SU371672A1 - PIEZOELECTRIC FILTRPAT [NTVO "11ShG! Splp - Google Patents

Description

one

The invention relates to components of radio equipment and can be used, for example, in systems of electro-acoustics, automation and electronics.

The well-known piezoelectric filter containing a ceramic disk with circular electrodes polarized in thickness operates either at the fundamental frequency of radial oscillations of the disk or at its first overtone, as a result of which its operating frequency range is bounded below by values of the order of kHz.

The aim of the invention is to extend the operating frequency range to lower frequencies.

This is achieved by the fact that the ceramic disk is made with a sector notch, and the electrodes on both sides of the disk are separated along the average length of the disk circumference.

The drawing shows the proposed piezoelectric filter.

It contains a ceramic disk J polarized in thickness, made of a sector cut, and round electrodes 2, 3 and 4, 5, respectively, on the upper and lower sides of the disk. Electrodes 2, 3 and 4, 5 are divided along the average length of the disk circumference.

The operation of the piezoelectric filter is based on the fact that when the input voltage is applied to electrodes 2, 4 or 3, 5, the exciting electric field coincides in one of its half-periods with the polarization direction of the ceramic disk / in the area under the input electrodes, and in the other half-period opposite to it, which causes periodic radial and tangential deformations of the expansion-contraction of the disk area under the input electrodes. At the same time, due to the above features of the filter, the tangential deformation of the inner or outer disk area causes bending along the face of the whole structure: tangential expansion, for example, the annular disk area under the electrodes 3, 5 due to the elastic connection of the outer and inner parts of the disk causes the inner area of the disk under the electrodes 2, 4; In the other half-period of the exciting stress, the deformation polarity changes sign and, as a result, the disc with a sector cut experiences elastic bending oscillations on the face.

The middle part of the piezoelectric filter is defined by the expression:

yy r-m

/with

.)

where / С / и is the frequency constant of the bending along the contour of the oscillations determined by

density and other constant piezo materials,

R is the radius of the ceramic disk, b is for the arc of the sector cut along

the average disk circumference, t is a constant coefficient taking into account the influence of the depth of the radial sector cut. when, where / o is the depth of cut,

 with (, l, 5R. lo

As can be seen, the average frequency of the filter increases with decreasing disk radius and shower length of the sector cut, i.e. with increasing m of the central angle of cut a, and decreases with increasing depth of the sector cut. With a narrow sector cut-out (1-2 arc degrees), reaching the center of the disk, the average frequency of the filter operating on bending oscillations on the edge is almost

6 times lower than the main resonance frequency of the radial oscillations of the same geometrical dimensions.

The frequency response of the filter has a damping pole to the right or left of the passband, depending on the choice of the corresponding electrodes as input and output.

Subject invention

A piezoelectric filter containing a circularly thickened ceramic disc with round electrodes, characterized in that, in order to extend the operating frequency range to lower frequencies, said disc is made with a sector cut, and the electrodes on both sides of the disc are separated along the average circumference disk.