SAW resonator and double-band-pass SAW filter

Abstract

The invention provides a surface acoustic wave (SAW) resonator and a double-band-pass SAW filter. According to the SAW resonator disclosed by the invention, the cycle length of the electrode in the middle resonance region is reduced, and the maximum cycle length of the electrode in the middle resonance region is smaller than the minimum cycle length of the electrodes in the other resonance regions, so that two resonance peak responses are excited at the same time. The double-band-pass SAW filter formed based on the SAW resonators with the double harmonic peaks can form a double-band-pass transmission effect, and compared with an existing SAW filter, only half of the SAW resonators need to be used, so that the area of a device is greatly reduced, the miniaturization development of the device is facilitated, and the cost is reduced. In addition, the double-band-pass SAW filter can achieve high isolation more easily, and the overall performance of the device can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor device manufacturing, and particularly relates to a SAW resonator and a dual-bandpass SAW filter. Background Art

[0002] With the rapid development of 5G communication technology, the market demand for radio frequency filters in the 5G frequency band has increased sharply. As one of the effective solutions to realize high-performance radio frequency filtering components, the Surface Acoustic Wave (SAW) filter has the advantages of high performance, low cost, and small device size, and has been widely used in various communication devices.

[0003] Please refer to Figure 1 and Figure 2 , the SAW filter is composed of multiple SAW resonators 10. The Inter Digital Transducer (IDT) in each SAW resonator includes multiple electrodes 100. In the existing SAW resonator 10, the period length p of each electrode 100 is kept consistent. And the resonant frequency f of the SAW resonator 10 is determined by the period length p of the electrode 100 and satisfies f = v / (2*p), where v is the sound velocity of the surface acoustic wave. Based on this, the existing SAW resonator 10 can only excite a single resonant peak response, so the SAW filter can only pass signals of a specific frequency. However, at this stage, the communication frequency band is becoming increasingly crowded, and the single-bandpass SAW filter will be difficult to continue. In response, the existing process forms a dual-bandpass SAW filter by connecting two SAW filters with different bandpasses in parallel.

[0004] As Figure 2 shown, the input ends and output ends of the first bandpass filter and the second bandpass filter in the dual-bandpass SAW filter are respectively connected correspondingly to realize sharing of the input and output ends. Among them, each bandpass filter includes SAW resonators 10 connected in series and SAW resonators 10 connected in parallel. For the convenience of description, it is assumed that three SAW resonators 10 are connected in series and two SAW resonators 10 are connected in parallel in both the first bandpass filter and the second bandpass filter. And the types of the SAW resonators 10 in the same bandpass filter are the same, and the types of the SAW resonators 10 in different bandpass filters are different. Thus, through simulation, Figure 3The shown admittance response simulation diagram, where the red curve dB(Y(1,1)) is the admittance response of the series SAW resonator 10 in the first bandpass filter, and the pink curve dB(Y(2,2)) is the admittance response of the parallel SAW resonator 10 in the first bandpass filter; the blue curve dB(Y(3,3)) is the admittance response of the series SAW resonator 10 in the second bandpass filter, and the green curve dB(Y(4,4)) is the admittance response of the parallel SAW resonator 10 in the second bandpass filter. Also, in combination with Figure 4 As can be seen from the shown dB(S(2,1)) curve, the series SAW resonator 10 and the parallel SAW resonator 10 in the first bandpass filter form the first bandpass; the series SAW resonator 10 and the parallel SAW resonator 10 in the second bandpass filter form another bandpass with a different frequency band, and finally form the Figure 4 transmission response of the shown dual-band SAW filter.

[0005] However, the existing dual-band SAW filter requires the use of two SAW filters, resulting in a large occupied area and being difficult to meet the requirements of miniaturized device design. Moreover, since the two SAW filters share the input and output ports, it is also very difficult to improve the isolation between the two bandpasses.

[0006] Therefore, there is an urgent need for a new dual-band SAW filter to solve the above technical problems. Summary of the Invention

[0007] The object of the present invention is to provide a SAW resonator and a dual-band SAW filter to solve at least one of the problems of how to reduce the occupied area of the dual-band SAW filter and how to optimize the isolation between the two bandpasses in the dual-band SAW filter.

[0008] To solve the above technical problems, the present invention provides a SAW resonator, including: a piezoelectric substrate and interdigital transducers located on the piezoelectric substrate; wherein,

[0009] the interdigital transducers include multiple electrodes arranged at intervals and staggered, and at least some of the electrodes have different periodic lengths; and, the piezoelectric substrate is divided into multiple resonance regions, and the maximum periodic length of the electrodes in the middle resonance region is less than the minimum periodic length of the electrodes in the remaining resonance regions, so as to be able to excite two resonance peak responses.

