KR102031717B1 - Compact surface acoustic wave filter - Google Patents

Abstract

An embodiment of the invention includes at least two or more Interdigital Transducers (IDTs) disposed on a piezoelectric plate, and two identical first single channel grating reflectors and a second single channel grating reflector, wherein the IDTs and the Single channel grating reflectors are disposed in one elastic channel, and the IDTs are arranged in line between the first single channel grating reflector and the second single channel grating reflector, the electrodes of the IDTs and the single channel grating reflector These electrodes provide a compact surface acoustic wave filter, having the same thickness and arranged in parallel with each other at regular intervals.

Description

Compact Surface Acoustic Wave Filter {COMPACT SURFACE ACOUSTIC WAVE FILTER}

The present invention relates to a surface acoustic wave filter (hereinafter referred to as a SAW filter), and more particularly to a compact surface acoustic wave filter having a small size to have a small input loss.

In general, a SAW device is used as a filter that forms a comb-shaped transducer with a metal electrode on a piezoelectric substrate and passes an electric field to delay electromagnetic waves or pass only a specific frequency signal.

The SAW filter has an interdigital transducer (IDT) installed at each of the input terminal and the output terminal. When an electrical signal is applied to the piezoelectric object at the input terminal, the SAW filter is converted into a mechanical signal. By converting the output, a specific frequency band is passed and the remaining frequency bands are blocked.

At this time, particularly important among the performance of the SAW filter is to have a small insertion loss in the passband, and to have a high attenuation outside the passband. Therefore, even if they have the same passband, the smaller the insertion loss, the better the performance of the filter. Therefore, it is important to reduce the insertion loss.

The background art described above is technical information possessed by the inventors for the derivation of the present invention or acquired in the derivation process of the present invention, and is not necessarily known technology disclosed to the general public before the present application.

Korean Unexamined Patent Publication No. 10-2005-0091552

It is an object of the present invention to provide a compact surface acoustic wave filter having a low input loss using a coupled resonator filter (CRF).

An embodiment of the invention includes at least two or more Interdigital Transducers (IDTs) disposed on a piezoelectric plate, and two identical first single channel grating reflectors and a second single channel grating reflector, wherein the IDTs and the Single channel grating reflectors are disposed in one elastic channel, and the IDTs are arranged in line between the first single channel grating reflector and the second single channel grating reflector, the electrodes of the IDTs and the single channel grating reflector These electrodes provide a compact surface acoustic wave filter, having the same thickness and arranged in parallel with each other at regular intervals.

In this case, each of the IDTs includes two busbars, and the busbars may be perpendicular to the electrodes of the IDTs and may be located outside the elastic channel.

In this case, the single channel grating reflectors include two or more electrodes, the electrodes of the IDTs are equal in length to each other, the electrodes of the single channel grating reflectors are the same in length and longer than the electrodes of the IDTs. Can be.

The intermediate grating reflector may further include an intermediate grating reflector disposed on the single channel on the piezoelectric plate, and the electrodes of the intermediate grating reflector may have the same thickness as those of the electrodes of the single channel grating reflectors and be disposed in parallel with each other.

In this case, the IDTs are configured of the same first sub IDT set and the second sub IDT set, each of the sub IDT sets includes two or more IDTs, and the intermediate grating reflector is disposed in a line between the sub IDT sets. Can be.

In this case, the electrodes of the IDTs, the electrodes of the single channel grating reflectors and the electrodes of the intermediate grating reflector may be disposed at regular intervals from each other.

In this case, the intermediate grating reflector may include as many electrodes as the inverse of the grating reflection coefficient.

In this case, the busbars may be thicker than the electrodes of the IDTs, the electrodes of the intermediate grating reflector and the electrodes of the single channel grating reflectors.

In this case, two bus bars positioned symmetrically from a central axis among the bus bars positioned on the same side with respect to the elastic channel are connected to an input terminal, and the central axis is perpendicular to the elastic channel, and the first single channel grating reflector and It may have the same distance from the second single channel grating reflector.

At this time, the desired resonant frequency band of the elastic channel may include 452MHz.

The compact surface acoustic wave resonator according to an embodiment of the present invention can reduce the input loss by reducing the size rather than simply connecting the CRFs.

