Abstract: A surface acoustic wave filter apparatus includes a plurality of stages of multi-mode filters defined by edge-reflection type surface acoustic wave devices and electrically connected in series with each other. The plurality of stages of multi-mode filters are provided on a common piezoelectric substrate and arranged in a direction which is substantially perpendicular to the propagation direction of surface acoustic waves. Ground electrodes are located between the stages of the plurality of stages of multi-mode filters.

Abstract: An edge reflection longitudinally coupled surface acoustic wave filter utilizing an SH-type surface wave includes a piezoelectric substrate having two opposing edge surfaces, and first and second interdigital transducers each having a plurality of electrode fingers and being arranged on the piezoelectric substrate such that a shear horizontal surface wave excited by one of the first and second interdigital transducers is reflected between the two opposing edge surfaces to form a standing wave. Attenuation poles of frequency characteristics of the first and second interdigital transducers are adjacent to the frequency position of spurious responses determined by the distance between the two opposing edge surfaces.

Abstract: A transversal-coupled resonator type surface acoustic wave filter includes a piezoelectric substrate and first and second interdigital transducers. The piezoelectric substrate has a pair of substrate edges which are substantially parallel to each other and reflect a shear horizontal type surface wave excited and propagated on a surface of the piezoelectric substrate in a direction perpendicular to the substrate edges. The first and second interdigital transducers have the same resonance characteristics and are provided on the piezoelectric substrate. Each of the first and second interdigital transducers includes a pair of outermost electrode fingers which are arranged to be flush with the substrate edges of the piezoelectric substrate, respectively and a pair of adjacent electrode fingers which are adjacent to the pair of the outermost electrode fingers, respectively.

Abstract: A double-mode SAW filter of a longitudinally coupling type utilizing an SH-type surface wave, which is structured with first and second IDTs formed on said piezoelectric substrate to cause reflection of an SH-type surface wave between opposite two end faces, thereby creating a standing wave.

Abstract: An end face reflection type surface wave resonator utilizing SH type surface waves capable of providing a plurality of resonance characteristics is formed as a single element. In the surface wave resonator, surface waves are reflected between two opposite end faces of a piezoelectric substrate. The surface wave resonator has IDTs that form first and second resonant units. The distance L between the two end faces is selected to be within a range expressed by (.lambda..sub.1 /2).times.N.sub.1 .+-.(.lambda..sub.1 /20) (N.sub.1 is an integral number) where .lambda.1 represents the wavelength of a surface wave excited by the first resonant unit. The distance L is chosen to be out of a range expressed by (.lambda..sub.2 /2).times.N.sub.2 .+-.(.lambda..sub.1 /20) (N.sub.2 is an integral number) where .lambda..sub.2 represents the wavelength of a surface wave excited by the second resonant unit.

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: A SAW resonator for forming a frequency trap has a surface wave substrate and at least one interdigital transducer located on the surface wave substrate. The interdigital transducer includes a pair of comb-shaped electrodes each having a plurality of electrode fingers arranged so that the pair of comb-shaped electrodes interdigitates with each other. An overlapping width of the electrode fingers of the interdigital transducer is set such that in an impedance-frequency characteristic a transverse mode ripple occurring between a resonance point and an antiresonance point is located at the antiresonance point.

Abstract: A surface acoustic wave device which is a surface acoustic wave resonator utilizing an SH-type surface wave, wherein a resin layer made of a resin material in the form of gel or having a Shore hardness of not more than 30 is formed so as to coat at least an interdigital transducer formed on the upper surface of a piezoelectric substrate.

Abstract: A surface wave device utilizing a surface wave of an SH type whose displacement is mainly displacement in the direction perpendicular to the direction of the surface wave propagation, the above piezoelectric substrate being made of a piezoelectric material whose ratio of the elastic stiffness constant C.sub.33.sup.D to the elastic stiffness constant C.sub.44.sup.E is more than 4.