CN116032238A - Interdigital transducer and honeycomb structure surface acoustic wave filter - Google Patents

Abstract

The present invention relates to the technical field of surface acoustic wave filters, in particular to an interdigital transducer and a honeycomb structure surface acoustic wave filter; the interdigital transducer includes a first bus bar, a second bus bar, and a reflection grid And the interdigitated electrodes arranged between the first bus bar and the second bus bar; the first interdigitated electrodes and the second interdigitated electrodes are surrounded by the first bus bar, the second bus bar and the reflective grid to form a positive six Interdigital transducer with polygonal structure. The current connection can be made on the bus bar on any side of the hexagon, thereby reducing the metal winding structure, which is beneficial to reducing the area of the surface acoustic wave layout and reducing the product cost. And because the interdigital transducer is a regular hexagon, it will form an included angle relative to the main part, which can reflect sound waves, reduce bus bar leakage waves, and improve the performance index of the surface acoustic wave filter.

Description

An interdigital transducer and a honeycomb structure surface acoustic wave filter

technical field

The invention relates to the technical field of surface acoustic wave filters, in particular to an interdigital transducer and a honeycomb structure surface acoustic wave filter.

Background technique

With the continuous development of communication technology, the demand for miniaturization of devices in mobile communication equipment is becoming more and more urgent, especially in the aspect of SAW filters; SAW filters are mostly used in terminal equipment; in order to reduce SAW The volume of the filter, reducing the plane area of the surface acoustic wave filter is very important, and how to ensure the power capacity and electrical performance, to minimize the plane area of the surface acoustic wave filter has always been an important research direction .

The surface acoustic wave filter converts the electrical signal on the interdigital transducer (IDT: Interdigitaltransducer) into mechanical energy through the inverse piezoelectric effect of the piezoelectric material, and uses the piezoelectric effect on the other side of the interdigital transducer to convert the mechanical energy It is converted into an electrical signal to achieve frequency selection; the interdigital transducer of a conventional surface acoustic wave filter is generally composed of a rectangular structure (see Figure 1). Due to structural limitations, there are many special restrictions on the layout, resulting in an excessively large circuit area ; If the area of the interdigital transducer is reduced, problems such as reduced power tolerance and reduced electrical performance will occur.

Contents of the invention

In order to solve the above-mentioned problems in the prior art, the present invention provides an interdigital transducer and a surface acoustic wave filter with a honeycomb structure, which can at least reduce the circuit area without affecting the power tolerance and electrical performance.

An interdigital transducer comprising:

Piezoelectric substrate;

Two reflective grids;

a first bus bar and a second bus bar arranged at intervals on the piezoelectric substrate;

A plurality of first interdigitated electrodes and a plurality of second interdigitated electrodes are alternately arranged between the first bus bar and the second bus bar;

The first interdigitated electrode is led out from the first bus bar and extends toward the second bus bar, and the extension end of the first interdigitated electrode leaves a gap with the second bus bar;

The second interdigitated electrode is led out from the second bus bar and extends toward the first bus bar, and the extension end of the second interdigitated electrode has a gap with the first bus bar;

The first bus bar, the second bus bar and the reflective grid enclose the first interdigital electrode and the second interdigital electrode to form an interdigital transducer with a regular n-gon structure, where n≥6 and is 2 Integer multiples.

The present invention arranges the interdigital transducer with regular n-gon structure, and n≥6, which is an integer multiple of 2, so that current connection can be made on the bus bar on any side of the n-gon, thereby reducing the metal The wire-wound structure is conducive to reducing the area of the surface acoustic wave layout and reducing product costs.

And because the interdigital transducer is a regular n-gon, it will form an included angle relative to the main part, which can reflect sound waves, reduce bus bar leakage waves, and improve the performance index of the surface acoustic wave filter.

Preferably, said n is equal to 6. That is, the present invention preferably adopts an interdigital transducer with a regular hexagonal structure, which can be used for current connection on the bus bar on any side, reducing the metal winding structure, which is beneficial to reducing the area of the surface acoustic wave layout and reducing product costs. and because the interdigital transducer is a regular hexagon, the angle formed between adjacent sides of the regular hexagon can reflect sound waves, reduce bus bar leakage waves, and improve the performance index of the surface acoustic wave filter.

Preferably, any one of the bus bars is connected to a reflection grid, and a gap is reserved between another bus bar and another reflection grid.

Preferably, the two bus bars are respectively connected to one of the reflective grids.

Preferably, there is a gap between the two bus bars and the reflective grid.

