SU1104363A1 - Acoustic unit - Google Patents

Abstract

An ACOUSTIC UNIT containing a delay line of surface acoustic waves consisting of a waveguide and transducers placed on its surface and a broadband amplifier connected between the transducers, characterized in that, in order to extend the functionality, the delay line is made in the form of a cylindrical waveguide 3 piezoelectric material with flanges, with the transducers placed around the circumference on the flange surfaces, and the transition from the flange to the inner surface of the cylinder is made iusom R of curvature, conditions selected from R 5-

Description

Output

Phage. The invention relates to a measurement technique, in particular, to the linear dimensions of products, and can be used for precision control of the diameter of a microbial. An acoustic unit is known that includes a delay line for surface acoustic waves, consisting of a waveguide and transducers placed on its surface, and a broadband amplifier connected between transducers. The delay line is the frequency-generating element of the oscillator ll. This block prevents the diameter of the microwire from being monitored, since surface acoustic waves (SAW) are excited on the surface of a planar waveguide. The aim of the invention is to expand the functionality. The goal is achieved by the fact that in an acoustic unit containing a delay line of surface acoustic waves, consisting of a waveguide and transducers placed on its surface, and a broadband amplifier connected between the transducers, the delay line is made in the form of a cylindrical waveguide of piezoelectric material with flanges, the converters are placed circumferentially on the surfaces of the flanges, and the transition from the flange to the inner surface of the cylinder is made with a radius R rounding, selected from Word R 5- (8-10) A, where L - length of the surface acoustic wave. FIG. 1 shows a diagram of an acoustic unit; in fig. 2 is a view A of FIG. one; in fig. 3 shows the dependence of the surfactant velocity on the gap between the microwire and the internal diameter of the waveguide; FIG. 4 - a variant of the acoustic unit included in the differential circuit. The acoustic unit (Fig. 1) contains the SAW delay line 1, which is the frequency-generating element of the auto-generator (not shown), the input 2 and the output 3 converters of the delay line 1 are connected respectively to the output and the input of the broadband amplifier 4. The SAW delay line 1 is made of piezoelectric material in the form of a circular fiber waveguide 5 with flanges 6 and 7. Input 2 and output 3 anti-SAF pin-to-pin converters (IDT) are placed around the circumference (FIG. 2) on the corresponding external end surfaces of the flanges 6 and 7 of the waveguide 5 either using piezoelectric films (for example, zinc oxide ZnO). The flanges 6 and 7 along the radius R rounding go into the through channel 8 of the waveguide 5. To reduce the series resistance of the electrode structure to the required level, the electrode structure of the IDT 2 and 3 can be divided into segments (Fig.2) controlled in parallel (electrical connection of the segments IDT 2 and their connection to the amplifier 4 is carried out in a known manner). In the embodiment of the device constructed according to the differential scheme (Fig. 4), the device contains another SAW generator 9, similar to the first one, and a mixer 10. The microwire 11 is pulled into the opening 8 of the waveguide 5. The monitoring process is carried out as follows. With the help of the input circular IDP 2, surfactants are excited on the torp surface of the flange 6, due to the fact that the end surface of the flange 6 is symmetrically rounded with a rounding radius R5 (8-10) 1 (where Ti is the length of the surfactant) and passes into the internal through channel 8 of the waveguide 5, Surfactants without significant losses to the generation of parasitic body waves are directed along the inner surface of the fiber waveguide 5. The radius of rounding does not make sense to choose more than ten L due to the change in the path of propagation of the surfactant. The diameter of the end surfaces of the flanges 6 and 7 is chosen from the possibility of implementing the required radius I, rounding and placing on the end parts of these surfaces the corresponding IDT surfactant 2 and 3. The waves propagating along the inner surface of the waveguide 5 have Rayleigh-like axial waves. and radial components and do not have an azimuth component. The resulting energy distribution has circular symmetry and decreases approximately exponentially with changes in the radius of the inner surface of channel 8. Dispersion coupling for the main surface mode. propagating along the inner surface of the waveguide 5 surfactant, the equation is, .pS ,,. 2J. T, tmrT Р where P (p - / c; Lt (() is the radius of the through channel 8, 3,., P - respectively, constant propagation of the surface mode of the volume longitudinal mode and the volume transverse mode, - modified function Bessel i Using SAF 3 located on the end surface of flange 7, surfactant is received in the same way as ILS 2. Amplifier 4 is inserted into the feedback circuits with a gain sufficient to compensate for the total losses in the delay line 1. Frequencies at which excitation is possible surfactant generator, described by the equation 2iin cOrl. (V + oSe, where co is the generation frequency, (He is the electrical total phase shift in IDT 2 and 3 and amplifier 4, V is the speed along the internal surface of the waveguide 5 SAW, U is the working length on delay line 1 (distance between IDC centers 2 and 3). The thickness of the walls 6 of the circular waveguide 5 in its non-thickened part should be chosen equal to 6 (5-10) L. In this case, the parasitic bulk modes are removed by absorption on the outer surface of the waveguide 5, since they usually have large penetration depths, the main one and therefore removed as the waves propagate Thus, in the absence of a con- trollable microwire, a pure single-mode mode of generation with a frequency of COP is provided. A controlled microwire 11, filled with electrically conductive material or electrically coated, is guided into the through channel 8 of the waveguide 5. The presence of the electrically conducting microwire 11 in the channel 8 causes the tangential components to propagate along the internal surface of the piezoelectric waveguide 5 surfactant. the magnetic field, which leads to a decrease in the velocity V of the propagation of surfactants. With increasing or decreasing the diameter of the monitored microwire 11, the gap between its surface and the surrounding microwire with the inner surface of the waveguide 5 decreases or increases, which leads to a corresponding change in the SAW velocity. The magnitude of the change in the constant distribution of the p p -p surfactant with a change in the diameter J of the microporous 11 as a function of the normalized RP gap between the surface of the microwire 11 and the inner surface of the waveguide 5 can be found from l) 2 eo ptgph С-Т Г, .. Т -V ,, -T, 1-1112. where) (t ..,) J is the electromechanical coupling coefficient, .., EXU is a dielectric constant of a piezoelectric waveguide, 8 is a dielectric constant of free space. An example of a change in the velocity V. A PV in the function of the normalized gap Zb is shown in FIG. 3. The maximum magnitude of the change in the JiV velocity of the surfactant can be estimated from us4. Catch, VI „- Where VQ is the SAW speed for the fully electrically shorted internal surface of the waveguide 5 h (D-d), D 2r is the diameter of the through channel 8, VQQ is the speed in the absence of microwire. Thus, when the diameter of the microwire changes, the speed and magnitude of the phase delay of the SAW generator 1 delay line 1 are modulated and, therefore, the DSO generation frequency changes. To obtain accurate frequency control, the oscillator must contain an element with a phase response varying rapidly with frequency. The slope of the phase response cj (x, / d is proportional to the length of the delay line 1, therefore, it is advisable to choose this length to be from hundreds to thousands of surfactant lengths. For the same purpose to ensure the most accurate control of the diameter of the microwire 11, the difference between the diameter O of channel 8 and the average expected diameter The d microwire (initial gap) is chosen small, up to fractions of the length of the surfactant (Fig. 2).

