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The angle of cut of a quartz resonator blank is corrected by a photolytic etching technique whereby an intensity gradient of photon energy is developed across the surface crystal blank which is to be corrected. The intensity gradient is generated by means of a lens system located intermediate a photon source and the crystal blank the surface of which has been treated with a photolytic etchant. The lens system includes at least one lens having a region of variable transmissivity of photon energy so that the amount of photon energy impinging on the crystal determines the depth of surface erosion. Additionally, the etching operation is controlled by means of a programmed digital computer which controls the contour of the face being etched upon receiving feedback information from X-ray apparatus which examines and monitors the etching for providing closed-loop control. (Author)

This invention relates to the correction of the orientation angle or angle of cut of quartz crystal blanks which substantially eliminates the initial formation of mesas and the subsequent lapping operation, as heretofore required, by providing a controlled linear etching gradient across opposing faces of a crystal plate or blank which is to be corrected. A beam for either ion etching or photolytic etching is repeatedly scanned across the face of the crystal plate in a multi-line raster pattern under the control of a microprocessor or mini-computer which controls the contour of the face being etched. X-ray apparatus monitors the etching and feeds information back to the computing apparatus for providing a closed loop control. The scanning includes either intensity modulation or velocity modulation of the beam, or succeeding scan lines are repetitively scanned a greater number of times than the respective preceding lines causing increasing amounts of the surface to be eroded as the scanning operation proceeds. (Author)

This invention relates to methods and apparatus for contactless, non-destructiveresistivity measurements on semiconducting crystalline material, for example, gallium arsenide. The material to be tested is formed into a disc which is supported within an air gap. The holder for the disc is such as to support the disc only about its outer edges; thus, the disc is free to vibrate piezoelectrically. A measuring circuit connected to the electrodes, which establish the air gap, applies an alternating electric field in the air gap which causes the crystal to vibrate. By adjusting the frequency of excitation, resonance may be established in the crystal and by comparing the current drawn through the air gap with graphs previously established for material of the type under test, the resistivity of the disc can be determined. (Author)

The invention is an improved manufacturing technique for producing a certain class of Surface Acoustic Wave (SAW) devices, namely those having input and output transducers in close proximity. A much higher manufacturing yield results from eliminating the cutting of a slot in the substrate between input and output transducers as formerly done. This frequently destructive step is replaced by ion-milling of a deep groove between the ports and backfilling with a metal of proper configuration to provide electromagnetic shielding. The technique produces a new device that is at least equal to the prior art in rejection of unwanted couplings between input and output. (Author)

An arrangement is disclosed for piezoelectric resonators utilizing linear and parallel sides or flats located on the periphery and opposite ends of the resonator. These sides are lcoated normal to the axes wherein collinear forces applied to the resonator produce a desired effect upon its natural resonant frequency. For technical sensor applications this aspect is maximized while for applications requiring a stable frequency or time base this effect is minimized. The outline peripheral shpae of the resonators utilizing this mounting arrangement varies in accordance with the crystallorgraphic orientation present in each resonator., Continuation of PAT-APPL-145 180, AD-D007 630.

In a preferred embodiment, the invention comprises an acoustic diffractometer in which acoustic waves (phonons) are diffracted through a piezoelectric superlattice, analogous to a diffraction grating, over an arbitrarily wide frequency range, including the desired 100-300 GHz range. Advantageously, the piezoelectric superlattice is formed from a high-resistivity, semi-conducting crystalline material, for example, materials in the cubic class 43 m. This class includes most of the II-VI and III-V compounds, such as GaAs and GaAlAs. The foregoing and other objects and advantages of the invention will appear from the following description. In the description reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration and not of limitation a preferred embodiment. Such description does not represent the full scope of the invention, but rather the invention may be employed in different arrangements as will be appreciated by those skilled in the art. (Author)

An arrangement is disclosed for piezoelectric resonators utilizing linear and parallel sides or flats located on the periphery and opposite ends of the resonator. These sides are located normal to the axes wherein collinear forces applied to the resonator produce a desired effect upon its natural resonant frequency. For mechanical sensor applications this effect is maximized while for applications requiring a stable frequency or time base this effect is minimized. The outline peripheral shape of the resonators utilizing this mounting arrangement varies in accordance with the crystallographic orientation present in each resonator. (Author)

This invention relates to an external source of electromagnetic energy which is applied to quartz in addition to the conventional heating and DC bias electric field. The source can be either coherent or incoherent. The wavelengths can range from the infrared through the visible into the ultraviolet. (Author)

It is therefore an object of the present invention to provide an acceleration resistant crystal configuration which is acceleration resistant along all directions. It is another object of the present invention to provide an acceleration resistant crystal configuration which is rugged and is highly resistant to breakage. In brief, these and other objects of the invention are achieved by having two crystals which are electrically coupled or mechanically coupled, or both electrically and mechanically coupled together. At least two axes of one crystal are disposed in anti-parallel relationship with the corresponding axes of the other crystal.

