Acoustoelectronic transducers with contactless sensitive elements

Abstract

The classification of acousto-electronic transducers of physical quantities created using primary transducers of surface acoustic waves (SAW) is carried out. It is based on SAW phase velocity and acoustic length of the delay line (resonator) change as a result of beam or membrane acoustic line deformation; environmental impact on the surface of acoustic line (molecular weight and gas concentration, temperature, humidity); coefficient of SAW reflection from interdigital transducers connected with external sensing elements affected by temperature, humidity, electromagnetic radiation; SAW phase velocity at wave electric field perturbation by a membrane; acoustic length of the delay line while moving SAW receiver in the electric field that extends on the surface of piezoelectric acoustic line.The proposed mathematical model of acousto-electronic transducer based on the use of phase velocity surface acoustic wave dispersion as a result of SAW electric field perturbation by a membrane allows to determine the requirements to the SAW-module structural and electric parameters depending on the set metrological parameters of the transducer. While using an acoustic line from niobium lithium YZ-cut at a frequency of 69.76 MHz experimentally obtained the conversion factor of micro-displacements equal to 11.7 ns/μm and pressure equal to 0.23 ns/mmHg. The proposed functional scheme allows to create highly sensitive transducers of micro-displacement, pressure, acceleration, hydro-acoustic signals on the basis of a universal secondary acousto-electronic transducer, while the construction of primary transducer (membrane) is determined by set conversion factor and dynamic range of the measured physical quantity.The mathematical model of acousto-electronic transducer using the change of acoustic length of the delay line during the SAW receiver movement in the SAW electric field extended on the surface of piezoelectric acoustic line allows to determine the requirements to the SAW-module structural and electronic parameters depending on the metrological parameters of the transducer of liner displacement up to 200 mm and more, and angular displacement up to 360 degrees.While using an acoustic line from niobium lithium YZ-cut at a frequency of 70 MHz experimentally obtained the conversion factor of linear displacement equal to 570 ns/μm and factor of angular displacement at a 20 mm radius of circular piezoelectric waveguide based on the structure zinc oxide-fused quarts equal to 57.8 ps/arcsec.The proposed transducers using SAW electric field extended to piezoelectric structures can be applied both at stationary and radiometric wireless systems.Ref. 21, fig.3.