JP4714885B2 - Elastic wave sensor - Google Patents

Description

  The present invention relates to an elastic wave sensor using an elastic wave such as a surface acoustic wave (SAW) or a transverse wave elastic wave (STW), and more particularly, to an elastic wave sensor having a sensitive film that is adsorptive to an object to be measured. .

  In an elastic wave sensor using an elastic wave such as a surface acoustic wave (SAW) or a transverse wave elastic wave (STW), a sensitive film that exhibits adsorptivity to an object to be measured is formed. When the sensitive film adsorbs the object to be measured, the oscillation frequency of the acoustic wave element changes. Therefore, the concentration of the object to be measured can be detected by detecting the change in the oscillation frequency with the frequency measuring device.

  However, when detecting the concentration of the object to be measured by detecting the change of the oscillation frequency with a frequency measuring device, a frequency measuring device for measuring the oscillation frequency is required, which increases the cost. There is.

  Therefore, Patent Document 1 discloses a conventional example of an elastic wave sensor that detects the concentration of an object to be measured without using a frequency measuring device. The elastic wave sensor of Patent Document 1 includes at least three oscillation loops including SAW filters on which sensitive films are formed. Each SAW filter has the same delay characteristics that change depending on the amount of the object to be measured of the sensitive film, and has different frequency characteristics in which the trap frequencies are different from each other.

  When the object to be measured is adsorbed to the sensitive film, the delay amount of each SAW filter changes, and the oscillation state of each oscillation loop changes. Specifically, the oscillation loop whose oscillation frequency is located in the trap stops oscillating, and the other oscillation loops maintain the oscillation. In the elastic wave sensor of Patent Document 1, this characteristic is used to detect the repetition direction and the number of times when each oscillation loop repeats in turn and stops oscillation, and without using a frequency measuring device. The concentration of the measurement object is detected.

  As another background art, a piezoelectric sensor using a crystal resonator disclosed in Patent Document 2 is disclosed. Non-Patent Document 1 discloses a weighting method for comb-shaped electrodes used in acoustic wave elements.

Japanese Patent Application Laid-Open No. 7-218481 Japanese Utility Model Publication No. 5-73560 Japan Society for the Promotion of Science Elastic Wave Element Technology 150th Edition, “Acoustic Wave Element Technology Handbook”, first edition, Ohmsha, November 30, 1991, p. 195,208

  In the elastic wave sensor of Patent Document 1, in order to detect the concentration of an object to be measured without using a frequency measuring device, at least three oscillation loops including a SAW (elastic wave) filter on which a sensitive film is formed are required. To do. Therefore, there is a problem that the number of parts increases, resulting in an increase in circuit scale and cost. In addition, the measurement accuracy of the object to be measured decreases due to variations in oscillation characteristics between the oscillation loops.

  An object of the present invention is to provide an elastic wave sensor capable of measuring an object to be measured without using a frequency measuring device and with one oscillation loop.

An elastic wave sensor according to the present invention includes an oscillation elastic wave element in which an excitation electrode for exciting an elastic wave and a reception electrode for converting the elastic wave into an electric signal are formed on a piezoelectric substrate, An oscillation loop in which an electrical signal converted by the electrode for excitation is input to the excitation electrode and an elastic wave formed on the piezoelectric substrate and excited by the excitation electrode are converted into an electrical signal and output. An output electrode, and on the oscillation acoustic wave element, a sensitive film exhibiting adsorptivity to the object to be measured is formed, and the output electrode has a level of the input acoustic wave. And the level of the electric signal to be output are changed so as to change according to a change in frequency, and the sensing film adsorbs the object to be measured, so that the output electrode can be used for the output. the frequency of the acoustic wave propagating to the electrode changes, electric for the output Level of the electric signal output from is summarized as changing.

  In this invention, when the sensitive film formed on the oscillation acoustic wave element adsorbs the object to be measured, the frequency of the oscillation signal circulating in the oscillation loop changes, and the acoustic wave propagating from the excitation electrode to the output electrode The frequency also changes. Here, the output electrode is formed so that the characteristic between the level of the input elastic wave and the level of the output electric signal changes according to the change in frequency, so that the sensitive film is measured. When an object is adsorbed, the level of the electrical signal output from the output electrode changes. Therefore, according to the present invention, by measuring the level of the electric signal output from the output electrode, it is possible to measure the object to be measured without using a frequency measuring device and with one oscillation loop. .

  The acoustic wave sensor according to the present invention includes an oscillation acoustic wave element in which an excitation electrode for exciting an acoustic wave and a reception electrode for converting the acoustic wave into an electric signal are formed on a piezoelectric substrate, An oscillation loop in which the electrical signal converted by the receiving electrode is input to the excitation electrode and an elastic wave formed on the piezoelectric substrate and excited by the excitation electrode are converted into an electrical signal. An output electrode that outputs, and a sensitive film that exhibits adsorptivity to the object to be measured is formed on the output electrode, and the output electrode has an elastic wave level to be input. And the level of the electric signal to be output are formed so as to change according to a change in frequency, and the sensitive film adsorbs the object to be measured, and is output from the output electrode. The gist is that the level of the electric signal changes.

