CN212695969U

CN212695969U - Surface acoustic wave filter

Info

Publication number: CN212695969U
Application number: CN202021485556.1U
Authority: CN
Inventors: 张太鑫; 卢翠; 王玉龙
Original assignee: Hebei Shishuo Microchip Technology Co ltd
Current assignee: Hebei Shishuo Microchip Technology Co ltd
Priority date: 2020-07-24
Filing date: 2020-07-24
Publication date: 2021-03-12
Anticipated expiration: 2030-07-24

Abstract

The application discloses a surface acoustic wave filter. The method comprises the following steps: the device comprises a piezoelectric wafer, and a first channel and a second channel which are arranged on the piezoelectric wafer; the method specifically comprises the steps that a first channel and a second channel of a two-stage coupling cascade structure are designed on a piezoelectric substrate, the first channel and the second channel respectively comprise two reflecting gratings and three interdigital transducers arranged side by side, and the interdigital transducers are used for replacing the intervals of the interdigital transducers, so that the body wave radiation is effectively reduced, and the filter loss is reduced; furthermore, a grounding finger is designed between the bus bars of each interdigital transducer, one end of the grounding finger is connected with the bus bar on the upper side of the interdigital transducer, the other end of the grounding finger is connected with the bus bar on the lower side of the interdigital transducer, the grounding finger is connected to the ground, the size of the grounding pad is effectively reduced, and the effect of reducing the size of the filter is achieved.

Description

Surface acoustic wave filter

Technical Field

The present disclosure relates generally to the field of filtering devices, and more particularly to a surface acoustic wave filter.

Background

The surface acoustic wave filter mainly utilizes the piezoelectric property of piezoelectric materials, utilizes an input transducer and an output transducer to convert input signals of electric waves into mechanical energy, and converts the mechanical energy into electric signals after processing, so as to achieve the aims of filtering unnecessary signals and noises and improving the receiving quality.

The insertion loss of the existing design scheme with the relative bandwidth of about 4 percent in the surface acoustic wave filter is generally more than 2dB and is as small as 1.6 dB; the size of the chip is relatively large, and the device with the center frequency of about 150MHz is at least arranged in a shell of 9mm x 7mm, so that the device occupies a large space; therefore, improvement of the existing surface acoustic wave filter is desired.

Disclosure of Invention

In view of the above-mentioned drawbacks and deficiencies of the prior art, it is desirable to provide a surface acoustic wave filter that reduces bulk wave radiation, reduces filter loss, effectively reduces device size, has a simple structure, and is easy to implement.

In a first aspect, the present application provides a surface acoustic wave filter comprising: the piezoelectric device comprises a piezoelectric substrate, and a first channel and a second channel which are arranged on the piezoelectric substrate;

the first channel and the second channel are in a two-stage coupling cascade structure; the first and second channels each include: two reflection gratings and three interdigital transducers positioned between the two reflection gratings; the interdigital transducers are arranged side by side, and each interdigital transducer is provided with a bus bar on the upper side and the lower side respectively.

According to the technical scheme provided by the embodiment of the application, the interdigital transducer comprises: a plurality of pairs of interdigital electrodes; and each pair of interdigital electrodes is provided with two interdigital strips, and the two interdigital strips are respectively connected with different bus bars.

According to the technical scheme provided by the embodiment of the application, a grounding finger is arranged between the bus bars of each interdigital transducer.

According to the technical scheme provided by the embodiment of the application, the first channel and the second channel are cascaded in an end-to-end series connection mode.

According to the technical scheme provided by the embodiment of the application, the piezoelectric substrate is a lithium tantalate or lithium niobate wafer.

In summary, the present technical solution specifically discloses a specific structure of a surface acoustic wave filter. The method specifically comprises the steps that a first channel and a second channel of a two-stage coupling cascade structure are designed on a piezoelectric substrate, the first channel and the second channel respectively comprise two reflecting gratings and three interdigital transducers arranged side by side, and the interdigital transducers are used for replacing the intervals of the interdigital transducers, so that the body wave radiation is effectively reduced, and the filter loss is reduced;

furthermore, a grounding finger is designed between the bus bars of each interdigital transducer, one end of the grounding finger is connected with the bus bar on the upper side of the interdigital transducer, the other end of the grounding finger is connected with the bus bar on the lower side of the interdigital transducer, the grounding finger is connected to the ground, the size of the grounding pad is effectively reduced, and the effect of reducing the size of the filter is achieved.

Drawings

Other features, objects and advantages of the present application will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, made with reference to the accompanying drawings in which:

fig. 1 is a schematic diagram of a structure of a surface acoustic wave filter.

Fig. 2 is a schematic structural view of the interdigital strip.

Reference numbers in the figures: 1. a first channel; 2. a second channel; 3. an interdigital transducer; 4. a reflective grating; 5. a bus bar; 6. a ground finger; 7. an interdigitated finger.

Detailed Description

The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.

