摘要:
In a surface acoustic wave device in which balanced terminals extend from series IDTs, noise coming from an electrical-potential signal at the series connection point of the series IDTs is removed to improve the degree of balance. A surface acoustic wave filter includes a pair of surface acoustic wave reflectors disposed on a piezoelectric substrate along the propagation direction of surface acoustic waves, and a plurality of IDTs disposed between the two surface acoustic wave reflectors. Two opposing electrode fingers of the IDTs, which are series IDTs, are connected to corresponding balanced terminals, and the series connection point thereof is grounded. As a result, noise coming from an abnormal electrical-potential signal generated at the series connection point is removed to improve the degree of balance between the balanced terminals.
摘要:
A surface acoustic wave (SAW) filter includes a piezoelectric substrate. A resin pattern having a permittivity less than that of the piezoelectric substrate and first and second conductor patterns are disposed on the piezoelectric substrate. The first conductor pattern defines two one-terminal-pair SAW resonators and two longitudinally coupled resonator SAW filters. A portion of the second conductor pattern defines wiring traces having different potentials. Portions of the wiring traces facing each other in a plan view are disposed on the resin pattern.
摘要:
A longitudinally-coupled-resonator-type surface acoustic wave filter includes three interdigital transducers provided on a piezoelectric substrate in the direction in which surface acoustic waves propagate. An interdigital transducer disposed at the approximate center among the three interdigital transducers of the longitudinally-coupled-resonator-type surface acoustic wave filter is divided into two parts substantially symmetrically in the propagation direction of the surface acoustic waves and the two parts are connected to balanced signal terminals, respectively. Left and right interdigital transducers of which the polarities are inverted relative to each other are connected to an unbalanced signal terminal to provide a balanced-to-unbalanced conversion function. A reactance component provided on the piezoelectric substrate, inside a package, or outside the package is connected to either of the balanced signal terminals.
摘要:
An elastic wave filter device having improved sharpness of filter characteristics includes a longitudinally-coupled resonator-type elastic wave filter section including first to third IDT electrodes each including a plurality of electrode fingers, and first and second reflectors. The first to third IDT electrodes include narrower-pitch portions provided in end portions thereof, which are each adjacent to another IDT electrode in a direction of propagation of elastic waves, each of the narrower-pitch portions having a smaller period of electrode fingers than a period of electrode fingers in the remaining portion of the relevant IDT electrode. The number of electrode fingers in the narrower-pitch portion of the second IDT electrode, which is disposed on the side closer to the first IDT electrode, and the number of electrode fingers in the narrower-pitch portion of the second IDT electrode, which is disposed on the side closer to the third IDT electrode, differ from each other.
摘要:
An elastic wave device includes an unbalanced terminal and first and second balanced terminals. A longitudinally-coupled-resonator-type first elastic wave filter is provided between the unbalanced terminal and the first balanced terminal. An elastic wave filter, which is connected in parallel with the first elastic wave filter, is connected between the unbalanced terminal and the second balanced terminal. The current paths through which IDT electrodes of the elastic wave filters of the elastic wave device are connected to ground terminals, are not symmetrical.
摘要:
An acoustic wave filter device includes first to fourth longitudinally coupled resonator type surface acoustic wave filters that are configured such that the first and second filters are connected to a first balanced signal terminal, the third and fourth filters are connected to a second balanced signal terminal, and a transmission phase of a signal output from the first balanced signal terminal relative to an input signal differs by about 180 degrees with respect to a transmission phase of a signal output from the second balanced signal terminal relative to an input signal. In addition, the number of pairs of electrode fingers of at least one of IDTs of at least one of the first to fourth longitudinally coupled resonator type surface acoustic wave filters is different from the number of pairs of electrode fingers of corresponding IDTs of the remaining first to fourth filters.
摘要:
A surface acoustic wave device includes a substrate, a plurality of terminals including at least an unbalanced terminal and balanced terminals, and at least one of surface acoustic wave element disposed between the unbalanced terminal and the two balanced terminals. Different signal lines connected to the same surface acoustic wave element intersect through insulating films.
摘要:
In a longitudinally-coupled-resonator surface acoustic wave filter unit having a first interdigital transducer, a central interdigital transducer, a second interdigital transducer, and first and second reflectors arranged such that the interdigital transducers are provided therebetween, for one comb electrode of the central interdigital transducer, first and second comb electrodes, which are substantially symmetrically bisected along a surface-acoustic-wave propagation direction, are provided. Between the first and second comb electrodes, a design parameter of at least one of the interdigital transducers, and the reflectors is set to be different from one another.
摘要:
A SAW filter includes a plurality of IDTs arranged on substrate along a SAW propagation direction, and balanced signal terminals connected to an IDT. The SAW filter is a floating balanced type. The plurality of IDTs are arranged so as to provide a horizontally asymmetrical structure with respect to an imaginary axis that is positioned at the approximate center of the center IDT in the SAW propagation direction and which is substantially perpendicular to the SAW propagation direction. Thus, a SAW filter having filtering characteristics and a balance-to-unbalance conversion function is achieved with high balance between the balanced signal terminals.
摘要:
A surface acoustic wave device having an unbalanced-to-balanced conversion function, which is capable of improving balanced characteristics, includes a first resonator filter and a second resonator filter, having a plurality of interdigital transducers disposed along the propagation direction of a surface acoustic wave. The surface acoustic wave device has an unbalanced-to-balanced conversion function as a result of the phase of the second resonator filter being reversed by 180° with respect to that of the first resonator filter. The surface acoustic wave device further includes a first resonator connected in series to an unbalanced signal terminal side of the first resonator filter, and a second resonator connected in series to an unbalanced signal terminal side of the second resonator filter. The first resonator and the second resonator have different design parameters.