A method and apparatus for determining anomalies in the frequency- or admittance-temperature characteristic of a piezoelectric crystal resonator by inserting a variable capacitance network in series with the crystal and electronically sweeping the value of the capacitance network by a control voltage applied thereto while the temperature remains constant and noting any abrupt change in the resonance frequency characteristic. (Author), Supersedes PAT-APPL-870 694-78, AD-D006 417.

The quest for high stability crystal resonators for advanced frequency control applications has led very recently to a number of far-reaching developments. As the level of frequency stability has improved over the years, various factors that were once imperceptible have become nonnegligible, and their influences have had to be eliminated, reduced, or compensated. At present, the most obvious contributors to resonator performance have been enumerated. It is important to continue to catalog less obvious effects, and to evaluate critically at what level their influences make an appearance in the error budget of the resonator. We consider a number of influences that are more-or-less subtle. Each is examined to see what contribution it makes to resonator performance. It is apparent that some have to be taken into account in present-day applications; others may become important as future stability specifications become even more stringent. (Author)

Effects of mass-loading and harmonic on the resonance and antiresonance temperature behavior of a piezoelectric plate vibrator are described, in the one dimensional approximation, for thickness- and lateral-field excitation. Applications to rotated-Y-cut quartz cuts are given.

Analog network representations are given for crossed-field and in-line excitation of acoustic surface waves on piezoelectric crystals. Advantages of the analog formulation of the circuits are discussed and compared with earlier models. Enhanced physical insight, flexibility in adapting the circuits to describe modifications in device structure, and a rational approach to the approximation problem are the primary motivations for adopting models of this kind. Appendices describe electric field calculations, lumped element transmission line approximations, and piezoelectric forces produced by electrode arrays.

Quartz crystal resonators have been employed in a number of thermometer applications. We have recently discovered two new thermometric cuts; one exhibits a high degree of linearity over a wide temperature range; the other is located in the vicinity of the stress compensated locus. These doubly rotated cuts were found by calculations based on the thickness - vibration theory for ideal plates. This paper presents theoretical and experimental results concerning the frequency-temperature characteristics of these quartz resonators., This article is from the Proceedings of the Symposium on Frequency Control (36th Annual), 2-4 Jun 82, Philadelphia, PA., AD-A130 811, p290-296.

PROCESSING, CONTROL, FREQUENCY, EQUIVALENT CIRCUITSA class of novel frequency-selective devices, called stacked-crystal filters, is discussed in terms of a microwave network approach that leads to a systematic procedure for their analysis and design. These devices consist of two or more crystal plates that are stacked together, with thin electrodes being provided between some or all of the adjacent interfaces for the purpose of translating mechanical properties into electrical signals via piezoelectric coupling. In such a configuration, the electro-mechanical coupling that occurs at the plate surfaces produces selective interactions between the elastic modes in each crystal plate, as well as between these modes and all of the modes in the other plates included in a stack. A judicious combination of materials and dimensions can therefore provide a very wide range of desired filtering characteristics. (Modified author abstract)

The patent provides an electromechanical delay line with variable acoustic length. It provides precise adjustment of the delay.

An object of this invention is to provide a single piezoelectric crystal element having a plurality of useful modes of motion that may be used simultaneously for high frequency operation. Another object of this invention is to provide a piezoelectric crystal element having a plurality of independently controlled frequencies whose properties can be calculated in advance, and which can be used for equally exciting the two thickness shear modes of a piezoelectric quartz element. Another object of this invention is to reduce the number and cost of crystals used in electric wave filter systems and other wave transmission networks.

RAL-FIELD EXCITATION MAY BE USED TO DRIVE ONE OR ANY COMBINATION OF THE PLATES. A canonic element, consisting of two layers, forms the basis for deriving the network representation, which is then generalized to stacks of any number of strata. In a vibrating system of this type, the crystal comprising each layer is represented, in the bulk, by three acoustic transmission lines. Each interface, however, appears as lumped transformer elements coupling together the six transmission lines incident upon that boundary from the media on both sides. Incorporation of the piezoelectric drive mechanism is shown to require an additional simple network and interconnection. The analysis brings under systematic treatment crystal resonators and filters, delay lines, and pulse and code generators. Some practical applications are illustrated by computer simulation of new device characteristics. (Author)

Techniques for crystal measurements are reviewed in broad terms with emphasis on their common aspects. The technique proposed by the IEEE Subcommittee on Crystal Measurements for standard reference purposes are discussed in some detail, and the rationale that led to this selection presented. The paper includes an analysis of round robin results. (Author)