1 is a diagram illustrating a structure of a coupled resonator filter (CRF) according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a structure of a surface acoustic wave filter in which two coupling resonance filters shown in FIG. 1 are electrically connected in parallel.
3 is a graph illustrating a simulation result of input loss of a surface acoustic wave filter in which two coupling resonance filters are electrically connected in parallel.
4 is an enlarged graph of a neighborhood of a pass band in the graph illustrated in FIG. 3.
5 is a graph illustrating simulation results of input loss of a surface acoustic wave filter in which two coupling resonance filters are electrically connected in parallel according to the number of electrodes of a grating reflector.
6 is an enlarged graph of a neighborhood of a pass band in the graph illustrated in FIG. 5.
7 is a view showing the structure of a compact surface acoustic wave filter according to an embodiment of the present invention.
8 is a view showing the structure of a compact surface acoustic wave filter according to an embodiment of the present invention.
9 is a view showing the structure of a compact surface acoustic wave filter according to an embodiment of the present invention.
10 is a graph showing the results of measuring the input loss and the simulation results of the compact surface acoustic wave filter according to an embodiment of the present invention.
11 is a view showing the structure of a compact surface acoustic wave filter according to an embodiment of the present invention.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. Effects and features of the present invention, and methods of achieving them will be apparent with reference to the embodiments described below in detail together with the drawings. Here, the repeated description, well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention, and detailed description of the configuration will be omitted. Embodiments of the present invention are provided to more completely describe the present invention to those skilled in the art. Accordingly, the shape and size of elements in the drawings may be exaggerated for clarity.

However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms by selectively combining all or some of the embodiments. In the following embodiments, the terms first, second, etc. are used for the purpose of distinguishing one component from other components rather than a restrictive meaning. In addition, singular forms also include plural forms unless the context clearly indicates otherwise. In addition, the terms including or have means that the features or components described in the specification are present, and does not preclude the possibility of adding one or more other features or components.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, and the same or corresponding components will be denoted by the same reference numerals, and redundant description thereof will be omitted. .

1 is a diagram illustrating a structure of a coupled resonator filter (CRF) 100 according to an embodiment of the present invention.

Referring to FIG. 1, a two-port coupled resonance filter 100 according to an embodiment of the present invention includes two IDTs 101 and 102 and two identical single channel grating reflectors 103 and 104. piezoelectric substrate). Here, the IDTs 101, 102 and the single channel grating reflectors 103, 104 are arranged in one elastic channel.

In this case, the single channel grating reflectors 103 and 104 may include two or more electrodes.

In this case, the electrodes of the IDTs 101 and 102 and the electrodes of the single channel grating reflectors 103 and 104 have the same thickness, are parallel to each other, and may be disposed at the same interval from each other.

In this case, the electrodes of the IDTs 101 and 102 have the same length, and the electrodes of the single channel grating reflectors 103 and 104 have the same length and are longer than the electrodes of the IDTs 101 and 102. Can be.

At this time, the busbars of the IDTs 101 and 102 may be perpendicular to the IDT electrodes, and may be thicker than the IDT electrodes.

At this time, the input terminal 105 and the output terminal 106 may be connected to two bus bars diagonally across the elastic channel. The remaining two busbars may be grounded.

Typically, the coupling resonant filter 100 is small in size but may not be suitable for applications at high power levels.

2 is a diagram illustrating a structure of the surface acoustic wave filter 200 in which two coupling resonance filters shown in FIG. 1 are electrically connected in parallel.

Referring to FIG. 2, the surface acoustic wave filter 200 electrically connecting two coupled resonance filters shown in FIG. 1 to four IDTs 201, 202, 203, and 204 and the same four single channel grating reflectors may be used. 205, 206, 207, and 208 are disposed on the piezoelectric plate. Here, IDTs 201, 202, 203, 204 and single channel grating reflectors 205, 206, 207, 208 are disposed in one elastic channel 211.

Here, although FIG. 2 merely electrically connects the two coupling resonance filters in parallel, more coupling resonance filters may be connected in parallel to one elastic channel in order to reduce input loss.

In this case, the single channel grating reflectors 205, 206, 207, and 208 may include two or more electrodes.

In this case, the electrodes of the IDTs 201, 202, 203, and 204 have the same length, and the electrodes of the single channel grating reflectors 205, 206, 207, and 208 have the same length, and the IDTs 201, 202, The length may be longer than the electrodes of 203 and 204.

