Broadband electromagnetic acoustic transducers

A broadband electromagnetic acoustic transducer for use with an electrically conductive object, comprising:

• a plurality of alternately oriented magnets aligned along a propagation direction to establish a static magnetic field which is periodically alternately oriented such that the ratio of adjacent periods of said field is constant;
• and
• an electrical conductor for inducing eddy currents in said object when an alternating current is applied to said conductor,
• said magnets and said conductor being so oriented that the vector product of said magnetic field and said eddy currents produces an instantaneous force field in said object, said force field being periodically alternately directed with a logarithmic periodicity such that the ratio of adjacent alternating periods within said force field is constant.

A broadband electromagnetic acoustic transducer for use with an electrically conductive object, comprising:

• a source of magnetic flux for establishing a static magnetic field in said object;
• and
• a serpentine electrical conductor for inducing eddy currents in said object when an alternating current is applied to said conductor, the conductor including a plurality of periodically alternately oriented parallel elements perpendicular to a propagation direction such that the ratio of adjacent periods is constant,
• said magnetic field and said conductor being so oriented that the vector product of said magnetic field and said eddy currents produces an instantaneous force field in said object, said force field being periodically alternately directed with a logarithmic periodicity such that the ratio of adjacent alternating periods within said force field is constant.

A broadband electromagnetic acoustic transducer for use with an electrically conductive object, comprising:

• a first plurality of alternately oriented magnets aligned along a propagation direction;
• a second plurality of alternately oriented magnets aligned along said propagation direction and adjacent to said first plurality such that adjacent magnets in said first and second pluralities are alternately oriented, said magnets establishing a periodic alternately oriented static magnetic field such that the ratio of adjacent periods of said field in said propagation direction is constant;
• and
• an electrical conductor for inducing eddy currents in said object when an alternating current is applied to said conductor, said conductor including:
• a first conducting element extending under said first plurality of magnets,
• a second conducting element extending under said second plurality of magnets, and
• a connecting conducting element linking said first and second conducting elements,
• said magnets and said conductor being so oriented that the vector product of said magnetic field and said eddy currents produces an instantaneous force field in said object, said force field being periodically alternately directed with a logarithmic periodicity such that the ratio of adjacent alternating periods within said force field is constant.

A method of generating a broadband acoustic wave in an electrically conductive object, comprising the steps of:

• providing a source of magnetic flux to establish a static magnetic field in the object;
• providing an electrical conductor to induce eddy currents in the object when an alternating current is applied to the conductor;
• and
• orienting the source of magnetic flux and the conductor so that the vector product of the magnetic field and the eddy currents produces an instantaneous force field in the object, the force field being periodically alternately directed with a logarithmic periodicity such that the ratio of adjacent alternating periods within the force field is constant.