  In this invention, the output electrode for converting the elastic wave excited by the excitation electrode into an electric signal has a characteristic between the level of the input elastic wave and the level of the electric signal to be output changed in frequency. When the sensitive film formed on the output electrode adsorbs the object to be measured, the level of the electric signal output from the output electrode changes. Therefore, according to the present invention, by measuring the level of the electric signal output from the output electrode, it is possible to measure the object to be measured without using a frequency measuring device and with one oscillation loop. .

  In the acoustic wave sensor according to the present invention, a plurality of the output electrodes are formed on the piezoelectric substrate, and each of the output electrodes exhibits absorptivity to different types of objects to be measured. A sensitive film may be formed. In this way, it is possible to measure a plurality of types of objects to be measured without using a frequency measuring device and with one oscillation loop.

  The acoustic wave sensor according to the present invention includes an oscillation acoustic wave element in which an excitation electrode for exciting an acoustic wave and a reception electrode for converting the acoustic wave into an electric signal are formed on a piezoelectric substrate, An oscillation loop in which an electrical signal converted by the receiving electrode is input to the excitation electrode, an input electrode for converting the electrical signal in the oscillation loop to an elastic wave, and the elastic wave to an electrical signal And an output acoustic wave element formed on a piezoelectric substrate, and on the oscillation acoustic wave element, there is a sensitive film exhibiting adsorptivity to the object to be measured. In the acoustic wave element for detection, the characteristic between the level of the electric signal input to the input electrode and the level of the electric signal output from the output electrode changes according to a change in frequency. The sensitive film adsorbs the object to be measured. In Rukoto, and summarized in that the level of the electric signal output from the output electrode is changed.

  In the present invention, when the sensitive film formed on the oscillation acoustic wave element adsorbs the object to be measured, the frequency of the oscillation signal circulating in the oscillation loop changes and is input to the input electrode of the detection acoustic wave element. The frequency of the electrical signal changes. Here, the detection acoustic wave element is formed such that the characteristic between the level of the electric signal input to the input electrode and the level of the electric signal output from the output electrode changes according to the change in frequency. Therefore, when the sensitive film adsorbs the object to be measured, the level of the electrical signal output from the output electrode of the detection acoustic wave element changes. Therefore, according to the present invention, by measuring the level of the electric signal output from the output electrode, it is possible to measure the object to be measured without using a frequency measuring device and with one oscillation loop. .

  The acoustic wave sensor according to the present invention includes an oscillation acoustic wave element in which an excitation electrode for exciting an acoustic wave and a reception electrode for converting the acoustic wave into an electric signal are formed on a piezoelectric substrate, An oscillation loop in which an electrical signal converted by the receiving electrode is input to the excitation electrode, an input electrode for converting the electrical signal in the oscillation loop to an elastic wave, and the elastic wave to an electrical signal And an output acoustic wave element formed on a piezoelectric substrate, and at least one of the input electrode and the output electrode on the object to be measured A sensitive film showing adsorptivity is formed, and the acoustic wave element for detection has a characteristic between a level of an electric signal input to the input electrode and a level of an electric signal output from the output electrode. It is formed to change according to the change of frequency, and the front By sensitive film adsorbs the object to be measured, and summarized in that the level of the electric signal output from the output electrode is changed.

  In the present invention, the acoustic wave element for detection to which an electric signal in the oscillation loop is input has a characteristic between the level of the electric signal input to the input electrode and the level of the electric signal output from the output electrode. When the sensitive film formed on at least one of the input electrode and the output electrode adsorbs the object to be measured, the detection acoustic wave element The level of the electric signal output from the output electrode changes. Therefore, according to the present invention, by measuring the level of the electric signal output from the output electrode, it is possible to measure the object to be measured without using a frequency measuring device and with one oscillation loop. .

  In the acoustic wave sensor according to the present invention, a plurality of the acoustic wave elements for detection are provided, and at least one of the detection acoustic wave elements on the input electrode and the output electrode is of a different type. A sensitive film exhibiting adsorptivity to the object to be measured may be formed. In this way, it is possible to measure a plurality of types of objects to be measured without using a frequency measuring device and with one oscillation loop.

  In the acoustic wave sensor according to the present invention having the detection acoustic wave element, the oscillation acoustic wave element and the piezoelectric substrate used in the detection acoustic wave element may be shared. In this way, the measurement accuracy of the object to be measured can be further improved.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

“Embodiment 1”
FIG. 1 is a diagram showing an outline of the configuration of an elastic wave sensor according to Embodiment 1 of the present invention. In the acoustic wave sensor according to the present embodiment, an oscillation loop 20 including an oscillation acoustic wave element 12 and an amplifier AMP1 is formed.

  The oscillation acoustic wave element 12 is configured by forming an excitation comb electrode 12 a and a reception comb electrode 12 b on the piezoelectric substrate 10. The excitation comb electrode 12 a excites an elastic wave to the piezoelectric substrate 10. The elastic wave excited by the excitation comb electrode 12a propagates to both sides of the excitation comb electrode 12a.

  The receiving comb electrode 12b is arranged at a predetermined distance from the exciting comb electrode 12a on one side in the propagation direction of the elastic wave excited by the exciting comb electrode 12a. The receiving comb electrode 12b receives the elastic wave excited by the exciting comb electrode 12a and converts it into an electrical signal. The electric signal converted by the receiving comb electrode 12b is amplified by the amplifier AMP1 and then input to the excitation comb electrode 12a. As a result, an oscillation signal having a frequency within the pass band of the oscillation acoustic wave element 12 and having a phase characteristic of the oscillation loop 20 of 2nπ [rad] (n is an integer) circulates in the oscillation loop 20.