In this case, the electrodes of the IDTs 201, 202, 203, and 204 and the electrodes of the single channel grating reflectors 205, 206, 207, and 208 have the same thickness and may be disposed in parallel to each other.

In this case, the two single channel grating reflectors 206 and 207 positioned between the IDTs 201, 202, 203 and 204 may be disposed to have a gap of a predetermined distance from each other. And the electrodes of the IDTs 201, 202, 203, 204 and the electrodes of the single channel grating reflectors 205, 206, 207, 208 except for the gap between the single channel grating reflectors 206, 207. They may be arranged at equal intervals from each other.

In this case, the busbars of the IDTs 201, 202, 203, and 204 may be perpendicular to the IDT electrodes, and may be thicker than the IDT electrodes.

At this time, two inner busbars of the busbars located on the same side with respect to the elastic channel 211 are connected to the input terminal 209, and two outer busbars of the busbars located on the opposite side thereof are output terminals 210. It can be connected with. The remaining busbars can then be grounded. Here, the inner busbars are adjacent to the single channel grating reflectors 206 and 207 located between the IDTs, and the outer busbars are adjacent to the single channel grating reflectors 205 and 208 located outside the IDTs. It can mean a bus bar.

As such, when two coupling resonance filters are electrically connected in parallel, the volume becomes large due to the distance between the coupling resonance filters.

3 is a graph illustrating a simulation result of input loss of a surface acoustic wave filter in which two coupling resonance filters are electrically connected in parallel.

Referring to FIG. 3, the surface acoustic wave filter in which two coupling resonance filters are electrically connected in parallel has a pass band of about 885 MHz. And, the loss of input is greater when acoustic interaction occurs (dotted and dashed lines) than when acoustic interaction does not occur (solid lines).

In this case, the acoustic interaction between the coupling resonance filters becomes smaller as the number of electrodes of the grating reflectors increases. In particular, the acoustic interaction becomes small when the number of electrodes of the grating reflectors is larger than the inverse of the grating reflection coefficient κ. Here, the grating reflection coefficient represents the reflectance for a single electrode of the grating reflector.

Therefore, it is desired to reduce the input loss of the surface acoustic wave filter by reducing or eliminating acoustic interaction.

4 is an enlarged graph of a neighborhood of a pass band in the graph illustrated in FIG. 3.

Referring to FIG. 4, the input loss is greater in the case where acoustic interaction takes place at about 875 MHz to 900 MHz that is near the pass band (dotted and dashed lines) than in the case where no acoustic interaction occurs (solid line).

Therefore, it is desired to reduce the input loss of the surface acoustic wave filter by reducing or eliminating acoustic interaction.

FIG. 5 is a graph illustrating simulation results of input loss of a surface acoustic wave filter in which two coupling resonance filters are electrically connected in parallel, according to the number of electrodes of a grating reflector.

Referring to FIG. 5, the surface acoustic wave filter in which two coupling resonance filters are electrically connected in parallel has a pass band of about 885 MHz. In addition, the dashed-dotted line shows the result of simulating input loss in the case of 40 electrodes of a grating reflector, and the solid line shows the result of simulating input loss in the case of four grating reflectors.

At this time, when the grating reflection coefficient is 0.1, the input loss is smaller in and out of the band than when the electrode of the grating reflector is 40 (one dashed line) and when the electrode of the grating reflector is 4 (solid line). That is, since the inverse of the grating reflection coefficient is 10, in the case of 40 electrodes of the grating reflector, the acoustic interaction is small and the input loss is small. On the other hand, in the case of four electrodes of the grating reflector, the acoustic interaction is large and the input loss is large. That is, when there are few electrodes of the grating reflector, a large part of the surface acoustic wave energy is lost to the outside from the coupling resonant filters, and when there are many electrodes of the grating reflector, the adjacent coupling resonant filter acts as an efficient reflector so that the surface acoustic wave energy The loss of less.

Thus, by increasing the electrodes of the grating reflector, the acoustic interaction can be reduced, thereby reducing the input loss of the surface acoustic wave filter.

6 is an enlarged graph of a neighborhood of a pass band in the graph illustrated in FIG. 5.

Referring to FIG. 6, the input loss is smaller when the grating reflector has 40 electrodes (one dashed line) at about 875 MHz to 900 MHz near the pass band as compared with the 4 electrodes of the grating reflector (solid line).

