Temperature Coefficient Of Delay Time Research Articles

RF Filter using Boundary Acoustic Wave

In this paper, we report a new structure of a shear horizontal (SH) type boundary acoustic wave for cellular phone applications. Such a structure composed of electrodes with a low shear wave velocity between two materials, namely, the SiO2 film/Au-electrode/LiNbO3 substrate, is proposed. The ladder filter used in this paper had this structure. By changing the propagation angle of the acoustic wave, the electromechanical coupling factor k2 range from 0 to 16% was obtained, as well as a normalized bandwidth range 0.67 to 1.85 fold as large as that of a 36–46°Y–X LiTaO3 leaky surface acoustic wave (LT-LSAW) filter. In addition, an excellent temperature coefficient of delay time (TCD=25 ppm/°C) and a large mutual coupling coefficient κ12 (=0.15) were also obtained.

Characteristics of AlN Thin Films Deposited by Electron Cyclotron Resonance Dual-Ion-Beam Sputtering and Their Application to GHz-Band Surface Acoustic Wave Devices

A (001) plane of hexagonal aluminum nitride (AlN) has been deposited on R-plane sapphire ((1 1̄·2)Al2O3) with inclination of about 26° against the substrate by electron cyclotron resonance (ECR) dual-ion-beam sputtering. A shear horizon (SH) wave as well as a modified Rayleigh wave could be excited on this AlN film. The phase velocities of the SH wave (V SH) and Rayleigh wave (V R) were 6000∼6730 m/s and 5600∼5950 m/s, respectively. V R has no effect on the propagation direction. However, V SH has considerable influence on the propagation direction, and becomes maximum at the propagation direction of 45 degrees against [12·0]AlN. The insertion loss and temperature coefficient of delay time (TCD) of the 1.21-GHz-band two-port-type resonator using SH waves were 7.5 dB and 35.4 ppm/°C, respectively. These values are acceptable for practical use.

Preparation of aluminum nitride thin films by reactive sputtering and their applications to GHz-band surface acoustic wave devices

Single crystal aluminum nitride (AlN) thin films were prepared by a low-temperature reactive sputtering on basal plane sapphire [(001)Al2O3] at a substrate temperature of less than 315 °C. Surface acoustic wave (SAW) characteristics with an interdigital transducer /(001)AlN/(001)Al2O3 structure were investigated. The phase velocity and temperature coefficient of delay time are 5750–5765 m/s and 55–63 ppm/°C at KH=1.2–1.6, respectively. Resonator-type 1-GHz-band SAW filters with its structure were fabricated. The insertion loss and suppression were 23 dB and more than 20 dB, respectively.

Control of second‐order temperature coefficients of delay time for saw propagating in thin‐film layers

AbstractIn a surface acoustic wave substrate with a “piezoelectric thin‐film/substrate” configuration, the temperature coefficients of the acoustic constants of the Ta2O5 and ZnO thin films were determined by means of the least square method based on the experimental values of the temperature coefficients of the acoustic constants. Also, with regard to the two‐layered model of a “piezoelectric thin‐film/piezoelectric thin‐film/substrate” configuration, the surface acoustic wave speed, electromechanical coupling coefficient and temperature characteristics were computed and the combinations of the film thicknesses were derived for a first‐order zero‐temperature coefficient. Further, it is recognized that the ZnO thin film and the Ta2O5 thin film have second‐order delay time temperature dependences with opposite signs and then a method is proposed for controlling the first‐ and second‐order temperature coefficients in a two‐layered substrate. It is found experimentally and theoretically that there exists a highly stable substrate which exhibits a third‐order characteristic at an appropriate film thickness.

Control of Second Order Temperature Coefficient of SAW Propagating in Thin Film Layers

This study proposes the control method of the 1st- and 2nd-order temperature coefficients of two-layer substrate composed of ZnO and Ta2O5 thin films which have the 2nd-order temperature coefficients of delay time with the signs opposite to each other. As a result, a stable SAW substrate of [Ta2O5/ZnO/Fused quartz] showing the 3rd-order characteristics was developed.

A simplified model to predict the linear temperature coefficient of a CMOS inverter's delay time

The Curve-fitting equation A/(1 + BT) is used in this study of the temperature dependence of a MOSFET's drain current. This leads to a simplified delay-time model in predicting the temperature coefficient of delay-time for a CMOS circuit. Good agreement is obtained between the measured CMOS ring-oscillator delay time and the simplified model. Both the experimental and computer-simulated data suggest that the half-supply point can be used to estimate the temperature coefficient of CMOS delay time.

Deposition of Ta2O5 Thin Film and Application to SAW Devices.

Crystallized Ta2O5 thin film have been deposited on fused quartz substrate by reactive dc diode sputtering. Crystalline structure and piezoelectric properties of the Ta2O5 thin film were investigated. Surface acoustic wave (SAW) properties, including a phase velocity, a coupling coefficient, a temperature coefficient of delay, and a propagation loss, were measured for SAW propagating in the Ta2O5 thin film on fused quartz substrate. The coupling coefficient K2 is 0.7% for hk=1.6. The first-order temperature coefficient of delay time is zero for hk=1.78.

