Abstract: A surface acoustic wave filter having a ladder type circuit configuration, includes series resonators provided as part of a series arm disposed between input and output terminals and parallel resonators included in a plurality of parallel arms, respectively, defined between the series arm and a reference potential. The series resonators and parallel resonators each include a one-port surface acoustic wave resonator, the parallel resonators are arranged alternately with the series resonators along a direction from the input terminal toward the output terminal, and the resonant frequency of at least one parallel resonator is different from the resonant frequencies of the other parallel resonators.

Abstract: A surface acoustic wave filter having a ladder type circuit configuration includes a series resonator in a series arm provided between input and output terminals and a parallel resonator included in a parallel arm provided between the series arm and a reference potential. The surface acoustic wave filter includes a piezoelectric substrate, and a plurality of one-port surface acoustic wave resonators disposed on the piezoelectric substrate and arranged to define the series resonator and the parallel resonator. The one-port surface acoustic wave resonators include interdigital transducers. A gap length or distance between a first bus bar of the interdigital transducer of at least one of the surface acoustic wave resonators and the tip of an electrode finger connected to a second bus bar which is disposed opposite to the first bus bar has a value of up to about 1.0 &lgr; in which &lgr; represents the wave length of a surface acoustic wave.

Abstract: A surface acoustic wave filter includes a surface acoustic wave filter element and a package for holding the surface acoustic wave filter element. The surface acoustic wave filter element includes a plurality of series arm resonators and first, second and third parallel arm resonators each disposed on a piezoelectric substrate so as to define a ladder-type circuit. The first and second parallel arm resonators are close to input and output terminals of the filter element, respectively. Reference potential electrodes of the first and second parallel arm resonators are electrically connected to first and second electrode lands which are provided on the package and electrically isolated from each other while a reference potential electrode of the third parallel arm resonator is short-circuited with the reference potential electrode of either the first or second parallel arm resonator within the package.

Abstract: A surface acoustic wave filter significantly improves attenuation in the stopband by using a spurious component to improve the filter characteristics. The filter includes a surface acoustic wave substrate and a series resonator having a resonant frequency and an antiresonant frequency. The series resonator is electrically disposed between an input terminal and an output terminal in series so as to define a series arm. The filter also includes at least one parallel resonator having a resonant frequency and an antiresonant frequency which is substantially identical to the resonant frequency of the series resonator. The at least one parallel resonator is electrically disposed between the series arm and a ground terminal so as to define a first parallel arm. The series arm and the parallel arm define a ladder circuit such that the surface acoustic wave filter has a predetermined pass band.

Abstract: A surface acoustic wave filter has a ladder type filter circuit including a plurality of series arm resonators and a plurality of parallel arm resonators. The electrostatic capacitance of at least one of the parallel arm resonators is larger than that of another of the parallel arm resonators, and the length of a bonding wire connecting the parallel arm resonator having the larger electrostatic capacitance to a ground potential of a package is greater than that of a bonding wire connecting the another of the parallel arm resonators not having the larger electrostatic capacitance to the ground potential, such that the values of additional inductances created by the bonding wires are different from each other. In this manner, attenuation poles are distributed so that the amount of attenuation in the stop band on the low-frequency side is greatly increased.

Abstract: A surface acoustic wave (SAW) filter has a ladder-shaped circuit in which first one-port SAW resonators are connected between an input terminal and an output terminal as series resonators and second one-port SAW resonators are connected as parallel resonators. The antiresonant frequency of the second one-port SAW resonators matches the resonant frequency of the first one-port SAW resonators. The distances between interdigital transducers and reflectors of the second one-port SAW resonators are specified such that a spurious component is generated at a frequency between the resonant frequency of the second one-port SAW resonators and the transmission band of the filter in order to improve attenuation characteristics in a blocking band in the vicinity of the transmission band.

Abstract: A surface acoustic wave (SAW) filter includes a plurality of interdigital transducers located on a piezoelectric substrate along a surface wave propagation direction, at least a single one-port SAW resonator being connected in parallel with an output side of the SAW filter, while the resonance frequency (f.sub.0) of the SAW resonator is set in frequency region level which is lower than the pass band of the SAW filter.

Abstract: A surface acoustic wave (SAW) filter includes a plurality of interdigital transducers located on a piezoelectric substrate along a surface wave propagation direction, at least a single one-port SAW resonator connected in series with an output side of the SAW filter, while the resonance frequency of the SAW resonator is set at a level which is higher than the passband of the SAW filter.