  The oscillating acoustic wave element 12 is formed with a sensitive film 18 that is adsorbable to the object to be measured and is made of, for example, a protein. In the example shown in FIG. 1, a sensitive film 18 is formed on the excitation comb electrode 12a, the reception comb electrode 12b, and the elastic wave propagation path between the excitation comb electrode 12a and the reception comb electrode 12b. Shows the case. Here, as an example of the combination of the measurement object and the sensitive film 18 that adsorbs the measurement object, the measurement object is a C-reactive protein (CRP) antigen, and the sensitive film 18 is an anti-CRP monoclonal antibody. It is.

  The output comb-shaped electrode 16 is formed on the piezoelectric substrate 10 and is arranged on the other side in the propagation direction of the elastic wave excited by the excitation comb-shaped electrode 12a with a predetermined interval from the excitation comb-shaped electrode 12a. Yes. The output comb-shaped electrode 16 converts the elastic wave excited by the excitation comb-shaped electrode 12a into an electric signal and outputs it. The electric signal output from the output comb electrode 16 is amplified by the amplifier AMP2 and then detected by the detector DET, so that the level is detected. Note that the sensitive film 18 is not formed on the output comb-shaped electrode 16, and the output comb-shaped electrode 16 does not exhibit adsorptivity to the object to be measured.

  Further, as shown in FIG. 2, the output comb-shaped electrode 16 has a gain characteristic between the level of the input elastic wave and the level of the output electric signal in its passband (the elastic wave can be converted into an electric signal). In such a case, the characteristics are reduced with increasing frequency. This characteristic can be realized by applying a known weighting method disclosed in Non-Patent Document 1, such as an apodized electrode or a thinned-out electrode, to the comb electrode 16 for output.

  On the other hand, for the oscillating acoustic wave element 12, as shown in FIG. 3, the insertion loss (gain) between the input electric signal level to the excitation comb electrode 12a and the output electric signal level from the receiving comb electrode 12b is obtained. The characteristic does not substantially change even if the frequency changes in the pass band.

  As the oscillation acoustic wave element 12 here, for example, a SAW element using SAW (Rayleigh wave) propagating on the surface of the piezoelectric substrate 10 can be used. Alternatively, an STW element using STW (bulk wave) propagating in the vicinity of the surface of the piezoelectric substrate 10 can be used as the oscillation acoustic wave element 12. When an STW element is used as the oscillating elastic wave element 12, the propagation loss of the elastic wave (STW) due to the formation of the sensitive film 18 on the elastic wave propagation path can be reduced. The sensitive film 18 can also be formed on the oscillation acoustic wave element 12 with a gold film (not shown) interposed therebetween.

  In the acoustic wave sensor shown in FIG. 1, when the sensitive film 18 adsorbs the object to be measured, the pass characteristic of the oscillation acoustic wave element 12 changes, so that the frequency of the oscillation signal circulating in the oscillation loop 20 changes. As a result, the frequency of the elastic wave propagating from the excitation comb electrode 12a to the output comb electrode 16 changes. Here, the output comb-shaped electrode 16 has a characteristic in which the gain characteristic between the input elastic wave level and the output electric signal level changes with a change in the frequency of the elastic wave. Is absorbed, the level of the electric signal output from the output comb-shaped electrode 16 changes. Therefore, the concentration of the object to be measured can be detected by detecting the level of the electrical signal output from the comb electrode 16 for output by the detector DET.

  Note that the pass band of the output comb-shaped electrode 16 is set so as to include a variable range of the frequency of the oscillation signal circulating in the oscillation loop 20. Here, the pass band of the output comb electrode 16 can be adjusted, for example, by setting the number of electrode fingers of the output comb electrode 16.

  As described above, in this embodiment, since the concentration of the object to be measured can be detected by detecting the level of the electrical signal output from the output comb-shaped electrode 16, a frequency measuring device is used. In addition, the object to be measured can be measured with one oscillation loop 20. Unlike Patent Documents 1 and 2, since the object to be measured can be measured by one oscillation loop 20, the number of parts can be reduced. Therefore, reduction in circuit scale and cost reduction can be realized. Furthermore, since oscillation characteristics do not vary among a plurality of oscillation loops, the measurement accuracy of the object to be measured can be improved.

  In addition, since the comb electrode 12a for excitation and the comb electrode 12b for reception of the oscillation acoustic wave element 12 and the comb electrode 16 for output are formed on the common piezoelectric substrate 10, changes in external environment such as temperature are changed. It is possible to suppress the difference in characteristics between the oscillation acoustic wave element 12 and the output comb electrode 16 from being different. Therefore, the measurement accuracy of the object to be measured can be further improved.

  In the description of the present embodiment, the gain characteristic between the input acoustic wave level to the output comb electrode 16 and the output electric signal level from the output comb electrode 16 is a frequency in the pass band of the output comb electrode 16. The case where the characteristics are reduced with increase in the above has been described. However, the gain characteristic between the input acoustic wave level to the output comb electrode 16 and the output electric signal level from the output comb electrode 16 increases as the frequency increases in the pass band of the output comb electrode 16. May be.