[0010] Optionally, in the SAW resonator, in at least some of the resonance regions, the periodic lengths of the electrodes in the same resonance region are the same.

[0011] Optionally, in the SAW resonator described above, the periodic lengths of the electrodes in the middle resonator region are the same; and, the periodic lengths of the electrodes in the remaining resonator regions are the same; and the periodic length of the electrodes satisfies the following formula:

[0012] 0.92P 1 ≤P 2 ≤0.96P 1

[0013] where P 1 is the periodic length of the electrodes in the remaining resonator regions; P 2 is the periodic length of the electrodes in the middle resonator region.

[0014] Optionally, in the SAW resonator described above, the multiple resonator regions are linearly distributed, and in the two resonator regions adjacent to the middle resonator region, the periodic lengths of the electrodes in the same resonator region are the same; and,

[0015] the difference P D1 in the periodic lengths of the electrodes in the two resonator regions adjacent to the middle resonator region satisfies the following formula:

[0016] |P D1 |≤3%P 3 ; or |P D1 |≤3%P 4

[0017] where P 3 is the periodic length of the electrodes in one of the two resonator regions adjacent to the middle resonator region; P 4 is the periodic length of the electrodes in the other of the two resonator regions adjacent to the middle resonator region.

[0018] Optionally, in the SAW resonator described above, in the remaining resonator regions, the periodic lengths of the electrodes in the same resonator region are the same, and the difference P D2 in the periodic lengths of the electrodes in two adjacent resonator regions satisfies the following formula:

[0019] |P D2 |≤3%P 5

[0020] where P 5 is the periodic length of the electrodes in the resonator region adjacent to the middle resonator region among the two adjacent resonator regions in the remaining resonator regions.

[0021] Optionally, in the SAW resonator, each of the resonant regions includes a plurality of the electrodes; and in at least some of the resonant regions, the periodic lengths of at least some of the electrodes located in the same resonant region are different.

[0022] Optionally, in the SAW resonator, when the periodic lengths of at least some of the electrodes in the resonant region are different, one of the electrodes located on the side of the resonant region is used as a reference electrode, and the periodic lengths of the electrodes in the resonant region satisfy the following formula:

[0023] |P D3 |≤3%P 6

[0024] Wherein, P 6 is the periodic length of the reference electrode; P D3 is the difference between the periodic length of the reference electrode and the periodic length of any other electrode in the resonant region.

[0025] Optionally, in the SAW resonator, the number of the electrodes in the middle resonant region ranges from 5 to 30, and the total number of the electrodes in the remaining resonant regions is greater than twice the number of the electrodes in the middle resonant region.

[0026] Optionally, in the SAW resonator, the SAW resonator further includes a plurality of reflection gratings; the plurality of reflection gratings are located on the piezoelectric substrate and are arranged close to the side of the interdigital transducer.

[0027] Based on the same concept, the present invention further provides a dual-bandpass SAW filter, which includes a plurality of resonators; some of the resonators are connected in series to form a series circuit; the remaining resonators are connected in parallel to the series circuit and form a parallel circuit; wherein,

[0028] At least one of the resonators in the series circuit is the SAW resonator; at least one of the resonators in the parallel circuit is the SAW resonator, so that the dual-bandpass SAW filter can simultaneously open two bandpasses.

[0029] In summary, the present invention provides a SAW resonator and a dual-bandpass SAW filter. Compared with the prior art, in the SAW resonator of the present invention, the period length of the electrodes in the middle resonator region is reduced, and the maximum period length of the electrodes in the middle resonator region is made less than the minimum period length of the electrodes in the other resonator regions, thereby achieving the simultaneous excitation of two resonance peak responses. Moreover, the dual-bandpass SAW filter composed of the SAW resonator based on dual resonance peaks can not only form a dual-bandpass transmission effect, but also, compared with the existing SAW filters, only half the number of SAW resonators need to be used, thus greatly reducing the device area, facilitating the miniaturization development of the device, and reducing costs. In addition, the dual-bandpass SAW filter is also easier to achieve high isolation, which is conducive to improving the overall performance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Those of ordinary skill in the art will understand that the provided drawings are used to better understand the present invention and do not constitute any limitation to the scope of the present invention.

[0031] Figure 1 is a schematic diagram showing that the period lengths of all the electrodes in the interdigital transducer in the prior art are the same.

[0032] Figure 2 is a schematic structural diagram of a dual-bandpass SAW filter in the prior art.

[0033] Figure 3 is a simulation diagram of the admittance response of the series-parallel circuit of each filter in the dual-bandpass SAW filter in the prior art.

