BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multilayer triplexer including a multilayer substrate in which substrate layers are stacked on one another.

2. Description of the Related Art

Triplexers are widely used in electronic devices such as mobile communication devices, most notably mobile phones and smartphones. For example, International Publication No. 2008/075691 discloses a triplexer.FIG. 9illustrates a triplexer1000, which is the triplexer disclosed in International Publication No. 2008/075691.

The triplexer1000includes a common terminal Pc, a first branch terminal P1, a second branch terminal P2, and a third branch terminal P3.

The triplexer1000also includes a first band-pass filter portion bpf1for a low band, a second band-pass filter portion bpf2for a middle band, and a third band-pass filter portion bpf3for a high band. The triplexer1000also includes two phase adjustment circuits, namely, a phase adjustment circuit Y1and a phase adjustment circuit Y2. The triplexer1000also includes a first parallel resonant circuit X1, a second parallel resonant circuit X2, and a third parallel resonant circuit X3.

The first parallel resonant circuit X1, the second parallel resonant circuit X2, and the third parallel resonant circuit X3each include a coil and a capacitor connected in parallel and have, for example, the function of adjusting the impedance.

The triplexer1000is configured as follows. As a signal path for the low band, the first parallel resonant circuit X1, the phase adjustment circuit Y1, and the first band-pass filter portion bpf1are serially connected between the common terminal Pc and the first branch terminal P1. As a signal path for the middle band, the second parallel resonant circuit X2, the phase adjustment circuit Y2, and the second band-pass filter portion bpf2are serially connected between the common terminal Pc and the second branch terminal P2. As a signal path for the high band, the third parallel resonant circuit X3and the third band-pass filter portion bpf3are serially connected between the common terminal Pc and the third branch terminal P3.

A disadvantage of the triplexer1000is that signals in a band may be mixed with signals in another band through the capacitor of the first parallel resonant circuit X1, the capacitor of the second parallel resonant circuit X2, or the capacitor of the third parallel resonant circuit X3.

Most capacitors tend to allow passage of signals of high frequencies. Consequently, signals in the middle band or signals in the high band may, for example, enter the signal path for the low band through the capacitor of the first parallel resonant circuit X1. Similarly, signals in the high band may enter the signal path for the middle band through the capacitor of the second parallel resonant circuit X2.

The characteristics or the reliability of the triplexer1000may deteriorate due to mixing of signals in a band with signals in another band through the capacitor of the first parallel resonant circuit X1, the capacitor of the second parallel resonant circuit X2, or the capacitor of the third parallel resonant circuit X3.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide multilayer triplexers that each eliminate or reduce the possibility that signals in a band will pass through a stray capacitance and will consequently be mixed with signals in another band.

A multilayer triplexer according to a preferred embodiment includes a multilayer body including substrate layers stacked on one another; a common terminal, a first branch terminal, a second branch terminal, and a third branch terminal on a surface of the multilayer body; a first filter, a second filter, and a third filter in the multilayer body, the first filter being connected to a path extending from the common terminal to the first branch terminal, the second filter being connected to a path extending from the common terminal to the second branch terminal, the third filter being connected to a path extending from the common terminal to the third branch terminal; a first coil connected between the common terminal and the first filter; a second coil connected between the common terminal and the second filter; and a third coil connected between the common terminal and the third filter. The first to third coils each include a coil conductor pattern between ones of the substrate layers of the multilayer body. The coil conductor pattern of the first coil, the coil conductor pattern of the second coil, and the coil conductor pattern of the third coil do not overlap each other when the multilayer is viewed in the direction in which the substrate layers are stacked on one another.

In a multilayer triplexer according to a preferred embodiment of the present invention, the first coil, the second coil, and the third coil each have a winding axis parallel or substantially parallel to the direction in which the substrate layers are stacked on one another.

In a multilayer triplexer according to a preferred embodiment of the present invention, the coil conductor pattern of the least one of the first to third coils includes a first coil conductor pattern and a second coil conductor pattern between respective ones of the substrate layers and are U-shaped. The first coil conductor pattern partially overlaps the second coil conductor pattern in a width direction when the multilayer body is viewed in a direction in which the substrate layers are stacked on one another. The second coil conductor pattern partially overlaps the first coil conductor pattern in the width direction when the multilayer body is viewed in a direction in which the substrate layers are stacked on one another. Of a plurality of coil conductor patterns included in the same coil, a coil conductor pattern between two layers and a coil conductor pattern between another two layers may have stray capacitance arising therebetween when these coil conductor patterns entirely overlap each other.

When the first and second coil conductor patterns do not coincide with each other in the width direction, the stray capacitance is able to be reduced or prevented. This layout eliminates or reduces the possibility that signals in a band will pass through the stray capacitance and will consequently be mixed with signals in another band.

In a multilayer triplexer according to a preferred embodiment of the present invention, when the multilayer body is viewed in the direction in which the plurality of substrate layers are stacked on one another, the coil conductor pattern of one of the first to third coils encloses a region whose area is larger than an area of a region enclosed by the coil conductor pattern of any other coil and includes a third coil conductor pattern and a fourth coil conductor pattern between respective ones of the substrate layers and are U-shaped. The third and fourth coil conductor patterns entirely or substantially entirely overlap each other in a width direction. One of the first to third coils that requires an inductance value larger than the inductance value required by any other coil may have the following features.

As described above, the area of the region enclosed by the coil conductor pattern of the coil concerned is larger than the area of the region enclosed by the coil conductor pattern of any other coil. Of a plurality of coil conductor patterns included in the same coil, a coil conductor pattern between two layers and a coil conductor pattern between another two layers entirely overlap each other in the width direction. As a result of these features, a larger inductance value is able to be obtained.

The first filter, the second filter, and the third filter may be LC filters.

Multilayer triplexers according to preferred embodiments the present invention each include the first coil connected as a stage preceding the first filter, the second coil connected as a stage preceding the second filter, and a third coil connected as a stage preceding the third filter. Unlike the triplexer known in the art, the multilayer triplexers according to preferred embodiments of the present invention do not include parallel resonant circuits each of which include a coil and a capacitor and connected as a stage preceding a corresponding filter. These multilayer triplexers thus eliminate the possibility that signals in a band will pass through a capacitor of a parallel resonant circuit and will consequently be mixed with signals in another band.

In multilayer triplexers according to preferred embodiments of the present invention, the coil conductor pattern of the first coil, the coil conductor pattern of the second coil, and the coil conductor pattern of the third coil do not overlap each other when the multilayer body is seen through in the direction in which the substrate layers are stacked on one another. As a result of this feature, stray capacitance between the coil conductor patterns of different ones of these coils is able to be reduced or prevented. The multilayer triplexer thus eliminates or reduces the possibility that signals in a band will pass through the stray capacitance and will consequently be mixed with signals in another band.

The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.