  In the description of the present embodiment, the sensitive film 18 is formed on the excitation comb electrode 12a, the reception comb electrode 12b, and the elastic wave propagation path between the excitation comb electrode 12a and the reception comb electrode 12b. Explained the case. However, the sensitive film 18 is formed on at least one of the excitation comb electrode 12a, the reception comb electrode 12b, and the elastic wave propagation path between the excitation comb electrode 12a and the reception comb electrode 12b. Then, the level of the electric signal output from the output comb-shaped electrode 16 can be changed by the adsorption of the measurement object by the sensitive film 18. For example, as shown in FIG. 4, the sensitive film 18 is not formed on the excitation comb electrode 12a and the reception comb electrode 12b, and an elastic wave between the excitation comb electrode 12a and the reception comb electrode 12b. The sensitive film 18 may be formed only on the propagation path.

  In the elastic wave sensor shown in FIG. 4, when the sensitive film 18 adsorbs the object to be measured, the propagation speed of the elastic wave propagating from the excitation comb electrode 12 a to the reception comb electrode 12 b changes to circulate the oscillation loop 20. The frequency of the oscillation signal is changed. 1, the frequency of the elastic wave propagating from the excitation comb electrode 12a to the output comb electrode 16 changes, and the level of the electrical signal output from the output comb electrode 16 changes. . Therefore, the concentration of the object to be measured can be detected by detecting the level of the electrical signal output from the comb electrode 16 for output by the detector DET.

  In the description of the present embodiment, the case where the receiving comb electrode 12b and the output comb electrode 16 are arranged on both sides of the excitation comb electrode 12a has been described. However, as shown in FIGS. 5 and 6, the receiving comb electrode 12b and the output comb electrode 16 may be disposed on one side of the excitation comb electrode 12a.

  In the acoustic wave sensor shown in FIGS. 5 and 6, the length of the portion of the excitation comb electrode 12a that excites the acoustic wave (the opening length of the excitation comb electrode 12a) a receives the acoustic wave of the reception comb electrode 12b. The length of the portion to be received (opening length of the receiving comb electrode 12b) b and the length of the portion receiving the acoustic wave of the output comb electrode 16 (opening length of the output comb electrode 16) c is longer than the sum b + c. The receiving comb electrode 12b and the output comb electrode 16 are arranged so that the openings thereof are opposed to the openings of the excitation comb electrode 12a, and the propagation direction of the elastic wave excited by the excitation comb electrode 12a A predetermined distance is provided in the substantially vertical direction. The arrangement of the receiving comb electrode 12b and the output comb electrode 16 allows the elastic wave excited by the excitation comb electrode 12a to be detected by both the receiving comb electrode 12b and the output comb electrode 16.

  5 shows the case where the sensitive film 18 is formed on the excitation comb electrode 12a, the reception comb electrode 12b, and the elastic wave propagation path between the excitation comb electrode 12a and the reception comb electrode 12b. Is shown. On the other hand, FIG. 6 shows that the sensitive film 18 is not formed on the excitation comb electrode 12a and the reception comb electrode 12b, but only on the elastic wave propagation path between the excitation comb electrode 12a and the reception comb electrode 12b. The case where the sensitive film | membrane 18 is formed is shown. Other configurations are the same as those shown in FIG.

  Also in the elastic wave sensor shown in FIGS. 5 and 6, when the sensitive film 18 adsorbs the object to be measured, the frequency of the oscillation signal circulating in the oscillation loop 20 changes. 1, the frequency of the elastic wave propagating from the excitation comb electrode 12a to the output comb electrode 16 changes, and the level of the electrical signal output from the output comb electrode 16 changes. . Therefore, by detecting the level of the electric signal output from the comb electrode 16 for output by the detector DET, it is possible to detect the concentration of the object to be measured without using the frequency measuring device and with one oscillation loop 20. it can.

“Embodiment 2”
FIG. 7 is a diagram showing an outline of the configuration of an elastic wave sensor according to Embodiment 2 of the present invention. In the present embodiment, the sensitive film 18 is not formed on the oscillating elastic wave element 12, and the oscillating elastic wave element 12 does not exhibit adsorptivity to the object to be measured. A sensitive film 18 is formed on the output comb-shaped electrode 16. Other configurations are the same as those shown in FIG.

  In the acoustic wave sensor shown in FIG. 7, even if the sensitive film 18 adsorbs the object to be measured, the frequency of the oscillation signal circulating in the oscillation loop 20 does not change, so that the excitation comb electrode 12 a is changed to the output comb electrode 16. The frequency of the propagating elastic wave does not change. However, when the sensitive film 18 adsorbs the object to be measured, the pass band of the output comb-shaped electrode 16 is shifted. Here, as shown in FIG. 2, the output comb-shaped electrode 16 has a characteristic in which the gain characteristic between the input elastic wave level and the output electric signal level changes with a change in frequency. When the object to be measured is adsorbed, the level of the electric signal output from the output comb-shaped electrode 16 changes. Therefore, the concentration of the object to be measured can be detected by detecting the level of the electrical signal output from the comb electrode 16 for output by the detector DET.