Example one

Please refer to fig. 1, which illustrates a schematic structural diagram of a first embodiment of a saw filter provided by the present application, including: the device comprises a piezoelectric substrate, and a first channel 1 and a second channel 2 which are arranged on the piezoelectric substrate;

the first channel 1 and the second channel 2 are in a two-stage coupling cascade structure; the first channel 1 and the second channel 2 each comprise: two reflection gratings 4 and three interdigital transducers 3 positioned between the two reflection gratings 4; three interdigital transducer 3 sets up side by side, and every interdigital transducer 3's upper and lower both sides are provided with busbar 5 respectively.

In this embodiment, the first channel 1 and the second channel 2 are disposed on the piezoelectric substrate, and the two channels are in a two-stage coupling cascade structure, and can be cascaded in an end-to-end series connection manner; the system comprises a first channel 1 and a second channel 2, wherein one channel is an input transducer, and the other channel is an output transducer;

the three interdigital transducers 3 are arranged between the two reflecting gratings 4, are arranged side by side and are used for generating surface acoustic waves; the interval of the transducer is replaced by the interval, so that the body wave radiation is effectively reduced, and the filter loss is reduced;

the reflecting grating 4 is used for reflecting the surface acoustic wave generated by the interdigital transducer 3;

the bus bars 5 are arranged on the upper side and the lower side of each interdigital transducer 3, and the bus bars 5 are electrically connected with the reflecting grids 4 and used for conducting electric signals; here, the bus bar functions differently depending on the position thereof, and includes: an input terminal, an output terminal and a ground terminal; the input end or the output end is directly connected with an input bonding pad and an output bonding pad of the tube shell through overvoltage welding wires, and the grounding end is connected with a grounding bonding pad of the tube shell.

In any preferred embodiment, the interdigital transducer 3 comprises: a plurality of pairs of interdigital electrodes; each pair of interdigital electrodes is provided with two interdigital strips 7, and the two interdigital strips 7 are respectively connected with different bus bars 5.

In the present embodiment, the interdigital transducer 3 is composed of a plurality of pairs of interdigital electrodes, each pair of interdigital electrodes includes two interdigital strips 7, and one interdigital strip 7 is connected to the bus bar 5 on the upper side of the interdigital transducer 3, and the other interdigital strip 7 is connected to the bus bar 5 on the lower side of the interdigital transducer 3, forming an alternate connection form;

wherein the number of pairs of interdigital electrodes is at least sixty pairs; the interdigital strip 7 is a metal interdigital strip manufactured on a piezoelectric substrate by adopting a semiconductor planar process, and the conversion between electric energy and mechanical energy is realized by utilizing a piezoelectric effect and an inverse piezoelectric effect.

In any preferred embodiment, a grounding finger 6 is provided between the bus bars 5 of each of the interdigital transducers 3.

In the conventional grounding design of the filter, the adopted grounding pad needs to be separately connected with a bonding wire, and due to the bonding process, the molding size of the grounding pad is larger (generally not less than 150nm x 150nm), so that the size of a chip is larger; in the embodiment, the grounding finger 6 is arranged between the bus bars 5 of each interdigital transducer 3, one end of the grounding finger 6 is connected with the bus bar 5 on the upper side of the interdigital transducer 3, the other end of the grounding finger 6 is connected with the bus bar 5 on the lower side of the interdigital transducer 3, and the grounding finger 6 is connected to the ground, so that the size of a grounding pad is effectively reduced, and the effect of reducing the size of a filter is achieved; the width of the filter can be reduced by 0.4mm, and in other embodiments, other size values can be reduced.

In any preferred embodiment, the piezoelectric substrate is a lithium tantalate or lithium niobate wafer.

In this embodiment, the piezoelectric substrate is made of lithium tantalate or lithium niobate wafer, and other materials may be used according to actual needs.

The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of the invention as referred to in the present application is not limited to the embodiments with a specific combination of the above-mentioned features, but also covers other embodiments with any combination of the above-mentioned features or their equivalents without departing from the inventive concept. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.

Claims

1. A surface acoustic wave filter, comprising: the device comprises a piezoelectric substrate, and a first channel (1) and a second channel (2) which are arranged on the piezoelectric substrate;

the first channel (1) and the second channel (2) are in a two-stage coupling cascade structure; the first channel (1) and the second channel (2) each comprise: two reflection gratings (4) and three interdigital transducers (3) positioned between the two reflection gratings (4); the interdigital transducers (3) are arranged side by side, and each of the upper side and the lower side of each interdigital transducer (3) is provided with a bus bar (5) respectively.

2. A surface acoustic wave filter according to claim 1, characterized in that said interdigital transducer (3) comprises: a plurality of pairs of interdigital electrodes; each pair of interdigital electrodes is provided with two interdigital strips (7), and the two interdigital strips (7) are respectively connected with different bus bars (5).

3. A surface acoustic wave filter as set forth in claim 1, characterized in that a ground finger (6) is provided between the bus bars (5) of each of said interdigital transducers (3).

4. A surface acoustic wave filter as claimed in claim 1, characterized in that said first channel (1) and said second channel (2) are cascaded in an end-to-end series connection.

5. A surface acoustic wave filter as set forth in claim 1, wherein said piezoelectric substrate is a lithium tantalate or lithium niobate wafer.