Power Flow Angle Research Articles

Surface Acoustic Wave Properties of La3Ga5SiO14 (LANGASITE) Single Crystals

Theoretical and experimental results have shown the potential usefulness of La3Ga5SiO14 (LGS) for surface acoustic wave (SAW) applications. The existence of orientations with zero-temperature coefficient of delay (TCD) have been calculated by the computer analysis. A simulation of the temperature-compensated Rayleigh SAWs located around both (0°, 140°, 25°) and (15°, 151°, 40.5°) with the Rayleigh SAW velocity v of 2762 and 2860 m/s, coupling coefficient k2 of 0.38 and 0.41%, and power flow angle PFA of 2 and 0°, has been carried out. The Rayleigh SAW velocity v is lower than those of other SAW materials, which enables miniaturization of SAW design.

PERFORMANCE PREDICTION MODELS FOR TURNING WITH ROUNDED CORNER PLANE FACED LATHE TOOLS. I. THEORETICAL DEVELOPMENT

ABSTRACT In this paper the need for reliable quantitative machining performance information for efficient and effective use of machining operations is discussed, as are the recent developments of predictive models for forces and power in practical machining operations based on the 'unified mechanics of cutting approach'. This investigation is aimed at extending this mechanics of cutting approach to turning with rounded corner plane faced lathe tools. Three predictive models for the forces, power and chip flow angle based on the 'unified mechanics of cutting approach1 have been developed while the surface roughness models have been based on the feed marks generated on the machined surface allowing for the precise tool corner profile. The first force model is based on the modified mechanics of cutting analyses for single edge tools while the two alternative models are based on the generalised mechanics of cutting analyses for single edge and multi-edge form tools for the turning cut as a whole. The predictive force models incorporate the effects of the major tool geometrical variables including the corner radius, the cutting conditions as well as the effect of TiN coating. This first paper will outline the development of the models while the proposed models will be numerically tested and experimentally verified qualitatively and quantitatively in the subsequent parts of this investigation.

Paratellurite: Propagation of the slow shear wave in the (001) plane. New formulations for the acoustic velocity and divergence

The propagation of the slow shear wave in paratellurite with an angular tilt θ from the [110] axis in the (001) plane is considered. Original formulations are given for the acoustic velocity, the power flow angle, and the acoustic divergence. For a small angular deviation, the acoustic spreading is greatly reduced. This configuration can be used for multichannel Bragg cells. In order to demonstrate the feasibility of such a device, a three-channel Bragg cell (θ=5°) has been designed and successfully tested.

Characteristics of Rayleigh and Leaky Surface Acoustic WavePropagating on a La3Ga5SiO14 Substrate

The propagation characteristics of Rayleigh waves on a La3Ga5SiO14 substrate are theoretically investigated for all cuts and propagation directions. The results of the phase velocity, electro-mechanical coupling constant (K2), power flow angle (PFA) and temperature coefficient of delay (TCD) are shown as contour maps. The maximum value of K2 of a Rayleigh wave is 0.55%, and about 0.5% with zero TCD. These values are about 2–3 times larger than those of quartz. It is found that some cuts exist, which do not have a Rayleigh wave. The characteristics of leaky surface acoustic wave (SAW) on Z-cut La3Ga5SiO14 are also shown.

K-cut quartz SAW resonators for stable frequency sources

A new type of quartz SAW resonator for use as a stable frequency source has been developed. It was studied from the point of view of frequency instability caused by transient thermal behavior, and a new angle of cut named the K-cut for quartz SAW resonators was found. The static and dynamic frequency temperature coefficients are both zero at a room temperature. Taking into consideration the influence of the electrode-film thickness, the width modes of the waves, and power-flow angles, optimized resonators and oscillators were designed. These devices had frequency stability of 2x10(-10) for the mean time of 0.01 s.

Design technique for nonlinear phase SAW filters using slanted finger interdigital transducers

This paper describes a useful design technique to achieve a nonlinear phase SAW filter using slanted finger interdigital transducers (SFITs) or tapered interdigital transducers which are suitable for wide-band filters in intermediate frequency stages. A required nonlinear phase response in the passband can be obtained by changing center-to-center distances between input and output SFITs along an axis perpendicular to the SAW propagation axis. The design is based on a building-block approach in the frequency domain. A nonlinear phase SAW filter with a center frequency of 70 MHz and a fractional bandwidth of about 10% is demonstrated on x-cut 112.2 degrees y-propagating LiTaO(3 ). Because the substrate has a power flow angle of 1.55 degrees, the SFIT pattern is tilted along that angle. Good agreement between theoretical and experimental results is obtained.