A surface acoustic wave filter with a honeycomb structure, comprising:

a set of series resonators and a set of parallel resonators connected between the input and output of the SAW filter;

The resonator adopts the structure of the interdigital transducer described in the present invention.

Preferably, the resonators in the series resonator group and the parallel resonator group are arranged in a honeycomb shape on the substrate.

Preferably, the series resonator group includes a first series resonator unit, a second series resonator unit, a third series resonator unit and a fourth series resonator unit connected in series in sequence;

The parallel resonator unit includes:

The input end is connected to the first parallel resonator unit between the first series resonator unit and the second series resonator unit, and the output terminal signal of the first parallel resonator unit is grounded;

The input end is connected to the second parallel resonator unit between the second series resonator unit and the third series resonator unit, and the output terminal signal of the second parallel resonator unit is grounded;

The input terminal is connected to the third parallel resonator unit between the third series resonator unit and the fourth series resonator unit, and the signal output terminal of the third parallel resonator unit is grounded.

Preferably, each of the first series resonator unit, the second series resonator unit and the third series resonator unit includes two resonators connected in series.

Preferably, the fourth series resonator unit includes one resonator.

Preferably, each of the first parallel resonator unit and the third parallel resonator unit includes one resonator.

Preferably, the second parallel resonator unit includes two series resonators.

The beneficial effects of the present invention at least include:

The present invention arranges the interdigital transducer with regular n-gon structure, and n≥6, which is an integer multiple of 2, so that current connection can be made on the bus bar on any side of the n-gon, thereby reducing the metal The wire-wound structure is conducive to reducing the area of the surface acoustic wave layout and reducing product costs.

And because the interdigital transducer is a regular n-gon, it will form an included angle relative to the main part, which can reflect sound waves, reduce bus bar leakage waves, and improve the performance index of the surface acoustic wave filter.

Description of drawings

FIG. 1 is a schematic diagram of the overall composition of a conventional interdigital transducer provided by the present invention.

Fig. 2 is a schematic diagram of the overall composition of the interdigital transducer provided by the present invention.

Fig. 3 is a schematic diagram of the circuit structure of an embodiment of the surface acoustic wave filter provided by the present invention.

FIG. 4 is a schematic layout diagram of a conventional IDT provided by the present invention.

FIG. 5 is a schematic diagram of the layout of the interdigital transducer provided by the present invention.

FIG. 6 is a schematic structural diagram of various bus bars of the interdigital transducer provided by the present invention.

Fig. 7 is a performance test comparison chart provided by the present invention.

Reference signs:

1. First bus bar; 2. Second bus bar; 3. Interdigital transducer; 4. Reflective grating; 5. Angle.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Referring to shown in accompanying drawing 2, a kind of interdigital transducer, its overall shape is a regular hexagon, comprising:

Piezoelectric substrate;

A first bus bar 1 and a second bus bar 2 arranged at intervals on the piezoelectric substrate;

A plurality of first interdigitated electrodes and a plurality of second interdigitated electrodes are alternately arranged between the first bus bar 1 and the second bus bar 2;

The first interdigitated electrode is led out from the first bus bar 1 and extends toward the second bus bar 2, and a gap is reserved between the extension end of the first interdigitated electrode and the second bus bar 3;

The second interdigitated electrode is drawn from the second bus bar 2 and extends toward the first bus bar 1, and the extension end of the second interdigitated electrode has a gap with the first bus bar 1;

The first bus bar 1 and the second bus bar 2 are respectively connected with a reflective grid;

The first bus bar 1 , the second bus bar 2 and the reflective grid 4 surround the first interdigital electrode and the second interdigital electrode to form an interdigital transducer 3 with a regular hexagonal structure.

Referring to Figure 2, it can be seen that since the IDT 3 is in the shape of a hexagon, the interdigital electrodes at the angle 5 of the hexagon will be partially reduced, so that the angle 5 of this part can reflect sound waves and reduce confluence Leaky waves, thereby improving the performance index of the surface acoustic wave filter.

Referring to accompanying drawing 3 and shown in accompanying drawing 5, a kind of surface acoustic wave filter of honeycomb structure comprises:

a set of series resonators and a set of parallel resonators connected between the input and output of the SAW filter;

The resonator adopts the structure of the interdigital transducer 3 described in this embodiment.

As a further implementation manner in this embodiment, the resonators in the series resonator group and the parallel resonator group are arranged in a honeycomb shape on the substrate.

