A multiplexer includes filters on one principal surface of a mounting substrate and having mutually different frequency bands, and an inductance element which is incorporated in the mounting substrate and one end of which is connected to one end of the filter. The other end of the inductance element and one end of each of the filters, are connected to each other at a common connection point. The inductance element is defined by spiral wiring conductors disposed in first and second wiring layers provided in an inner layer of the mounting substrate. The mounting substrate includes third and fourth wiring layers which are adjacent to the first and second wiring layers, and in which no ground pattern is provided in a portion corresponding to a formation region of the inductance element.

A high-frequency module includes a longitudinally coupled surface acoustic wave filter and a low-noise amplifier that is connected to the surface acoustic wave filter. The input impedance of the surface acoustic wave filter connected to the low-noise amplifier differs from the output impedance thereof. On a Smith chart, the output impedance in the pass band of the surface acoustic wave filter is present in a region between a first output impedance and a second output impedance, the first output impedance being the output impedance of the surface acoustic wave filter where a gain of the low-noise amplifier is maximum, the second output impedance being the output impedance of the surface acoustic wave filter where a noise figure of the low-noise amplifier is minimum.

A multiplexer includes filters on one principal surface of a mounting substrate and having mutually different frequency bands, and an inductance element which is incorporated in the mounting substrate and one end of which is connected to one end of the filter. The other end of the inductance element and one end of each of the filters, are connected to each other at a common connection point. The inductance element is defined by spiral wiring conductors disposed in first and second wiring layers provided in an inner layer of the mounting substrate. The mounting substrate includes third and fourth wiring layers which are adjacent to the first and second wiring layers, and in which no ground pattern is provided in a portion corresponding to a formation region of the inductance element.

A multiplexer includes filters on one principal surface of a mounting substrate and having mutually different frequency bands, and an inductance element which is incorporated in the mounting substrate and one end of which is connected to one end of the filter. The other end of the inductance element and one end of each of the filters, are connected to each other at a common connection point. The inductance element is defined by spiral wiring conductors disposed in first and second wiring layers provided in an inner layer of the mounting substrate. The mounting substrate includes third and fourth wiring layers which are adjacent to the first and second wiring layers, and in which no ground pattern is provided in a portion corresponding to a formation region of the inductance element.

A multiplexer includes a transmission-side filter, a reception-side filter, and a cancel circuit connected between a node M and a node N to cancel out a component in a predetermined frequency band that flows along first and second paths. The cancel circuit includes at least one longitudinally-coupled resonator. An average pitch between electrode fingers of interdigital transducer electrodes of the at least one longitudinally-coupled resonator is narrower than an average pitch between electrode fingers of interdigital transducer electrodes of each of series arm resonators and parallel arm resonators that determine the pass band of the transmission-side filter and an average pitch between electrode fingers of interdigital transducer electrodes of each of series arm resonators and parallel arm resonators that determine the pass band of the reception-side filter.

An elastic wave device includes a first filter including an elastic wave resonator and a second filter connected to an antenna common terminal via a common node. When a first pass band of the first filter and second pass bands of the second filters are F1 and F2, respectively, F1<F2. The first filter includes at least one elastic wave resonator, and the elastic wave resonator uses Rayleigh waves propagating on a piezoelectric substrate made of LiNbO.sub.3, IDT electrodes including a Pt film on a piezoelectric layer made of LiNbO.sub.3, and a silicon oxide film covering the IDT electrodes. The thickness of the silicon oxide layer is about 33% or less of the wavelength of the IDT electrodes.

A multiplexer includes a common connection terminal on a first surface of a substrate and to be connected to an antenna element, and transmission-side and reception-side elastic wave filters of Band25 and Band66 mounted on a second surface of the substrate opposite the first surface, that are connected to the common connection terminal, and that have pass bands different from each other. The transmission-side elastic wave filter of Band66 is located nearest on the substrate to the common connection terminal among the elastic wave filters.

A multiplexer includes filters on one principal surface of a mounting substrate and having mutually different frequency bands, and an inductance element which is incorporated in the mounting substrate and one end of which is connected to one end of the filter. The other end of the inductance element and one end of each of the filters, are connected to each other at a common connection point. The inductance element is defined by spiral wiring conductors disposed in first and second wiring layers provided in an inner layer of the mounting substrate. The mounting substrate includes third and fourth wiring layers which are adjacent to the first and second wiring layers, and in which no ground pattern is provided in a portion corresponding to a formation region of the inductance element.

A filter device includes at least one parallel arm resonator and series arm resonators including at least one first series arm resonator and at least one second series arm resonator being different from each other, a resonant frequency of the first series arm resonator is higher than a pass band of the filter device, the second series arm resonator has a series connection configuration in which at least two series arm resonators are connected in series to each other, anti-resonant frequencies of the at least two series arm resonators are different from each other, and the resonant frequency of the first series arm resonator is between the anti-resonant frequency of the series arm resonator on a lowest frequency side of the second series arm resonator and the anti-resonant frequency of the series arm resonator on a highest frequency side of the second series arm resonator.

A multiplexer includes filters on one principal surface of a mounting substrate and having mutually different frequency bands, and an inductance element which is incorporated in the mounting substrate and one end of which is connected to one end of the filter. The other end of the inductance element and one end of each of the filters, are connected to each other at a common connection point. The inductance element is defined by spiral wiring conductors disposed in first and second wiring layers provided in an inner layer of the mounting substrate. The mounting substrate includes third and fourth wiring layers which are adjacent to the first and second wiring layers, and in which no ground pattern is provided in a portion corresponding to a formation region of the inductance element.