DE1616355C - Electromechanical converter - Google Patents

Description

3 4

Furthermore, the invention is further developed in that the coupling increases significantly above 20 °.

that the electrodes the parallel crystal surfaces treatment efficiency is remarkable, and the

cover completely or for the most part. The form of oscillation deviates from pure oscillation

In the following the invention is based on an in from. The rotation indicated is also an extensive one Drawing illustrated embodiment 5 of the optimum to the effect that the frequency spacing explained in more detail. The drawing shows between resonance and anti-resonance, where-

Fi g. 1 is a diagram to explain the invention made possible by a larger operating frequency range

proper orientation, light is.

Fig. 2 is a perspective view of an orientation The preferred orientation here is in combination

management form of the transducer with according to the invention io menhang with a plate-shaped piezoelectric

oriented crystal surfaces and attached to them- see single crystal has been described because it is

th electrodes and, this is a configuration that is suitable for the

3 shows a view of elastic waves over most transducer forms. For this

supporting device with a transducer according to the purpose is the distance between the parallel crystal,

F i g. 2. ^T 15 surfaces or the thickness of the plate about half a

Fig. 1 shows the 15 ° ± 5 ° rotation of the crystal wavelength at the center frequency, that is, the thickness of the surfaces around the x-axis out of the xz-plane is on the order of millimeters or in the position in which the LiTaO ₃ crystal the attached below. The other, large dimensions have certain optimal converter properties. A men is generally based on design considerations, crystal 20 provided with two parallel surfaces, for example on the basis of the desired and / or plate, which is based on this condition, permissible resistance value, capacitance value, etc., is hereinafter referred to as 15 ⁹ ± 5 ° -; tz plate on the electrodes. A reasonable measure for the wall drawing, lerplatten is that its large dimensions, so

In FIG. 2, a 15 ° + 5 ° -; tz plate 1 from the width and length of which is at least five times the LiTaO ₃ between electrodes 2 and 3, 25 plate thickness. More generally, however, that applied by any conventional method, the propagation of the elastic waves, which entz. B. can be deposited or plated. when an electric field is generated in the thickness of such electrodes can cover the entire main surface dimension corresponding crystallographic direction of the wall (illustrated case) or generation in the 15 ° + 5 ° -xz plate, to which only a small one Area thereof in order to minimize undesired advantages regardless of the crystal coupling. The elec- trician leads. Accordingly, there is a vibrational connection to the electrodes via lead separation together with a good efficiency rating 4 and 5. The converter shown can serve as a degree and a wide operating frequency range in the resonator, for example the function of a suitably cut body of any filter or a frequency standard take over, or 35 thickness, as long as the electrodes on the through which it can be part of a larger device, with orientation of the 15 ° ± 5 ° -xz plate certain areas of a delay line. be ordered or as long as the corresponding

The device according to FIG. 3 is a common form of shear vibration caused by any

delay line with a transducer 10 which is transmitted corresponding means.

According to the converter design according to FIG. 2 from 40. In the above-described devices, a plate-shaped piezoelectric single crystal, crystal sections are provided which have two planes 11 made of LiTaO ₃ with two surfaces that are clockwise 10 to parallel each under one of the invented 20 ° around the x- Axis rotated out of the xz plane, have corresponding parallel surfaces and alignment associated with this; but there are also other electrodes 12 and 13 constructed. The electrodes. .45 versions are possible in which the specified are provided via conductors 14 and 15 at an orientation not shown. For example, the signal source is connected. The elastic wave generated by the electrical signal, which is common for resonator applications, is then coupled into one or both of the main surfaces so with contours to acoustic medium 16, which is made of quartz, that the wave movement hits a desired glass, metal or any other suitable 50 th part of the plate. This can consist of material. For certain applications it is advisable to use appropriate chamfering of a case to use LiTaO ₃ or both surfaces on the effective area for the part 16, since it has been found that this material surrounding edge zones or - in extreme cases - material is unusual low attenuation, in particular by using one or two convex surfaces for frequencies above 1 MHz. After reaching 55 chen. Another embodiment, sometimes referred to as the waveform trap at the other end of the acoustic medium 16, has the elastic wave with the aid of a rotated thickened electrodes which are only attached to the desired single crystal body 21 having second transducer part of the plate. The effect of this is again converted into an electrical signal, and the structure is that the wave movement on that signal is then connected to the electrical. 60 to limit part of the crystal, which is located between the 22 and 23 together with the associated connecting leads electrodes. Accordingly, it is adopted for application 24 and 25. application of the present invention to such

It should be emphasized that the specified angle of rotation kri- embodiment only necessary that the upper table is. For rotations, which with respect to the xz-plane surface parts of the main surfaces, which are for the transmission are substantially below 10 °, the 65 of the elastic waves provided, the angege-strain waveform reached measurable values. Have orientation for Drebenes.