As a possible implementation manner in this embodiment, the series resonator group includes a first series resonator unit, a second series resonator unit, a third series resonator unit and a fourth series resonator unit connected in series in sequence ;

The parallel resonator unit includes:

The input end is connected to the first parallel resonator unit between the first series resonator unit and the second series resonator unit, and the output terminal signal of the first parallel resonator unit is grounded;

The input end is connected to the second parallel resonator unit between the second series resonator unit and the third series resonator unit, and the output terminal signal of the second parallel resonator unit is grounded;

The input terminal is connected to the third parallel resonator unit between the third series resonator unit and the fourth series resonator unit, and the signal output terminal of the third parallel resonator unit is grounded.

Specifically, as shown in FIG. 3, the first series resonator unit includes two resonators S1 connected in series;

The second series resonator unit comprises two resonators S2 connected in series with each other;

The third series resonator unit comprises two resonators S3 connected in series with each other;

The fourth series resonator unit includes a resonator S4;

The first resonator unit, the second resonator unit, the third resonator unit and the fourth resonator unit are connected in series from the input end to the output end of the surface acoustic wave filter.

The first parallel resonator unit includes a resonator P1;

The second parallel resonator unit includes two resonators P2 connected in series;

The third parallel resonator unit includes a resonator P3.

As a possible implementation in this embodiment, Fig. 6 is a schematic structural diagram of various bus bars of the interdigital transducer provided by the present invention. The interdigital transducer in Fig. 6a is in the shape of a regular hexagon as a whole. The reflective grids at both ends of the resonator have a triangular structure, and the resonator itself has an octagonal shape. A plurality of first interdigitated electrodes and a plurality of second interdigitated electrodes are arranged alternately between the first bus bar 1 and the second bus bar 2 , and there is a gap between the two bus bars and the reflective grid.

As a possible implementation in this embodiment, the interdigital transducer in FIG. 6 b is in the shape of a regular hexagon as a whole, wherein the reflective grids at both ends of the resonator are in a triangular structure, and the resonator itself is in an octagonal shape. The first bus bar 1 is connected to the reflection grid on the left, and the second bus bar 2 is connected to the reflection grid on the right.

As a possible implementation in this embodiment, the interdigital transducer in FIG. 6 c is in the shape of a regular hexagon as a whole, wherein the reflective grids at both ends of the resonator are in a triangular structure, and the resonator itself is in an octagonal shape. There are gaps between the first bus bar 1 and the reflective grids at both ends, and they are not connected. The second bus bar 2 is connected to the reflection grid on the right, and the reflection grid at the left end is not connected to any bus bar.

As a possible implementation in this embodiment, the interdigital transducer in Fig. 6d is in the shape of a regular hexagon as a whole, wherein the reflective grids at both ends of the resonator are in a triangular structure, and the resonator itself is in an octagonal shape. There are gaps between the first bus bar 1 and the reflective grids at both ends, and they are not connected. The second bus bar 2 is connected to the reflective grid on the left, and the reflective grid at the right end is not connected to any bus bar.

In order to further prove the beneficial effects obtained by the present invention, the existing surface acoustic wave filter and the surface acoustic wave filter proposed by the present invention are tested below;

Referring to accompanying drawing 1 shown is the structural representation of existing surface acoustic wave filter, and it also comprises:

A first bus bar 1 and a second bus bar 2 arranged at intervals on the piezoelectric substrate;

reflective grid 4;

A plurality of interdigitated electrodes are arranged between the first bus bar 1 and the second bus bar 2, and two adjacent interdigitated electrodes are led out from the first bus bar 1 and the second bus bar 2 respectively;

The interdigitated electrodes drawn from the first bus bar 1 extend toward the second bus bar 2, and a gap is reserved between the extension end and the second bus bar 2;

The interdigitated electrodes drawn from the second bus bar 2 extend toward the first bus bar 1 , and a gap is left between the extension end and the first bus bar 1 .

Referring again to appendix 3 and accompanying drawing 4, accompanying drawing 4 is a surface acoustic wave filter structure using an existing interdigital transducer 3 for layout arrangement; FIG. 3 is a schematic diagram of the corresponding circuit connection.

Referring to Figure 7, S(16,17) is the test result of the surface acoustic wave filter using the existing interdigital transducer 3 for layout arrangement; S(24,25) is the regular hexagon of the present invention The test result of the surface acoustic wave filter that honeycomb interdigital transducer constitutes; Based on this, it can be known that the passband performance is basically unchanged; The connecting wires between the interdigital transducers are reduced, and the flexibility of placement of the interdigital transducers on the layout is greatly improved.

It can be seen from the above that the present invention reduces the circuit area without affecting the power tolerance and electrical performance; and greatly improves the flexibility of placing the IDT on the layout.

