Abstract: A duplexer includes: a transmit filter that is connected between an antenna terminal and a transmit terminal and has a plurality of acoustic wave resonators; a receive filter that is connected between the antenna terminal and a receive terminal and has a plurality of acoustic wave resonators; and a delay line or a longitudinal coupling type resonator that is connected in parallel with at least one of the plurality of acoustic wave resonators of the transmit filter and the plurality of acoustic wave resonators of the receive filter and has at least two IDTs (Interdigital Transducers).

Abstract: A duplexer includes an unbalanced transmitting filter; a balanced receiving filter; a transmitting port connected to the transmitting filter; and a first receiving port and a second receiving port connected to the receiving filter. The duplexer also includes an electromagnetic coupling portion connected between the transmitting port and the first receiving port and between the transmitting port and the second receiving port. The electromagnetic coupling portion adjusts the phase between electric power that flows from the transmitting port to the first receiving port and electric power that flows from the transmitting port to the second receiving port.

Abstract: The filter includes one or more series resonators and one or more parallel resonators. An inductance is connected in series to at least a parallel resonator of the parallel resonators, and a antiresonance frequency of the parallel resonator to which the inductance is connected in series is equal to or higher than that of the series resonators. The duplexer, the communication module and the communication device are provided with the filter.

Abstract: A duplexer includes an unbalanced transmitting filter; a balanced receiving filter; a transmitting port connected to the transmitting filter; and a first receiving port and a second receiving port connected to the receiving filter. The duplexer also includes an electromagnetic coupling portion connected between the transmitting port and the first receiving port and between the transmitting port and the second receiving port. The electromagnetic coupling portion adjusts the phase between electric power that flows from the transmitting port to the first receiving port and electric power that flows from the transmitting port to the second receiving port.

Abstract: A ladder filter includes at least one series resonator connected in series between an input terminal and an output terminal, at least one parallel resonator connected in parallel with the at least one series resonator, and an inductor connected in parallel with the at least one series resonator. The at least one series resonator and the inductor generate a first attenuation pole at a frequency equal to or lower than a frequency band defined by the at least one series resonator and the at least one parallel resonator. The first attenuation pole is located at a frequency that is equal to or higher than a resonance frequency of a parallel resonator that is included in the at least one parallel resonator and has a highest resonance frequency and that is equal to or lower than a high-frequency end of the pass band.

Abstract: There is provided a piezoelectric thin film resonator that decreases only transverse mode waves selectively while maintaining resonance characteristics due to original thickness longitudinal vibration. The piezoelectric thin film resonator includes: a piezoelectric film (14); a first electrode (15a) formed on a first principal surface of the piezoelectric film (14); and a second electrode (13) formed on a second principal surface of the piezoelectric film (14) opposite to the first principal surface. The resonator has a resonance region (20) where the first electrode (15a) and the second electrode (13) are opposed to each other. An electrically discontinuous portion (18a) that is insulated from the first electrode (15a) is provided on the first principal surface of the piezoelectric film (14) in the resonance region (20), and the electrically discontinuous portion (18a) is surrounded by the first electrode (15a) on the first principal surface.

Abstract: A filter includes at least one series resonator and parallel resonators, the at least one series resonator and the parallel resonators including excitation electrodes and reflectors, the parallel resonators having different resonance frequencies, and at least one of the parallel resonators other than the parallel resonator having the highest resonance frequency being configured to have a pitch of reflectors that is smaller than that of excitation electrodes.

Abstract: A ladder filter includes at least one series resonator connected in series between an input terminal and an output terminal, at least one parallel resonator connected in parallel with the at least one series resonator, an additional resonator connected in series between the at least one series resonator and one of the input terminal and the output terminal, and an inductor connected in series to the additional resonator, the additional resonator having a resonance frequency higher than an anti-resonance frequency of the at least one series resonator.

Abstract: A piezoelectric thin film resonator includes a substrate, a lower electrode provided on the substrate, a piezoelectric film provided on the lower electrode, and an upper electrode provided on the piezoelectric film. At least a portion of the upper electrode and that of the lower electrode oppose each other through the piezoelectric film, and at least a portion of the periphery of the upper electrode is reversely tapered.

Abstract: A duplexer with a reduced filter loss is provided. The duplexer includes two or more filters F1 and F2 that are connected to a common terminal and that have different passbands. At least one of the filters F1 and F2 includes a plurality of series resonators S1 to Sn connected in series to a path between an input terminal and an output terminal of the filter, and parallel resonators P1 to Pm connected in parallel to the above-mentioned path. An inductance L1 is connected in parallel to at least one of the series resonators, and the series resonator S1 having the inductance L1 connected in parallel thereto is divided into a plurality of resonators S11 to S13 connected in series.

