CN108933579B - A surface acoustic wave single-ended pair resonator - Google Patents

Abstract

The invention relates to a surface acoustic wave single-ended pair resonator. The single-ended pair resonator comprises: a piezoelectric substrate, a first interdigital transducer, a first reflection grid and a second reflection grid; a first interdigital The transducer is arranged on the piezoelectric substrate, the first reflection grid and the second reflection grid have the same structure, and are symmetrically arranged at both ends of the first interdigital transducer; it also includes: a sensitive film and a second interdigital transducer The second interdigital transducer is arranged between the first reflection grid and the second reflection grid, and the second interdigital transducer is connected with the upper and lower return bars of the first interdigital transducer; the sensitive film is arranged on the The intermediate position of the first interdigital transducer and the second interdigital transducer. The resonator of the present invention, by adding an interdigital transducer, ensures the advantages of high quality factor and low loss of the resonator, and helps to improve the detection sensitivity, consistency and stability of the sensor. At the same time, a sensitive film is built between the two interdigital transducers, which overcomes the problem of the film-forming area of the sensitive film, and is easily applied to the sensor field.

Description

A surface acoustic wave single-ended pair resonator

technical field

The invention relates to the field of surface acoustic wave devices, in particular to a surface acoustic wave single-ended pair resonator.

Background technique

A surface acoustic wave sensor is a new type of micro-acoustic sensor developed in recent years. It uses a surface acoustic wave device as a sensing element to pass the measured information through the change of the speed or frequency of the surface acoustic wave in the surface acoustic wave device. It is reflected and converted into an electrical signal output by the sensor. SAW sensors can accurately measure physical, chemical and other information (such as temperature, stress, gas density). Due to its small size, SAW devices are hailed as creating a new era of wireless and small sensors; at the same time, they have strong compatibility with integrated circuits and have been widely used in analog and digital communication and sensing fields. The surface acoustic wave sensor can concentrate the signal on the surface of the substrate, has a high working frequency, has extremely high information sensitivity accuracy, can quickly convert the detected information into electrical signal output, and has the characteristics of real-time information detection; The wave sensor also has the advantages of miniaturization, integration, passive, low cost, low power consumption, direct frequency signal output and so on. At present, various types of surface acoustic wave pressure sensors, surface acoustic wave temperature sensors, surface acoustic wave biological gene sensors, surface acoustic wave chemical gas sensors and smart sensors have been formed in China.

SAW sensors have two basic configurations, delay line type and resonant type. Among them, the delay line type and the resonance type surface acoustic wave sensor are both constituted by the piezoelectric substrate, the first interdigital transducer and the emission grid in structure. Mauder and Rapp et al. respectively compared the oscillators of these two structures applied to the sensor: for the SAW delay line, the phase effect from the oscillation loop is very small, and the acoustic wave attenuation caused by the cover film material is relatively small, and the delay is relatively small. Lines readily provide separate film-forming areas. But the disadvantage of SAW delay lines is the relatively large insertion loss. The SAW resonator has the characteristics of high quality factor and low loss, and the oscillator composed of it as a frequency control element is easy to oscillate and can obtain good frequency stability. However, it is difficult for the resonator to provide a separate sensitive film formation area, which limits the application of the self-assembled sensitive film formation method that requires an active gold film.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention proposes a surface acoustic wave single-ended pair resonator.

The invention provides a surface acoustic wave single-ended pair resonator, comprising: a piezoelectric substrate, a first interdigital transducer, a first reflection grid and a second reflection grid; the first interdigital transducer is provided with On the piezoelectric substrate, the first reflection grid and the second reflection grid have the same structure, and are symmetrically arranged at both ends of the first interdigital transducer; further comprising: a sensitive film and a second reflection grid two-finger transducer;

The second interdigital transducer is arranged between the first reflection grid and the second reflection grid, and the upper and lower return bars of the second interdigital transducer and the first interdigital transducer connected; the sensitive film is arranged in the middle position of the first interdigital transducer and the second interdigital transducer.

Preferably, the first interdigital transducer and the second interdigital transducer have the same structure and are antisymmetrically placed.

Preferably, the second interdigital transducer is disposed between the first interdigital transducer and the second reflection grating.

