Abstract: The thermodynamics-based signal receiver transforms contiguous segments of a received signal into thermodynamics-related quantities using an analog of a statistical-mechanics-related quantities using an analog of a statistical-mechanics expression for a thermodynamic variable and uses these thermodynamics-related quantities as the means to measure changes in the signal as a function of time or origin. The changes that are of interest are those associated with either signal level or signal structure. Signal-processing analogs of statistical mechanics expressions for thermodynamic variables are measures that respond in some fashion to either type of change. By comparing thermodynamics-related transformations of received signals, one can obtain information about the emitters of the received signals and the nature of the medium through which the signals were propagated.

Abstract: The entropy-based signal receiver uses the entropy of a received signal or a quantity that is closely related to entropy as the means to measure changes in the signal as a function of time or origin. The changes that are of interest are those associated with either signal level or signal structure. Entropy is a measure that responds in some fashion to either type of change. The entropy-based signal receiver transforms time segments of a received signal into entropy-related quantities. By comparing entropy-related quantities of received signals, one can obtain information about the emitters of the received signals and the nature of the medium through which the signals were propagated. The sensitivity of the entropy-based receiver is significantly better than the more conventional energy-based receiver in detecting the changes in a signal that result from reflection or scattering by inhomogeneities in a wave-propagating medium.

Abstract: An ultrasonic unipolar pulse/echo instrument uses active switches and a timing and drive circuitry to control electrical energy to a transducer, the discharging of the transducer, and the opening of an electrical pathway to the receiving circuitry for the returning echoes. The active switches utilize MOSFET devices along with decoupling circuitry to insure the preservation of the unipolar nature of the pulses, insure fast transition times, and maintain broad band width and time resolution. A housing contains the various circuitry and switches and allows connection to a power supply and a movable ultrasonic transducer. The circuitry maintains low impedance input to the transducer during transmitting cycles, and high impedance between the transducer and the receiving circuit during receive cycles to maintain the unipolar pulse shape. A unipolar pulse is valuable for nondestructive evaluation, a prime use for the present instrument.

Abstract: An apparatus and method for nonuniform poling of piezoelectric transducers includes machining one or more indentation into an end of a piezoelectric rod and cutting the rod to present a thickened disk shape. Highly electrically conductive material is deposited on at least the indentations in the one end and on at least portions of the opposite face of the member. One or more electrodes are configured to matingly fit within the indentations on the one face of the disk, with a like number of electrodes being positionable on the opposite face of the material. Electrical power is then applied to the electrodes in desired amounts, polarity, and duration. The indentations vary the electrical field produced within the piezoelectric material to produce nonuniform poling in the material. The thick disk is then cut to remove the indentations and to present a thin, flat two sided disk for installation in a conventional piezoelectric transducer probe.