[0034] Figure 4 is a simulation diagram of the dual-bandpass transmission response of the dual-bandpass SAW filter in the prior art.

[0035] Figure 5 is a schematic structural diagram of the SAW resonator in the first example in the embodiments of the present invention.

[0036] Figure 6 is in the embodiments of the present invention Figure 5 the A-A' cross-sectional view of the SAW resonator shown.

[0037] Figure 7 is a schematic structural diagram of the SAW resonator in the second example in the embodiments of the present invention.

[0038] Figure 8 is a schematic structural diagram of a SAW resonator in the third example in the embodiments of the present invention.

[0039] Figure 9 is a schematic structural diagram of another SAW resonator in the third example in the embodiments of the present invention.

[0040] Figure 10 It is a schematic structural diagram of a SAW resonator in the fourth example of the embodiments of the present invention.

[0041] Figure 11 In the embodiments of the present invention Figure 10 It is a schematic diagram of the first resonance region in the SAW resonator shown.

[0042] Figure 12 It is a schematic structural diagram of another SAW resonator in the fourth example of the embodiments of the present invention.

[0043] Figure 13 It is a response simulation diagram of two resonance peaks of the SAW resonator in the embodiments of the present invention.

[0044] Figure 14 It is a schematic structural diagram of a dual-band SAW filter in the embodiments of the present invention.

[0045] Figure 15 It is a dual-band transmission response simulation diagram of the dual-band SAW filter in the embodiments of the present invention.

[0046] And, in the drawings:

[0047] 10 - SAW resonator; 100 - electrode;

[0048] 20 - SAW resonator; 200 - piezoelectric substrate; 201 - interdigital transducer; 201a - first resonance region; 201b - second resonance region; 201c - third resonance region; 201d - fourth resonance region; 201e - fifth resonance region; 2010 - electrode; 2010b - first electrode; 2010c - second electrode; 2010d - third electrode; 2010e - fourth electrode; 202 - reflection grating. Detailed implementation manners

[0049] To make the objectives, advantages and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the accompanying drawings are all in very simplified forms and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the objectives of the embodiments of the present invention. In addition, the structures shown in the accompanying drawings are often part of the actual structures. In particular, the emphases to be shown in each of the accompanying drawings are different, and sometimes different scales are used. It should also be understood that unless otherwise specified or indicated, the terms "first", "second", "third", etc. in the description are only used to distinguish the various components, elements, steps, etc. in the description, rather than to represent the logical relationship or sequential relationship, etc. between the various components, elements, steps. And, in this specification, the X-axis, Y-axis and Z-axis directions are respectively three mutually perpendicular directions in three-dimensional space.

[0050] Please refer toFigure 5 and Figure 6 Figure 6 , this embodiment provides a SAW resonator 20, including: a piezoelectric substrate 200 and an interdigital transducer 201 located on the piezoelectric substrate 200; wherein, the interdigital transducer 201 includes a plurality of electrodes 2010 arranged at intervals and staggered, and the periodic lengths of at least some of the electrodes 2010 are different; and, the piezoelectric substrate 200 is divided into a plurality of resonance regions, and the maximum periodic length of the electrodes 2010 in the middle resonance region is less than the minimum periodic length of the electrodes 2010 in the remaining resonance regions, so as to be able to excite two resonance peak responses.

[0051] Based on this, the SAW resonator 20 provided in this embodiment realizes exciting two resonance peak responses by reducing the periodic length of the electrodes 2010 in the middle resonance region of the interdigital transducer 201.

[0052] The following specifically describes the SAW resonator 20 provided in this embodiment with reference to the attached Figures 5 to 15 Figures 5 to 15 , specifically describe the SAW resonator 20 provided in this embodiment.

[0053] Please continue to refer to Figure 5 and Figure 6 Figure 6 , the SAW resonator 20 includes: a piezoelectric substrate 200 and an interdigital transducer 201. Among them, the piezoelectric substrate 200 has a piezoelectric effect, and the conversion between an electrical signal and an acoustic wave signal can be realized by using the piezoelectric effect. Optionally, the material of the piezoelectric substrate 200 includes but is not limited to quartz, lithium niobate, lithium tantalate, aluminum nitride; and the piezoelectric substrate 200 can also be a multi-layer composite substrate formed by stacking multiple different substrate materials, such as a multi-layer composite substrate of lithium tantalate / silicon dioxide / silicon, or a multi-layer composite substrate of aluminum nitride / diamond, etc. The interdigital transducer 201 is located on the piezoelectric substrate 200 and is composed of a plurality of electrodes 2010 arranged at intervals and staggered. The interaction between the interdigital transducer 201 and the piezoelectric substrate 200 can realize the mutual conversion of electrical signals and acoustic wave signals. Optionally, the material of the electrodes 2010 includes but is not limited to metal aluminum, copper, gold, titanium; and the electrodes 2010 can also be a combination of multiple metals stacked.