Preferably, the sensitive film is deposited in the area formed by the connection between the first interdigital transducer and the upper and lower return bars of the second interdigital transducer, and does not contact the first interdigital transducer and the second interdigital transducer.

Preferably, after the left and right sound waves generated by the first interdigital transducer and the second interdigital transducer are superimposed, the energy is concentrated in the sensitive membrane area.

Preferably, the sensitive film is a conductive sensitive film and a high viscosity sensitive film.

The single-ended pair resonator of the present invention ensures the advantages of high quality factor and low loss of the resonator by adding an interdigital transducer, and helps to improve the detection sensitivity, consistency and stability of the sensor. At the same time, a sensitive film is built between the two interdigital transducers, which overcomes the problem of the film-forming area of the sensitive film, and can be easily applied to the sensor field. In addition, when depositing the sensitive film, it is avoided that the sensitive film touches the electrodes of the interdigital strips, so as to ensure that the performance and quality factor of the transducer are not affected.

Description of drawings

1 is a schematic diagram of a surface acoustic wave single-ended pair resonator in the prior art;

Fig. 2 is the amplitude distribution figure of surface acoustic wave when single-ended pair resonator in the prior art is resonant frequency;

3 is a schematic diagram of a surface acoustic wave single-ended pair resonator provided by an embodiment of the present invention;

FIG. 4 is a distribution diagram of the amplitude of the surface acoustic wave at the resonance frequency of the single-ended pair resonator provided by the embodiment of the present invention.

Detailed ways

In order to express the technical solutions and advantages of the embodiments of the present invention more clearly, the technical solutions of the present invention are further described in detail below through the accompanying drawings and embodiments.

FIG. 1 shows a surface acoustic wave single-ended pair resonator in the prior art, including a piezoelectric substrate 11 , a first interdigital transducer 12 , a first reflection grid 13 and a second reflection grid 14 . In the single-ended pair resonator, the first interdigital transducer 12 is arranged on the piezoelectric substrate 11, and the first reflection grid 13 and the second reflection grid 14 are symmetrically arranged on the first interdigital transducer, respectively. 12, wherein the structures of the first reflection grating 13 and the second reflection grating 14 are completely the same.

According to the acoustic theory, the amplitude expression of the surface acoustic wave of the piezoelectric substrate 11 of the single-ended pair resonator is:

Among them, a ^± (x, y) represents the right and left propagating surface acoustic waves in the periodic medium, A ^± (x, y) represents the amplitude of the right and left propagating surface acoustic waves in the periodic medium, and k is The wave number of the surface acoustic wave propagating along the x direction, k ₀ is the wave number of the unperturbed surface acoustic wave.

According to the coupled mode equation, we can get:

δ=k-jγ _α +κ ₁₁ -k ₀

Among them, κ ₁₁ and κ ₁₂ are the coupled mode parameters, α is the excitation coefficient, γ _α is the decay constant, γ is the anisotropy parameter, and V is the voltage applied between the electrodes.

The right and left propagating surface acoustic waves are obtained by calculation, and the amplitude distribution of the surface acoustic wave of the piezoelectric substrate 11 can be obtained after superposition:

In one embodiment, as shown in FIG. 2 , the amplitude distribution of the surface acoustic wave of the single-ended pair resonator at the resonant frequency in the prior art is shown, and the acoustic wave energy is mainly concentrated in the middle region of the single-ended pair resonator, and the The amplitude is around 95. Although the single-ended pair resonator of this structure has the advantages of low loss and high quality factor, its sensitivity is relatively low, and it is difficult to apply to the sensor field due to the lack of coating area.

In order to overcome this problem, a SAW single-ended pair resonator as shown in FIG. 3 adds a sensitive film 15 and a second interdigital transducer 16 to the existing SAW single-ended pair resonator . The second interdigital transducer 16 is disposed between the first reflection grating 13 and the second reflection grating 14 , either on the left side of the first interdigital transducer 12 or on the side of the first interdigital transducer 12 . On the right side (shown in FIG. 3 is the right side of the first interdigital transducer 12 ), the sensitive film is arranged in the middle of the first interdigital transducer 12 and the second interdigital transducer 16 .

Optionally, the deposition method used for the sensitive film 15 may be conventional coating, spraying, etc. to achieve the deposition of the sensitive film 15 .

