Piezoelectric and ferroelectric properties of bismuth sodium titanate, (Bi_1/2Na_1/2)TiO₃(BNT)-based solid solution, that is, (Bi_1/2Na_1/2)_(1-x)(Pb_aBa_b)_xTiO₃(a+b=1)_??_BNPB(100x-100a/100b)_??_, are studied on their piezoelectric properties from the viewpoint of a new group of lead-free or low-lead-content piezoelectric ceramics with a rhombohedral(F_α)-tetragonal(F_β)morphotropic phase boundary(MPB). It is evident that the MPB seems to be remarkably efficacious in promoting piezoelectric and pyroelectric activities by electrical poling.
X-ray diffraction data, dielectric properties and D-E hysteresis loops show that the MPB exist near (Bi_1/2Na_1/2)TiO₃_??_BNT_??_at x=0.13_??_0.14, 0.08_??_0.09 and 0.06_??_0.07 in the case of b=0, b=0.5 and b=1, respectively. BNPB ceramics are superior for piezoelectric ceramics in high frequency ultrasonic uses, or special piezoelectric actuator materials with a lower free permittivity, ε^T₃₃/ε₀, and a high electromechanical coupling factor, k₃₃, along with a high mechanical strength.

抄録全体を表示

Many spurious vibrations can be supported in rectangular AT-cut quartz resonators. These vibrations generally belong to the modes with phase reversals along both the X and Z' axes. The two-dimensional coupled vibrations of thickness-shear and thickness-flexure have been previously analyzed. In this paper, the coupled vibrations of face-shear and face-flexure are also analyzed.
The analysis of face-shear and face-flexure is based on the Mindlin's plate equations and the plane-stress approximation. A one-dimensional finite element technique is effectively applied to solve the two equations, in which the coupling with the thickness-shear and thickness-flexure are omitted. The change of resonant frequencies are calculated as a function of Z'-length, and compared with the experiments. The results shows that almost all the spurious resonances in rectangular AT-cut quartz resonators belong to the thickness-flexure, face-shear and face-flexure. It is also shown that the plane-stress approximation is effective to predict the frequencies of the coupled vibrations of face-shear and face-flexure.

抄録全体を表示

This paper describes the influence on various characteristics such as resonant frequency, frequency temperature behavior and electrical equivalent circuit parameters due to a dimension of supporting portions and thickness for a new shape GT cut quartz crystal resonator. It was reported by one of the authors that the new shape GT cut resonator which is manufactured by an etching process, has more excellent frequency temperature behavior than the conventional GT plate manufactured by a mechanical process. Since it consists of a vibrational portion and two supporting portions and is a coupling resonator coupled between width extensional mode and length extensional mode, the dimension of the supporting portions and thickness greatly inflluence the frequency temperature behavior and electrical characteristics. The object of this paper is to clarify resonant frequency, frequency temperature behavior and electrical equivalent circuit parameters versus width of the elastic parts for the supporting portions and/or thickness. As a result, the first order temperature coefficient of the width extensional mode becomes small markedly as width of the elastic parts increases. The present resonator is also found to have an increasing series resistance and a decreasing quality factor according to increase of thickness.

抄録全体を表示

In this paper, a new calculation method for start-up time of crystal oscillators is described. First, the definition and the calculation method mentioned in one of the publications of International Electrotechnical Commission (IEC) are discussed. Then, a new definition suitable for practical circuit design is proposed and a new calculation method for start-up time on a bipolar transistor oscillator with the Colpitts configuration is described. Finally, it is shown that the start-up times of two oscillator circuits with different design policies are calculated and good agreements with experiments are obtained.

抄録全体を表示

A theoretical method for determining circuit parameters of equivalent circuits is described for the analysis of excitation and reflection characteristics of double electrode SAW interdigital transducers (DIDT). Admittance mismatch for single electrode SAW interdigital transducers, dispersion characteristics of an infinite arrary corresponding to an electrically shorted or opened DIDT and static capacitance for one pair of DIDT, which are necessary for determining circuit parameters, are calculated by using the finite-element method. Therefore in this approach, all the effects of piezoelectric perturbation, mechanical perturbation, ecergy storage, and anisotropy of substrate are taken into account. Numerical examples are presented for the circuit parameters of DIDTs on several piezoelectric substrates. For a 128° Y-X LiNbO₃ substrate, excitation and reflection characteristics are calculated and the computed results agree well with the experimental results.

