JP4696550B2 - Usage of surface acoustic wave device - Google Patents

Description

  The present invention relates to a method of using a surface acoustic wave element having an annular surface acoustic wave propagation path.

  A substrate having a surface capable of exciting a surface acoustic wave (SAW) and capable of propagating the excited surface acoustic wave, and exciting the surface acoustic wave on the surface of the substrate along the surface. BACKGROUND ART A surface acoustic wave element including an electroacoustic transducer that propagates the surface acoustic wave and can receive the surface acoustic wave propagating is well known.

  The surface acoustic wave element is used as a delay line, an oscillation element, a resonance element, a frequency selection element, for example, various sensors including a chemical sensor, a biosensor, and a pressure sensor, or a remote tag.

  In this case, the surface acoustic wave is generated between the surface of the substrate and the thin film covering the corridor wave or Rayleigh wave propagating along the surface of the substrate or the material different from the material constituting the substrate. Includes boundary waves propagating along the interface.

  International publication WO 01/45255 A1 discloses a spherical surface acoustic wave element. The substrate of the spherical surface acoustic wave element has a spherical surface that can excite the surface acoustic wave and propagate the excited surface acoustic wave. The electroacoustic transducer of the spherical surface acoustic wave element is arranged in a band having a predetermined width that is continuous in an annular shape on the spherical surface of the base, and the surface acoustic wave excited on the surface. Is propagated along the direction in which the bands are continuous and repeatedly circulated.

In the spherical surface acoustic wave element, the surface acoustic wave excited by the electroacoustic transducer is substantially attenuated within the surface acoustic wave propagation band in the annular surface acoustic wave propagation band on the surface of the substrate. The surface can be circulated repeatedly without the need to do so.
International Publication WO 01/45255 A1

  A spherical surface acoustic wave element is formed by forming a comb-like electrode on the surface of a spherical, for example, piezoelectric crystal substrate. An electric field is applied to the interdigital electrode, thereby exciting a surface acoustic wave on the surface of the sphere and causing the sphere surface to make multiple turns.

  When a piezoelectric crystal is used for a spherical substrate, the path through which the surface acoustic wave can be excited is determined by the material of the piezoelectric crystal and its crystal axis, and has been studied. In a spherical surface acoustic wave device, when the electrode width of the interdigital electrode is designed within a predetermined range determined by the surface acoustic wave wavelength and the sphere surface diameter, the surface acoustic wave circulates in a beam shape and is almost out of the beam. It is known that it does not leak energy. Even if the material is fixed at a location away from the beam or the material is contacted from both poles, the influence on the propagation of the surface acoustic wave on the spherical surface is observed in the conventional measurement. It has not been.

  The surface acoustic wave travels multiple times and propagates a long distance in a limited area.When there is a change in the propagation state based on the change in the state of the spherical surface, It is expected to be an ultra-sensitive sensor because it can detect changes in phase (phase change) and surface acoustic wave intensity with high sensitivity.

  However, when a burst signal having a predetermined frequency is input and the phase of the signal accompanying the subsequent lap is measured, the intensity decreases with the lap (as time elapses from the time of excitation). When amplifying the output signal from the element, the number of laps increases, and as the lap time increases, the gain must be significantly increased, either a variable gain circuit, a variable attenuator, or We had to deal with it by using an expensive, very dynamic range digitizer or using a log amp.

  In addition, when using a conventional spherical surface acoustic wave device, an irregular behavior of the phase of the output signal may be observed when the ambient temperature changes depending on the lap time and the frequency of the excited surface acoustic wave. This was a problem in terms of ensuring measurement stability.

  The present invention has been made under the above circumstances, and an object of the present invention is to easily input a burst signal having a predetermined frequency and measure the phase of the signal accompanying the subsequent lap, and further, the lap time Another object of the present invention is to provide a method of using a surface acoustic wave device that can ensure measurement stability even with the frequency of the surface acoustic wave excited.

