Abstract: A 5-IDT balanced SAW filter suppresses and prevents generation of a ripple within a pass band and exhibits excellent filter characteristics. The 5-IDT longitudinally coupled resonator-type SAW filter has a balanced-to-unbalanced conversion function. In areas in which first to fifth IDTs are adjacent to each other, each of the IDTs includes a narrow-pitched electrode finger portion. The IDTs are configured such that one condition selected from among conditions (1) to (3) and one condition selected from among conditions (4) to (6) are satisfied when the numbers and pitches of electrode fingers in the narrow-pitched electrode finger portions of the first to fifth IDTs 11 to 15 are denoted by N1 and P1, N2a and P2a, N2b and P2b, N3 and P3, N4a and P4a, N4b and P4b, and N5 and P5, respectively: Condition (1): When N1=N3=N5, 0.99?P1/P3?1.008 and P1=P5 Condition (2): When N1=N5<N3, 0.9?P1/P3<1 and P1=P5 Condition (3): When N3<N1=N5, 1<P1/P3?1.1 and P1=P5 Condition (4): When N2a=N2b=N4a=N4b, 0.

Abstract: In a balanced SAW filter, a second IDT and a fourth IDT of a five IDT type first longitudinally-coupled-resonator SAW filter element are connected via first and second wiring lines to a seventh IDT and a ninth IDT of a five IDT type second longitudinally-coupled-resonator SAW filter element, respectively. First, third, and fifth IDTs are connected to an unbalanced terminal. A sixth IDT and a first sub-IDT portion are connected to a first balanced terminal. A second sub-IDT portion and a tenth IDT are connected to a second balanced terminal. The IDTs are arranged such that the phase of an electrical signal transmitted through the first wiring line differs by 180 degrees from the phase of an electrical signal transmitted through the second wiring line.

Abstract: In a balanced SAW filter, a third IDT of a first SAW filter element includes first and second IDT segments, and similarly, an eighth IDT of a second SAW filter element includes first and second IDT segments. A first IDT, the first IDT segment, the second IDT segment, and a fifth IDT included in the first SAW filter element are respectively connected to a sixth IDT, the first IDT segment, the second IDT segment, and a tenth IDT segment included in the second SAW filter element by first to fourth wiring lines. The phase of electric signals transmitted through the first and third wiring lines differs from the phase of electric signals transmitted through the second and fourth wiring lines by 180°.

Abstract: A surface acoustic wave filter includes first to fifth IDTs arranged on a piezoelectric substrate along a surface acoustic wave propagation direction. The second IDT and the fourth IDT have a phase difference of 180° with respect to each other. The second and fourth IDTs are connected to an unbalanced terminal. The third IDT includes a first sub-IDT portion and a second sub-IDT portion. The first IDT and the first sub-IDT portion are connected to a first balanced terminal, and the second sub-IDT portion and the fifth IDT are connected to a second balanced terminal. The following conditions: 1.55?N3/N1?2.58 and N1=N5 are satisfied, where N1 denotes the number of electrode fingers that determines the center frequency of the first IDT, N3 denotes the number of electrode fingers that determines the center frequency of the third IDT, and N5 denotes the number of electrode fingers that determines the center frequency of the fifth IDT.

Abstract: In a balanced-type surface acoustic wave filter, a first longitudinally coupled resonator surface acoustic wave filter unit connected to an unbalanced signal terminal is connected in a cascade arrangement to a second longitudinally coupled resonator surface acoustic wave filter unit connected to a first balanced signal terminal and a second balanced signal terminal. When the number of electrode fingers included in each of narrow pitch electrode finger portions in a center second IDT of the first longitudinally coupled resonator surface acoustic wave filter unit is defined as N1, and the number of electrode fingers included in each of narrow pitch electrode finger portions in a center fifth IDT of the second longitudinally coupled resonator surface acoustic wave filter unit is defined as N2, the numbers N1 and N2 are set to N1>N2.

Abstract: 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.

Abstract: 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.

Abstract: A SAW device includes two surface-acoustic-wave filter elements arranged so as to have a balanced-to-unbalanced conversion function. The surface-acoustic-wave filter elements include two first reflectors and two second reflectors. In each surface-acoustic-wave filter element, three IDTs are arranged on a piezoelectric substrate in a direction in which surface acoustic waves are transmitted so as to be positioned between one first reflector and one second reflector. The first reflectors differ in structure from the second reflectors.

