterized in that: The total number of transducer fingers NF is: Among them, i is the serial number of the inversion amplitude sorted by size, I is the total serial number of the inversion amplitude sorted by size, is the number of inversion fingers with inversion amplitude i, is the inversion amplitude of each finger with inversion amplitude i, N Idt is the number of fingers of an IDT without phase inversion fingers with the same capacitance.

8. The transducer structure according to claim 1, characterized in that: The transducer finger aperture is: in, is the number of inversion fingers with inversion amplitude i, is the inversion amplitude of each finger with inversion amplitude i, W0 is the finger aperture of the IDT without inversion finger with the same capacitance, N Idt is the number of fingers of an IDT without phase inversion fingers with the same capacitance.

9. The transducer structure according to claim 1, characterized in that: The inverted part of the finger is connected as a whole with the adjacent inverted finger.

10. The transducer structure according to claim 1, characterized in that: The remaining part of the phase-inverting finger except the phase-inverting part is provided with a suspended part, and the suspended part is not connected to the bus bar.

11. A surface acoustic wave resonator, characterized in that: Including ordinary SAW filters, or surface acoustic wave filters with composite stacked wafers, or surface acoustic wave filters with bonding wafer as substrate, or surface acoustic wave filters with IHP / POI wafer as substrate, At least one transducer structure described in any one of claims 1 to 10 of the present invention is arranged in the ordinary SAW filter, or the surface acoustic wave filter of the composite stacked wafer, or the surface acoustic wave filter with the bonding wafer as the substrate, or the surface acoustic wave filter with the IHP / POI wafer as the substrate.

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