To reduce the influence of external factors on the accuracy of control, in particular, temperature stabilization in a wide range, the acoustic unit contains another SAW generator 9 (Fig. 4), similar to the first one. The controlled microwire 11 is fed into the through channel of only the first SAW generator. When the microwire 11 is controlled by this generator, the difference frequency allocated by the mixer 10 becomes proportional to the magnitude of the change in the diameter of the microwire. The change in temperature in this case does not lead to a change in the difference frequency at the output of the mixer 10.

View A FIG. g

The device is especially effective for controlling very small changes in the diameter of a microwire, which is provided by a very high short-term stability of the SAW generator (up to 1 CG), by the interaction of the entire surface of the microwire (circumferentially in cross section) with the electromagnetic field accompanying the SAW, rather sharply depending on the speed V SAW from the normalized air gap pb, by removing the parasitic oscillation modes by selecting the wall thickness of the circular waveguide.

The use of the device in ultrasonic micro welders for welding IC elements allows an increase in the yield ratio of ICs by lowering the coefficient of variation and increasing the mechanical strength of the joints. 0.2 0.2 Fig.Z 0.5j3h 0,

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Claims (1)

ACOUSTIC UNIT containing a delay line of surface acoustic waves, consisting of a waveguide and transducers placed on its surface, and included between the transducers a broadband amplifier, characterized in that, in order to expand the functionality, the delay line is made in the form of a cylindrical waveguide made of a piezoelectric material with flanges, while the transducers are placed around the circumference on the surfaces of the flanges, and the transition from the flange to the inner surface of the cylinder is made radius R of curvature, conditions selected from R 5- (8-10) Ά, where Ά - the length of the surface acoustic wave.