Surface Acoustic Wave Characteristics of a ZnO/Quartz Substrate Structure Having a Large Electromechanical Coupling Factor and a Small Temperature Coefficient

A substrate having a suitable electromechanical coupling factor (k s) value and a good temperature coefficient of frequency (TCF) is required for an applications of resonator surface acoustic wave (SAW) filters and rudder-type SAW filters requiring a specific bandwidth, because their bandwidth largely depends on the coupling factor of the substrate. Although a quartz substrate for SAW devices provides a good TCF, the electromechanical coupling factor obtained is small. The author speculated that an excellent TCF and an appropriate electromechanical coupling factor could be realized by combination of a quartz substrate having a positive TCF and a ZnO film having a negative TCF. As a result of theoretical and experimental investigations performed using a 29°45' rotated Y and a 42°45' rotated Y 35°X propagating quartz substrate, an excellent TCF (≈0 ppm/°C) and an appropriate coupling factor (k s=0.1–0.11; k s2=0.01–0.0121) were realized with a zero degree power flow angle on the structure of IDT/ZnO/quartz or IDT/ZnO/shorted-plane/quartz for the first time.

Overview of SAW materials.

There is now a rich variety of piezoelectric materials available for surface acoustic wave applications. These include crystals in symmetry classes mm2, 32, 3m, 4mm, 6mm, and 4a3m. Classes 6mm and 4a3m include most of the binary semiconductors, such as gallium arsenide and related alloys, making integrated acoustic/electronic devices possible. Depending upon use, the SAW substrate material may be chosen to have certain combinations: piezocoupling, temperature coefficient of frequency or delay, small coupling to bulk modes, low sensitivity to acceleration or thermal transients, high acoustic Q, small power flow angle, etc. In this paper, these and other criteria are discussed broadly, with illustrations of pertinent materials and orientations. Also given are recommendations of substances for which the material constants are well enough known to be practical, as well as indications for necessary future work in growth and characterization. A broadband equivalent electrical network for SAW propagation is presented, by means of which the appropriate material parameters may be extracted from network analyzer measurements. The circuit can also serve to represent the salient features of devices in their working environments.

Lithium niobate thin films deposited on silicon substrates and their SAW applications

Abstract Lithium niobate has a number of attractive piezoelectric and ferroelectric properties that have been exploited for many applications. The main purpose of our work was to grow lithium niobate thin films on silicon substrates and make surface acoustic wave (SAW) devices. Theoretical curves of SAW properties of bulk crystals and films lithium niobate on silicon with a coating of silicon oxide were also obtained. The theoretical results include elastic wave properties (velocities and power flow angle) in lithium niobate bulk crystals and SAW properties (velocities and coupling coefficients). Thin films of lithium niobate have been deposited on Si (100) substrates (with SiO2 coatings) by rf magnetron sputtering. Lithium niobate film samples with very good transparency and uniformity were obtained. The film samples were structurally analyzed using Bragg x-ray diffraction (XRD). Lithium niobate XRD peaks for specific sputtering conditions corresponding to thin film orientation of (012), (104) and (110) ...

Suppression of bulk-wave responses in SAW devices using the difference of power flow angles

If spurious bulk-waves are radiated from the launching interdigital transducers (IDT's) in surface acoustic wave (SAW) devices, it is possible to reduce bulk-wave responses by steering the beams out of the receiving IDT by use of the difference of power flow angles (PFA's) between SAWs and bulk-waves. The spurious bulk wave suppression scheme is clarified. A new crystal cut with excellently suppressed bulk-wave responses using this scheme is located for quartz. >

Longitudinal horizontally polarized leaky and non-leaky SAW in lithium tetraborate

Unknown LH type leaky and non-leaky waves were theoretically found and examined in lithium tetraborate. The waves have very promising parameters: high velocity, strong piezoelectric coupling, zero power flow angle and small temperature coefficients of delay. The theory of exceptional waves proved to be very useful to investigate the acoustic anisotropy and to search for the cuts where leaky and non-leaky SAW can exist.

Doubly rotated SAW quartz cuts with low sensitivity to stress and temperature effects exhibiting a power flow angle close to zero

Three doubly rotated quartz cuts for surface acoustic wave (SAW) devices have been theoretically found exhibiting a very low sensitivity to radial in-plane stresses and to statical temperature effects and also presenting a very small power flow angle. Such a conjunction of these phenomena offers new perspectives in the design of very high stability SAW resonators.

Computer-Aided Predictive Models for Fundamental Rotary Tool Cutting Processes

Mechanics of cutting analyses for fundamental ‘self-propelled’ and driven rotary tool cutting processes aimed at gaining an understanding of the practical rotary tool turning and face milling operations are presented. It is shown that these fundamental rotary tool processes can be directly related to the ‘classical’ orthogonal and oblique cutting processes used to study the fundamentals of conventional machining and develop predictive models for the more complex practical turning, drilling and milling operations. Based on the unified mechanics of cutting approach, computer-aided cutting models for predicting the force components, power and chip flow angle in the fundamental rotary tool processes are discussed, experimentally verified and numerically studied. The difficulties of extending these models to the practical rotary tool operations are briefly discussed.

