Abstract: A piezoelectric device includes a stacked crystal filter, a supporting substrate and an acoustic reflector between the filter and substrate for suppressing undesired resonant frequencies. The acoustic reflector includes a set of quarter wavelength layers of alternating higher and lower impedances. The reflector provides a large reflection coefficient for a bandwidth that encompasses only desired frequencies generated by the stacked crystal filter. By changing the nature of the material and the number of layers, the bandwidth and center frequency of the acoustic reflector may be varied to encompass a desired range of frequencies. To reduce the magnitude of side lobes at undesired frequencies, the impedance differences between layers of the reflector are reduced with depth into the reflector. The side lobes may also be reduced by serially connecting two stacked crystal filters having acoustic reflectors of the same material but with a different number of quarter wavelength layers.

Abstract: Resonator fabricating method and apparatus employ the resonance conditions of the piezoelectric resonator itself to control an RF-powered plasma etching or deposition process. In its basic implementation, the apparatus does not require monitoring of the resonant frequency of the resonator as it is being trimmed. Rather, the resonator provides an impedance which changes as the plasma action changes the thickness of the resonator and thereby changes the resonant frequency of the piezoelectric resonator. The changing impedance in turn changes the rate of plasma action until the action substantially stops with the resonant frequency of the resonator substantially equal to the frequency of the RF source.

Abstract: An acoustic shear wave resonator comprising a piezoelectric film having its C-axis substantially inclined from the film normal such that the shear wave coupling coefficient significantly exceeds the longitudinal wave coupling coefficient, whereby the film is capable of shear wave resonance, and means for exciting said film to resonate. The film is prepared by deposition in a dc planar magnetron sputtering system to which a supplemental electric field is applied. The resonator structure may also include a semiconductor material having a positive temperature coefficient of resonance such that the resonator has a temperature coefficient of resonance approaching 0 ppm/.degree.C.

Abstract: An acoustic shear wave resonator comprising a piezoelectric film having its C-axis substantially inclined from the film normal such that the shear wave coupling coefficient significantly exceeds the longitudinal wave coupling coefficient, whereby the film is capable of shear wave resonance, and means for exciting said film to resonate. The film is prepared by deposition in a dc planar magnetron sputtering system to which a supplemental electric field is applied. The resonator structure may also include a semiconductor material having a positive temperature coefficient of resonance such that the resonator has a temperature coefficient of resonance approaching 0 ppm/.degree.C.

Abstract: A method of fabricating an acoustic wave resonator wherein all processing steps are accomplished from a single side of said substrate. The method involves deposition of a multi-layered Al/AlN structure on a GaAs substrate followed by a series of fabrication steps to define a resonator from said composite. The resulting resonator comprises an AlN layer between two Al layers and another layer of AlN on an exterior of one of said Al layers.

Abstract: A method of fabricating an acoustic wave resonator wherein all processing steps are accomplished from a single side of said substrate. The method involves deposition of a multi-layered Al/AlN structure on a GaAs substrate followed by a series of fabrication steps to define a resonator from said composite. The resulting resonator comprises an AlN layer between two Al layers and another layer of AlN on an exterior of one of said Al layers.

Abstract: An instrument having a multi-segmented cup core of a high permeability material with a center post. The outer wall of the cup contains equidistant holes and slots through which a plurality of individual windings are constructed to form a circular array of pick-up coils. A primary winding or search coil is constructed around the center post. Excitation of the search coil induces eddy currents in adjacent multi-layered bolt hole regions which in turn produce a voltage in each of the pick-up coils. As a crack in the material under test will cause an abnormal distribution of eddy currents, a comparison of the voltage measurements of the specimen under test with those of a reference sample will detect the presence of a crack and its corresponding orientation.

Abstract: An eddy current type of inspection device having input signal coils on cores radially arranged around a center and having outer ends of the cores which rest against a surface of a metal assembly to be tested for defects. The input coils are energized by an AC signal of different phase for each respective coil so that a rotating magnetic field is produced in the assembly being tested. An output sensor coil is mounted at the center of the tester immediately adjacent to such test surface for coupling out a signal induced from the rotating field. A specific embodiment has three coils physically spaced 120.degree. apart, for energizing by a three-phase power source.

Abstract: An ultrasonic phased array imaging system having a received signal encoding and correlating system. Pulse echoes picked up by each of the plurality of transducers are passed by a timed gate signal only during a predetermined time interval when a return signal from a focal point is expected to arrive. The return signal is also encoded by a chirp waveform. All gated chirp signals are fed to a dispersive transversal filter where their sum occurs simultaneously.

Abstract: An output electrode which is angularly oriented with respect to the reading and scanning electrode is used with associated circuitry to provide a two dimensional image scan for an acousto-optical cell. The output electrode is an interdigitally shaped echelon and intercepts the output signal at a position which is determined by the transit time to a selected step of the echelon.