Abstract: A surface acoustic wave device is constructed to operate using an SH type surface acoustic wave and so that the surface acoustic wave is reflected by two opposite edges of the device. The surface acoustic wave device includes a piezoelectric substrate having first and second main surfaces and the two edges arranged opposite to each other and which connect the first and second main surfaces, respectively, and an interdigital transducer having a pair of interdigital electrodes provided on the first main surface of the piezoelectric substrate and arranged so that the electrode fingers thereof are interdigitated with each other. The electrode fingers of the interdigital electrodes include a plurality of split electrodes, except for the electrode fingers located at the outermost sides in the surface acoustic wave propagation direction. The electrode fingers on the outermost sides have a width that is different from that of the split electrodes.

Abstract: An edge reflection type surface acoustic wave filter includes a piezoelectric substrate having two opposing edges and at least one interdigital transducer. The interdigital transducer includes split electrodes of paired electrode fingers arranged on the piezoelectric substrate such that a shear horizontal (SH-type) surface acoustic wave is excited on the piezoelectric substrate and is reflected between the two opposing edges. Each of the edges is preferably located at a distance of at least about {fraction (&lgr;/2)}-{fraction (5&lgr;/128)} from a center of the paired equipotential electrode fingers, located at the respective outermost portions, in the surface acoustic wave propagation direction, of the interdigital transducer and less than about {fraction (&lgr;/2)} from the center of the paired equipotential electrode fingers, where &lgr; is a wavelength of the SH-type surface acoustic wave excited on the piezoelectric substrate.

Abstract: A ladder filter includes a plurality of series arm resonators and a plurality of parallel arm resonators. The series arm resonators are connected in series to form a series arm of a ladder circuit and are located at a first integrated region. Each series arm resonator includes an edge-reflection surface acoustic wave (SAW) resonator which has a piezoelectric material portion and a pair of edges thereof and utilizes a shear horizontal surface acoustic wave to be excited on the piezoelectric material portion. Each of the parallel arm resonators is connected in parallel between the series arm and a ground potential to form a parallel arm of a ladder circuit. Each of the parallel arm resonators includes an edge reflection SAW resonator which has a piezoelectric material portion with a pair of edges thereof and utilizes a shear horizontal surface acoustic wave to be excited on the piezoelectric material portion.

Abstract: An end-face reflecting-type surface wave resonator using the SH-type surface wave achieves two types of resonance characteristics by use of only a single device. An interdigital transducer having a pair of comb-like electrodes are formed on a piezoelectric substrate having two oppositely-facing end faces. The interdigital transducer has two peaks of main lobes and are assigned with weights so that the two peaks of main lobes substantially coincide with frequency positions of attenuation poles disposed across a main lobe of a virtual normal-type interdigital transducer having the same number of pairs of electrodes as the weighted interdigital transducer. Thus, two types of resonance characteristics can be obtained.

Abstract: A free edge reflective-type surface wave resonator for reflecting SH-type surface waves between two confronting free edges of a piezoelectric substrate includes a piezoelectric substrate having two confronting free edges and an interdigital transducer having a plurality of electrode fingers which are weighted by a cross width weighting method or an electrode thinning method. The weighting of the electrode fingers is performed so that an attenuation pole of a main lobe of the weighted IDT is located outside of a frequency of an attenuation pole of a normal non-weighted IDT which has the same number of electrode finger pairs as the weighted IDT. The weighting of the electrodes is such that the main lobe of the weighted IDT and a plurality of resonance characteristics determined by the attenuation poles of the normal unweighted IDT are obtained.

Abstract: A single-chip piezoelectric resonator using SH type surface waves has an interdigital transducer formed on a piezoelectric substrate. The interdigital transducer is designed to have two or more resonance characteristics, for example, by using a pair of thinned-out comb-shaped electrodes with mutually interlocking fingers protruding towards each other. Such an interdigital transducer may be formed also by using a pair of comb-shaped electrodes with the lengths of their mutually pointing fingers varied. A trap circuit with two sufficiently separated trap frequencies and improved attenuation characteristics at these two trap frequencies can be formed by forming two interdigital transducers of the kind described above on a single piezoelectric substrate so as to provide two resonant units each having two resonance characteristics. Alternatively, two piezoelectric resonators of the kind described above may be connected in parallel to provide two resonance characteristics.

Abstract: An end face reflection type surface wave resonator utilizing a surface wave of an SH type is constructed by forming comb electrodes on one major surface of a piezoelectric substrate, which constitute an IDT, and forming grooves extending from one major surface to the other major surface to form a pair of end faces on which a surface wave is to be reflected the resonator having piezoelectric plate portions outside the grooves.