SU1272520A1 - Piezoelectric transducer - Google Patents

Description

The invention relates to the field of communication technology, in particular to piezoelectric acoustic transducers.

The aim of the invention is to increase sensitivity and resolution.

The drawing shows a diagram of a piezoelectric sensor.

The piezoelectric sensor contains a piezoelectric plate 1 with the first, second and third electrodes 2-4 placed on it, the first and second membranes 5 and 6, the housing 7, and the fastening element 8 with a portion 9 of a smaller thickness, while the piezoelectric plate 1 is fixed between the centers of the membranes 5 'and 6, each of which is electrically connected to the electrodes 3 and 4 through capacitors 10 and 11 with grounding, the semicircular fastening element 8 with a section 9 of smaller thickness is parallel to the membranes 5 and 6 and is welded in diameter to the first electrode 2, which is electrically from one with a difference generator 12.

The piezoelectric sensor operates as follows.

In fact, two piezoresonators are made on piezoelectric plate 1. Piezo resonator portions are quartz piezoceramic plates 1 disposed between the metal deposited on it ¹ electrodes 2-4. The resonant frequencies of the piezoresonators depend on the elastic constants of the piezoelectric plate 1 and, therefore, on the magnitude and, due to the anisotropic properties of single-crystal quartz, on the direction of mechanical stresses in the piezoelectric plate.

The difference generator provides excitation in piezoresonators of two oscillations with frequencies £, and ί ₂ in the frequency range 25τ-40 MHz. Moreover, the frequencies 1, and ί ₂ differ by no less than the value of the resonance gaps of the piezoresonators. The output signal of the generator 12, and, accordingly, of the entire sensor, is the oscillation of the difference frequency.

p ’I D 2 I

The oscillation of the difference frequency is distinguished by means of an LC-difference circuit tuned to approximately 1 _p frequency and connected to the active element of the difference generator and included in the generator 12.,

Impact In acoustic vibrations + vibrations, membranes 5 and 6 and piezoelectric plate 1 move along its axis. Moreover, acoustic frequency fluctuations up to 10 kHz cause the displacement of the centers of the membranes 5 and 6.

Section 9 of the smaller thickness of the mounting element 8, made in the form of two profiled grooves located one opposite the other on both sides parallel to the piezoelectric plate 1, is designed to reduce the resistance of the mounting element to acoustic impact and thereby increase the microphone sensitivity and resolution. With a decrease in the distance between the smaller section 9 and the piezoelectric plate 1, the degree of deflection of the piezoelectric plate increases, which causes the bending of two resonators in different directions and, consequently, a change in their resonant frequencies 1, and £ _r in different directions. In this case, the absolute tuning of the frequency 1p of the output oscillation is equal to the sum of the tuning of the frequencies 1, and 1 ₂ bl _p = ii, <· а £ ₂ . ·

The relative tuning of the difference frequency is N times larger than the relative tuning of the frequencies ί, and d £ p af, ip i,

In addition, due to the possibility of ensuring a positive correlation of the noise variations of the £ 8, £ £ ₁ frequencies £, and the choice of a certain ratio between the capacitors of capacitors 10 and 11, the noise variations, 81 _{p of the} frequency £ _{p of the} output difference oscillation can ideally be reduced to zero. Thus, the intrinsic frequency noise of the sensor is reduced to zero, due to which the level of the equivalent sound pressure of the device can be reduced to zero. That is, the piezoelectric sensor may not have a dynamic range limitation from the bottom and may have a higher resolution.

Claims (1)

The invention relates to the field of communications, in particular to piezoelectric acoustic transducers. The aim of the invention is to increase the sensitivity and resolution. The drawing shows a diagram of a piezoelectric sensor. The piezoelectric sensor contains a piezo plate 1 with the first, second and third electrodes 2-A placed on it, the first and second membranes 5 and 6, the housing 7, and also the fastening element 8 with a portion 9 of lesser thickness, while the piezo plate 1 is fixed between the centers of the membranes 5 and 6, each of which is electrically connected to electrodes 3 and 4 through capacitors 10 and 11 with grounding, a semi-circular fastening element 8 with a smaller thickness section 9 is arranged parallel to the membranes 5 and 6 and is welded along the diameter to the first electrode 2, which is electricallyoedinen with a difference generator 12. The operation of the piezoelectric sensor is as follows. On the piezoplastin 1, virtually two piezoresonators were made. Piezo resonators are parts of a quartz piezoplate 1, located between the metal electrodes 2-4 deposited on it. The resonant frequencies of piezoresonators hang from elastic constant piezoplates 1 and, therefore, on the magnitude and effect of the anisotropic properties of single crystal quartz from the direction of mechanical stresses in the piezoplates. The differential generator provides excitation in piezoresonators of two oscillations with frequencies f, and fj in the frequency range 257-40 MHz. Moreover, they often differ by no less than the magnitude of the resonance gaps of piezoresonators. The output signal of the generator 12, and accordingly the entire sensor, is the oscillation of the differential frequency IP 1 1, - H. The oscillation of the differential frequency is selected by means of an LC-differential circuit tuned approximately to the frequency ip and connected to the active element of the differential generator and the input the composition of the generator 12. Impact B acoustic oscillations leads to the movement of the membranes 5 and 6 and piezoplates 1 along its axis. Moreover, acoustic oscillations of frequencies up to 10 kHz cause displacement of the Centers of the membranes 5 and 6. Section 9 of a lesser thickness of the fastening element 8, made in the form of two shaped grooves located one opposite the other on both sides parallel to the piezoplate 1, is intended to reduce the resistance of the fastening element to acoustic effects and the most enhanced microphone sensitivity and resolution. With a decrease in the distance between the thinner section 9 and piezoplate 1, the degree of deflection of the piezoplate increases, which causes the two resonators to bend in different directions and, therefore, their resonant frequencies change: {, {, in different directions. In this case, the absolute frequency tuning in the output oscillation is equal to the sum of the adjustments f, and 2 frequencies bt ii, f ui. “.Pu. ,, .., The relative rearrangement of the difference frequency is N times greater than the relative frequency tuning f, and f ufp uf, ip i, In addition, due to the possibility of providing a positive correlation frequency i, noise variations 8f , i choosing a certain ratio between the capacitors of capacitors 10 and 11, the noise variations, Sfp of the frequency tp of the output difference oscillation, can ideally be reduced to zero. Thereby, the natural frequency noise of the sensor is reduced to zero, so that the equivalent sound pressure level of the device can be zeroed out. That is, a piezoelectric sensor may not have a lower dynamic range limit and have a higher resolution. Formula Shadow Invention Piezoelectric Sensor Containing Piezo Plate with First and Secondary Pto312725204 ring electrodes, body, element of this piezoplastinl ustaiorlena Me) iyiy thinning fastening, connected by smembranes, and the high fastening element of the piezoelectric plate and casing is filled in a semicircular membrane, generator, electrically connected-connected to the first electrode, on with the first electrode, about the t-pyzoplastin, there is a third elec-trophic, with the aim being that the second and third electro-sensitization and the rare-type are located from opposite its capacity, its body of the sides of the fastening element and electrically filled in the form of a cylinder, are face-joined through capacitors whose membranes are fixed, with a common tire.