Showing papers on "Interdigital transducer published in 1970"

Optical probing of surface acoustic waves

Abstract: Light diffraction by surface acoustic waves is used in studying the propagation characteristics of Rayleigh waves on y-cut z-oriented LiNbO 3 . In reflection, only the surface deformation contributes to the diffracted light. In transmission, the photoelastic effect, which is incident beam polarization dependent, must also be considered. Such optical probing has been used to study the Fresnel diffraction radiation pattern of an interdigital transducer, to measure beam steering effects related to transducer misalignment on an anisotropic substrate, and to measure reflection and transmission coefficients of an electrically loaded transducer. Attenuation measurements have been made over frequencies as high as 3.5 GHz. The power dependence of attenuation and harmonic generation is also examined.

Surface Wave Grating Reflectors and Resonators

Abstract: The realization of complex microsound circuits would be greatly facilitated if one were able, efficiently to reflect the surface waves. For example, such reflectors are required for making a "short-circuited" stub, or for a low mode-order resonator. It is known that the interdigital transducer can reflect a surface wave, with rather low losses; however, this approach involves the use of an external inductive tuning circuit, which must be attached to the transducer in order to resonate its self-capacitance. It is therefore a method which cannot be used in those situations where the primary objective is the achievement of very large component densities.

Electrical and Mechanical Loading of a Piezoelectric Surface Supporting Surface Waves

Abstract: The influence of surface loading on the propagation of surface waves on a piezoelectric substrate is analyzed. Both mechanical and electrical loading are described by means of a simple first‐order perturbation theory. General formulas for the perturbation of the surface‐wave phase velocity caused by deposition of a uniform thin film or by electrical interaction with an adjacent conducting or semiconducting medium are developed. The scattering of surface waves from discrete strips is also analyzed. Results from scattering and wave‐propagation analysis are utilized to describe the interdigital surface‐wave transducer. An equivalent circuit for a basic transducer element is developed, and the total transducer is analyzed by means of transmission‐line theory applied to a network of cascade‐coupled elements. The effect of electrode mass loading is specially treated, and the results are compared with measurements made on a Y‐cut Z‐propagation LiNbO3 crystal.

Broadband, high frequency, thin film piezoelectric transducers

Abstract: Piezoelectric thin film transducers are provided in a form to match the impedance of a transmission line. The transducer structure includes a plurality of serially connected transducer elements on a single substrate provided by a first pattern of electrodes on the substrate, a single layer of piezoelectric material overlying the first electrode pattern and a second electrode pattern overlying the piezoelectric layer with selective connections between electrodes of the first and second patterns, such structure being directly amenable to fabrication by thin film technology. Such an arrangement provides greatly increased bandwidth characteristics and improved conversion efficiency.

Hybrid surface-wave transducer

Abstract: A transducer for generating and detecting surface elastic waves in a non-piezoelectric material may include an interdigital electrode array coupled to a piezoelectric crystal. The crystal is mechanically coupled to the non-piezoelectric material through an acoustical transmissive medium.

Optical probing of bulk waves present in acoustic surface wave delay lines

Abstract: Diffraction of laser light from bulk waves present in a LiNbO3 surface wave delay line has been used to probe surface wave mode conversion. Up to 4% of the power present in a surface wave incident on a reactively loaded interdigital transducer has been observed to be scattered into shear waves. In addition, a driven interdigital transducer has been seen to radiate bulk waves with directivity properties well described by a phased array antenna model.

Measured electrical characteristics of interdigital surface wave transducers on lithium niobate

Abstract: The radiation resistance and reactance as a function of frequency has been measured for interdigital comb structures used for generating z propagating surface waves on a yz surface of LiNbO3. The quantities reveal a basic asymmetry about the center frequency of surface wave generation due to the simultaneous launching of bulk waves.

Surface wave transducer for digital signals

Abstract: Surface wave transducers of the interdigital type for generating and detecting return to zero pulse sequences of surface waves are disclosed. The transducer, which is located on the surface of a suitable surface wave medium, is an interdigitated electrode array including main electrodes that are perpendicular to the transducer leads and auxiliary electrodes that are inclined at an angle to the main electrodes.

Piezoelectric coupling coefficient of interdigital Rayleigh-wave transducers

Abstract: The letter describes the theoretical dependence of the piezoelectric coupling coefficient and capacitance of an interdigital Rayleigh-wave transducer on the ratio electrode-width/gap-between-electrodes.

Optical Probing of Acoustic Surface Waves

Abstract: Light diffraction by acoustic surface waves is used as a probe to study the propagation characteristics of Rayleigh waves on y‐cut z‐oriented LiNbO3. Both the surface deformation and the periodic variation of the index of refraction in the medium, which diffracts the transmitted light beam, are related to the particle displacements of the propagating Rayleigh waves. For the reflected beam, only the surface deformation contributes to the diffracted light. Experimental demonstrations of using the optical probe to observe the Fresnel diffraction of a rectangular interdigital transducer to measure the transmission and reflection coefficients of a transducer and to determine the propagation characteristics, such as velocity, attenuation of Rayleigh waves on a LiNbO3 substrate and on a metalized LiNbO3 substrate, will be discussed.

Piezoelectric coupling coefficient of Bleustein-Gulyaev waves

Abstract: Five different theoretical methods of assessing the piezoelectric coupling coefficient of Bleustein-Gulyaev waves are described and compared. The dependence of the coupling of an interdigital transducer on the electrode-width/gap-between-electrodes ratio is described.

An Apparatus for Measuring the Velocity and Energy Flow Direction of Ultrasonic Surface Waves

Abstract: An apparatus is described which can be used to measure the velocity of Rayleigh waves and direction of energy flow throughout any given plane in a piezoelectric material. Some results are presented for part of the X‐Z plane in lithium niobate. Additionally, with the use of a thin film transducer the measurements can be extended to non‐piezoelectric materials.

Wide-band transducer for surface elastic waves

Abstract: A log-periodic interdigital transducer for surface elastic waves was fabricated and shown to have good agreement with an approximate analytical model. Experiments were performed on a mechanically variable delay line.

New type of Rayleigh-wave transducer on piezoelectric ceramics

Abstract: An interdigital transducer on a piezoelectric ceramic with the polarisation directed from one comb to the other is described. The efficiency is determined by complex-admittance measurements.