Growth and Properties of Li2B4O7 Single Crystal for SAW Device Applications

Large Li2B4O7 single crystals, up to 45 mm in diameter, have been successfully grown along the X- and Z-axis by Czochralski technique. Fundamental phsyical and chemical properties were determined, and basic SAW properties were studied for the various surface orientations and SAW propagation directions from theoretical and experimental points of view. It was found that there were useful substrate orientations for SAW resonators and narrow bandpass SAW filters around the rotated X-cut, Z-propagation, where SAW propagation delay time was a parabolic function of temperature and SAW coupling factor k2 was approximately 1%. When a SAW propagates along the Z-direction on the 28° rotated X-cut substrate, the temperature coefficient of delay time (TCD) is zero at 20°C and the second order TCD is 0.27 ppm/°C2, k2 is 0.8% and SAW velocity vs is 3470 m/s. The bulk wave spurious signal response level is lower by -20 dB than the SAW fundamental response level.

Surface acoustic wave properties of (Pb,Ln)(Ti, Mn, In)O3 ceramics (Ln = La and Nd)

The surface acoustic wave properties of PbTiO3 ceramics are improved. The ceramic systems investigated are (Pb,Ln)(Ti,Mn,In)O3(Ln = La,Nd). The temperature coefficients of delay time are lowered to 46×10−6/ °C, when Ln is La. A zero temperature coefficient of delay can be achieved when Ln is Nd. The Nd and In substitution also cause the electromechanical coupling factor to increase and the dielectric constant to decrease.

Temperature-Stable SiO2/LiTaO3 Structure for SAW Devices

A temperature dependence of delay time and phase velocity of SAW on a layered structure of SiO2/X-115°Y LiTaO3 was studied. A zero temperature coefficient of delay time was obtained for a normalized SiO2 film thickness of k·h≃1.0 at room temperature. The temperature variation of delay time observed was less than 10 ppm in a temperature range from 0°C to 60°C. The bandpass filter characteristics with a center frequency of 170 MHz were also demonstrated.

Surface acoustic wave characteristics of (Ba2−xSrx)TiSi2O8 crystals

The surface acoustic wave characteristics of fresnoite (Ba2TiSi2O8) crystals are improved. The temperature coefficients of delay time are greatly lowered, with almost no change in the electromechanical coupling factor, as the result of partial substitution of Sr for Ba, particularly in (Ba2−xSrx)TiSi2O8 crystals. These crystals have temperature coefficients of delay comparable to LiTaO3, while their electromechanical coupling factors are twice as large.

耐食性インバー，エリンバー型Fe-Cr-B系非晶質合金

Amorphous (Fe(1-x)Cr(x))85B15 alloys (x = 0 to 0.15) were prepared from the melts by rapid quenching using a single roller techinque, and their Invar and Elinvar characteristics and corrosion resistance were investigated. With an increase in chromium content the Curie temperature and the saturation magnetic moment per iron atom decreased monotonically, while the crystallization temperature incresed gradually. The thermal expansion coefficient alpha around room temperature became slightly larger with increasing chromium content. Nevertheless, these amorphous alloys exhibited excellent Invar characteristics below the Curie temperature. The value of Young's modulus increased remarkably in a relatively low magnetic field and then saturated at a field of about 80 kA/m, showing a large delta E effect. Its value as well as a longitudinal linear magnetostriction became smaller with an increase in chromium content. The temperature coefficient of Young's modulus changed from postive to negative, and the temperature range showing the Elinvar characteristics became narrower with chromium content. The temperature coefficient of delay time determined from the values of alpha and e was very small. The corrosion resistance of these alloys was extremely improved by chromium addition.

The Magnetostrictive Delay Line Characteristics in Co–Fe–Cr and Co–Fe–Cr–Ni Alloy Systems

The temperature coefficient of delay time, αD, at 0 to 40°C and the maximum gradient of magnetostriction in the applied magnetic field, (dλ⁄dH)m, at room temperature have been measured with the annealed alloys in the Co–Fe–Cr system, the Co–Fe–Cr-16.7% Ni system and the Co–Fe–Cr-28.6% Ni system. It has been found that in Co-31.0% Fe-9.0% Cr alloy the αD has such a small value as −0.42×10−5. The (dλ⁄dH)m is 0.36×10−6/Oe which is comparable with the absolute value of −0.39×10−6/Oe in nickel. The αD, for Co-37.8% Fe-4.3% Cr-16.7% Ni alloy also shows a very small value of −0.07×10−5, while its (dλ⁄dH)m shows a very large value of 0.80×10−6/Oe which is about two times greater than the absolute value of nickel and five times greater than that of Ni-Span C. And Co-50.0% Fe-2.4% Cr-28.6% Ni alloy has a small value of −0.21×10−5 for αD and 0.19×10−6/Oe for (dλ⁄dH)m which is about half of the absolute value for nickel. Among these alloys, a Co-37.8% Fe-4.3% Cr-16.7% Ni alloy not only exhibit excellent characteristics of the magnetostrictive delay line but also can easily be cold worked. Therefore, the alloy seems to be a material suitable for the delay line.