Thus, by increasing the electrodes of the grating reflector, the acoustic interaction can be reduced, thereby reducing the input loss of the surface acoustic wave filter.

7 is a view showing the structure of a compact surface acoustic wave filter 700 according to an embodiment of the present invention.

Referring to FIG. 7, the compact surface acoustic wave filter 700 according to an embodiment of the present invention may include four IDTs 701, 702, 703, and 704, two identical single channel grating reflectors 705, and 707. An intermediate grating reflector 706 is disposed on the piezoelectric plate. Here, IDTs 701, 702, 703, 704, single channel grating reflectors 705, 707 and intermediate grating reflector 706 are disposed in one elastic channel 710.

In this case, the IDTs 701, 702, 703, and 704 may be configured of two sub IDT sets that are identical to each other. That is, the IDTs included in the first sub IDT set may be two IDTs 701 and 702, and the IDTs included in the second sub IDT set may be two IDTs 703 and 704. In this case, the IDT 701 and the IDT 703 are the same, and the IDT 702 and the IDT 704 are the same. And, the sub IDT set may be composed of two or more IDTs. For example, each sub IDT set may include 2, 3, 5 or more IDTs.

In this case, the intermediate grating reflectors 706 may be arranged in series between the sub IDT sets. That is, the compact surface acoustic wave filter 700 according to an embodiment of the present invention is a “single channel grating reflector 705-sub IDT set-intermediate grating reflector 706-sub IDT set-single channel grating reflector 707”. Structure or “single channel grating reflector 705-IDTs 701, 702-intermediate grating reflector 706-IDTs 703, 704-single channel grating reflector 707” in series. have.

Here, although the compact surface acoustic wave filter 700 of FIG. 7 simply includes four IDTs, the present invention is not limited thereto and may include a larger number of IDTs. In addition, although the compact surface acoustic wave filter 700 of FIG. 7 includes an intermediate grating reflector 706, the present invention is not limited thereto and may include an IDT instead of the intermediate grating reflector 706.

In addition, in the compact surface acoustic wave filter 700 according to the exemplary embodiment of the present invention, single channel grating reflectors (see 206 and 207 of FIG. 2) located between IDTs are connected to one intermediate grating. It can be seen as forming a reflector 706. In this case, the compact surface acoustic wave filter 700 is smaller in size by the gap between two single channel grating reflectors (206 and 207 of FIG. 2) compared to the surface acoustic wave filter 200 of FIG. 2.

In this case, the single channel grating reflectors 705 and 707 may include two or more electrodes.

In this case, the intermediate grating reflector 706 may include two or more electrodes. In particular, the intermediate grating reflector 706 may include as many electrodes as the inverse of the grating reflection coefficient κ. In this case, the impedance matrix Y of the compact surface acoustic wave filter 700 which is electrically connected in parallel with the two coupling resonance filters according to the embodiment of the present invention is equal to twice the impedance matrix y of each coupling resonance filter. same. That is, the impedance matrix (Y) of a filter consisting of "single channel grating reflector-sub IDT set-middle grating reflector-sub IDT set-single channel grating reflector" is referred to as "single channel grating reflector-sub IDT set-middle grating reflector". The relationship between the impedance matrix y of the configured filter and Equation 1 below is satisfied.

[Equation 1]

In this case, the electrodes of the IDTs 701, 702, 703, and 704 are the same in length, the electrodes of the single channel grating reflectors 705 and 707 and the electrodes of the intermediate grating reflector 706 are equal in length to each other. The length may be longer than the electrodes of fields 701, 702, 703, 704.

At this time, the electrodes of the IDTs 701, 702, 703, 704, the electrodes of the single channel grating reflectors 705, 707 and the electrodes of the intermediate grating reflector 706 have the same thickness and are arranged in parallel with each other. Can be.

In this case, the electrodes of the IDTs 701, 702, 703, and 704, the electrodes of the single channel grating reflectors 705 and 707, and the electrodes of the intermediate grating reflector 706 may be disposed at the same distance from each other.

At this time, the bus bars of the IDTs 701, 702, 703, and 704 are perpendicular to the IDT electrodes, and may have a thickness greater than that of the IDT electrodes.