  The pass band of the output comb-shaped electrode 16 is set so as to always include the frequency of the oscillation signal circulating in the oscillation loop 20 within the variable (shift) range. Here, the pass band of the output comb electrode 16 can be adjusted, for example, by setting the number of electrode fingers of the output comb electrode 16.

  Also in the present embodiment, it is possible to measure the object to be measured with one oscillation loop 20 without using a frequency measuring device. Therefore, reduction in circuit scale and cost reduction can be realized. And since the dispersion | variation in the oscillation characteristic does not generate | occur | produce between several oscillation loops, the measurement precision of a to-be-measured object can be improved. In addition, since it is possible to suppress changes in characteristics with respect to changes in the external environment such as temperature between the oscillation acoustic wave element 12 and the output comb-shaped electrode 16, it is possible to further improve the measurement accuracy of the object to be measured. Can do.

  In the description of the present embodiment, the case where the receiving comb electrode 12b and the output comb electrode 16 are arranged on both sides of the excitation comb electrode 12a has been described. However, as shown in FIG. 8, the receiving comb electrode 12b and the output comb electrode 16 may be arranged on one side of the excitation comb electrode 12a.

  In the acoustic wave sensor shown in FIG. 8, a plurality of output comb electrodes 16-1, 16-2 and 16-3 are formed on the piezoelectric substrate 10. The length of the portion of the excitation comb electrode 12a that excites the elastic wave (the opening length of the excitation comb electrode 12a) a is the length of the portion of the reception comb electrode 12b that receives the elastic wave (the reception comb electrode 12a). 12b) and the length of the portion for receiving the elastic wave of the output comb electrode 16-1 (opening length of the output comb electrode 16-1) c and the elastic wave of the output comb electrode 16-2. The length of the portion (opening length of the output comb electrode 16-2) d and the length of the portion receiving the elastic wave of the output comb electrode 16-3 (opening length of the output comb electrode 16-3) e It is longer than the sum b + c + d + e. Further, the receiving comb electrode 12b and the output comb electrodes 16-1, 16-2, 16-3 are arranged so that their openings face the openings of the excitation comb electrode 12a, and the excitation comb electrode 12a. A predetermined distance is arranged in a direction substantially perpendicular to the propagation direction of the elastic wave to be excited more. Due to the arrangement of the receiving comb electrode 12b and the output comb electrodes 16-1, 16-2, 16-3, the elastic waves excited by the excitation comb electrode 12a are received by the receiving comb electrode 12b and the output comb electrode 16-. 1, 16-2, 16-3.

  Further, the sensitive films 18-1, 18-2, 18-3 are formed on the output comb-shaped electrodes 16-1, 16-2, 16-3, respectively. Here, each of the sensitive films 18-1, 18-2, and 18-3 exhibits adsorptivity to different types of objects to be measured A, B, and C. Although not shown in FIG. 8, the electric signals output from the output comb-shaped electrodes 16-1, 16-2, and 16-3 are amplified by an amplifier and then detected by a detector. Each level is detected. Other configurations are the same as those shown in FIG.

  In the acoustic wave sensor shown in FIG. 8, when the sensitive film 18-1 adsorbs the object A, the pass band of the output comb-shaped electrode 16-1 shifts. At this time, since the other sensitive films 18-2 and 18-3 do not adsorb the object A to be measured, the pass bands of the output comb-shaped electrodes 16-2 and 16-3 do not shift. Therefore, the level of the electric signal output from the output comb electrode 16-1 changes, and the level of the electric signal output from the output comb electrodes 16-2 and 16-3 does not change. Similarly, when the sensitive film 18-2 adsorbs the measurement object B, the level of the electrical signal output from the output comb electrode 16-2 changes and is output from the output comb electrodes 16-1 and 16-3. The level of the electrical signal does not change. When the sensitive film 18-3 adsorbs the object C to be measured, the level of the electrical signal output from the output comb electrode 16-3 changes and is output from the output comb electrodes 16-1 and 16-2. The level of the electrical signal does not change. Therefore, by detecting the level of the electric signal output from each of the output comb-shaped electrodes 16-1, 16-2, 16-3, a plurality of types can be obtained by using one oscillation loop 20 without using a frequency measuring device. It is possible to detect the concentrations of the objects to be measured A, B, and C.

“Embodiment 3”
FIG. 9 is a diagram showing a schematic configuration of an elastic wave sensor according to Embodiment 3 of the present invention. In the present embodiment, in addition to the oscillation acoustic wave element 12 in the oscillation loop 20, a detection acoustic wave element 22 is provided.

  The detection acoustic wave element 22 is configured by forming the input comb electrode 14 and the output comb electrode 16 on the piezoelectric substrate 10. The comb electrode 14 for input is connected to the oscillation loop 20 at the output position of the amplifier AMP1, and converts an electric signal in the oscillation loop 20 into an elastic wave. The output comb electrode 16 is arranged at a predetermined interval from the input comb electrode 14 on one side in the propagation direction of the elastic wave excited by the input comb electrode 14. The output comb electrode 16 converts the elastic wave excited by the input comb electrode 14 into an electrical signal and outputs the electrical signal. In addition, the sensitive film | membrane 18 is not formed on the elastic wave element 22 for a detection, and the elastic wave element 22 for a detection does not show adsorption property with respect to a to-be-measured object.