[0054] Also, in some examples, the SAW resonator 20 further includes a reflection grating 202. The reflection grating 202 is located on the piezoelectric substrate 200 and is disposed near the side of the interdigital transducer 201. The function of the reflection grating 202 is to reflect acoustic waves, enabling the acoustic waves to propagate back and forth between the interdigital transducers 201 and form resonance. Moreover, by adjusting the structure and position of the reflection grating 202, precise control over the acoustic wave propagation path and reflection characteristics can be achieved, thereby optimizing the performance of the SAW resonator 20. It should be noted that in some other examples, the reflection grating 202 may not be provided within the SAW resonator 20. Herein, the corresponding drawings of this embodiment are all exemplified by setting the reflection grating 202 to illustrate the SAW resonator 20 provided in this embodiment.

[0055] Furthermore, in this embodiment, at least some of the periodic lengths of the electrodes 2010 of the interdigital transducer 201 are different. Also, the piezoelectric substrate 200 is divided into multiple resonance regions, and the maximum periodic length of the electrodes 2010 in the middle resonance region is less than the minimum periodic length of the electrodes 2010 in the remaining resonance regions, so as to be able to excite two resonance peak responses.

[0056] Specifically, the multiple resonance regions are linearly distributed along the X-axis direction, and multiple electrodes 2010 are provided in each resonance region. The periodic lengths of the electrodes 2010 located in the same resonance region may be the same or different. It should be noted that in the actual process, the structural process parameters related to the interdigital transducer 201 mainly include the metal duty cycle and the periodic length. Among them, the metal duty cycle refers to the ratio of the metal structure width of each electrode 2010 to the periodic length; and the periodic length of the electrode 2010 refers to, in the X-axis direction, the sum of half of the distance between the electrode 2010 and the adjacent two electrodes 2010 and the width of the electrode 2010. Therefore, different periodic lengths mean that their overall lengths are different, which may be different in spacing, and / or different in the width of the electrode 2010. And for different periodic lengths, the corresponding metal duty cycles may be the same or different, and this embodiment does not make specific limitations in this regard.

[0057] In the first example, the periodic lengths of the electrodes 2010 in the middle resonance region are the same; and, the periodic lengths of the electrodes 2010 in the remaining each resonance region are the same, and the periodic length of the electrode 2010 satisfies the following formula (1):

[0058] 0.92P 1 ≤P 2 ≤0.96P 1 Formula (1);

[0059] Wherein, P1 is the period length of the electrode 2010 in the remaining resonant regions; P 2 is the period length of the electrode 2010 in the middle resonant region. Optionally, 0.93P 1 ≤P 2 ≤0.94P 1 . And under the setting of the period length of the electrode 2010 corresponding to formula (1), two different resonant peak responses can be excited, which is beneficial to realizing the preparation of a dual-bandpass filter.

[0060] For example Figure 5 and Figure 6 as shown, the piezoelectric substrate 200 is divided into three resonant regions, namely: the first resonant region 201a, the second resonant region 201b, and the third resonant region 201c. The first resonant region 201a is located in the middle position, and the second resonant region 201b and the third resonant region 201c are located on both sides of the first resonant region 201a. Among them, the period lengths of the electrodes 2010 in the second resonant region 201b and the third resonant region 201c are the same, and are denoted as the first period length P 1 . If there are other resonant regions divided on the piezoelectric substrate 200, then the period lengths of the electrodes 2010 in the other resonant regions except the first resonant region 201a are all the first period length P 1 . And the period lengths of the electrodes 2010 in the first resonant region 201a located in the middle position are the same, and are denoted as the second period length P 2 . The second period length P 2 is less than the first period length P 1 , and satisfies the above formula (1).

[0061] In the second example, the period lengths of the electrodes 2010 in the middle resonant region can be the same or different. And in the two resonant regions adjacent to the middle resonant region, the period lengths of the electrodes 2010 in the same resonant region are the same. And the difference P D1 between the period lengths of the electrodes 2010 in the two resonant regions adjacent to the middle resonant region satisfies the following formula (2):

[0062] |P D1 |≤3%P 3 ; or |P D1 |≤3%P 4 Formula (2);

[0063] wherein, P 3 is the period length of the electrode 2010 in one of the two adjacent resonant regions; P 4is the period length of the electrode 2010 in the other of the two adjacent resonant regions. In other words, regardless of whether the period lengths of the electrodes 2010 in the middle resonant region are the same, the electrodes 2010 in the two adjacent resonant regions are the same within their corresponding resonant regions, but the difference in the period lengths of the electrodes 2010 in these two resonant regions satisfies the above formula (2). And optionally, |P D1 | ≤ 2%P 3 ; or |P D1 | ≤ 2%P 4 .