In describing the embodiments of the present invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "straight", "horizontal", " Orientations or positional relationships indicated by "center", "top", "bottom", "top", "bottom", "inner", "outer", "inner", "outer", etc. are based on the orientation or position shown in the drawings The positional relationship is only for the purpose of describing the present invention and simplifying the description, but does not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention. Wherein, "inside" refers to an internal or enclosed area or space. "Periphery" refers to the area around a particular component or a particular area.

In the description of the embodiments of the present invention, the terms "first", "second", "third", and "fourth" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implying The number of technical characteristics indicated. Thus, a feature defined as "first", "second", "third" and "fourth" may expressly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

In the description of the embodiments of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection", "connection", and "assembly" should be understood in a broad sense, for example, it may be fixed The connection can also be a detachable connection or an integral connection; it can be a direct connection or an indirect connection through an intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations.

In the description of the embodiments of the present invention, specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in an appropriate manner.

In the description of the embodiments of the present invention, it should be understood that "-" and "~" represent the same range of two numerical values, and the range includes the endpoint. For example: "A-B" means greater than or equal to A, and less than or equal to the range of B. "A~B'' indicates the range greater than or equal to A and less than or equal to B.

In the description of the embodiments of the present invention, the term "and/or" herein is only an association relationship describing associated objects, which means that there may be three relationships, for example, A and/or B, which can mean: exist alone A, A and B exist at the same time, and B exists alone. In addition, the character "/" in this article generally indicates that the contextual objects are an "or" relationship.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications and substitutions can be made to these embodiments without departing from the principle and spirit of the present invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (10)

1. An interdigital transducer comprising:

a piezoelectric substrate;

two reflective gratings;

a first bus bar and a second bus bar arranged on the piezoelectric substrate at an opposite interval;

a plurality of first interdigital electrodes and a plurality of second interdigital electrodes are alternately arranged between the first bus bar and the second bus bar;

the first interdigital electrode is led out from the first bus bar and extends towards the second bus bar, and a gap is reserved between the extending end of the first interdigital electrode and the second bus bar;

the second interdigital electrode is led out from the second bus bar and extends towards the first bus bar, and a gap is reserved between the extending end of the second interdigital electrode and the first bus bar;

the first bus bar, the second bus bar and the reflecting grating encircle the first interdigital electrode and the second interdigital electrode to form an interdigital transducer with a positive n-shaped structure, wherein n is more than or equal to 6 and is an integer multiple of 2.

2. An interdigital transducer according to claim 1, wherein n is equal to 6.

3. An interdigital transducer according to claim 1, wherein any one of the bus bars is connected to one of the reflective gratings, and a gap is left between the other bus bar and the other reflective grating.

4. An interdigital transducer according to claim 1, wherein two of the bus bars are each connected to one of the reflective gratings.

5. An interdigital transducer according to claim 1, wherein a gap is maintained between both of the bus bars and the reflective grating.

6. A surface acoustic wave filter of a honeycomb structure, comprising:

a series resonator group and a parallel resonator group connected between input and output ends of the surface acoustic wave filter;

the resonator adopts the structure of the interdigital transducer as claimed in any one of claims 1 to 5.

7. The surface acoustic wave filter of a honeycomb structure according to claim 6, wherein the resonators in the series resonator group and the parallel resonator group are arranged in a honeycomb shape on the substrate.

8. The surface acoustic wave filter of claim 7, wherein the series resonator group includes a first series resonator unit, a second series resonator unit, a third series resonator unit, and a fourth series resonator unit, which are sequentially connected in series.

9. The surface acoustic wave filter of a honeycomb structure according to claim 6, wherein the parallel resonator group comprises:

the input end of the first parallel resonator unit is connected between the first series resonator unit and the second series resonator unit, and the output end of the first parallel resonator unit is grounded;

the input end of the second parallel resonator unit is connected between the second series resonator unit and the third series resonator unit, and the output end of the second parallel resonator unit is grounded;

and a third parallel resonator unit having an input terminal connected between the third series resonator unit and the fourth series resonator unit, and an output terminal of the third parallel resonator unit being signal-grounded.

10. The surface acoustic wave filter of a honeycomb structure according to claim 9, wherein the first series resonator unit, the second series resonator unit, and the third series resonator unit each include two resonators connected in series with each other;

the fourth series resonator unit includes one resonator;

the first parallel resonator unit and the third parallel resonator unit each include one resonator;

the second parallel resonator unit includes two resonators connected in series.

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