1 sheet of drawings

Claims (3)

1 2 coming sections in the crystal pulling process. The invention is based on the object 1. Electromechanical transducer in the form of a single crystal made of LiTaO _3, a piezoelectric single crystal with two parallel 5 electromechanical transducers available to stel surfaces, made of LiTaO ₃ and with len, which has a high degree of efficiency when converting electrodes to generate a electrical FeI- between elastic energy and elektromagnedes guaranteed in at least a part of the crystal of vertical energy, and that is seen when excited, characterized in that the parallel surfaces of the crystal (1, 11, io and completely absent annoying oscillation 21) clockwise by an angle of 10. up to 20 ° around the Ar-axis out of the; cz-plane - The solution to this problem was tedious and are rotated. "Difficult investigations on the lithium tantalate system 2. Converter according to claim 1, characterized in advance, which has been found to be a critical one draws that the distance between the two 15 gives orientation, which leads to an optimalization of the parallel surfaces of the crystal (1, 11, 21). Properties of one made from this material at most equal to one fifth of the width of the transducer. Surface is. LiTaO ₃ is a trigonal crystal of the space group 3. Converter according to claim 1 or 2, characterized in that R 3 c. For the sake of simplicity, it is common practice characterized in that the electrodes (2, 3; 12,13; ao to describe the system as hexagonal, with three 22, 23) the parallel surfaces of the crystal mirror planes instead of three slip planes parallel to the opti-1; 11; 21) completely or for the most part see axis are present. Cover the chosen noun, klatur (see "Standards on Piezoelectric Crystals" Proc. IRE, Vol. 37, No. 12, 1949) is based on the The drawing of the optical axis as the z-axis and on the designation of the α-axis (each of the three for »» 'Optical axis and also to the mirror planes vertical axes) than the x-axis. The y-axis is then the one on both the x and the The invention relates to an electromechanical axis that is perpendicular to the z-axis. It is common to have one niche transducers in the form of a piezoelectric orientation, which none of the through the respective Single crystal with two parallel surfaces, the planes defined by pairs of coordinate axes LiTaO ₃ consists and speaks with electrodes for generating, as rotated out of that plane of an electric field in at least one part define which of the desired orientation on of the crystal is provided. 35 is closest. Finding Components Made of Piezoelectric Material Using this definition, there is the has long been used as circuit elements to solve the problem according to the invention, frequency control in filter arrangement for electromagnetic starting from an electromechanical converter table waves, in oscillator arrangements and in the above-mentioned type, in that the par- stronger arrangements use. Clockwise from the British 40 allelic surfaces of the single crystal Patent specification 655 073 is designed as a piezoelectric material at an angle of 10 to 20 ° around the x-axis rial C _e G ₁₄ N, O _e (ethylene diamine tartrate, ÄDT) in the xz plane are turned out, knows. Since ADT is a very temperature-sensitive "In the orientation provided according to the invention Material is the result of the above-mentioned printing of the parallel surfaces of the single crystal The task is based on measures known in writing, 45 practically exclusively the form of the shear vibration for ÄDT crystals, crystal sections with an approximate stimulus, and this leads to a coupling coefficient to find the temperature stability. of the order of 45%. The shear In contrast, the invention is based on the second-order descent mode and expansion coverage, that a certain orientation of a mode are both reduced to a value Lithium tantalate crystal both to a pure shear 50 which can hardly be measured with conventional methods. Waveform as well as a high coupling efficiency can therefore be assumed for these waveforms leads. . men that they are 30 db below the excited Lithium tantalate is more recently in terms of its form of vibration. Equally important is the piezoelectric properties and its peculiarities - the fact that the predominant oscillation in relation to elastic waves is examined 55 form pure. It is easy to see that in Verworden (76, Physical Review, 1886, 12/15/49). The use of such an orientation in the electro-special interest in lithium tantalate for the use of mechanical converters ensures that a conversion in an electromechanical converter is effective conversion between elastic energy, special to the directional coupling coefficient, and electromagnetic energy, and of 40% or more and to its extraordinary 60 with a practically complete absence of disturbing high elastic Q-values within a frequency waveform. With this orientation for the area that extends far into the megahertz range consisting of LiTaO ₃ , a single crystal is consequently stretched (see 48, Journal of the American Ceramic Optimalization of the Converter Properties of this Society, 112 [1965]). 'Materials achieved. Furthermore, this material is known to 65 An expedient embodiment of the invention possessing further desirable properties is that the distance between the par- wic z. B. physical and chemical resistance. allelic crystal surfaces at most equal to one In addition, LiTaO., In large, practically full fifths of the width of the surfaces.