A duplexer includes a first band-pass filter and a second band-pass filter with a pass-band lower than the first band-pass filter. The first band-pass filter includes an unbalanced surface acoustic wave filter. First, second and third signal wire electrodes and a ground wire electrode are provided on a piezoelectric substrate in the first band-pass filter, and a bridging area is provided where any one of the first, second and third signal wire electrodes bridges the ground wire electrode. A width of a portion of the signal wire electrode that opposes the ground wire electrode with an interlayer insulating film located therebetween is greater than a width of a portion of the signal wire electrode other than the bridging area so that a low-pass filter capacitor is provided.

A high frequency module includes a first external connection terminal, a second external connection terminal, a filter unit, a first matching circuit, and a second matching circuit. The filter unit is connected between the first external connection terminal and the second external connection terminal. The first matching circuit is connected between the first external connection terminal and the filter unit. The second matching circuit is connected between the second external connection terminal and the filter unit. The first matching circuit and the second matching circuit are inductively or capacitively coupled to each other.

The present invention relates to a capacitor for a SAW filter, the SAW filter, and a method of manufacturing thereof, and more specifically, to a capacitor for a SAW filter including a first metal layer formed on a substrate; an insulation layer formed on the first metal layer; and a second metal layer formed on the insulation layer and overlapped with partially or totally of the first metal layer, in which the insulation layer is formed to be extended to the top of an IDT formed on the substrate, the SAW filter on which such a capacitor for a SAW filter is mounted, and a method of manufacturing thereof.

A high-frequency module includes a filter unit and first and second external connection terminals. The filter unit includes first and second terminals and a plurality of SAW resonators. The plurality of SAW resonators are connected to one another by connection conductors. A matching element is connected between the first terminal and the first external connection terminal, and a matching element is connected between the second terminal and the second external connection terminal. At least one of the matching elements is inductively coupled or capacitively coupled to at least one of the connection conductors located at a position such that at least one of the SAW resonators is interposed between the matching element and the connection conductor.

A multiplexer includes: one or more transmit filters that are connected between an antenna terminal and one or more transmit terminals; one or more receive filters that are connected between the antenna terminal and one or more receive terminals; and a circuit that includes a longitudinally coupled acoustic wave filter and is connected in parallel to one or more series resonators of a first filter that is one of the one or more transmit filters and the one or more receive filters and includes the one or more series resonators and one or more parallel resonators each formed of a piezoelectric thin film resonator, wherein the longitudinally coupled acoustic wave filter is formed of IDTs formed on a chip of a second filter that is another one of the one or more transmit filters and the one or more receive filters and formed of a surface acoustic wave resonator.

A ladder filter includes serial arm resonators in a serial arm and parallel arm resonators in parallel arms. A resonant frequency of at least one of the serial arm resonators is lower than a relevant band. An anti-resonant frequency of at least one of the parallel arm resonators is higher than the relevant band. The ladder filter includes one or more capacitances provided in at least one of the serial arm and the parallel arms. The capacitances are not provided in one or more of the parallel arms in which the one or more parallel arm resonators are provided.