Abstract: A method of producing a piezoelectric thin film resonator is provided. A sacrificial layer is formed on a part of the piezoelectric film. The sacrificial layer is patterned, and thereafter an upper electrode is formed on the piezoelectric layer. The method further includes removing the sacrificial layer formed on the piezoelectric layer; and patterning the piezoelectric film. In the step of removing the sacrificial layer, the sacrificial layer is removed such that at least a portion of the periphery of the upper electrode has a reversely tapered shape that reflects the tapered portion of the sacrificial layer, and in the step of patterning the piezoelectric film, the piezoelectric film is removed such that a lower end of the reversely tapered periphery of the upper electrode is placed so as to coincide with or to be in the vicinity of an end portion of the patterned piezoelectric film.

Abstract: A method for manufacturing an acoustic wave device includes: bonding a piezoelectric substrate to a first surface of a first support substrate; thinning the piezoelectric substrate after the bonding to thus form a piezoelectric layer; forming a first electrode on a first surface of the piezoelectric layer; forming holes in the first support substrate located below the first electrode; and bonding a second support substrate to a second surface of the first support substrate opposite to the first surface after the forming of holes.

Abstract: A piezoelectric thin-film resonator includes a substrate, a lower electrode provided on the substrate, a piezoelectric film provided on the substrate and the lower electrode, an upper electrode provided on the piezoelectric film, and an additional pattern, a cavity being formed between the lower electrode and the substrate in a resonance portion in which the lower electrode and the upper electrode face each other through the piezoelectric film, the additional pattern being provided in a position that is on the lower electrode and includes an interface between the resonance portion and a non-resonance portion.

Abstract: A filter element includes a plurality of multilayer filters that are connected in cascade, each of the plurality of multilayer filters including a plurality of piezoelectric thin-film resonators stacked vertically, each of the piezoelectric thin-film resonators including a piezoelectric film and a pair of first electrodes between which the piezoelectric film is interposed, and a capacitor connected between an input terminal of one of the plurality of multilayer filters of a preceding stage and an input terminal of another one of the plurality of multilayer filters of a following stage, exciting directions of piezoelectric thin-film resonators to which the input terminals of the multilayer filters of the preceding and following stages are connected being opposite to each other.

Abstract: A duplexer with a reduced filter loss is provided. The duplexer includes two or more filters F1 and F2 that are connected to a common terminal and that have different passbands. At least one of the filters F1 and F2 includes a plurality of series resonators S1 to Sn connected in series to a path between an input terminal and an output terminal of the filter, and parallel resonators P1 to Pm connected in parallel to the above-mentioned path. An inductance L1 is connected in parallel to at least one of the series resonators, and the series resonator S1 having the inductance L1 connected in parallel thereto is divided into a plurality of resonators S11 to S13 connected in series.

Abstract: A duplexer includes: an insulation substrate having an upper surface on which a transmission filter and a reception filter are mounted, and a lower surface on which a foot pad layer electrically connected to the transmission filter and the reception filter is formed; a transmission pad provided on the upper surface and electrically connected to the transmission filter; a reception pad provided on the upper surface and electrically connected to the reception filter, a ring-shaped electrode provided on the upper surface and configured to surround the transmission pad and the reception pad; a ground foot pad included in the foot pad layer, and a via interconnection configured to electrically interconnect the ring-shaped electrode and the ground foot pad and to be provided in the ring-shaped electrode in a section along a shorter one of routes that connect the transmission pad and the reception pad to each other along the ring-shaped electrode.

Abstract: A filter circuit includes a filter part connected between an input terminal and an output terminal and configured to have a passband, and a path connected in parallel with the filter part between the input terminal and the output terminal, the path having an impedance that enables a first signal passing through the path from the input terminal to the output terminal and a second signal passing through the filter part from the input terminal to the output terminal to have an opposite phase relationship in a frequency band outside of the passband and have almost equal amplitudes in the frequency band.

Abstract: In one aspect of the invention, a duplexer including a multilayer substrate with multiple stacked layers and a back surface with a rectangular shape is disclosed. An antenna terminal, a transmission terminal, a reception terminal, a ground terminal, and a conductor are provided in various positions on the multilayer substrate for improved performance.

Abstract: A filter includes: a first filter unit includes: a series resonators connected in series to each other between a first input terminal and a first output terminal; a parallel resonators each having one end connected to one terminal of each of the series resonators; and a common inductance having one end connected to the other ends of the parallel resonators and the other end connected to a ground terminal, and a second filter unit includes: a series resonators connected in series to each other between a second input terminal and a second output terminal; a parallel resonators each having one end connected to one terminal of each of the series resonators; and a common inductance having one end connected to the other ends of the parallel resonators and the other end connected to the ground terminal.

Abstract: A piezoelectric thin film resonant element includes a resonant portion having a laminate structure made up of a lower electrode, an upper electrode and a piezoelectric film arranged between these two electrodes. The lower electrode has an ellipsoidal plan-view shape and an outer circumference formed with an inclined portion inclined at an angle (about 30° for example) lying within a range of 25° through 55°. The upper electrode has an ellipsoidal plan-view shape. An additional film is provided on the upper electrode at a portion corresponding to the inclined portion of the lower electrode.