[0064] For example Figure 7 as shown, the piezoelectric substrate 200 is divided into a first resonant region 201a, a second resonant region 201b, and a third resonant region 201c. The first resonant region 201a is located in the middle position, and the second resonant region 201b and the third resonant region 201c are the two resonant regions adjacent to the first resonant region 201a. Among them, the period lengths of the electrodes 2010 in the second resonant region 201b are the same, and are denoted as the third period length P 3 ; the period lengths of the electrodes 2010 in the third resonant region 201c are the same, and are denoted as the fourth period length P 4 . Based on this, |P D1 | = |P 3 - P 4 |, and satisfies the above formula (2).

[0065] It should be noted that in the second example, the maximum period length of the electrodes 2010 in the middle resonant region is still less than the minimum period length of the electrodes 2010 in the remaining resonant regions to ensure that two resonant peak responses can be excited. For the design of the period lengths of the electrodes 2010 in the two adjacent resonant regions, the actual size change is very small, so not only will no additional resonant peaks be added, but it is also beneficial to suppress the stray effect, optimize the waveform, and thus improve the device performance.

[0066] Furthermore, when the number of resonant regions in the second example is greater than three, when the period lengths of the electrodes 2010 in each of the resonant regions on both sides of the middle resonant region satisfy a certain size range, the effect of suppressing the stray effect and optimizing the waveform can also be achieved without adding additional resonant peaks. Based on this, in the third example, in the remaining resonant regions, the period lengths of the electrodes 2010 in the same resonant region are the same, and the difference in the period lengths of the electrodes 2010 in two adjacent resonant regions P D2 satisfies the following formula (3):

[0067] |P D2|≤3%P 5 Formula (3);

[0068] Wherein, P 5 is the period length of the electrode 2010 of the one adjacent to the middle resonator region among the remaining two adjacent resonator regions. Optionally, |P D2 |≤2%P 5 .

[0069] For example Figure 8 and Figure 9 As shown, the piezoelectric substrate 200 is divided into a first resonator region 201a, a second resonator region 201b, a third resonator region 201c, a fourth resonator region 201d, and a fifth resonator region 201e. The first resonator region 201a is located in the middle position, and in the third example, the period lengths of the electrodes 2010 in the first resonator region 201a may be the same or different. The second resonator region 201b and the third resonator region 201c are two resonator regions adjacent to the first resonator region 201a. And the period lengths of the electrodes 2010 in the second resonator region 201b are the same, and the period lengths of the electrodes 2010 in the third resonator region 201c are the same; and, the relationship between the period length of the electrode 2010 in the second resonator region 201b and the period length of the electrode 2010 in the third resonator region 201c satisfies the above formula (2). The fourth resonator region 201d is located on the side of the second resonator region 201b away from the first resonator region 201a, and the fifth resonator region 201e is located on the side of the third resonator region 201c away from the first resonator region 201a. And the period lengths of the electrodes 2010 in the fourth resonator region 201d are the same, and the period lengths of the electrodes 2010 in the fifth resonator region 201e are the same.

[0070] Based on this, the second resonator region 201b and the fourth resonator region 201d are adjacent and both are located on the same side of the first resonator region 201a. Wherein, the second resonator region 201b is closer to the first resonator region 201a than the fourth resonator region 201d, then the period length of the electrode 2010 in the second resonator region 201b can be denoted as P 5 , and the period length of the electrode 2010 in the fourth resonator region 201d is denoted as P 5 ’, |P D2 | = |P 5 – P 5’|, and satisfies the above formula (3). Similarly, the fifth resonance region 201e and the third resonance region 201c are also adjacent and both located on the same side of the first resonance region 201a. Among them, the third resonance region 201c is closer to the first resonance region 201a than the fifth resonance region 201e, and the periodic length of the electrode 2010 in the third resonance region 201c can be denoted as P 5 , while the periodic length of the electrode 2010 in the fifth resonance region 201e is denoted as P 5 ”, |P D2 | = |P 5 – P 5 ”|, and satisfies the above formula (3). It should be noted that P 5 refers to the periodic length of the electrode 2010 in a resonance region that is closer to the first resonance region 201a among two adjacent resonance regions. Then, the electrode 2010 in the second resonance region 201b and the third resonance region 201c can have the same periodic length of the electrode 2010 as shown in Figure 8 , or can have different periodic lengths of the electrode 2010 as shown in Figure 9 . And in other examples, assuming that there are several resonance regions provided on the side of the fourth resonance region 201d away from the second resonance region 201b, and / or there are several resonance regions provided on the side of the fifth resonance region 201e away from the third resonance region 201c, then, except for the first resonance region 201a, the periodic length of the electrode 2010 in each of the remaining resonance regions is the one that is closer to the first resonance region 201a compared with the resonance region adjacent to itself and is denoted as P 5 .

