Raytheon Company

Frank Sandy

Manfred B Schulz

Clarence J Dunnrowicz

A transducer for a SAW device having withdrawal weighting combined with series sections weighting to achieve a desired frequency response. Withdrawal weighting is employed where the impulse response can be adequately approximated by a withdrawal pattern with series sections electrodes being used to provide the additional weighting required. Additionally, electrodes using a different number of series sections are separated by a gap a few wavelengths wide in order to avoid sharp discontinuities.

Combining series sections weighting with withdrawal weighting in SAW

A surface acoustic wave low loss filter device having input and output transducers located along opposed sides of a rectangular propagation path with frequency selective reflective gratings at each of the four corners of the rectangle. Two traveling surface waves traverse the device along opposed paths encountering frequency filtering at the gratings. The two waves arrive at the output transducer additively in phase eliminating the bidirectionality loss normally associated with surface acoustic wave devices. At frequencies for which the gratings are reflective there can be nearly lossless transmission from input to output. At all other frequencies, transmission between input and output transducers is negligible. The device has high sidelobe rejection, adjustable passband skirt slopes, and an adjustable bandwidth.

Surface acoustic wave ring filter

A reflective grating for a surface acoustic wave device is formed of interleaved sets of contiguous metal strips deposited on the surface of the device. The metal in one set of the strips has a density greater than that of the acoustic propagating medium of the device while the metal of the second set of strips has a density essentially equal to that of the acoustic propagating medium of the device. Typically, a piezoelectric material such as a crystal of quartz or a crystal of lithium niobate is utilized as the base material of the device with the grating being formed of an overlay of alternating strips of gold and aluminum.

Surface acoustic wave grating

Surface acoustic wave devices are disclosed which have enhanced reflectivity gratings with conductive stripes between grooves in the substrate or conductive stripes within the grooves. For lithium niobate substrates, aluminum stripes coupled together and positioned between grooves or unconnected and positioned within the grooves are preferred. For quartz substrates, gold stripes within the grooves are used. Methods for fabricating such structures are also disclosed.

Surface wave device having enhanced reflectivity gratings

A surface acoustic wave device having substantially all of the surface wave energy produced at an input transducer coupled to the output utilization means. Plural reflecting means upon the surface of a piezoelectric substrate reflect surface waves produced by the input transducer in plural directions. The passband characteristics of the device are determined by the interaction of the transfer properties of each of the reflecters as well as those of the input and output transducers. Devices are described having extremely low insertion loss and wide bandwidth with low sidelobes and steep passband skirts.

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Lexington, MA, United States of America

Frank Sandy