To achieve as mentioned above object of the present invention, the use of spherical shaped surface acoustic wave device in accordance with the invention:
A three-dimensional substrate having a perfect spherical surface capable of propagating surface acoustic waves, and the surface acoustic waves that excite the surface acoustic waves on the surface and propagate and circulate the surface acoustic waves along the surface and propagate through the surface And a three-dimensional substrate support that supports the three-dimensional substrate so as not to block propagation of the surface acoustic waves excited on the surface by the electroacoustic transducer on the surface. Have
Surface area of the portion not in contact with the external substance which inhibits the propagation of pre-Symbol 3-dimensional substrate support and a surface acoustic wave Te complete spherical surface smell of the 3-dimensional substrate, the entire full sphere shape table surface of the three-dimensional substrate Using a spherical surface acoustic wave element that is 95% or more with respect to the area and in which the three-dimensional substrate is made of a piezoelectric crystal material,
Electrical signals to excite the inputted surface acoustic wave to the electro-acoustic transducer element is a burst signal is limited in time, the after termination of excitation of a surface acoustic wave, the circulation of the surface acoustic wave in the sphere-shaped surface in after time the attenuation rate changes per hour of the intensity of the high frequency signal from the electroacoustic transducer to attenuate with the measurement of the phase or the intensity of the high-frequency signal output from the electroacoustic transducer based on measuring the propagation state before Symbol surface acoustic wave,
It is characterized by that.

In order to achieve the object of the present invention as described above, another method of using a spherical surface acoustic wave device according to the present invention is as follows: The attenuation rate per time of the high-frequency signal intensity from the electroacoustic transducer is changed. wherein in after time when measuring the propagation state of the surface acoustic wave, the attenuation ratio per time prior to the time when the attenuation rate changes (a) and the time per behind the time when the attenuation rate changes The propagation state of the surface acoustic wave is measured using the output from the electroacoustic transducer at the time when the difference from the attenuation factor (B) becomes larger than 5 dB .

  According to the surface acoustic wave device according to the present invention which is configured as described above, a burst signal having a predetermined frequency is input, and the phase of the signal accompanying the subsequent round is measured. In addition, the measurement stability can be ensured by the circulation time and the frequency of the excited surface acoustic wave.

  The surface acoustic wave referred to as surface acoustic wave in the present invention may be an acoustic wave that propagates while concentrating energy on the surface, and even if it is a corridor wave that propagates along the spherical surface inside the sphere, it is a leaky surface acoustic wave. Alternatively, a pseudo surface acoustic wave may be used.

  The electroacoustic transducer has a function of exciting surface acoustic waves (converting an electrical signal into a surface acoustic wave) and one that detects circulating surface acoustic waves by the same electroacoustic transducer. Alternatively, separate electroacoustic transducers may be assigned to the two roles.

The inventor has determined that the surface area of the three-dimensional substrate that is not in contact with the three-dimensional substrate support and the external material that inhibits the propagation of the surface acoustic wave is the total surface area of the three-dimensional substrate. if 95% or more Te, excited first attenuated more than 40dB in the intensity of surface acoustic wave detected propagation of surface acoustic waves circulate on spherical-shaped surface with a small attenuation rate than had been observed prior are there that the time to be there, it was discovered it was able to detect fine-weak output.

  In the present invention, “the time at which the rate of attenuation per time of the intensity of the high-frequency signal from the electroacoustic transducer changes” actually means that the surface acoustic wave excited by the interdigital electrode is the circular path as described below. When obstructed by an elastic wave absorber or diffuser over an area of 5% or more of the area on the surface of the sphere that is 30 ° or more away from the central angle of the sphere (an elastic wave absorber having an area of 95% or more) Or at least having a diffuser) and an attenuation curve of the output from the electroacoustic transducer obtained when not obstructing. Actually, it can be experimentally determined by the time when the attenuation rate of the output per hour changes with and without inhibition.

  The present invention will be described using embodiments with reference to the accompanying drawings.

  In the spherical surface acoustic wave element 10 shown in FIGS. 1A and 1B, the crystal sphere 11 is a perfect sphere having a diameter of 1 cm. In this element, the electroacoustic transducer is gold and The interdigital electrode 12 is formed by depositing a chromium film on the surface of the crystal ball 11 and patterning it by etching by photolithography. The interdigital electrode 12 is excited on the equator with the Z axis of the crystal ball 11 as the ground axis and from the interdigital electrode 12. The surface acoustic wave 14 is formed in an orientation (Z-axis cylinder) that goes around the equator, and is supported by a ring-shaped Teflon (registered trademark) support 16 by cutting a pipe with a diameter of 5 mm.