[0071] It can be understood that the above three examples mainly illustrate with the assumption that the periodic lengths of the electrodes 2010 in the same resonance region are the same. However, in other examples, the periodic lengths of the electrodes 2010 in the same resonance region can be different. Further, as shown in Figures 10 to 12 , when at least some of the electrodes 2010 in the resonance region have different periodic lengths, taking an electrode 2010 on the side of the resonance region as the reference electrode 2010a, and the periodic lengths of the remaining electrodes 2010 satisfy the following formula (4):

[0072] |P D3 | ≤ 3%P 6 Formula (4);

[0073] Among them, P 6 is the periodic length of the reference electrode 2010a; P D3is the difference in the period lengths between the reference electrode 2010a and any other arbitrary electrode 2010 in the resonant region. Optionally, |P D3 | ≤ 2% P 6 .

[0074] Specifically, in the fourth example, as Figure 10 and Figure 11 shown, the piezoelectric substrate 200 is divided into a first resonant region 201a, a second resonant region 201b, a third resonant region 201c, a fourth resonant region 201d, and a fifth resonant region 201e. The first resonant region 201a is located in the middle position, and the second resonant region 201b, the third resonant region 201c, the fourth resonant region 201d, and the fifth resonant region 201e are respectively located on both sides of the first resonant region 201a. Among them, there are at least some electrodes 2010 with different period lengths in the first resonant region 201a. That is, all the electrodes 2010 in the first resonant region 201a have different period lengths, or some of the electrodes 2010 have the same period length, and some of the electrodes 2010 have different period lengths. For example Figure 11 shown in the enlarged schematic diagram of the first resonant region 201a, the five electrodes 2010 in the first resonant region 201a have different period lengths. Among them, taking the leftmost electrode 2010 in the figure as the reference electrode 2010a, and the electrodes 2010 on one side of the reference electrode 2010a are sequentially named: the first electrode 2010b, the second electrode 2010c, the third electrode 2010d, and the fourth electrode 2010e. Among them, the period length of the reference electrode 2010a is denoted as P 6 , the period length of the first electrode 2010b is denoted as P 61 , the period length of the second electrode 2010c is denoted as P 62 , the period length of the third electrode 2010d is denoted as P 63 , and the period length of the fourth electrode 2010e is denoted as P 64 . And the difference P 6 between the period length of any one of the second electrode 2010c, the third electrode 2010d, and the fourth electrode 2010e and the period length P D3 of the reference electrode 2010a all satisfies the above formula (4). That is, |P D3 = P 61 - P 6 | ≤ 3% P 6 , |P D3 = P 62 - P 6 | ≤ 3% P 6 , |P D3 = P63 -P 6 |≤3% P 6 ,|P D3 =P 64 -P 6 |≤3% P 6 。In other examples, the rightmost electrode 2010 of the diagram can also be used as the reference electrode 2010a, and this embodiment does not make specific limitations on this.

[0075] Based on this, the period lengths of each of the electrodes 2010 in any one or more of the first resonant region 201a, the second resonant region 201b, the third resonant region 201c, the fourth resonant region 201d, and the fifth resonant region 201e can be different. Exemplarily, in Figure 10 the shown SAW resonator 20, only the period lengths of each of the electrodes 2010 in the middle first resonant region 201a are different, while the other electrodes 2010 are the same within the corresponding resonant regions. Or, in Figure 12 the shown SAW resonator 20, the period lengths of each of the electrodes 2010 in each resonant region are different. Or, in some or all of the resonant regions, the period lengths of some of the electrodes 2010 in the same resonant region are different, and the period lengths of the remaining electrodes 2010 are the same. This embodiment does not make specific limitations on the period length dimensions of each of the electrodes 2010 in each resonant region, but it is necessary to satisfy that the maximum period length of the electrodes 2010 in the middle resonant region is less than the minimum period length of the electrodes 2010 in the remaining resonant regions, so as to ensure that two resonant peak responses can be excited to meet the filtering requirements of the dual-bandpass. And, under the constraints of the above formulas (1) to (4), the spurious effect can be suppressed, the waveform can be optimized, and the device performance can be improved without adding additional resonant peaks.

