Showing papers on "Interdigital transducer published in 1978"
TL;DR: In this paper, it was shown that the interaction of magnetostatic waves with a current can be characterized by a coupling constant analogous to, but much greater than, the piezoelectric coupling constant.
Abstract: It is shown that the interaction of magnetostatic waves with a current can be characterized by a coupling constant analogous to, but much greater than, the piezoelectric coupling constant. The theory is applied both to surface and forward‐traveling volume magnetostatic waves, and the problems of excitation, reflection, and absorption by a single microstrip and by a narrow‐band interdigital transducer are treated. It is found that the coupling constant is close to 0.5 for any reciprocal wave, and is greater for any nonreciprocal wave, when the transducer is in contact with the magnetic medium. These values are too large to allow effective signal processing, since the emitted waves react strongly on the transducer; narrow‐band transducers must be lifted above the surface so as to weaken the coupling.
98 citations
TL;DR: In this paper, the design and operation of a magnetostatic wave transducer is described, which is formed from an interdigital arrangement of narrow, open circuited microstrip fingers, each half an electromagnetic wavelength long.
Abstract: The design and operation of a novel type of magnetostatic wave transducer is described. The transducer is formed from an interdigital arrangement of narrow, open circuited microstrip fingers, each half an electromagnetic wavelength long. Experimental results in the frequency range 9–9.4 GHz are presented for 2, 4 and 10 finger transducers which are in good agreement with the sin(Nx/2)/sin(x/2) response predicted by simple theory.
17 citations
TL;DR: In this paper, an interdigital transducer was used to excite SAW on non-piezoelectric materials by using a fluid couplant, which matched the tangential k vectors of the surface waves.
Abstract: An interdigital transducer deposited on a piezoelectric substrate has been used to excite SAW on nonpiezoelectric materials by using a fluid couplant. The piezoelectric substrate is held at an angle to the nonpiezoelectric material so as to match the tangential k vectors of the surface waves. Experiments have been carried out with a LiNbO3 piezoelectric substrate and a ceramic such as SiC or Si3N4 with a fluid couplant. At a center frequency of 100 MHz, the estimated conversion efficiency of the surface wave from the piezoelectric to the nonpiezoelectric material is −3.5 dB. The results compare favorably with a normal mode coupling theory we have developed which predicts −2.7 dB efficiency.
14 citations
TL;DR: In this paper, the dynamic magnetic fields surrounding an array of flat conductors above a ground plane in which the current distribution is allowed to vary are modeled and the resulting solutions are used to calculate space-harmonic curves and to derive a new transducer model including electrical inductance, eddy current resistance, acoustic impedance, and transducers efficiency.
Abstract: Previous models for Rayleigh‐ and Lamb‐wave electromagnetic transducers have been based on the assumption that the current distribution in each transducer conductor is uniform. We present solutions for the dynamic magnetic fields surrounding an array of flat conductors above a ground plane in which the current distribution is allowed to vary. The resulting solutions are used to calculate space‐harmonic curves and to derive a new transducer model including electrical inductance, eddy current resistance, acoustic impedance, and transducer efficiency. A direct analogy to the interdigital transducer is established. For fundamental frequency operation, this model is nearly equivalent to previous flat field models, provided the conductor width/spacing ratio is 1/2 or less. For harmonic transducer operation, the present analysis is substantially different from other models and it matches data more accurately. A method for measuring the individual insertion loss of dissimilar transducers in a lossy medium is presented.
13 citations
Patent•
25 Aug 1978TL;DR: An acousto-electric convolver having a relatively long effective interaction region for counter-propagating surface acoustic waves and, therefore, a relatively large time-band with product implemented by distributing a coupler, such as a multistrip coupler or an array of interdigital transducer taps, over a plurality of parallel-connected single-channel acoustic-electric convolvers is described in this paper.
Abstract: An acousto-electric convolver having a relatively long effective interaction region for counter-propagating surface acoustic waves and, therefore, a relatively large time-bandwith product implemented by distributing a coupler, such as a multistrip coupler or an array of interdigital transducer taps, over a plurality of parallel-connected single-channel acousto-electric convolvers.
13 citations
TL;DR: In this article, the static capacitance of an interdigital structure in multi-Iayered media has been calculated for a surface acoustic wave interdigital transducer on an oxidized silicon substrate with a piezoelectric overlay.
Abstract: The static capacitance of an interdigital structure in multi-Iayered media has been calculated. Numerical results are given for a surface acoustic wave interdigital transducer on an oxidized silicon substrate with a piezoelectric overlay. The capacitance is derived in terms of the layer thicknesses for zero and infinite substrate resistivity.
12 citations
Patent•
11 Jul 1978
TL;DR: An acoustic surface wave interdigital transducer comprises a main and auxiliary rows of electrodes arranged on a piezoelectric substrate as discussed by the authors, where the main row of electrodes comprises a first group of electrodes galvanically connected to a first contact area and a second group parallel to the electrodes of the first group and disposed there between so that there are formed overlapping portions having the same length.
Abstract: An acoustic surface wave interdigital transducer comprises a main and auxiliary rows of electrodes arranged on a piezoelectric substrate. The main row of electrodes comprises a first group of electrodes galvanically connected to a first contact area and a second group of electrodes parallel to the electrodes of the first group and disposed therebetween so that there are formed overlapping portions having the same length. The auxiliary row of electrodes comprises a third group of electrodes galvanically coupled to the second contact area and a fourth group of electrodes parallel to the electrodes of the third group connected directly to the corresponding electrodes of the second group of the main row and disposed between the electrodes of the third group so as to form overlapping portions of electrodes of both groups, said portions having a variable length. The electrodes of the second group of the main row are connected to the second contact area through capacitances. The distances between the longitudinal axes of the adjacent electrodes of the third and fourth groups of the auxiliary row differ from the distances between the longitudinal axes of the electrodes of the first and second groups of the main row. An acoustic surface wave filter built around the above described acoustic surface wave transducer.