抄録全体を表示

This paper describes a new weighting method for SAW filters to increase the out-of-band rejection level and its application. The present method is to weight the number of finger pairs in the interdigitated interdigital transducer (IIDT) which are composed of overlapping electrodes of the same length. To calculate the optimum weighting condition, the IIDT structure with two reflectors has been expressed by ten port network model based on equivalent circuit model developed by W. R. Smith. Using this method, we designed and fabricated 800 MHz bandpass filters for portable telephones. We mounted them in small leadless chip carriers which were 5mm× 5mm×1.6mm in size. The characteristics of frequency response was 3.5dB maximum insertion Itss in pass-band, 24 dB stop-band rejection, and 1.75 input-voltage standing wave ratio between -30°C and 70°C. We also designed and fabricated 1.5 GHz band SAW filters for a future cellular telephone system. An IDT pattern with 0.7μm line-and-space was deliniated by g-line projection type stepper.

抄録全体を表示

SAW filters offer advantages in that they are small, do not need adjustment, and are highly reproducible and reliable. However, their applications to the radio communication equipments have been limited due to the large insertion losses. The transceivers used in mobile radios require not only high-performance but also miniature devices. System constructions of 800-MHz cellular-mobile telephones are determined by the original designs of each country in the world. The increase of the frequency bandwidth used in mobile telephones has been proposed in almost all countries to achieve more numbers of telephone channels.
In this paper, several new technologies are reported to realize high-performance and low-loss SAW filters used in ultra-wideband mobile telephone systems. New configurations for wideband SAW band-pass filters which were used as the receiver filters and the transmitter pre-filters were invented. They had low-loss and sharp-cutoff frequency characteristics. New configurations for wideband SAW band-rejection filters which were used as the transmitter final stage filters were also invented. They had low-loss and high-power characteristics. The frequency responses of the miniature antenna duplexer module which includes the above SAW filters as well as the receiver low noise amplifier are also presented.

抄録全体を表示

When we have been manufacturing ZnO/glass SAW filters, the trouble has happened that the frequency of filter changed largely when the production lot of glass sheets changed. The other trouble has happened that the SAW filters of same production lot of glass sheet had double peak frequency distribution of largely separated. Previously it has been considered that the frequency deviation in the ZnO/glass SAW filters was dependent on the elastic quality of the ZnO thin films, the thickness of the ZnO films, and soon. But, we have noticed that the frequency deviation in ZnO/glass SAW filters was dependent on the deviation of elastic quality in the glass substrates. We have measured the leaky SAW (LSAW) velocities of two kinds of glass substrates, P-glass and B-glass, by LFB acoustic microscopy technique. As the result, we have discovered the large LSAW deviation in P-glass substrates between different production lots of glass sheets, and large LSAW deviation in B-glass substrates in one production lot of glass sheets. We investigated a cause of LSAW deviation still more, discovered that large LSAW deviation in glass substrates was dependent on the heat treatments process in the production of glass sheets. We have calculated the elastic constants, C₁₁, C₁₂, C₄₄ of glass substrates of different LSAW velocity, using experimental results of LSAW velocity, longitudinal velocity, and the density of glass substrates. Consequently, it has become clear that the two glass substrates with the different LSAW velocity (both P-glass and B-glass) had different densities and more different elastic constants.

抄録全体を表示

Magnetostatic wave (MSW) devices are potentially very promising for carrying out signal processing directly at microwave frequencies and are receiving much attention recently. Although development of a general design theory based on an equivalent circuit model is essential to make a significant advance in signal processing capabilities of the MSW devices, relatively few design theories were discussed in the past. In this paper, we extended and improved the general equivalent circuit approach to the magnetostatic wave devices we proposed and discussed earlier. Based on the definitions of the purely magnetostatic terminal parameters and the magnetostatic characterisic impedance, the electro-magnetostatic energy conversion is discussed and the appropriate general equivalent circuit models for the MSW devices are developed. Calculated insertion losses for various MSW devices are in excellent agreement with experimental results.

抄録全体を表示

As is well-known, magnetostatic surface waves exhibit a strong effect of power saturation on their devices, and even in the magnetostatic volume wave devices this phenomenon is often observed, if a thin yttrium iron garnet film is used. These effects are due to a spontaneous transfer of motion from magnetostatic waves to spin waves. So saturation power level is studied based on Suhl's theory. Numerical results are found to be in good agreement with experimental data. Dependence of saturation power level on sample geometry and each of three fundamental magnetostatic modes is discussed.

抄録全体を表示

The paper describes the development of ultrasonic transducers employing ZnO-film/Al-foil composite structure, and discusses their application to a scanning acoustic microscope (SAM) in VHF and UHF ranges.
It is theoretically shown that high performance ultrasonic transducers with low conversion loss and wide bandwidth can be realised by properly determining the thicknesses of the Al-foil and ZnO-film, and the effective diameter of the transducer.
The conversion loss of 6.7dB and -3dB bandwidth of 9.4% were experimentally achieved at the centre frequency of 142MHz, and the loss mechanism was discussed. A beam-focussing concave transducer was fabricated and applied to an SAM. SAM images revealed that the proposed transducers can be applied to various acoustic imaging systems.

