Katsutoshi Sakurai

Presentation of a New Equivalent Circuit of a Piezoelectric Transformer under High-Power Operation

In this paper, the power transmission characteristics of a piezoelectric transformer are considered. As a result, the following has been clarified: the frequency of the maximum step-up voltage ratio coincided with the resonance frequency, and the frequency of maximum efficiency approximately coincided with the intermediate frequency between the resonance and anti-resonance frequencies. However, conventional equivalent circuits cannot represent these phenomena. In this paper, we have proposed an improved equivalent circuit that was useful for presenting the tendency of the experimental results. The specific future of this circuit is that the series and parallel resistances that present high-power operation loss are included. The method used to derive the proposed equivalent circuit is described and some experimental and calculated results are shown.

Luminescence Properties of Amorphous Carbon Films Formed Using Supermagnetron Plasma

Polymer-like amorphous carbon (a-COx:H and a-CNx:H) films were deposited using two types of supermagnetron plasma, i.e., Ar sputter and i-C4H10/N2 chemical vapor deposition (CVD), respectively. The sp2 clustering of these films was proved experimentally by Raman scattering and the estimation of optical band gap. The photoluminescence (PL) and electroluminescence (EL) properties of these films were measured and analyzed. As a result, a-COx:H films deposited by Ar sputtering showed similar peak energies for PL and EL (1.9–2.0 eV), while a-CNx:H films deposited by i-C4H10/N2 CVD showed large shifts between peak energies for PL (2.2 eV) and EL (1.7 eV). The differences in peak energies in the latter were ascribed to the luminescence characteristics caused by sp2 clusters embedded in the sp3 carbon matrix.

Finite-Element Analysis of Trident-Type Tuning Fork Resonator for Vibratory Gyroscope.

We have investigated the possibility of producing a highly stable piezoelectric vibratory gyroscope. In order to achieve such a gyroscope, a trident-type tuning fork resonator was adopted, because it has good inherent vibrational characteristics for its support conditions. However from a practical viewpoint, the tuning fork must be studied with the aim of achieving very high stability, and high performance as an angular rate sensor. Therefore, we investigated the detailed vibrational displacement characteristics using finite-element methods and showed that unnecessary vibration of the tuning fork influenced the sensitivity of the gyroscope. That is, this paper concerns the dimensional conditions of the tuning fork for decreasing vibrational displacements at its base portion. We also report the measured characteristic of the angular rate sensor using such an improved tuning fork.

Experimental Considerations on the Piezoelectric Vibratory Gyrosensor Using a Trident Tuning-Fork Resonator

This paper concerns the piezoelectric vibratory gyrosensor using a trident tuning-fork resonator characterized by high stability. In the first part of this paper, the methods of adjusting the resonance frequencies are discussed. Then the investigations to compensate the imbalance in a trident tuning-fork resonator are shown. Moreover, we constructed an experimental gyrosensor based on these results, using differential detection to eliminate the leakage output signals. A miniature piezoelectric vibratory gyrosensor with superior linearity could be achieved.

Basic Investigation on Achieving High Resonance Quality Factor of Piezoelectric Vibrator

This paper deals with basic experiments on achieving the high resonance quality factor of a piezoelectric vibrator by applying negative elements of the negative impedance converter (NIC) circuit. Based upon the method described here, the experiments have proven that the resonance quality factor of a piezoelectric ceramic vibrator could be increased by about 50 times, and moreover, in proportion to becomes the increase of the resonance quality factor, the measured displacement of the vibrator large.

Q-Value Control of Piezoelectric Vibrator Using Operational Amplifier Circuit

In application of a piezoelectric vibrator to some electronic devices such as gyro-sensors and piezoelectric ceramic transducers, it is very useful if the value of the resonance quality factor (Q-value) can be controlled electrically. For achievement of such an ideal, application of a negative impedance converter circuit (NIC circuit) to a piezoelectric vibrator is considered in this work. We applied several negative circuit elements to a piezoelectric vibrator in order to control the Q-value and achieve high performance of it. That is, this work deals with Q-value control of a piezoelectric vibrator by series connection of the NIC circuit, consisting of an operational amplifier, to the vibrator.

Piezoelectric vibratory gyrosensor using a trident tuning‐fork resonator

A piezoelectric vibratory gyrosensor, constructed using a trident tuning‐fork resonator, is characterized by superior support construction. That is, for a trident tuning‐fork, the vibrational loss with its support condition becomes so small that a gyrosensor has good performance compared with other existing type resonators. First, the vibration modes of a trident tuning‐fork have been investigated, and suitable clamping conditions are clarified using finite‐element analysis. Then, the method of adjusting the resonance frequencies between driving and detecting vibration modes and the influences of arm imbalance were studied. Moreover, when detecting the angular rates using a prototype trident tuning‐fork resonator, the leakage output signal was apparently eliminated by connecting a differential circuit. As a result, a small‐sized piezoelectric vibratory gyrosensor having good gyro‐characteristics could be measured.

Damped Capacitance Elimination in Piezoelectric Vibrator Using Operational Amplifier Circuit.

We discuss the elimination of damped capacitance from the equivalent circuit of a piezoelectric vibrator, which is achieved using an operational amplifier circuit. First, we describe the theoretical principle of a basic damped capacitance elimination circuit, and then report the experimental investigation of the circuit. We conclude that the circuit proposed here is very effective in eliminating the damped capacitance in a piezoelectric vibrator and therefore the range of application of vibrators can be increased.

Piezoelectric Ceramic Oscillator Using Damped Capacitance Elimination Technique

The temperature stability of a piezoelectric ceramic oscillator is improved, using the damped capacitance elimination technique, which is performed using an operational amplifier circuit. In order to improve the temperature stability, an electrostatic capacitance such that its temperature characteristic can cancel a change of the oscillation frequency is also applied in the circuit. The theoretical principle of the damped capacitance elimination circuit and the experimental results are described. The circuit proposed here is effective in improving the temperature stability of the piezoelectric ceramic oscillator.

Oxidation of Amorphous Carbon Films by Ultraviolet Light Irradiation and Thermal Annealing

Using polymer-like amorphous carbon films deposited using supermagnetron plasma, ultraviolet light irradiation and thermal annealing effects in air were studied. Upper and lower electrode rf powers (UPRF/LORF) were selected to be 5/5 W, and such films were deposited using i-C4H10, and N2 or H2 plasma chemical vapor deposition (CVD). For comparison, polymer-like amorphous carbon films were deposited using Ar magnetron sputtering. By X-ray fluorescence spectroscopy (XFS), an increase in oxygen atom concentration and a small change in nitrogen atom concentration were observed under both ultraviolet (UV) light exposure and thermal annealing.