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Microwave Theory and Techniques, IEEE Transactions on

Issue 11 • Date November 1969

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Displaying Results 1 - 25 of 32
  • Table of contents - November, 1969

    Page(s): 797
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  • Editor's Note

    Page(s): 798
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  • Introduction

    Page(s): 799
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  • Information for authors

    Page(s): 1052
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  • Piezoelectric Elastic Surface Waves in Anisotropic Layered Media

    Page(s): 920 - 926
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    Solutions for surface elastic waves propagating in a layered media consisting of a CdS film on a fused quartz substrate have been found. Piezoelectric coupling in the CdS has been included. The Rayleigh, Sezawa, and Love modes are discussed. The surface wave velocity, mechanical displacements, and electric fields are found as a function of layer thickness for the Rayleigb and Sezawa modes. Velocity dispersion was experimentally measured and found to be in good agreement with theory. View full abstract»

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  • Microsound Surface Waveguides

    Page(s): 882 - 892
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    An important requirement for the development of surface wave microsound systems is the ability to guide the energy. The theoretical and experimental progress towards this aim is reviewed. Some preliminary results on topographic guides are presented. Measurement techniques make use of phase-sensitive laser probes to detect the CW surface waves. The technique permits very accurate determination of dispersion characteristics. View full abstract»

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  • Characteristics of Microwave Acoustic Transducers for Volume Wave Excitation

    Page(s): 927 - 941
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    Transducers which utilize acoustoelectric conversion in a piezoelectric film, plate, or surface have found wide application for generating planar volume-acoustic waves at microwave frequencies. A review is given of the electrical impedance, conversion loss, and bandwidth characteristics for piezoelectric film or plate transducers which vibrate in one-dimensional thickness extensional or shear modes. The transducer response is related to the electric and acoustic parameters that describe the transducer configuration, and experimental examples are given to illustrate the operation of typical transducer configurations. Methods for achieving low conversion loss and/or broad bandwidth are discussed and experimental examples given. Tables of bulk material constants are supplied for commonly used plate and film devices, and transducer fabrication methods are reviewed. Other types of volume wave transducers, such as those utilizing a single piezoelectric surface, a diffusion layer in a piezoelectric semiconductor, or mode conversion at a boundary are also briefly discussed. View full abstract»

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  • Microwave Acoustic Devices for Pulse Compression Filters

    Page(s): 968 - 986
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    The ability of devices based on the phenomena of magnetoelastic waves, acoustic bulk waves, acoustic surface waves, and the optoacoustic interaction to fulfill the requirements for a dispersive filter for a pulse compression RADAR are reviewed. The performance and current limitations of devices that use techniques employing these effects are described. The discussion is generally limited to devices which have been operated in the frequency range above 100 MHz. For comparison, other solid-state techniques that do not employ acoustic waves which can be used to make dispersive filter are described. View full abstract»

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  • Some Problems in the Theory of Guided Microsonic Waves

    Page(s): 893 - 904
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    The wave equation for elastic waves in an isotropic solid is solved generally in Cartesian and in circular cylindrical coordinates. The solutions are applied in the study of a variety of guiding structures of circular and rectangular symmetry. In general, the wave functions do not satisfy the boundary conditions, but in special cases they do. From a study of these special cases it is possible to arrive at some useful results and to general principles which give some insight into the behavior of waveguides in general. The results and observations obtained are compared and where appropriate, with corresponding results for electromagnetic waveguides. View full abstract»

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  • Microwave Variable Delay Devices

    Page(s): 986 - 997
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    Needs for nondispersive microwave variable delay devices exist in RADAR, communication, ECM, and test systems. Methods which have been investigated to satisfy these needs are reviewed in this paper. Techniques that employ solid-state microwave acoustic interactions and that have promise of satisfying some of the microwave variable delay requirements are described in detail, and their present capabilities and potential capabilities are discussed. One technique employing magnetoelastic waves is particularly promising and the state of the art of this technique is analyzed thoroughly. View full abstract»

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  • Determination of Microwave Transducer and Delay-Line Properties with a Modified Nodal Shift Method

    Page(s): 942 - 956
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    A mathematical analysis of the input impedance to a single-ended delay line is given and the developed formulas are applied to the experimental data to yield: sound velocity and round-trip time in the delay medium, electromechanical coupling coefficient, series resistance, transducer capacity, and the acoustical loss and mismatch which is caused by the electrode structure. A measuring technique similar to the nodal shift method has been introduced. View full abstract»

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  • Elastic Surface Waves Guided by Thin Films: Gold on Fused Quartz