  As described above, in this embodiment, the excitation comb electrode 12a, the reception comb electrode 12b, the input comb electrode 14 and the output comb electrode 16 are formed on the common piezoelectric substrate 10. The piezoelectric substrate 10 used for the oscillation acoustic wave element 12 and the detection acoustic wave element 22 is shared. As shown in FIG. 9, the oscillation acoustic wave element 12 and the detection acoustic wave element 22 are arranged so that the acoustic wave propagation directions are substantially parallel, and the oscillation acoustic wave element 12 is excited. The elastic wave and the elastic wave excited by the detection elastic wave element 22 do not interfere with each other, and are arranged at a predetermined distance with respect to the elastic wave propagation direction and the substantially vertical direction.

  Here, as the acoustic wave elements 12 and 22, for example, SAW elements using SAW (Rayleigh waves) propagating on the surface of the piezoelectric substrate 10 can be used. Alternatively, STW elements using STW (bulk waves) that propagate near the surface of the piezoelectric substrate 10 can be used as the acoustic wave elements 12 and 22.

  Furthermore, for the detection acoustic wave element 22 in the present embodiment, as shown in FIG. 10, the level of the electrical signal input to the input comb electrode 14 and the level of the electrical signal output from the output comb electrode 16 The insertion loss (gain) characteristic between them is formed so as to decrease with increasing frequency in the pass band. This characteristic can be realized by applying a known weighting method disclosed in Non-Patent Document 1, such as an apodized electrode or a thinned-out electrode, to at least one of the input comb electrode 14 and the output comb electrode 16. it can. Other configurations are the same as those shown in FIG.

  In the acoustic wave sensor shown in FIG. 9, when the sensitive film 18 adsorbs the object to be measured, the pass characteristic of the oscillation acoustic wave element 12 changes, so that the frequency of the oscillation signal circulating in the oscillation loop 20 changes. As a result, the frequency of the electric signal input to the input comb electrode 14 of the detection acoustic wave element 22 changes. Here, the detection acoustic wave element 22 has a characteristic in which an insertion loss (gain) characteristic between input and output changes with a change in frequency. Therefore, when the sensitive film 18 adsorbs an object to be measured, the detection elastic wave element 22 is elastic. The level of the electrical signal output from the output comb electrode 16 of the wave element 22 changes. Therefore, the concentration of the object to be measured can be detected by detecting the level of the electrical signal output from the comb electrode 16 for output by the detector DET.

  The pass band of the detection acoustic wave element 22 is set so as to include a variable range of the frequency of the oscillation signal circulating in the oscillation loop 20. Here, the pass band of the detection acoustic wave element 22 can be adjusted, for example, by setting the number of electrode finger pairs of the input comb electrode 14 and the output comb electrode 16.

  Also in the present embodiment, it is possible to measure the object to be measured with one oscillation loop 20 without using a frequency measuring device. Therefore, reduction in circuit scale and cost reduction can be realized. And since the dispersion | variation in the oscillation characteristic does not generate | occur | produce between several oscillation loops, the measurement precision of a to-be-measured object can be improved.

  Further, the excitation comb electrode 12a and the reception comb electrode 12b of the oscillation acoustic wave element 12 and the input comb electrode 14 and the output comb electrode 16 of the detection acoustic wave element 22 are provided on a common piezoelectric substrate 10. Therefore, it is possible to suppress a change in characteristics due to a change in the external environment such as temperature between the oscillation acoustic wave element 12 and the detection acoustic wave element 22. Therefore, the measurement accuracy of the object to be measured can be further improved.

  In the description of this embodiment, the insertion loss (gain) characteristic between the input electric signal level to the input comb electrode 14 and the output electric signal level from the output comb electrode 16 is the detection acoustic wave element 22. The case has been described in which the characteristics decrease with an increase in frequency in the passband. However, the insertion loss (gain) characteristic between the input electric signal level to the input comb electrode 14 and the output electric signal level from the output comb electrode 16 increases as the frequency increases in the passband of the detection acoustic wave element 22. It may be an increasing characteristic.

  In the description of the present embodiment, the sensitive film 18 is formed on the excitation comb electrode 12a, the reception comb electrode 12b, and the elastic wave propagation path between the excitation comb electrode 12a and the reception comb electrode 12b. Explained the case. However, the sensitive film 18 is on the excitation comb electrode 12a, the reception comb electrode 12b, and the elastic wave propagation path between the excitation comb electrode 12a and the reception comb electrode 12b, as in the first embodiment. If formed at least one, the level of the electrical signal output from the output comb-shaped electrode 16 can be changed by the adsorption of the object to be measured by the sensitive film 18. For example, as shown in FIG. 11, the sensitive film 18 is not formed on the excitation comb electrode 12a and the reception comb electrode 12b, and an elastic wave between the excitation comb electrode 12a and the reception comb electrode 12b is formed. The sensitive film 18 may be formed only on the propagation path.

“Embodiment 4”
FIG. 12 is a diagram showing an outline of a configuration of an elastic wave sensor according to Embodiment 4 of the present invention. In this embodiment, the sensitive film 18 is not formed on the oscillating elastic wave element 12, and the oscillating elastic wave element 12 does not exhibit adsorptivity with respect to the object to be measured. A sensitive film 18 is formed on the input comb electrode 14 and the output comb electrode 16 of the detection acoustic wave element 22. Other configurations are the same as those shown in FIG.