[0076] Further, the number range of the electrodes 2010 in the middle resonant region is: 5 to 30, and the total number of the electrodes 2010 in the remaining resonant regions is greater than twice the number of the electrodes 2010 in the middle resonant region. Optionally, the number range of the electrodes 2010 in the middle resonant region is: 5 to 30. For example, the number of the electrodes 2010 in the middle resonant region is 5, and the total number of the electrodes 2010 in the other resonant regions is 12. It should be noted that the limitation on the number of the electrodes 2010 in this embodiment is aimed at forming a better resonant peak waveform to avoid the two resonant peaks being too close, so as to optimize the waveform.

[0077] Based on this, the SAW resonator 20 provided in this embodiment realizes exciting two resonance peaks by adjusting the maximum period length of the electrode 2010 in the middle resonance region to be less than the minimum period length of each electrode 2010 in the remaining resonance regions, which is beneficial to alleviating the problem of the increasingly crowded communication frequency band. Moreover, the period lengths of the electrodes 2010 in the remaining resonance regions of the SAW resonator 20 can be the same or different, and under the constraints of the above formulas (1) to (4), the spurious effect can be suppressed and the waveform can be optimized without adding additional resonance peaks, thereby improving the device performance. And to verify the double resonance peak response of the SAW resonator 20, the applicant Figure 5 simulates the SAW resonator 20 shown, and then obtains Figure 13 the admittance response shown. And it can be clearly seen from Figure 13 that the two waveforms of the red curve dB(Y(1,1)) form better resonance peaks.

[0078] Based on the same concept, this embodiment also provides a dual-bandpass SAW filter. Please refer to Figure 14 . The dual-bandpass SAW filter includes a plurality of resonators. Among them, some of the resonators are connected in series to form a series circuit; the remaining resonators are connected in parallel to the series circuit and form a parallel circuit; and at least one of the resonators in the series circuit is the above-mentioned SAW resonator 20; at least one of the resonators in the parallel circuit is the above-mentioned SAW resonator 20, so that the dual-bandpass SAW filter can simultaneously open two bandpasses. Optionally, all the resonators in the dual-bandpass SAW filter are the above-mentioned SAW resonators 20.

[0079] For example Figure 14 and Figure 15 shown, the dual-bandpass SAW filter includes five resonators, and all the resonators are the above-mentioned SAW resonators 20. Among them, three SAW resonators 20 are connected in series in sequence to form the series circuit; and the two endpoints of the series circuit are respectively the input end and the output end of the dual-bandpass SAW filter. The remaining two SAW resonators 20 are connected in parallel to form the parallel circuit. And one end of each SAW resonator 20 in the parallel circuit is connected to the connection end of two adjacent SAW resonators 20 in the series circuit, and the other end of each SAW resonator 20 in the parallel circuit is grounded. Since each SAW resonator 20 can excite two resonance peak responses, in Figure 14 the topological structure shown, the series circuit forms a double resonance peak response, and the parallel circuit can form another double resonance peak response. Then, by combining the two, dual-bandpass filtering can be achieved.

[0080] Exemplarily, assume that the three SAW resonators 20 in the series circuit are the same and are Figure 5 a kind of SAW resonator 20 as shown, and the two SAW resonators 20 in the parallel circuit are the same and are also Figure 5 a kind of SAW resonator 20 as shown; then, by simulating the dual-band SAW filter composed of these five SAW resonators 20, the Figure 15 transmission response of the dual-band SAW filter as shown can be obtained. According to Figure 15 it can be known that the red curve dB(Y(1,1)) is the admittance response of the SAW resonators 20 in parallel in the dual-band SAW filter, the blue curve dB(Y(2,2)) is the admittance response of the SAW resonators 20 in series in the dual-band SAW filter, and the pink curve dB(S(4,3)) is the overall transmission response of the dual-band SAW filter. Compared with the corresponding Figure 2 and Figure 4 prior art, the dual-band SAW filter provided in this embodiment only requires half the number of SAW resonators 20 to obtain the same dual-band output response. It not only greatly reduces the area size of the device, facilitates the miniaturization development of the device, and reduces costs, but also is easier to achieve high isolation. Moreover, based on the fine-tuning of the period length of the electrodes 2010 in each resonance region, the passband ripple of the dual-band SAW filter can be weakened, and the roll-off coefficient can be strengthened, which is beneficial to improving the overall performance of the device.