    Page(s): 904 - 911
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    To study some of the properties of acoustic waves guided by thin films, experiments on dispersion and transverse tightness of binding were performed in the frequency range 5 MHz to 14 MHz. The movable wedge technique of launching and receiving surface wave signals was utilized. The guidance structure consisted of thin gold films deposited on fused quartz. High resolution experimental results were obtained by modifying the wedges to have a very narrow active region. The data were compared to results predicted by a simplified theoretical model which we have developed. This model is complementary to that of Tiersten in that we match both components of the vector potential while in Tiersten's model one matches a single vector potential component and its normal derivative. Curves calculated by our approach appear to be virtually identical with those of Tiersten for the (width/thickness) ratios treated experimentally, but are much easier to obtain numerically for any particular value of the ratio. For smaller values of the (width/thickness) ratio, our model and that of Tiersten differ slightly. Data for dispersion and mode tightness of binding were found to be in substantial agreement with our theoretical predictions. In addition, the theoretical model predicts features such as location of low-frequency cutoffs and tightness of binding of the antisymmetric modes which have not been completely investigated experimentally. View full abstract»

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  • Piezoelectric Semiconductor Acoustic Delay Lines

    Page(s): 957 - 963
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    The delay of signals for microsecond time periods in monolithic structures using piezoelectric semiconductors is described. Thin resistive regions were formed by the diffusion of compensating impurities in semiconducting crystals of ZnO, CdS, CdSe, and GaAs and used as transducers for the excitation and detection of acoustic waves in the 30-MHz to 1.0-GHZ region. Time delays from 200 ns to 5.0 μs were achieved using simple acoustic transmission structures. Insertion loss values less than 10 dB were achieved in ZnO for microsecond delays up to 600 MHz. Frequency-tuned bandwidths of 70 to 90 percent were obtained. The frequency-loss characteristics of the delay structures could be quantitatively related to a simple theoretical model. The performance characteristics of representative matched and packaged acoustic delay lines is described. View full abstract»

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  • Accoustic Scattering Parameters of the Electrically Loaded Interdigital Surface Wave Transducer (Correspondence)

    Page(s): 1045 - 1046
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    Acoustic scattering parameters for the interdigital transducer are calculated as a function of electrical loading and frequency using an equivalent circuit model of the interdigital transducer. Measurements of the surface wave scattering parameters at 100 MHz are reported which are in close agreement with theory. Applications of the interdigital array as an efficient reflector of surface waves and as a weak low-reflecting tapping transducer are discussed. View full abstract»

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  • Application of Microwave Concepts to the Theory of Acoustic Fields and Waves in Solids

    Page(s): 800 - 811
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    During the past 20 years the value of the microwave approach to electromagnetic field problems has been amply demonstrated. The purpose of this paper is to show the basic similarity of acoustic and electromagnetic field equations and to exploit this fact in applying microwave methods to acoustic resonator and waveguide problems. This is accomplished most directly and efficiently by using symbolic notation, rather than tensor subscripts, for the acoustic fields. The usefulness of this notation is illustrated by the problems of plane wave propagation and piezoelectric stiffening in an anisotropic medium, and by derivations of Poynting's and reciprocity theorems for a piezoelectric medium. Piezoelectric resonators are treated in detail from the point of view of normal mode expansions. A general network representation is obtained and is applied to the disk transducer, as an example. Normal mode theory of piezoelectric waveguides is briefly sketched and a perturbation theorem, which can be applied to both resonator and waveguide problems, is derived. View full abstract»

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  • Guided-Wave Theory of Light Diffraction by Acoustic Microwaves

    Page(s): 1002 - 1020
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    The diffraction of a plane light wave incident obliquely upon an isotropic dielectric layer traversed longitudinally by an acoustic microwave is examined by means of a guided-wave approach. In addition to a considerable amount of physical insight, this approach provides a wide range of techniques that have already been developed extensively in the area of electromagnetic microwaves. As a consequence, available methods can be used to explain and express known aspects of the diffracted light in terms of simple guided-wave concepts which are applied herein to derive results that have not been available. It is shown that the difracted field within the dielectric layer, as well as in the exterior (air) medium, can be described by means of two alternative modal representations: 1) a description in terms of characteristic modes which progress independently of each other, and 2) a description in terms of coupled modes which interact with each other in the presence of the acoustic wave. While the two representations are equivalent, each has its own advantages and both are discussed in detail. It is also shown that these representations lead to equivalent networks that may be utilized to account for boundary conditions and for other features of the scattered field. In particular, diffraction phenomena in a Bragg regime are carefully investigated; qualitative and quantitative results are presented for situations wherein the orientation of the optic-acoustic interaction occurs at a Bragg angle of arbitrary order. View full abstract»

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  • Dispersive Rayleigh Wave Delay Line Utilizing Gold on Lithium Niobate (Correspondence)

    Page(s): 1043 - 1044
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    The dispersion characteristics have been obtained for a gold film overlay on lithium niobate into which Rayleigh waves around 100 MHz are injected. Phase and attenuation measurements are conducted continuously as the gold film is deposited under vacuum conditions. Linear increase of delay with frequency is observed for a gold thickness approximating 5000 Å. View full abstract»

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  • Analysis of Interdigital Surface Wave Transducers by Use of an Equivalent Circuit Model