  In the acoustic wave sensor shown in FIG. 12, even if the sensitive film 18 adsorbs the object to be measured, the frequency of the oscillation signal circulating in the oscillation loop 20 does not change. The frequency of the electric signal input to the terminal does not change. However, when the sensitive film 18 adsorbs the object to be measured, the pass band of the detection acoustic wave element 22 is shifted. Here, as shown in FIG. 10, the detection acoustic wave element 22 has a characteristic in which the insertion loss (gain) characteristic between the input and output changes as the frequency changes. Is absorbed, the level of the electric signal output from the comb electrode 16 for output of the acoustic wave element for detection 22 changes. Therefore, the concentration of the object to be measured can be detected by detecting the level of the electrical signal output from the comb electrode 16 for output by the detector DET.

  The passband of the detection acoustic wave element 22 is set so as to always include the frequency of the oscillation signal that circulates through the oscillation loop 20 within the variable (shift) range. Here, the pass band of the detection acoustic wave element 22 can be adjusted, for example, by setting the number of electrode finger pairs of the input comb electrode 14 and the output comb electrode 16.

  Also in the present embodiment, it is possible to measure the object to be measured with one oscillation loop 20 without using a frequency measuring device. Therefore, reduction in circuit scale and cost reduction can be realized. And since the dispersion | variation in the oscillation characteristic does not generate | occur | produce between several oscillation loops, the measurement precision of a to-be-measured object can be improved. In addition, it is possible to suppress changes in characteristics due to changes in the external environment such as temperature between the oscillation acoustic wave element 12 and the detection acoustic wave element 22. Therefore, the measurement accuracy of the object to be measured can be further improved.

  In the present embodiment, a plurality of detection acoustic wave elements 22-1 and 22-2 may be provided as shown in FIG.

  The oscillating elastic wave element 12 and the detecting elastic wave elements 22-1 and 22-2 in FIG. 13 are arranged so that the elastic wave propagation directions are substantially parallel, and the oscillating elastic wave element 12 is excited. The acoustic wave propagating direction, the elastic wave excited by the detecting elastic wave element 22-1 and the elastic wave excited by the detecting elastic wave element 22-2 do not interfere with each other with a predetermined distance in a direction substantially perpendicular to the elastic wave propagation direction. Has been placed. The electric signal in the oscillation loop 20 is input to the input comb electrodes 14-1 and 14-2.

  Further, a sensitive film 18-1 is formed on the input comb electrode 14-1 and the output comb electrode 16-1, and is formed on the input comb electrode 14-2 and the output comb electrode 16-2. A sensitive film 18-2 is formed. Here, each of the sensitive films 18-1 and 18-2 exhibits adsorptivity to different types of objects to be measured A and B, respectively. Although not shown in FIG. 13, the electric signals output from the output comb-shaped electrodes 16-1 and 16-2 are amplified by an amplifier and then detected by a detector. Are detected respectively. The other configuration is the same as the configuration shown in FIG.

  In the elastic wave sensor shown in FIG. 13, when the sensitive film 18-1 adsorbs the measurement object A, the pass band of the detection elastic wave element 22-1 is shifted. At this time, since the other sensitive film 18-2 does not adsorb the object A to be measured, the pass band of the acoustic wave element for detection 22-2 does not shift. Therefore, the level of the electrical signal output from the output comb electrode 16-1 changes, and the level of the electrical signal output from the output comb electrode 16-2 does not change. Similarly, when the sensitive film 18-2 adsorbs the measurement object B, the level of the electric signal output from the output comb electrode 16-2 changes, and the electric signal output from the output comb electrode 16-1 changes. The level does not change. Accordingly, by detecting the level of the electric signal output from each of the output comb-shaped electrodes 16-1 and 16-2, a plurality of types of objects to be measured can be obtained without using a frequency measuring device and with one oscillation loop 20. The concentrations of A and B can be detected.

  In the description of the present embodiment, the sensitive film 18 (18-) is formed on both the input comb electrode 14 (14-1, 14-2) and the output comb electrode 16 (16-1, 16-2). The case where 1, 18-2) is formed has been described. However, the sensitive film 18 (18-1, 18-2) is at least on the input comb electrode 14 (14-1, 14-2) and the output comb electrode 16 (16-1, 16-2). If formed into one, the electric signal output from the output comb-shaped electrode 16 (16-1, 16-2) is absorbed by the object to be measured by the sensitive film 18 (18-1, 18-2). The level can be changed.

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to such embodiment at all, and it can implement with a various form in the range which does not deviate from the summary of this invention. Of course.

