SU597064A1 - Non-dispersion ultrasonic delay line - Google Patents

Description

(54) UNIFIED ULTRASONIC DELAY LINE

The invention relates to ultrasonic delay lines and can be used in the radar, sonar and instrument-making industry.

Known ultrasonic delay lines with different time delays from frequency, made with a variable cross-section along the length of the duct tl. The disadvantages of such delay lines are the impossibility of ensuring a constant delay time in a given frequency range.

The known non-dispersive ultrasonic stripline of the delay line, in which the wave SKg of the Line Ss1 support propagates, contains a conduit in the form of a strip, on the side faces of which an absorber is placed, and on the ends are piezoelectric transducers 2. The thickness of the strip is selected by the formula

c1 $ ta. "

where d is the strip thickness;

Vj - elastic shear velocity

fwctx waves upper bound frequency

bandwidth that ydo

2

It eliminates the condition that the SH wave does not propagate, which mainly determines the level of spurious signals.

A disadvantage of a non-dispersive ultrasonic stripline delay line is the very small strip thickness at high upper limiting bandwidth frequencies, which leads to technological difficulties in installing piezoelectric transducers on the ends of the strip and, as a result, to the level of spurious signals.

The purpose of the invention is to expand the bandwidth of the passband and reduce the level of spurious signals.

This goal is achieved by the fact that in a non-dispersive ultrasonic delay line containing a sound duct in the form of a strip, on the side faces of which an absorber is placed, and on the face edges there are piezoelectric transducers, the strip from one side face to the other is made with a variable cross-section. Variable cross-section can be performed by reducing the thickness of the strip according to a linear law from one side face to another.

The drawing shows the proposed device.

The sound duct 1 of a non-dispersive ultrasonic delay line is made in the form of a strip of sound-conducting material, the thickness of which is made with a variable cross-section from one side face to another. At the ends of the conduit 1, there are input and output piezoelectric transducers 2 and 3, respectively, an absorber 4 is applied to its side faces, which serves to damp unwanted elastic waves that determine the level of spurious signals of the delay line. The specified configuration of Zvukovaya 1 is constant over the section. Along its entire length. The drawing shows the path of the rays in the pipeline: the solid line is the SHo wave, and the dotted line is the SH wave, which mainly determines the level of spurious signals in the delay line. The trajectory of the beam of the SH.j wave is bent from the axis .to the wide side face of the sound duct and the n-absorber 4 falls. This is due to the fact that the SH wave is dispersive, and the phase velocity of propagation of oscillations in the duct 1 depends on its thickness — as the thickness decreases, its magnitude increases. When the SH wave hits the absorber, the latter decays and does not hit the output transducer 3.

Thus in the proposed non-dispersive:.; Oh ultrasound line

delays provide bandwidth expansion and low false signals. At present, bandwidth expansion can only be achieved by reducing the thickness of the acoustic duct, which leads to an increase in the level of spurious signals due to the technological difficulties of installing piezoelectric transducers on the ends of the acoustic duct.

Claims (2)

Invention Formula 5) An ultrasonic delay line containing a suction line in the form of a strip, on the side faces of which an absorber is placed, and piezoelectric transducers placed on its end faces, is different from the fact that in order to expand the bandwidth reducing the level of spurious signals, the thickness of the strip from one side to another is made with a variable cross section. Sources of information taken into account in the examination: 30 1. US patent 3736532, cl. 333-30, 1973. 2. Maison U, Physical Acoustics, 1, Part A, Mir, 1966. t. 35