SU980250A1 - Piezoelectric resonator - Google Patents

Description

. (54) PIEZOELECTRIC RESONATOR

The invention relates to radio engineering, in particular, to stabilization and frequency control using piezoelectric resonators, can be used in various devices of radio engineering, automation, measurement technology and instrumentation.

. A piezoelectric device is known, comprising a housing with a piezoelectric element placed therein, a heat pipe and a thermal switch 1.

A disadvantage of this device is the impossibility of smoothly varying the controlled frequency in a wide range with unchanged stability.

The closest in technical essence to the present invention is an acoustic device containing two hermetic chambers filled with a gas mixture with low specific wave impedance, one of which is fixed on an additional piezoelectric. an element connected through a bimetal plate with a glass and a friend on a ferromagnetic membrane under which a solenoid is placed in a protective casing connected to a source of a control signal, with the piezoelectric elements fixed in hermetic chambers and made in the form of concave

.Disks facing each other with concave surfaces, and hermetic chambers, a cup and a protective casing are provided with elastic membranes.

A disadvantage of this device is that piezoelements in the form of concave discs of constant thickness have a low quality factor of oscillations due to the fact that the amplitude of oscillations

10 has a diameter comparable to the amplitude of oscillations in the center of the piezoelements and in the places of fixings there are significant energy losses by the piezoelectric elements, which are

15 one to two times greater than the loss in fluid. This leads to a significant reduction in the quality of oscillations of the system.

The purpose of the invention is to increase the goodness of the device.

Claims (3)

The goal is achieved by the fact that in a piezoelectric resonator containing three piezoelements and two sealed chambers placed in a housing, one of which is fixed on one piezoelectric element connected through a bimetallic plate with a glass, and the other on a ferromagnetic membrane, under which is in a protective A coaxially placed solenoid connected to the source of the control signal, the second and third piezoelectric elements are fixed in sealed chambers and facing each other with concave surfaces, and the sealed chambers, glass and the protective cover is provided with elastic membranes, the second and third {piezo elements are in the form of lenses t with different curvature of the concave and convex surfaces, the radii of curvature of which are chosen from the ratio - ,. 1 where V, V2 is the speed of sound in the lens material and in the medium between them, respectively; -h is the thickness of the lens in the center; 2E is the distance between the lenses in the center. If the parameters of the lenses are calculated by the formula obtained, then the radii of caustics in the piezoelectric elements and the liquid become equal, the loss of the system is significantly reduced. The drawing shows a piezoelectric resonator, a general view. The resonator contains two piezoelements 1 and 2, made in the form of concave-convex lenses with radii of curvature of various sizes, resonant chamber 3, third piezoelectric element 4, solenoid 5, ferromagnetic membrane b, elastic membranes 7-10, bimetallic plate I, hermetic chambers G2 and 13, filled with a low specific wave with resistance, a protective casing 14, one hundred kan 15, housing 16. The device works as follows. When voltage is applied to the electrodes of the piezoelectric elements 1 and 2, ultrasonic standing waves are set in the resonant chamber 3 with a frequency determined by the natural frequencies of these piezoelectric elements and the distance between them. When the distance between piezoelectric elements 1 and 2 decreases, the length of the ultrasonic standing wave decreases, and as the distance increases, the length of the ultrasonic standing wave in the resonant chamber 3 increases, so that the natural frequency of the piezoelectric resonator can be rearranged. When a control voltage is applied to the electrodes of the piezoelectric element 4, it, together with the hermetic chamber 12, begins to oscillate in accordance with the control voltage C, which allows frequency modulation of the resonant frequency of the device, since these oscillations change the distance Between piezoelectric elements 1 and 2. When applying a control voltage, piezoelectric element 4 allows b to carry out high-frequency modulation of the signal. Low-frequency modulation is carried out when the control voltage Ua is applied to the solenoid 5, under the deist which the ferromagnetic membrane b oscillates with the hermetic chamber 13, which leads to a change in the distance of the piezoelectric elements 1 and 2. The elastic membranes 7 and 10 equalize the pressure in equal volumes, which excludes the deformation of the piezoelectric elements D and 2 from the pressure change inside the resonant chamber 3 and, as a result, stabilizes the operation of the entire device. The bimetallic plate 11, depending on the temperature of the surrounding medium, moves the piezoelectric element 2 relative to the piezoelectric element 1, compensating the temperature coefficient of the velocity of ultrasound of the medium in the resonant chamber 3. The resonant chamber 3 can be filled with both gas and liquid, while using the temperature compensating fluid in the resonant chamber as the liquid medium makes it possible not to take into account the accuracy error of the resonant frequency from temperature. The proposed acoustic device with piezoelectric elements made of convex-concave lenses allows, in comparison with the known ones, to increase the quality factor of acoustic oscillations in the system, bring the value of quality factor to S, which is especially important for frequencies close to resonant frequencies of piezoelectric elements. The invention of the Piezo-electric res.onator contains three piezoelements and two hermetic chambers placed in a housing, one of which is fixed on one piezoelement, a bimetallic plate with a glass connected by a pair, and the other on a ferromagnetic membrane, under which a solenoid connected to the source of the control signal, the second and third piezoelectric elements are fixed in sealed chambers and facing one another the concave surfaces, and the sealed chambers, the cup and the protective casing provide Yeny elastic membranes, distinguishing, and and (in that, in order to increase the quality factor, the second and third piezoelements are made in the form of lenses with different curvature of the concave and -convex surfaces, the radii of curvature of which are selected from the ratio: IMJL (M i e V2 / where V, Vj h Ze 35HEGCP th at 15 . 5 9802506. the speed of sound in mate-, Sources of information, rial lenses and. in the context of the examination between them, respectively, -1. USSR author's certificate no; 545069, class H 03 H 9/18, 1975, the thickness of the lens in the center; 2. USSR author's certificate; distance between lens-5 696593, cl. H 03 H 9/00, 1978 (prom in the center. Type).