It is a figure which shows the outline of a structure of the elastic wave sensor which concerns on Embodiment 1 of this invention. It is a figure which shows an example of the gain characteristic between the input-output of the comb electrode for output. It is a figure which shows an example of the gain characteristic between the input-output of the elastic wave element for oscillation. It is a figure which shows the outline of the other structure of the elastic wave sensor which concerns on Embodiment 1 of this invention. It is a figure which shows the outline of the other structure of the elastic wave sensor which concerns on Embodiment 1 of this invention. It is a figure which shows the outline of the other structure of the elastic wave sensor which concerns on Embodiment 1 of this invention. It is a figure which shows the outline of a structure of the elastic wave sensor which concerns on Embodiment 2 of this invention. It is a figure which shows the outline of the other structure of the elastic wave sensor which concerns on Embodiment 2 of this invention. It is a figure which shows the outline of a structure of the elastic wave sensor which concerns on Embodiment 3 of this invention. It is a figure which shows an example of the gain characteristic between the input-output of the elastic wave element for a detection. It is a figure which shows the outline of the other structure of the elastic wave sensor which concerns on Embodiment 3 of this invention. It is a figure which shows the outline of a structure of the elastic wave sensor which concerns on Embodiment 4 of this invention. It is a figure which shows the outline of the other structure of the elastic wave sensor which concerns on Embodiment 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Piezoelectric substrate, 12 Oscillation acoustic wave element, 12a Excitation comb-shaped electrode, 12b Receiving comb-shaped electrode, 14 (14-1, 14-2) Input comb-shaped electrode, 16 (16-1, 16-2, 16 -3) Comb electrode for output, 18 (18-1, 18-2, 18-3) sensitive film, 20 oscillation loop, 22 (22-1, 22-2) acoustic wave element for detection, AMP1, AMP2 amplifier, DET detector.

Claims (7)

An electrical signal converted by the receiving electrode includes an oscillation acoustic wave element in which an excitation electrode for exciting an elastic wave and a receiving electrode for converting the elastic wave into an electric signal are formed on a piezoelectric substrate. An oscillation loop that is input to the excitation electrode;
An output electrode that is formed on the piezoelectric substrate and converts an elastic wave excited by the excitation electrode into an electric signal and outputs the electric signal;
Have
On the oscillating acoustic wave element, a sensitive film showing adsorptivity to the object to be measured is formed,
The output electrode is formed such that the characteristic between the level of the input elastic wave and the level of the electric signal to be output changes according to the change in frequency,
The frequency of the elastic wave propagating from the excitation electrode to the output electrode changes due to the sensitive film adsorbing the object to be measured, and the level of the electrical signal output from the output electrode changes. An elastic wave sensor. An electrical signal converted by the receiving electrode includes an oscillation acoustic wave element in which an excitation electrode for exciting an elastic wave and a receiving electrode for converting the elastic wave into an electric signal are formed on a piezoelectric substrate. An oscillation loop that is input to the excitation electrode;
An output electrode that is formed on the piezoelectric substrate and converts an elastic wave excited by the excitation electrode into an electric signal and outputs the electric signal;
Have
On the output electrode, a sensitive film showing adsorptivity to the object to be measured is formed,
The output electrode is formed such that the characteristic between the level of the input elastic wave and the level of the electric signal to be output changes according to the change in frequency,
The elastic wave sensor according to claim 1, wherein the level of an electric signal output from the output electrode is changed by adsorbing the object to be measured by the sensitive film. The elastic wave sensor according to claim 2,
A plurality of the output electrodes are formed on the piezoelectric substrate,
An elastic wave sensor, wherein a sensitive film that exhibits adsorptivity to different types of objects to be measured is formed on each output electrode. An electrical signal converted by the receiving electrode includes an oscillation acoustic wave element in which an excitation electrode for exciting an elastic wave and a receiving electrode for converting the elastic wave into an electric signal are formed on a piezoelectric substrate. An oscillation loop that is input to the excitation electrode;
An acoustic wave element for detection in which an input electrode for converting an electric signal in the oscillation loop into an elastic wave and an output electrode for converting the elastic wave into an electric signal and output are formed on a piezoelectric substrate;
Have
On the oscillating acoustic wave element, a sensitive film showing adsorptivity to the object to be measured is formed,
The detection acoustic wave element is formed such that a characteristic between a level of an electrical signal input to the input electrode and a level of an electrical signal output from the output electrode changes according to a change in frequency. And
The elastic wave sensor according to claim 1, wherein the level of an electric signal output from the output electrode is changed by adsorbing the object to be measured by the sensitive film. An electrical signal converted by the receiving electrode includes an oscillation acoustic wave element in which an excitation electrode for exciting an elastic wave and a receiving electrode for converting the elastic wave into an electric signal are formed on a piezoelectric substrate. An oscillation loop that is input to the excitation electrode;
An acoustic wave element for detection in which an input electrode for converting an electric signal in the oscillation loop into an elastic wave and an output electrode for converting the elastic wave into an electric signal and output are formed on a piezoelectric substrate;
Have
At least one of the input electrode and the output electrode is formed with a sensitive film that exhibits adsorptivity to the object to be measured,
The detection acoustic wave element is formed such that a characteristic between a level of an electrical signal input to the input electrode and a level of an electrical signal output from the output electrode changes according to a change in frequency. And
The elastic wave sensor according to claim 1, wherein the level of an electric signal output from the output electrode is changed by adsorbing the object to be measured by the sensitive film. The elastic wave sensor according to claim 5,
A plurality of the acoustic wave elements for detection are provided,
An elastic wave characterized in that at least one of the detection acoustic wave elements on the input electrode and the output electrode is formed with a sensitive film that exhibits adsorptivity to different types of objects to be measured. Sensor. It is an elastic wave sensor given in any 1 paragraph of Claims 4-6,
An acoustic wave sensor characterized in that a piezoelectric substrate used for the oscillation acoustic wave element and the detection acoustic wave element is shared.

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