Co-Fe-Cr系ならびにCo-Fe-Cr-Ni系合金の磁気ひずみ遅延線特性について

The temperature coefficient of delay time, αD, at 0 to 40°C and the maximum gradient of magnetostriction to magnetic field, (dλ⁄dH)m, at room temperature have been measured with the annealed alloys in the Co-Fe-Cr system, the Co-Fe-Cr-about 16.7% Ni system and the Co-Fe-Cr-about 28.6% Ni system. It has been found that in Co-31.0% Fe-9.0% Cr alloy the αD has such small value as −0.42×10−5. The (dλ⁄dH)m is 0.36×10−6/Oe and is comparable with the absolute value of −0.39×10−6/Oe in nickel. The αD for Co-37.8% Fe-4.3% Cr-16.7% Ni alloy also shows a very small value of −0.07×10−5, while its (dλ⁄dH)m shows a very large value of 0.80×10−6/Oe which is about two times greater than the absolute value of nickel and five times greater than that of Ni-Span C. And Co-50.0% Fe-2.4% Cr-28.6% Ni alloy has a small value of +0.21×10−5 for αD and 0.19×10−6/Oe for (dλ⁄dH)m which is about half of the absolute value of nickel. Among these alloys, Co-37.8% Fe-4.3% Cr-16.7% Ni alloy not only exhibit the excellent characteristics in its magnetostrictive delay line but also can easily be cold worked. Therefore, the alloy seems to be a material suitable for the delay line.

Miniaturization of Delay Lines Through the Use of the Dielectric and Structural Properties of Plastics

A miniaturized delay line wound on a sectionalized plastic spool is described. The surfaces of the spool and flange separators are coated with a silver paint which serves as a capacitor electrode. The other capacitor electrode is a winding conductor and the capacitance is derived from the wire insulation. To raise the capacitance the spaces between turns of the windings and between the windings and the flange or-core are filled with an oil having a dielectric constant somewhat greeter than air. The surface electrical resistance of a silver paint electrode has a significant effect on the output voltage loss and the capacitance of the delay line. In general, the thinner silver paint electrodes result in less output voltage loss and also lower capacitance. In view of the output voltage and the delay time of this delay line, suitable surface electrical resistance is 15 to 25 /Omeg /square, hence the effect of thickness of silver paint electrodes is discussed. The temperature coefficient of delay time is improved by using a filler oil with a negative temperature coefficient of dielectric constant. A further improvement is achieved by a newly developed packing method. The miniaturized delay line in a size of 11x14x45mm has a low output loss of 3 dB at 4 MHz.

Surface acoustic wave delay lines with small temperature coefficient

Surface acoustic wave delay lines having a vanishing first-order temperature coefficient of delay time near room temperature have been constructed. The devices were operated near 60 MHz and had about 5 µs delay. The surface waves, generated and received using interdigital electrodes, were propagated along the twofold crystallographic axis of ST-cut quartz. The phase delay change as a function of temperature has a parabolic temperature dependence with a second-order coefficient of approximately 31.5 × 10-9/° C2.

Limitations on the Performance of Ultrasonic Delay Lines Using Vitreous Silica as the Delay Medium

The information storage capabilities of ultrasonic delay lines using vitreous silica (a term used to denote both fused quartz made from powdered crystalline quartz and fused silica made by oxidation of SiCl4 in an oxygen-hydrogen flame) are limited at low frequencies by the variation in the shear wave phase velocity and at high frequencies by the attenuation-vs-frequency dependence of vitreous silica. Recent experimental data [D. B. Fraser, J. T. Krause, and A. H. Meitzler, Applied Physics Letters (In preparation)] on the shear attenuation coefficient versus frequency dependence and the constancy of shear wave phase velocity are presented and combined with analytical models to estimate the maximum digital signal storage capabilities of ultrasonic delay lines using vitreous silica. In addition, other factors influencing performance limits, such as the temperature dependence of loss, the temperature coefficient of delay time, and the magnitude of the acoustoelastic effect in vitreous silica, are discussed.

An Ultrasonic Study of Some Optical Glasses

Ultrasonic delay time in typical optical glasses was measured between -20° and 120°C using superposition method at 5 MHz, which assured the precision of 1 in 104. It was found out that the temperature coefficients of delay time of measured glasses lie in the range of ±50 ppm/°C, and shift from negative to positive as SiO2 content decreases. The frequency dependence of acoustic loss was also measured using pulse echo method up to 130 MHz, and was found to be in the range of 0.01∼0.03 dB per unit wavelength.