Abstract: In a balanced-type surface acoustic wave filter, IDTs in the center of each of first and second longitudinally coupled resonator type surface acoustic wave filter sections are connected to an unbalanced input terminal, first and third IDT sections on both the sides of the center IDT are connected to first and second balanced output terminals, respectively, the first and third IDTs have narrow pitch electrode finger sections N, and when an electrode finger pitch of the narrow pitch electrode finger section of the second IDT is P1, an electrode finger pitch of the narrow pitch electrode finger section of the first and third IDTs is P2, the number of electrode fingers of the second IDT except for the narrow pitch electrode finger section of the IDT is K1, and the number of electrode fingers of the first and third IDT except for the narrow pitch electrode finger section is K2, P1>P2 and 1.12?K1/K2?1.65 are satisfied.

Abstract: A surface acoustic wave filter includes a device chip, one principal surface of a piezoelectric substrate having a wiring pattern including IDTs and pads electrically connected to the IDTs, that is disposed so as to oppose a mount board, with the pads being electrically connected to lands of the mount board through bumps. A resin film covers the other principal surface of the piezoelectric substrate and the principal surface of the mount board to seal the device chip. In the piezoelectric substrate, the area of the one principal surface is greater than the area of the other principal surface.

Abstract: A surface acoustic wave device includes, on a piezoelectric substrate, at least one surface acoustic wave filter and at least one surface acoustic wave resonator that is connected in series and/or parallel to the surface acoustic wave filter. A film having a positive frequency-temperature characteristic is disposed so as to cover at least one of the at least one surface acoustic wave resonator, except for a region in which the surface acoustic wave filter is provided.

Abstract: A longitudinally coupled resonator type surface acoustic wave filter having a balance-unbalance conversion function achieves improved amplitude balance and phase balance. The surface acoustic wave filter includes first, second and third IDTs. The second IDT is positioned in the center of the three IDTs and has an even number of electrode fingers. The polarity of the electrode finger of the first IDT adjacent to the second IDT is opposite to the polarity of the electrode finger of the third IDT adjacent to the second IDT.

Abstract: A SAW filter includes at least two IDTs arranged along a SAW propagation direction on a piezoelectric substrate and first and second reflectors sandwiching the IDTs. A group of electrode fingers of each of the first and second reflectors is interdigital-width weighted. Further, a method of interdigital-width weighting of the electrode fingers of the first reflector is different from that of interdigital-width weighting of the electrode fingers of the second reflector.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A surface acoustic wave device has a balanced-to-unbalanced conversion function, in which the common mode in the vicinity of outside the passband is satisfactory. The surface acoustic wave device includes surface acoustic wave filters having interdigital transducers (IDTs) arranged along a surface acoustic wave propagation direction, which filters are provided on a piezoelectric substrate so as to have a balanced-to-unbalanced conversion function, and balanced signal terminals are correspondingly connected to the surface acoustic wave filters. Surface acoustic wave resonators including an interdigital transducer sandwiched between reflectors are correspondingly connected in series to the balanced signal terminals. The center-to-center distance between mutually adjacent electrode fingers in the reflectors and the interdigital transducer in one of the surface acoustic wave resonators differs from that of the other surface acoustic wave resonator.

Abstract: A plurality of surface acoustic wave filters having different center frequencies is provided on a piezoelectric substrate. Either input terminals or output terminals, or both input terminals and output terminals of the surface acoustic wave filters are integrated. Of the surface acoustic wave filters, a surface acoustic wave filter having a higher center frequency is configured so as to suppress a spurious response in the proximity of the high-frequency side in or outside a passband in the filter characteristics of a surface acoustic wave filter having a lower center frequency, for example, such that the width or pitch of electrode fingers in at least one region of reflectors differs from that in other regions.

Abstract: A surface acoustic wave device includes a piezoelectric substrate, at least one IDT disposed on the piezoelectric substrate, and an input end and an output end connected to the IDT. At least one of the input end and the output end includes a pair of balanced signal terminals, and a delay line or a reactance component connected to one of the pair of balanced signal terminals.

Abstract: A surface acoustic wave apparatus includes at least one longitudinally-coupled-resonator surface acoustic wave filter having at least three IDTs arranged on a piezoelectric substrate along the propagation direction of surface acoustic waves and at least one surface acoustic wave resonator that is connected in series to at least two of the IDTs of the longitudinally-coupled-resonator surface acoustic wave filter. The parasitic capacitance between the longitudinally-coupled-resonator surface acoustic wave filter and the surface acoustic wave resonator is about 6.5×102/f0 [pF] or less, where f0 represents the center frequency (MHz) within the pass band of the longitudinally-coupled-resonator surface acoustic wave filter.