Bridge methods are the most accurate means of determining the parameters of quartz vibrators, particularly in the VHF region, and above. Present and future crystal requirement specifications point toward the increasing use of such methods to obtain the accuracy necessary for both filter and oscillator applications. A practical difficulty which arises is that the ranges of any given bridge are not compatible with every immittance characteristic encountered with the various crystal types in use, particularly if measurements are to be made over substantially different portions of the region of resonance. One means of obviating this difficulty is to augment the crystal with another impedance element in series or parallel so that the behavior of the combination is accommodated within the bridge ranges; the value of the augmenting element is determined separately, usually on the same bridge. Thus a capacitance in parallel with the crystal is suitable for reducing the impedance variation when using impedance bridges which consider the unknown as a series combination of resistance and reactance, while a series element reduces the admittance variation in parallel bridges--those representing the unknown as a conductance and susceptance in parallel. It is one purpose of this technical report to discuss the applicability and limitations of this latter procedure, and describe how the crystal parameters are extracted from measurements of this type. (Author)

A most distinguishing and useful feature of lightly damped piezoelectric vibrators is the comparative sharpness of the mechanical resonances which may be excited. Consideration of the electrical behavior of a simple vibrator of this type leads to various criteria by which to describe the onset and extent of the region of resonance. It is shown that the equiimmittance point is a most convenient criterion for delimiting the resonance range, and, further, provides a measure assessing the validity of circle diagram representations. A comprehensive list of characteristic frequencies associated with the vibrator resonance is given with corresponding equations for their determination. (Author)

The extension of the design technique to permit the fabrication of units to 150 MHz is presented along with a discussion of the latitude which exists between the conflicting constraints imposed by the nature of the crystal element. Included are charts and nomograms to facilitate the design of these units, together with attainable motional parameter values consistent with an adequately suppressed unwanted mode spectrum. This new technology is also applicable to oscillator crystals. One area explored concerns the specific problem of achieving moderate mode suppression in VHF oscillator crystals which must work in fixed-tuned circuits. Here the operating characteristics of the oscillator are such that the use of conventional designs in the crystal fabrication results in poor equipment performance. The difficulties are resolved by using energy-trapped elliptical electrodes. Not only are the original motional resistance and capacitance values preserved, but all troublesome modes are suppressed by more than 8 dB; these units perform well in the equipment. The report concludes with a discussion of certain inherent boundaries on resonator design and performance arising from intrinsic properties of quartz and vibrator configuration. Based on the Bommel, Mason, and Warner curves these boundaries are related to practical frequency ranges, orders of overtone, and values of attainable Q, including Q enhancement by mode trapping and control. (Author)

This report is concerned with two crystal measurement instruments that have recently been developed. The first of these instruments is the Crystal Impedance (C.I.) Meter System covering the frequency range .8 to 20 MHz developed by Piezo Technology, Inc. This instrument is an outgrowth of the C. I. Meter, which has been in use for years, and it uses the C. I. Meter oscillator circuit as the heart of the instrument. The system is made up of several components, but the basic operation is based on a resistance substitution in the oscillator circuit. The other instrument is the Servo Bridge System covering the frequency range .8 to 200 MHz developed by Parzen Research Inc. This instrument provides a signal source to feed a bridge, which contains the crystal. It also includes a narrow band detector and a feedback network so that the signal source can be locked to the crystal frequency. The report describes both systems by simplified block diagrams and gives measurement results showing capabilities of the instruments. (Author)

The report offers a tutorial explanation of the phenomenon of resonance, particularly as it applies to vibrating systems driven by virtue of the piezoelectric effect. The discussion of the mechanical aspects of a vibrating bar is treated in elementary fashion so as not to obscure the physical attributes of the system. The evolution of the concept of an equivalent electrical circuit of a piezoelectric vibrator is traced historically. The parameters of this equivalent circuit are then derived in terms of the physical constants and dimensions of the simple bar resonator. The concept is general, however, and the treatment has equal validity when applied to thickness-shear resonators used as frequency selective elements in modern crystal oscillators and filters. Various characteristic frequencies associated with the circuit are defined and their significance examined. Some of these frequencies appear in connection with IEEE Standard 177 dealing with measurement of the equivalent circuit parameters. In view of the current interest in the measurement procedures, particularly bridge methods, additional useful critical frequencies are introduced with defining equations. One type of bridge measurement method (Schering bridge) is examined in some detail. Procedures by which the circuit parameters may be derived are discussed. (Author)

The equivalent circuit of a piezoelectric vibrator has associated with it a number of critical frequencies in the vicinity of the resonance region. Addition of a capacitor in series or in parallel with the resonator element results in a shifting of these frequencies. The standard practice for measuring the frequency of antiresonance quartz crystal units is to place the load capacitor in series with the crystal unit. The resonance frequency measured with the series capacitor is assumed to be equivalent to the antiresonance frequency obtained with the same capacitor placed in parallel with the crystal unit. The analysis given shows this to be the case only in the limit of lossless crystals, whereas a frequency difference of several parts per million may be encountered with practical units. A simple, approximate formula is derived for the frequency error, and examples are given. (Author)

The patent relates to crystals and particularly to very high frequency crystals. More particularly, this disclosure relates to techniques for increasing the fundamental resonant frequency of crystals beyond the limits of currently available mechanical techniques by reducing the thickness of a portion of the center of a standard crystal. This provides an effective resonant sector of an area and thickness that would be virtually impossible to manufacture or to mount by conventional techniques or use in existing mechanical structures.