Yoshinari Yamashita

TE Harmonic Overtone Mode Energy-Trapped Ceramic Filter with Narrow Frequency Tolerance

Experimental studies have been made on the suppression of two major spurious responses, i.e., inharmonic overtones and the 6th thickness-shear-mode harmonic overtone, to realize a 3rd overtone thickness-extension double-mode bandpass filter using PbTiO 3 ceramic substrates. Each leverage was found by investiging of low-symmetry electrode shapes and implementing the nonpolarized portion of the region between terminal pads on the piezoelectric substrate. The practical importance of the application of intermediate-frequency filters (IF filters) used in wireless communication systems depends on how the narrow frequency tolerance requirement is satisfied. A simple but accurate method of adjusting the center frequency of these filters is shown here.

An Ultrasonic Imaging System Using a Matrix-Type Transducer Array

We propose a method for imaging an objects surface using a matrix-type transducer array. The matrix-type transducer array has a simple structure with some line-electrode fingers on both sides of a piezoelectric ceramic plate. By a combination of electrical-mechanical scanning, we image of an objects surface using data of distance between the transducer and the object. The ultrasonic probe used in the present system requires without beam forming and no signal processing for focusing. We measure two objects: one has a multilayered structure consisting of three differently sized aluminum plates, the biggest plate having an area of 150 mm × 80 mm and 0.8–1.5 mm thickness; and the other is a radio-wave-absorbent block 100.5 mm × 100.5 mm × 18.5 mm in size with 5 × 5 holes in a grid made of ferrite. The ultrasonic probe operates at a frequency of 3.5 MHz and the sensing distance between the transducer and the measured object is about 80 mm. At this distance, the diameter of the ultrasonic beam launched from the transducer is about 13 mm. We obtained a height resolution of ±0.2 mm and a spatial resolution of about 3.0 mm.

Inharmonic Overtone Spurious Mode Suppression by Partial Mass-Loading onto the Electrode for Energy-Trapped-Type Thickness-Extensional-Mode Piezoelectric Ceramic Resonators.

Experimental studies have been performed on the suppression of the inharmonic overtone responses for realizing piezoelectric ceramic resonators with low resonance impedance compatible with a wide-area electrode(>15λ). The circumferential mass-loading onto the electrode is effective for the fabrication of an oscillator with a low oscillation startup voltage, without any jump to spurious frequencies. In addition, this technique results in a wide rejection bandwidth for TV/VCR adjacent-channel sound-carrier-signal traps. This effect (stepped energy-trapping) is observed to arise from the spatial vibration energy distribution dispersion by the additive weighting electrode using optical laser interferometry and finite- element-method analysis.