At this time, two inner busbars of the busbars located on the same side with respect to the elastic channel 710 are connected to the input terminal 708, and two outer busbars of the busbars located on the opposite side thereof are output terminals 709. It can be connected with. The remaining busbars can then be grounded. Here, the inner busbars are busbars adjacent to the intermediate grating reflector 706 located between the IDTs, and the outer busbars will mean busbars adjacent to the single channel grating reflectors 705 and 707 located outside the IDTs. Can be. Alternatively, two busbars symmetrically located from the center axis among the busbars located on the same side with respect to the elastic channel 710 are connected to the input terminal 708 and symmetrical from the center axis among the busbars located on the opposite side thereof. Two busbars may be connected to the output terminal 709. Here, the central axis may mean an axis perpendicular to the elastic channel 710 and having the same distance from the first single channel grating reflector 705 and the second single channel grating reflector 707.

At this time, the desired resonant frequency band of the elastic channel 710 may include 452MHz.

8 is a view showing the structure of a compact surface acoustic wave filter 800 according to an embodiment of the present invention.

Referring to FIG. 8, the compact surface acoustic wave filter 800 according to an embodiment of the present invention includes four IDTs 801, 802, 803, and 804, two identical single channel grating reflectors 805, 807, and An intermediate grating reflector 806 is disposed on the piezoelectric plate. Here, IDTs 801, 802, 803, 804, single channel grating reflectors 805, 807 and intermediate grating reflector 806 are disposed in one elastic channel 810. And, it is configured in line with the structure of "single channel grating reflector 805-IDTs 801, 802-intermediate grating reflector 806-IDTs 803, 804-single channel grating reflector 807." Can be.

In this case, the electrodes of the IDTs 801, 802, 803, and 804, the electrodes of the single channel grating reflectors 805 and 807 and the electrodes of the intermediate grating reflector 806 may be disposed at the same interval from each other.

The compact surface acoustic wave filter 800 shown in FIG. 8 is different from the number of electrodes of the intermediate grating reflector 806 when compared with the compact surface acoustic wave filter 700 shown in FIG. 7. That is, the input terminal 708 of FIG. 7 corresponds to the input terminal 808 of FIG. 8, and the output terminal 709 of FIG. 7 corresponds to the output terminal 809 of FIG. 8. Here, the compact surface acoustic wave filter 800 shown in FIG. 8 increases the number of electrodes of the intermediate grating reflector 806 to 6, thereby reducing input loss compared to the compact surface acoustic wave filter 700 shown in FIG.

9 is a view showing the structure of a compact surface acoustic wave filter 900 according to an embodiment of the present invention.

9, a compact surface acoustic wave filter 900 according to an embodiment of the present invention includes five IDTs 901, 902, 903, 904, 905 and two identical single channel grating reflectors 906, 907. ) Is placed on the piezoelectric plate. Here, IDTs 901, 902, 903, 904, 905 and single channel grating reflectors 906, 907 are disposed in one elastic channel 910. And, it may be configured to be connected in series in the structure of "single channel grating reflector 906-IDTs 901, 902, 903, 904, 905-single channel grating reflector 907".

The compact surface acoustic wave filter 900 shown in FIG. 9 includes an IDT 903 instead of the intermediate grating reflector 706 when compared to the compact surface acoustic wave filter 700 shown in FIG. same. That is, the input terminal 708 of FIG. 7 corresponds to the input terminal 908 of FIG. 9, and the output terminal 709 of FIG. 7 corresponds to the output terminal 909 of FIG. 9.

In this case as well, the electrodes of the IDTs 901, 902, 903, 904, 905 and the electrodes of the single channel grating reflectors 906, 907 are parallel to one another and are arranged at regular intervals.

10 is a graph showing the results of measuring the input loss and the simulation results of the compact surface acoustic wave filter according to an embodiment of the present invention.

In detail, FIG. 10 is a graph of an input loss for a compact surface acoustic wave filter according to an embodiment of the present invention in which a desired frequency of an elastic channel is 452 MHz. For the measurement, a compact surface acoustic wave filter in a 3x3 mm Surface-Mount Device (SMD) package was used. The compact surface acoustic wave filter is an electrically parallel connection of two coupled resonance filters consisting of five IDTs.