A high frequency signal having a frequency of 45 MHz and a burst signal width of 3 microseconds is input to the interdigital electrode 12 of the spherical surface acoustic wave element 10 using a contact electrode bar made of pure gold (contact area of 0.01 mm ² or less). In addition, a state in which the high-frequency output output from the same interdigital electrode 12 is attenuated as time passes is shown by a solid line in FIG. The horizontal axis indicates time, and the vertical axis indicates decibel display.

  Next, as shown in FIG. 1 (b), the Teflon (registered trademark) support 16 is removed, and the quartz ball 11 is supported at three positions 30 degrees or more away from the equator at three acute angles made of stainless steel. A similar intensity change of a signal output when the needle 18 is fixed is indicated by a broken line in FIG. In the case of this spherical surface acoustic wave element 10, the time required for one round is 0.01 msec, and for example, the time corresponding to 100 rounds is 1 msec.

The area of the contact point between the acute-angle support needle 18 and the crystal ball 11 is 0.01 mm ² or less, and even when combined, the surface area of the crystal ball 11 is 10000 mm ² or less of 1 / 10,000. It can be seen that the attenuation rate of the signal intensity is small with respect to the observation time (horizontal axis) at a time after a time corresponding to 120 laps or more (1.2 msec). The attenuation rate with respect to time is about 33 dB / msec from the first week to the 120th lap, and is about 20 dB / msec over 120 laps.

  In FIG. 1C, the attenuation rate change point GHP can naturally be expressed as the time when the differential coefficient of the attenuation rate takes a maximum.

  In the case of this spherical surface acoustic wave element 10, if the area of the elastic wave absorber or diffuser is at least 5% or less of the sphere surface and the phase of the output of the spherical surface acoustic wave element 10 is measured after 120 laps, Since the intensity does not change greatly with the change in the number of times, if you limit the input with an appropriate limiter and perform amplification with a constant amplification factor, when measuring the intensity change and phase change at different times of laps, It is clear that it is not necessary to incorporate a variable attenuator in front of the amplification component of the measurement circuit or to use a digitizer with a very large dynamic range, and it is clear that output measurement can be performed in a wide range of lap times. Naturally, since the surface acoustic wave 14 propagated for a very long time is detected and output as an electrical signal, the propagation state of the surface acoustic wave 14 can be monitored with high sensitivity.

  Next, a description will be given of how to generate conditions for generating an area where the elastic wave is absorbed and diffused and a region having a small attenuation rate.

  As shown in FIG. 2, at any location on the surface of the crystal sphere 11 (for example, point A, point B, point C), the propagation of the elastic wave 14 is inhibited by an area of 5% or more on the sphere surface. For example, when silicon rubber 20 having a tip cross-sectional diameter of D mm is brought into contact, it has been experimentally confirmed that it is difficult to observe the long-time rotation indicated by the broken line. The confirmation method is easy due to changes in the signal when the rods made of silicon rubber 20 having different diameters are pressed at various positions of the crystal ball 11, but are sufficiently separated from the circulation path 22 such as point C, for example. It is performed at a position 30 degrees away from the equator in the latitude direction. If it is close to the circulation path 22, the circulation phenomenon itself is inhibited.

When the diameter D of the silicon rubber 20 is in the case of 3 mm (2.2% of the spherical product), has been able to obtain a graph of output change close to the dashed line in the FIG. 1 (c), the diameter D of 5mm In the case (6.3%), the output was completely the same as the solid line except for the noise level, and a signal with a small attenuation rate per time could not be detected.

  Furthermore, in FIG. 2, when there was an external contact at points A and B, the signal output at a time farther than 1.3 msec in FIG. 1 (c) showed a drop of 10 dB or more, but 1 msec. The signal strength at the time was almost unchanged. The signal of the small attenuation region has sensitivity to detection of external deposits and wetting over a wide range of the sphere surface, and the surface state of the spherical surface acoustic wave element 10 can be verified according to the change of the signal. Is possible.

