Apparatus for efficiently converting microwave energy into acoustic energy

Claim 3

An apparatus according to claim 1, wherein said interface between said propagating means and said piezoelectric material to bring about said evanescent electric field is at a given angle to the propagating direction of said electromagnetic signal, said angle being measured from an axis normal to said nonconductive piezoelectric surface.

Claim 4

An apparatus according to claim 2, wherein said angle exceeds a predetermined critical angle, theta ic, defined by the equation: theta ic sin 1 epsilon 2/ epsilon 1 where epsilon 1 and epsilon 2 are the dielectric constants, respectfully of said electromagnetic signal propagating means and said piezoelectric material.

Claim 5

An apparatus according to claim 2, wherein said angle substantially determines the magnitude of the attenuation constant, Alpha , of said piezoelectric''s evanescent electric field, said attenuation constant, Alpha , defined by the equation: Alpha (2 pi Square Root epsilon 1)/( lambda ) Square Root sin2 theta i - epsilon 2/ epsilon 1 where epsilon 1 and epsilon 2 are the relative dielectric constants, respectfully, of said electromagnetic signal propagating means and said piezoelectric material, lambda is the electromagnetic wavelength at the frequency of said applied electromagnetic signal and theta i is the angle between said interface and the propagating direction of said electromagnetic signal, theta i being measured from an axis normal to said nonconductive piezoelectric surface.

Claim 6

An apparatus according to claim 2, wherein said angle substantially determines the magnitude of the difference in electric potential between said interface and an internal piezoelectric depth located substantially at Omega /2, where Omega is the acoustic wavelength at the frequency of said applied electromagnetic signal.

Claim 7

An apparatus according to claim 1, wherein said electromagnetic signal propagating means comprise a dielectric filled waveguide transmission line, said dielectric having an interface with said piezoelectric material.

Claim 8

An acoustic delay line comprising: a piezoelectric transducer of given dielectric constant in which an electromagnetic signal applied to a nonconducting piezoelectric surface can be made to establish an evanescent electric field, a dielectric filled waveguide transmission line having a dielectric constant greater than said given dielectric constant, means for angularly interfacing said nonconductive surface of said transducer to a dielectric surface at one end of said transmission line to bring about said evanescent electric field within said piezoelectric transducer, whereby said electromagnetic signal is converted to an acoustic signal, means for interfacing a surface of said piezoelectric transducer to a surface of an acouStic medium, whereby said acoustic signal generated in said transducer is coupled to said acoustic medium, means for converting said acoustic signal in said acoustic medium to an electric signal.

Claim 9

An acoustic delay line comprising: a piezoelectric transducer of given dielectric constant in which an electromagnetic signal applied to a nonconducting piezoelectric surface can be made to establish an evanescent electric field, a dielectric filled waveguide transmission line having a dielectric constant greater than said given dielectric constant, means for angularly interfacing said nonconductive surface of said transducer to a dielectric surface at one end of said transmission line to bring about said evanescent electric field within said piezoelectric transducer, whereby said electromagnetic signal is converted to an acoustic signal, means for interfacing a surface of said piezoelectric transducer to a surface of an acouStic medium, whereby said acoustic signal generated in said transducer is coupled to said acoustic medium, means for converting said acoustic signal in said acoustic medium to an electric signal.