抄録全体を表示

The performance of an interdigital transducer (IDT) for leaky Lamb waves operating at a liquidsolid interface, and a system of measuring the distribution of leaky surface acoustic wave (SAW) velocity and attenuation are described. A leaky Lamb wave device with three arched-IDTs on one surface of a thin piezoelectric ceramic plate is introduced for the measuring system. A compressional wave reradiated into a water layer from the surface of a test sample is detected as electrical signals with different delay times at two receiving IDTs. The phase and amplitude difference between the two delayed signals are dependent on the leaky SAW velocity and attenuation on the test sample. It is essential for measuring leaky SAW propagation characteristics that the incident angle of the longitudinal wave propagating in the water layer is in the vicinity of the Rayleigh critical angle. The present method has the advantage of a wide measurable region of SAW velocity in comparison to the use of a conventional type of leaky SAW transducer because of plural dispersive leaky Lamb modes. In a typical case of using of NEPEC-6 produced by Tokin Corp. for a piezoelectric substrate, the measurable regions of using leaky SAW and Lamb wave transducers are around 2, 150 m/s and 2, 000_??_7, 000 m/s, respectively.

抄録全体を表示

A new acoustic transducer with electronic focusing and scanning capabilities is presented. An interdigital transducer radiates acoustic waves in oblique directons with respect to the substrate surface when it is placed in water. A linear chirped interdigital transducer for the acoustic beam scanning was constructed on piezoelectric substrate. The chirped interdigital transducers consist of interdigital electrodes whose period and width are linearly changed. Moreover, the electrode is divided into several sections, each of which is placed to form a one dimensional Fresnel phase plate. In this structure, the focused acoustic beam scanning was achieved by changing the applied frequency. Experimental verification has been carried out using a chirped Fresnel phase plate type interdigital transducer which covers the frequency from 20 to 50MHz. A scan length of 9mm for a focused acoustic beam about 0.3mm in width has been obtained.

抄録全体を表示

This paper deals with the equivalent circuit of vibratory gyroscopes using the flexurally-vibrating double-resonant vibrator which has a square cross section or a regular triangular cross section. In the former resonator of a square cross section, two pairs of vibrational modes perpendicularly intersecting each other degenerate, and also three pairs of orthogonal vibrating modes degenerate in the latter resonator of a regular triangular cross section. It is clarified that the relations of coordinate transformation between the pairs of orthogonal vibrating modes in the respective resonators can be shown and considered by the equivalent circuit. Moreover, the equivalent electromechanical circuits of flexurally-vibrating resonator gyroscopes which are piezoelectrically driven and detected are given. These circuits will be useful for the simulation of characteristics and the design of a vibratory gyroscope.

抄録全体を表示

A hybrid transducer type ultrasonic motor consists of a torsional vibrator (TV) and a multilayered piezoelectric actuator (MPA). MPA vibrates longitudinally in the axial direction and controls the timing of contact between the rotor and the stator, while TV generates the rotational force. Applying sinusoidal voltages of the torsional resonance frequency to both parts with a certain phase difference, the rotor is driven to rotate at almost the same angular velocity as the torsional vibration. If we apply a DC voltage to TV, the angular position of the rotor can be displaced precisely.
Making use of these two ways of operation and the merits of the motor such as a high output torque at low speed, a large braking torque without energy consumption and a quick response, this paper presents a precise angular positioning control system. First we drive the rotor by the hybrid vibration of the stator to reach near the given end point quickly. Then, applying a DC voltage, the error is reduced by the static twist of stator. The resolution of the proposed system was 4.85×10^-6rad., which was equal to the resolution of the rotary optical encoder emplyed in this system.

抄録全体を表示

Usually frequency stabilized lasers have been used as light sources for high precise distance measurements. However, accuracy of those measurements is worse in air than in vacuum because wavelengths of such lasers fluctuate according to fluctuation of the refractive index of the air. Therefore a wavelength stabilized light source whose wavelength is not influenced by the refractive index of the air is desirable for distance measurements.
This paper describes a wavelength stabilized light source with a laser diode using a air-gap etalon as a standard of wavelength. As the optical length between two mirrors of the etalon changes according to the refractive index of the air, the wavelength in air can be stabilized. Our new wavelength control system does not require any electrical standard. At the same time the system realizes spectral linewidth reduction by widening the frequency range of it.
Experimental results are as follows: the wavelength stability in air estimated with square root of the Allan variance is 3.0×10^-9 (at 10 sec of integration time) and the spectral linewidth, that for free running is 10 MHz, is reduced to 650 KHz with electrical feedback.

抄録全体を表示