Referring to FIG. 10, it can be seen that a simulation result of input loss (solid line) and a measurement result of input loss (dashed line) of the compact surface acoustic wave filter according to an embodiment of the present invention are entirely in agreement. In particular, the input loss in the pass band shows little difference between the simulation result (solid line) and the measurement result (dotted line). Therefore, the compact surface acoustic wave filter according to the present invention can be seen that the effect is sufficiently confirmed by comparing the simulation results and the measurement results.

Therefore, as described above, the compact surface acoustic wave filter according to the embodiment of the present invention can reduce the input loss by combining two or more coupling resonance filters and reducing the size thereof.

11 is a view showing the structure of a compact surface acoustic wave filter 1100 according to an embodiment of the present invention.

In FIG. 11, the red dots 1101 and 1102 are connected to the input terminal and the output terminal, respectively, and the order thereof may be changed. The blue dots 1103 mean that they are grounded.

Particular implementations described in the present invention are examples, which in no way limit the scope of the present invention. For brevity of description, descriptions of conventional electronic configurations, control systems, software, and other functional aspects of the systems may be omitted. In addition, the connection or connection members of the lines between the components shown in the drawings are illustrative of the functional connection and / or physical or circuit connections as an example, in the actual device replaceable or additional various functional connections, physical It may be represented as a connection, or circuit connections. In addition, unless specifically mentioned, such as "essential", "important" may not be a necessary component for the application of the present invention.

Therefore, the spirit of the present invention should not be limited to the above-described embodiments, and the scope of the spirit of the present invention is defined not only in the claims below, but also in the ranges equivalent to or equivalent to those of the claims. Will belong to.

100: coupled resonance filter
101, 102: IDT 103, 104: grating reflector
200: surface acoustic wave filter
201, 202, 203, 204: IDT 205, 206, 207, 208: grating reflector
211: elastic channel
700: compact surface acoustic wave filter
701, 702, 703, 704: IDT 705, 707: single channel grating reflectors
706: intermediate grating reflector 710: elastic channel
800: compact surface acoustic wave filter
801, 802, 803, 804: IDT 805, 807: single channel grating reflector
806: intermediate grating reflector 810: elastic channel
900: compact surface acoustic wave filter
901, 902, 903, 904, 905: IDT 906, 907: single channel grating reflector
910: elastic channel
1100: compact surface acoustic wave filter

Claims (10)

At least two or more interdigital transducers (IDTs) disposed on the piezoelectric plate, and a first single channel grating reflector, a second single channel grating reflector, and an intermediate grating reflector,
The IDTs and the single channel grating reflectors are disposed on the piezoelectric plate in either direction,
The IDTs are arranged in line between the first single channel grating reflector and the second single channel grating reflector,
The electrodes of the IDTs and the electrodes of the single channel grating reflectors are equal in thickness and are arranged parallel to each other at regular intervals,
And the intermediate grating reflector comprises as many electrodes as an inverse of the grating reflection coefficient. The method according to claim 1,
The IDTs each comprising two busbars,
And said busbars are perpendicular to the electrodes of said IDTs. The method according to claim 2,
The single channel grating reflectors comprise two or more electrodes,
The electrodes of the IDTs are equal in length to each other,
And the electrodes of the single channel grating reflectors are equal in length to each other and longer in length than the electrodes of the IDTs. The method according to claim 3,
And the electrodes of the intermediate grating reflector are the same thickness as the electrodes of the single channel grating reflectors and are arranged parallel to each other. The method according to claim 4,
The IDTs are composed of the same first sub IDT set and the second sub IDT set,
The sub IDT sets each include two or more IDTs,
And said intermediate grating reflector is disposed between said first sub IDT set and said second sub IDT set. The method according to claim 5,
And the electrodes of the IDTs, the electrodes of the single channel grating reflectors and the electrodes of the intermediate grating reflector are arranged at regular intervals from each other. delete The method according to claim 6,
And the busbars are thicker in the thickness of the metal film than the electrodes of the IDTs, the electrodes of the intermediate grating reflector and the electrodes of the single channel grating reflectors. The method according to claim 8,
Two busbars symmetrically located from the central axis among the busbars located on the same side with respect to the elastic channel on the piezoelectric plate are connected to the input terminal
Wherein said central axis is perpendicular to said elastic channel and has the same distance from said first single channel grating reflector and said second single channel grating reflector. The method according to claim 9,
The resonant frequency band of the elastic channel comprises a 452MHz, compact surface acoustic wave filter.