    Page(s): 856 - 864
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    Immittance, transfer, and scattering characteristics are studied for acoustic surface wave transducers of the interdigital electrode form. Linear network models are used to represent the transducer as a chain of identical three-ports which are acoustically in cascade but electrically in parallel. Transducer operation at acoustic synchronism is described theoretically and compared to current experimental data for transducers operating at 100 MHz and fabricated on lithium niobate. Favorable lithium niobate configurations for efficient, broad-band transducer operation are given. Scattering characteristics as a function of electric load are discussed. Low values of acoustic reflection loss are predicted theoretically and observed experimentally when the electric load and transducer capacitance are in resonance. The frequency dependence of transducer radiation immittance is studied, and the response is found to be analogous to the response of an endfire antenna array. View full abstract»

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  • Surface Wave Delay Line Amplifiers

    Page(s): 912 - 920
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    The subject of acoustoelectric surface wave delay line amplification is reviewed. Two amplifier configurations are defined: the combined medium amplifier (CMA), and the separated medium amplifier (SMA). These configurations are compared and the problems associated with each one defined. A more detailed description of the SMA is given along with experimental results. A brief analysis is presented; two material constants are defined, and then used to compare materials in terms of SMA applicability at high frequencies. View full abstract»

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  • Microsound Components, Circuits, and Applications

    Page(s): 835 - 844
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    Surface acoustic wave components have been realized which perform the functions of transduction, amplification, and coupling. Applications are suggested which make use of these components. Exploratory work in connection with surface acoustic waveguides suggests the feasibility of acoustic analogs of conventional microwave transmission line (microsound) components on the surface of crystal and substrates. These microsound transmission lines, hybrids, and directional couplers interconnect microsound transducers, amplifiers, isolators, and phase shifters to form microsound circuits capable of autocorrelation, Fourier transformation, and cross correlation functions. Compatible component configurations are proposed and evaluated which perform these basic functions. The anticipated difficulties with their realization are discussed and the current status of critical problems including the epitaxial growth of thin films and submicron etching procedures will be given. Several circuits capable of performing correlation functions are given. View full abstract»

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  • Microwave Acoustic Simulation of Airborne RADAR Ground Echoes

    Page(s): 963 - 967
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    A method is described for generating simulated microwave frequency RADAR terrain echoes. This method makes it possible for the first time to realistically duplicate in the laboratory the principal characteristics of echoes due to RADAR motion and terrain roughness. These characteristics include variation of echo delay, Doppler shift, random fine structure, and their time variation. The simulation is based on modeling of the RADAR beam propagation and diffuse reflection processes by use of microwave acoustic energy in a solid medium. Scaling relations between RADAR and acoustic model parameters are derived. An experimental program was carried out whose purpose was to develop a practical solution to the problem of varying the distance between a microwave acoustic transducer and a reflecting surface, and to determine the overall feasibility of the simulation method. Results indicating its practicability are presented and directions for further work are suggested. View full abstract»

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  • Excitation of Elastic Waves in Crystals

    Page(s): 827 - 835
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    Excitation of elastic waves in a general anisotropic crystal is discussed. The crystal is supposed to be semi-infinite, bounded by a plane surface. The definition of an elastic impedance matrix for the medium and its use in the subsequent discussion emphasize the similarities with transmission line theory. The resulting expressions for the amplitudes of bulk waves and surface waves is expressed in a matrix formalism believed to have computational advantages. View full abstract»

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  • L-Band Variable-Delay-Time YIG-YAG-YIG and YAG-YIG-YAG Delay Lines

    Page(s): 997 - 1001
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    Two types of YIG variable-delay-time microwave delay lines are described. These are the YIG-YAG-YIG and YAG-YIG-YAG configurations, both of which provide ∼2 μs of variable delay in L-band. Two-port operation is achieved in both of these devices with leakage of the undelayed pulse between input and output being attenuated more than 100 dB. These are completely self-contained devices with internal permanent magnets and terminals for connecting a control signal to vary the delay time. Insertion loss, bandwidth, and VSWR data are presented as well as curves showing delay variation with control current. A comparison of these two types of delay lines is also presented, pointing out the advantages and disadvantages of each type. View full abstract»

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Aims & Scope

The IEEE Transactions on Microwave Theory and Techniques focuses on that part of engineering and theory associated with microwave/millimeter-wave components, devices, circuits, and systems involving the generation, modulation, demodulation, control, transmission, and detection of microwave signals. This includes scientific, technical, and industrial, activities. Microwave theory and techniques relates to electromagnetic waves usually in the frequency region between a few MHz and a THz; other spectral regions and wave types are included within the scope of the Society whenever basic microwave theory and techniques can yield useful results. Generally, this occurs in the theory of wave propagation in structures with dimensions comparable to a wavelength, and in the related techniques for analysis and design..

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Dominique Schreurs
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Jenshan Lin
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