  Using the spherical surface acoustic wave element 10, the substance that is attached to the surface of the spherical surface acoustic wave element 10 is output from the electroacoustic transducer (in this case, the interdigital electrode 12) as the amount thereof increases. The signal phase is delayed. Using this phenomenon, the phase change of the 45 MHz element when albumin is attached to the surface of the spherical surface acoustic wave element 10 is represented by the time of 0.7 msec, 1.3 msec, and 1.5 msec in FIG. As a result of measurement, the measured value fluctuated by 15% or more depending on the phase measured with a time signal of 1.3 msec. In the region where the measured value fluctuates, the difference (G) between the solid line and the broken line in FIG. 1C is in the range of 5 dB, and it was desired to measure at a time that is further away from that time.

  When measuring at a time of 0.7 msec, a high S / N ratio is obtained, but with a measurement of 1.5 msec, the S / N ratio decreases because the number of laps is large, but in practice, when detecting a very small amount of adhesion, The phase change can be measured greatly in proportion to the lap time at the time. As a result, since it is difficult to be limited by the minimum measurement unit in the phase measurement, it has an advantage that the most accurate measurement can be realized.

(A) is a figure which shows roughly the spherical surface acoustic wave element used for the comparison in the usage method of the spherical surface acoustic wave element according to one embodiment of this invention; It is a figure which shows roughly an example of the spherical surface acoustic wave element used in the usage method of the spherical surface acoustic wave element according to one embodiment of this invention; (c) is shown by (a) The figure which shows the fall of the signal strength with the progress of time in the spherical surface acoustic wave element which is a solid line, and the broken line the signal intensity with the passage of time in the spherical surface acoustic wave element shown in (b) It is. At any location on the surface of the crystal ball of the spherical surface acoustic wave element (for example, point A, point B, point C), the diameter of the tip cross-section that obstructs the propagation of the acoustic wave with an area of 5% or more on the sphere surface It is a perspective view which shows roughly the mode of the experiment which confirms that it is difficult to observe the circumference | surroundings for a long time shown with the said broken line, when a Dmm silicon rubber is made to contact.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Spherical surface acoustic wave element, 11 ... Quartz ball, 12 ... Interdigital electrode (electroacoustic transducer), 14 ... Surface acoustic wave, 16 ... Teflon (trademark) support body, 18 ... Stainless steel support needle, 20 ... Silicone rubber, 22 ... Circular route.

Claims (2)

A three-dimensional substrate having a perfect spherical surface capable of propagating surface acoustic waves, and the surface acoustic waves that excite the surface acoustic waves on the surface and propagate and circulate the surface acoustic waves along the surface and propagate through the surface And a three-dimensional substrate support that supports the three-dimensional substrate so as not to block propagation of the surface acoustic waves excited on the surface by the electroacoustic transducer on the surface. Have
Surface area of the portion not in contact with the external substance which inhibits the propagation of pre-Symbol 3-dimensional substrate support and a surface acoustic wave Te complete spherical surface smell of the 3-dimensional substrate, the entire full sphere shape table surface of the three-dimensional substrate Using a spherical surface acoustic wave element that is 95% or more with respect to the area and in which the three-dimensional substrate is made of a piezoelectric crystal material,
Electrical signals to excite the inputted surface acoustic wave to the electro-acoustic transducer element is a burst signal is limited in time, the after termination of excitation of a surface acoustic wave, the circulation of the surface acoustic wave in the sphere-shaped surface in after time the attenuation rate changes per hour of the intensity of the high frequency signal from the electroacoustic transducer to attenuate with the measurement of the phase or the intensity of the high-frequency signal output from the electroacoustic transducer based measure the propagation condition before Symbol surface acoustic waves, the use of spherical surface acoustic wave device characterized by. When measuring the propagation state of the surface acoustic wave at a time later than the time when the attenuation rate per hour of the high-frequency signal intensity from the electroacoustic transducer changes, per time before the time when the attenuation rate changes The output from the electroacoustic transducer at the time when the difference between the attenuation rate (A) and the attenuation rate per time (B) after the time when the attenuation rate changes is greater than 5 dB , 2. The method of using a spherical surface acoustic wave device according to claim 1, wherein a propagation state of the surface wave is measured.

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