Optionally, the sensitive film 15 is suitable for a variety of sensitive films, and has certain advantages in conductive sensitive films and high-viscosity sensitive films. By preferring conductive sensitive films and highly viscous sensitive films, the phenomenon that the deposition of other such sensitive films can lead to unusable devices or large loss of quality factor is avoided.

Optionally, the first interdigital transducer 12 and the second interdigital transducer 16 have the same structure and are placed anti-symmetrically, which is equivalent to doubling the number of interdigital finger strips 121, so that the single-ended pair resonator is at resonance. When the frequency is increased, the number of excited surface acoustic waves also doubles, and the amplitude after superposition also doubles.

Optionally, the return bars 122 of the first interdigital transducer 12 and the second interdigital transducer 16 should be connected, so as to ensure that a space for depositing the sensitive film 15 is planned between the two interdigital transducers. area.

Optionally, the sensitive film 15 does not contact the first interdigital transducer 12 and the second interdigital transducer 16 after deposition, so as to avoid damage to the transducer performance after the sensitive film 15 contacts the electrodes of the interdigital finger strip 121 , and at the same time The reduction of the transducer quality factor caused by the contact of the sensitive film 15 with the electrodes of the interdigital finger strips 121 is also avoided.

Due to the symmetrical structure of the surface acoustic wave single-ended pair resonator, the maximum amplitude of the surface acoustic waves propagating in the left and right directions appears in the middle position, so selecting the sensitive film 15 in the middle area can make the surface acoustic wave single-ended pair resonator. maximum sensitivity.

In one embodiment, FIG. 4 illustrates the distribution of the SAW amplitude of the single-ended pair resonator at the resonant frequency in the embodiment of the present invention, and the SAW amplitude is about 190. By comparing the prior art in FIG. 2 The amplitude of the surface acoustic wave of the single-ended pair of resonators, the amplitude of the single-ended pair of resonators of the present invention is twice that of the single-ended pair of resonators of the prior art, which can greatly improve the detection sensitivity, consistency and stability of the sensor, and provide The single-ended pair resonator can be easily applied to the sensor field by depositing a sensitive film.

It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any relationship between these entities or operations. any such actual relationship or sequence exists.

The specific embodiments described above further describe the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (6)

1. A surface acoustic wave single-ended pair resonator, comprising: a piezoelectric substrate (11), a first interdigital transducer (12), a first reflection grid (13) and a second reflection grid (14); The first interdigital transducer (12) is arranged on the piezoelectric substrate (11), and the first reflection grating (13) and the second reflection grating (14) have the same structure and are symmetrical are arranged at both ends of the first interdigital transducer (12); it is characterized in that it further comprises: a sensitive film (15) and a second interdigital transducer (16); The second interdigital transducer (16) is arranged between the first reflection grating (13) and the second reflection grating (14), and the second interdigital transducer (16) is connected to the The upper and lower return bars (122) of the first interdigital transducer (12) are connected; the sensitive film (15) is arranged between the first interdigital transducer (12) and the second interdigital transducer (12) The middle position of the energy device (16). 2. The surface acoustic wave single-ended pair resonator according to claim 1, wherein the first interdigital transducer (12) and the second interdigital transducer (16) have the same structure, Antisymmetric placement. 3. The surface acoustic wave single-ended pair resonator according to claim 1, wherein the second interdigital transducer (16) is arranged between the first interdigital transducer (12) and the between the second reflection gratings (14). 4. The surface acoustic wave single-ended pair resonator according to claim 1, wherein the sensitive film (15) is deposited on the first interdigital transducer (12) and the second interdigital transducer (12) The upper and lower return bars (122) of the transducer (16) are connected to form the area, and do not contact the first interdigital transducer (12) and the second interdigital transducer (16). 5. The surface acoustic wave single-ended pair resonator according to claim 1, wherein the left and right generated by the first interdigital transducer (12) and the second interdigital transducer (16) After the sound waves are superimposed, the energy is concentrated in the area of the sensitive film (15). 6. The surface acoustic wave single-ended pair resonator according to claim 1, wherein the sensitive film (15) is a conductive sensitive film and a high-viscosity sensitive film.

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