[0081] In summary, this embodiment provides a SAW resonator and a dual-band SAW filter. Among them, the SAW resonator 20 makes the maximum period length of the electrodes 2010 in the middle resonance region less than the minimum period length of the electrodes 2010 in the remaining resonance regions by reducing the period length of the electrodes 2010 in the middle resonance region, and realizes the simultaneous excitation of two resonance peak responses. And the dual-band SAW filter composed of the SAW resonators 20 based on dual resonance peaks can not only form a dual-band transmission effect, but also compared with the existing SAW filters, only half the number of SAW resonators 20 need to be used, so that the device area of the dual-band SAW filter is greatly reduced, which is beneficial to the miniaturization development of the device and reduces costs. In addition, the dual-band SAW filter is also easier to achieve high isolation, which is beneficial to improving the device performance. Furthermore, the SAW resonator 20 provided in this embodiment can suppress the spurious effect and optimize the waveform without increasing the resonance peak by fine-tuning the period length of the electrodes 2010 in each resonance region, so that the passband ripple of the dual-band SAW filter is weakened, the roll-off coefficient is strengthened, and the overall performance of the device is improved.

[0082] In addition, it should be recognized that although the present invention has been disclosed above in preferred embodiments, the above embodiments are not intended to limit the present invention. For any person skilled in the art, without departing from the scope of the technical solution of the present invention, many possible changes and modifications can be made to the technical solution of the present invention by using the technical content disclosed above, or it can be modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A SAW resonator, characterized in that: include: A piezoelectric substrate and an interdigital transducer located on the piezoelectric substrate; wherein, The interdigital transducer comprises a plurality of electrodes arranged in an interlaced manner, and at least some of the electrodes have different period lengths; Furthermore, the piezoelectric substrate is divided into a plurality of resonance regions, and the maximum period length of the electrodes in the middle resonance region is smaller than the minimum period length of the electrodes in the remaining resonance regions, so as to be able to excite two resonance peak responses.

2. The SAW resonator according to claim 1, characterized in that: In at least part of the resonance regions, the period lengths of the electrodes located in the same resonance region are the same.

3. The SAW resonator according to claim 2, characterized in that: The period lengths of the electrodes in the middle resonance zone are the same; and the period lengths of the electrodes in the remaining resonance zones are the same; and the period lengths of the electrodes satisfy the following formula: 0.92P1≤P2≤0.96P1 Wherein, P1 is the period length of the electrodes of the remaining resonance zones; P2 is the period length of the electrodes of the resonance zone located in the middle.

4. The SAW resonator according to claim 2, characterized in that: The plurality of resonance regions are distributed linearly, and in two resonance regions adjacent to the resonance region in the middle, the period lengths of the electrodes in the same resonance region are the same; as well as, The difference P between the period lengths of the electrodes of the two resonance regions adjacent to the resonance region located in the middle D1 Satisfies the following formula: |P D1 |≤3%P3; or |P D1 |≤3%P4 Among them, P3 is the period length of the electrode of one of the two resonance regions adjacent to the resonance region located in the middle; P4 is the period length of the electrode of the other of the two resonance regions adjacent to the resonance region located in the middle.

5. The SAW resonator according to claim 4, characterized in that In the remaining resonance regions, the period lengths of the electrodes in the same resonance region are the same, and the difference P between the period lengths of the electrodes in two adjacent resonance regions is D2 Satisfies the following formula: |P D2 |≤3%P5 Wherein, P5 is the period length of the electrode of one of the two adjacent resonance zones in the remaining resonance zones that is close to the resonance zone located in the middle.

6. The SAW resonator according to claim 1 or 2, characterized in that: Each of the resonance regions includes a plurality of the electrodes; and in at least some of the resonance regions, the period lengths of at least some of the electrodes in the same resonance region are different.

7. The SAW resonator according to claim 6, characterized in that When the period lengths of at least some of the electrodes in the resonance region are different, an electrode located at the side of the resonance region is used as a reference electrode, and the period lengths of the electrodes in the resonance region satisfy the following formula: |P D3 |≤3%P6 Wherein, P6 is the period length of the reference electrode; P D3 is the difference between the period lengths of the reference electrode and any other electrode in the resonance region.

8. The SAW resonator according to claim 1, characterized in that: The number of the electrodes in the middle resonance zone ranges from 5 to 30, and the total number of the electrodes in the remaining resonance zones is greater than twice the number of the electrodes in the middle resonance zone.

9. The SAW resonator according to claim 1, characterized in that: The SAW resonator further comprises a plurality of reflection gratings; the plurality of reflection gratings are located on the piezoelectric substrate and are arranged close to the side edge of the interdigital transducer.

10. A dual-bandpass SAW filter, characterized in that: It comprises a plurality of resonators; some of the resonators are connected in series to form a series circuit; the remaining resonators are connected in parallel to the series circuit to form a parallel circuit; wherein, At least one of the resonators in the series circuit is a SAW resonator as described in any one of claims 1 to 9; at least one of the resonators in the parallel circuit is a SAW resonator as described in any one of claims 1 to 9, so that the dual-bandpass SAW filter can open two bandpasses at the same time.

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