11 citations
TL;DR: In this paper, a theoretical analysis of the electric input admittance of an interdigital transducer in a layered, anisotropic, semiconducting structure is presented, where a Fourier-integral formalism is employed to express the electric charge distribution on the electrodes in terms of the applied voltages.
Abstract: A theoretical analysis of the electric input admittance of an interdigital transducer in a layered, anisotropic, semiconducting structure is presented. A Fourier-integral formalism is employed that enables usto express the electric charge distribution on the electrodes in terms of the applied voltages. The relation between the currents fed into the electrodes and the applied voltages leads to the input admittance. Numerical results are presented for the complex input admittance of a uniform interdigital transducer consisting of 14 electrodes in a CdS/SiO2/Si-configuration on a ground plane. The layer-thicknesses and conductivities of the various layers as well as the frequency of operation occur as parameters.
8 citations
TL;DR: In this article, the radiation patterns of bulk waves excited by an interdigital transducer have been observed for five cuts of LiNbO3 crystals using a frequency shift holographic method.
Abstract: The radiation patterns of bulk waves excited by an interdigital transducer have been observed for five cuts of LiNbO3 crystals using a frequency‐shift holographic method. The observation of surface acoustic waves through side planes was also done.
7 citations
TL;DR: In this paper, the theory and design of a new type of unidirectional transducer for Lamb-wave devices are described, which consists of three electrode groups, one common earth electrode and two interdigital electrode groups on the top surface.
Abstract: The theory and design of a new type of unidirectional transducer for Lamb‐wave devices are described The transducer consists of three electrode groups One of them is used as a common earth electrode and is on the bottom surface The others are interdigital electrode groups on the top surface The unidirectionality of this transducer can be realized under the phase condition of x+y=1/2, where 2πx is the phase difference arising from the geometry and 2πy is the phase difference of two electrical signals applied to the transducer
TL;DR: In this article, the analysis of quasiacoustic wave excitation by the uniform interdigital transducer is approached from a field point of view, where fields within the transducers are expressed in terms of a set of normal-mode functions which have been defined specifically for the interdigital array.
Abstract: The analysis of quasiacoustic‐wave excitation by the uniform interdigital transducer is approached from a field point of view. Fields within the transducer are expressed in terms of a set of normal‐mode functions which have been defined specifically for the interdigital array. Dispersion relations for these normal‐mode functions are found to display band‐gap regions with complex wave numbers. The complex wave number is responsible for the excitation process and permits a solution of the boundary conditions at both ends of the transducer structure. It is shown that the radiation fields excited by the transducer grow according to the dictates of a sine hyperbolic function from one end of the transducer to the other.
TL;DR: In this paper, a frequency-shift keying system using a three-phase interdigital transducer with two biphase inter-digital transducers with different center frequencies is described.
Abstract: A three-phase interdigital transducer has the characteristic of a bandpass filter with two centre frequencies. The directionality of the interdigital transducer depends upon the carrier frequency of a r.f. pulse applied to the transducer. A frequency-shift keying system using the characteristics described above is demonstrated. A surface acoustic wave delay line in the system uses two biphase interdigital transducers with different centre frequencies beside the three-phase transducer.
TL;DR: In this paper, the excitation function of an interdigital transducer was determined by measuring the discrete impulse response, taking into account the first seven harmonics of the frequency domain.
Abstract: The excitation function of an interdigital transducer (IDT) is determined by measuring the discrete impulse response, taking into account the first seven harmonics of the frequency domain. Using a time segregation method, all non-SAW time-domain components are suppressed. A single transducer is isolated by a method of autodeconvolution that utilizes a theoreticalIy derived phase function. The resulting excitation function provides experimental insight into the operation of IDT electrodes and compares well with the theoretical response of Smith and Pedler. The basic analysis technique can be used for other configurations, once the frequency-domain phase response of one transducer is known.
TL;DR: In this article, the beam steering along the z-axis was investigated and it was shown that even for these few-wavelengths long apertures, beam steering strongly limits the acoustic diffraction.
Abstract: Measurements and calculations of the surface acoustic wave (SAW) beam profile versus distance from very narrow interdigital transducer apertures are made in y-z LiNbO3 which exhibits strong beam steeringalong the z-axis. It is shown that even for these few-wavelengths long apertures the beam steering strongly limits the acoustic diffraction.
TL;DR: In this article, the authors defined the electromechanical coupling coefficient for the surface acoustic-wave interdigital transducer as the maximum fractional change in the time-averaged energy associated with a particular mode passing from one periodic section to the next.
Abstract: The electromechanical coupling coefficient for the surface‐acoustic‐wave interdigital transducer is defined as the maximum fractional change in the time‐averaged energy associated with a particular mode passing from one periodic section to the next. The result is compared with Berlincourt’s expression.
TL;DR: In this article, a model for length-expander composite transducers and resonators excited by a perpendicular electric field was developed for several structures of resonators made with metal and lithium niobate as piezoelectric materials.
Abstract: A model is developed for length-expander composite transducers and resonators excited by a perpendicular electric field. Theoretical and experimental results are reported for several structures of resonators made with metal and lithium niobate as piezoelectric materials.