Characteristics of Leaky Surface Wave Propagating on Li2B4O7 Substrate

The propagation characteristics of leaky surface wave on Li2B4O7 substrate were theoretically calculated for all cuts and propagation directions by changing Euler's angle. The theoretical contour maps for phase velocity, electromechanical coupling constant (K2), temperature coefficient of delay (TCD), propagation loss, and power flow angle (PFA) are displayed. Cuts with good propagation characteristics were theoretically discovered using leaky surface wave.

Measurement of surface acoustic wave slowness curves with a scanning laser acoustic microscope

The measurement of the velocity and power flow angle of surface acoustic waves (SAWs) using a scanning laser acoustic microscope is described. Data obtained from a single scan by the microscope and from a single direction of insonification are Fourier transformed from the spatial domain into the spatial frequency domain. The incident cw surface waves scatter from the sides of the sample into all possible wave vectors. Thus, the Fourier transform in the spatial frequency domain is the inverse velocity or slowness curve for surface waves propagating on the material. From this curve, the phase velocity, group velocity, and power flow angle versus propagation direction can be obtained. Experimental results for YZ lithium niobate, ST quartz, and (111) silicon are in good agreement with theoretical calculations.

Interactive Computer-Aided Analysis for Bulk Acoustic Waves in Materials of Arbitrary Anisotropy and Piezoelectricity

Absfmcf-A computer-aided analysis program is described which makes it possible to calculate interactively, on a personal computer, the main properties of bulk acoustic waves in materials of arbitrary anisotropy and piezoelectricity. Curves of the slownesses, the electromechanical coupling constants, and the power flow angles can be simultaneously displayed for propagation in an arbitrary plane. Numerical data for propagation in a particular direction is displayed by moving an electronic cursor to the desired direction. Examples are given illustrating the usefulness of the program in the design of bulk wave transducers, the calculation of acoustooptic figures of merit, and the calculation of cutoff velocities for surface waves on layered media. The program formulation uses the material constants of a rotated coordinate system which, while it may not be the most convenient approach for some specific crystal orientation, has the pedagogical advantages of yielding simple expressions for the group velocities, power-flow angles, and electromechanical coupling constants. This paper, although it does not contain any original material, brings together in one work results which come from many sources.

X-cut quartz for improved surface acoustic wave temperature stability

Theoretical and experimental investigations of surface acoustic wave (SAW) propagation on X-cut, 33.44° propagating quartz show that the temperature compensated orientation has better temperature stability (−0.0209 ppm/C2) than ST-cut quartz (−0.0370 ppm/C2). The orientation requires only a single rotation (33.44°) from the crystal axes. This is substantially simpler than previously reported cuts with comparable temperature stability which typically require three rotations. The X-cut orientation has a SAW velocity of 3175 m/sec, an electromechanical coupling (Δv/v) of 4×10−4, and a power flow angle of 2.7°.

Microwave Surface Acoustic Wave Materials

Abstract : The acoustic wave properties of several piezoelectric crystals and a layered structure have been theoretically and experimentally investigated for possible application in microwave acoustic devices. A search was made for crystals and layered structures having one or more of the following properties: (i) temperature compensation, (ii) high piezoelectric coupling, (iii) low power flow angle, (iv) low loss and (v) low or high acoustic wave velocities. The acoustic waves studied were the bulk acoustic waves (BAW), the surface acoustic waves (SAW), the pseudo SAW (PSAW), the plate modes and the surface skimming bulk waves (SSBW). The wave properties studied were the velocity, piezoelectric coupling, the temperature coefficient of delay, diffraction and attenuation. The layered geometries examined studied included fused silica on LiNbO3 and gold, aluminum and copper layers on quartz. The overlay structures were found to be more temperature stable than the single crystals. A theory describing the spectrum of acoustic waves emanating from an interdigital transducer was developed. Several promising cuts for SSBW in quartz were identified and studied both theoretically and experimentally. Finally, various prototype SSBW devices were fabricated and tested.

Temperature variation of SAW power flow angle

The power flow angle of surface acoustic waves in quartz not on a crystalline axis of symmetry is shown to vary rapidly with temperature. Experimental results and theoretical calculations are presented demonstrating the dependence of the acoustic power flow angle on a doubly rotated cut of quartz.

Surface acoustic wave characteristics of a single crystal of potassium lithium niobate

The surface acoustic wave (SAW) characteristics of a single crystal of potassium lithium niobate K2.98Li1.55Nb5.11O15 are calculated using published data. It is found that there are two sets of propagation planes and directions having zero temperature coefficient of SAW delay time. One set has a large electromechanical coupling factor (K2s=0.9%) and a zero power flow angle. The temperature stability of this crystal is located between that of T13TaSe4 and ST-cut quartz.