Selected transducer geometries including unbalanced split electrode and three electrode per wavelength structures are employed for use in wide band tapered SAW devices. Combining geometries useful in narrow bandwidth SAW filters for canceling reflected waves leading to triple transit interference, and electrode tapering useful in wide bandwidth SAW filters for permitting transduction of a wide range of surface acoustic wavelengths has the unexpected result of significantly reducing insertion loss and improving triple transit suppression over wider bandwidths than can be achieved with SPUDT designs on non-tapered devices. The interdigitized electrode fingers of opposing bus bars in the transducer have a tapered alignment wherein a period of electrode finger portions along an acoustic wave propagation axis decreases along a transducer dimension. In one embodiment, the transducer has spacing between the electrode fingers which provides two pairs of unbalanced split electrodes within a spacing length equal to its respective acoustic wavelength. The positions and widths of the fingers are such that SPUDT transduction and reflection conditions are satisfied. In an alternate embodiment, the transducer has three electrodes per acoustic wavelength wherein the electrode widths and gaps between electrodes vary to satisfy the SPUDT transduction and reflection conditions. The performance of each transducer is further enhanced with subtransducers for providing series-block weighting. The three electrode per wavelength finger geometry further includes line-width weighting for providing a fine weighting control to complement the inherently coarse weighting control of the series-block weighted transducer.

Weighted tapered spudt saw device

Disclosed are: a solid polymethylaluminoxane composition which does not utilize silica or the like, has the form of relatively fine particles, has more uniform particle sizes, and exhibits a high polymerization activity when used in the preparation of an olefin polymer; a process for producing the solid polymethylaluminoxane composition; a polymerization catalyst; and a process for producing an olefin polymer. Specifically disclosed are: a solid polymethylaluminoxane composition which has an aluminum content of 36 to 41 mass % and contains a methyl group derived from a trimethylaluminum moiety at a molar fraction of 12 mol % or less; a process for producing the solid polymethylaluminoxane composition, which comprises the step of heating an aromatic hydrocarbon solution containing polymethylaluminoxane and trimethylaluminum to cause the precipitation of the solid polymethylaluminoxane composition; a polymerization catalyst for an olefin, which comprises the solid polymethylaluminoxane composition and a transition metal compound as catalyst components; and a process for producing an olefin polymer by using the polymerization catalyst.

Solid polymethylaluminoxane composition and method for manufacturing same

An elastic wave filter includes electrode fingers, a first busbar and a second busbar, and inclined electrode portions each having a narrower distance between the electrode fingers from the first busbar toward the second busbar. The elastic wave filter includes a dummy electrode disposed in at least one of the input-side IDT electrode portion and the output-side IDT electrode portion to suppress reflection of a diffracted elastic wave by the busbar and to suppress spurious response at an end portion in a frequency pass-band. The dummy electrode has a width dimension and a pitch that are determined such that none of a period shorter than a shortest period of the electrode fingers and a period longer than a longest period of the electrode fingers is satisfied.

Elastic wave filter

PURPOSE: To improve the electromechanical coupling coefficient by selecting the film thickness of an electrode formed on the surface of an LiNbO 3 substrate to be a thickness in which a propagation speed of a surface acoustic wave is smaller than a propagation speed of a lateral bulk wave and coating the surface by a silicon dioxide. CONSTITUTION: An interdigital metallic electrode 2 is arranged on an LiNbO 3 single crystal substrate 1, and an SiO 2 film 3 is used to cover it. The metallic film forming the electrode is made up of a Cr film 2a, an Au film 2b and a Cr film 2a. The LiNbO 3 substrate is a Y substrate or a rotated Y plate, the direction of propagation of a surface acoustic wave is selected in the X direction, and the film thickness of the surface acoustic wave drive/extract electrode and the reflection electrode is selected to be a thickness in which a propagation speed of a surface acoustic wave is smaller than a propagation speed of a lateral bulk wave and the substrate surface on which the electrode is formed is coated by a non-stress silicon dioxide having a thickness of 15-35% of the wavelength of the surface acoustic wave. The non-stress silicon dioxide film is made by the CVD method. The electromechanical coupling coefficient of the resonator is set high and the characteristic suitable for a broad band filter or VCO is provided. COPYRIGHT: (C)1993,JPO&Japio

Surface acoustic wave element

To obtain a surface acoustic wave device which can be produced with ease at a low cost and can be reduced in size without causing deterioration of characteristics, a surface acoustic wave device having input and output transducers arranged alternately on the surface of a substrate for propagating a surface acoustic wave includes metal patterns provided outside the transducers along the extension line of the propagation path of the surface acoustic wave and having at least one surface inclined at an angle theta (5 DEG < theta <85 DEG or -85 DEG < theta <-5 DEG ) with respect to the propagation direction of the surface acoustic wave.

Surface acoustic wave device

PROBLEM TO BE SOLVED: To attain a SAW filter which is small-sized, low in cost and loss and has one input and two outputs or two inputs one outputs. SOLUTION: A SAW filter Fil1 which has a central frequency of a pass-band is f1 is connected to a SAW resonator Reso1 which has a frequency f1 as a resonance frequency. A SAW filter Fil2 which makes a frequency f2 a resonance frequency is connected to by a SAW resonator Reso2 which makes the frequency f2 a resonance frequency. Part of the SAW resonator Reso1 and the Reso2 are commonly connected and connected to an impedance matching circuit 10. The SAW filters Fil1 and Fil2, the SAW resonators Reso1 and Reso2 and a capacitor of the impedance matching circuit 10 are formed on a single SAW chip.

Toichi Kohda

Papers

Surface acoustic wave filter

Filter fuer elastische oberflaechenwellen Filters for elastic oberflaechenwellen

Filters for elastic oberflaechenwellen