DIRECTIONAL COUPLER

A directional coupler includes a main line, sub-lines, and a switch. The sub-lines are located at positions that enable the sub-lines to be electromagnetically coupled to the main line. The switch is coupled between an end portion sand an end portion of the sub-line. The switch is configured to switch connection of the end portion and the end portion between a shorted state and an open state.

BACKGROUND ART

Technical Field

The present invention relates to a directional coupler having a main line and a plurality of sub-lines.

Patent Document 1 describes a directional coupler having a main line and a plurality of coupled lines. The plurality of coupled lines include a first coupled line and a second coupled line that are positioned such that the first coupled line and the second coupled line are coupled to the main line via electromagnetic fields.

The directional coupler described in Patent Document includes a coupling output terminal, a termination resistance, and a switching circuit. The switching circuit switches between the first coupled line and the second coupled line and couple one of the first coupled line and the second coupled line to a coupling output terminal and a termination resistance.

BRIEF SUMMARY

With the configuration using a plurality of coupled lines (sub-lines) as described in Patent Document 1, the coupling capacitance between the main line and the sub-lines can degrade the transfer characteristic of radio-frequency signals communicated through the main line.

An object of the present invention is to suppress degradation of the transfer characteristic of radio-frequency signals communicated through a main line in a directional coupler having a plurality of sub-lines.

A directional coupler according to an aspect of the present invention includes a main line, a first sub-line, a second sub-line, and a first switching circuit. The first sub-line and the second sub-line are located at positions that enable the first sub-line and the second sub-line to be electromagnetically coupled to the main line. The first switching circuit is coupled between a first end and a second end of the first sub-line. The first switching circuit is configured to switch connection of the first end and the second end between a shorted state and an open state.

With this configuration, by bringing the first end and the second end of the first sub-line in the open state, the first sub-line can be used to obtain detected signals corresponding to radio-frequency signals communicated through the main line. By bringing the first end and the second end of the first sub-line in the shorted state, the coupling capacitance to the main line can be changed. As such, the attenuation pole in the transfer characteristic of the main line can be controlled, thereby suppressing degradation of the transfer characteristic of the main line.

According to the present invention, a directional coupler can suppress degradation of the transfer characteristic of radio-frequency signals communicated along the main line.

DETAILED DESCRIPTION

Summary of Present Invention

Hereinafter, a summary of the present invention will be described.

A directional coupler according to an aspect of the present invention includes a main line, a first sub-line and a second sub-line located at positions that enable the first sub-line and the second sub-line to be electromagnetically coupled to the main line, and a first switching circuit coupled between a first end and a second end of the first sub-line and configured to switch connection of the first end and the second end between a shorted state and an open state.

With this configuration, when the first end and the second end of the first sub-line are brought in the open state, the first sub-line can be used to obtain detected signals corresponding to radio-frequency signals communicated through the main line. When the first end and the second end of the first sub-line are brought in the shorted state, the coupling capacitance to the main line can be changed. As such, the attenuation pole in the transfer characteristic of the main line can be controlled, thereby suppressing degradation of the transfer characteristic of the main line.

For example, the directional coupler according to an aspect of the present invention may further include a coupling terminal and a termination circuit that are coupled to the first sub-line and the second sub-line, and a second switching circuit coupled between the first sub-line and the second sub-line, and the coupling terminal and the termination circuit.

With this configuration, a detected current communicated through the first sub-line or the second sub-line in any direction can be outputted from the coupling terminal. As a result, it is possible to reduce transfer loss of the main line, while constantly reaching a desired value or greater with respect to the degree of coupling over a wide frequency band.

For example, in the directional coupler according to an aspect of the present invention, the second switching circuit may be configured to switch the first sub-line and the second sub-line to couple one of the first sub-line and the second sub-line to the coupling terminal and the termination circuit.

This configuration can inhibit adverse effects such as power leakage, and as a result, desired characteristics are easily achieved.

For example, in the directional coupler according to an aspect of the present invention, the first switching circuit may be configured to, when the second switching circuit couples the second sub-line to the coupling terminal and the termination circuit, bring the first end and the second end of the first sub-line in the shorted state.

This configuration can inhibit adverse effects such as power leakage to the termination circuit and the coupling terminal, and as a result, desired characteristics are easily achieved.

For example, in the directional coupler according to an aspect of the present invention, the first switching circuit may be configured to, when the second switching circuit couples the first sub-line to the coupling terminal and the termination circuit, bring the first end and the second end of the first sub-line in the open state.

With this configuration, a detected current communicated through the first sub-line is outputted from the coupling terminal.

For example, in the directional coupler according to an aspect of the present invention, the second switching circuit may have a first connection mode in which the first end is coupled to the coupling terminal, and the second end is coupled to the termination circuit, and a second connection mode in which the second end is coupled to the termination circuit, and the first end is coupled to the coupling terminal; and the second switching circuit may be configured to switch between the first connection mode and the second connection mode.

With this configuration, a detected current communicated through the first sub-line in any direction can be outputted from the coupling terminal.

For example, in the directional coupler according to an aspect of the present invention, the second switching circuit may have a third connection mode in which the first end and the second end are coupled to each other; the second switching circuit may be configured to switch among the first connection mode, the second connection mode, and the third connection mode; and the shorted state of the first switching circuit may be achieved in the third connection mode.

With this configuration, either of a detected current communicated through the first sub-line and a detected current communicated through the second sub-line can be outputted from the coupling terminal by changing the connection mode.

For example, in the directional coupler according to an aspect of the present invention, the second switching circuit may include a first switch coupled between the first end and the coupling terminal, a second switch coupled between the second end and the coupling terminal, a third switch coupled between the first end and the termination circuit, and a fourth switch coupled between the second end and the termination circuit; the first switching circuit may be formed by a combination of the first switch and the second switch or a combination of the third switch and the fourth switch.

This configuration eliminates switches for controlling the shorted state of both ends of a corresponding sub-line not used for detection, thereby reducing the circuit size. Furthermore, the number of switches coupled to sub-lines but not used directly to switch outputs of detected signals is decreased. As a result, the degree of coupling in a desired frequency band is increased, and the effect of reducing transfer loss of the main line is improved.

For example, in the directional coupler according to an aspect of the present invention, the first switching circuit may be formed by a combination of the first switch and the second switch.

This configuration eliminates switches for controlling the shorted state of both ends of a corresponding sub-line not used for detection, thereby reducing the circuit size. Furthermore, the number of switches coupled to sub-lines but not used directly to switch outputs of detected signals is decreased. As a result, the degree of coupling in a desired frequency band is increased, and the effect of reducing transfer loss of the main line is improved.

For example, in the directional coupler according to an aspect of the present invention, the second switching circuit may include a fifth switch configured to switch connection of the first switch and the second switch, and the coupling terminal between the shorted state and the open state.

This configuration can inhibit adverse effects such as power leakage to the coupling terminal and adverse effects caused by other circuits coupled to the coupling terminal, and as a result, desired characteristics are easily achieved.

For example, in the directional coupler according to an aspect of the present invention, the fifth switch may be configured to, when the third connection mode is achieved by the first switch and the second switch, switch connection of the first switch and the second switch, and the coupling terminal, to the open state.

With this configuration, the sub-line with ends shorted is not coupled to the coupling terminal, and thus, impedance matching between the sub-line outputting a detected signal and the coupling terminal is more effectively provided.

For example, in the directional coupler according to an aspect of the present invention, the fifth switch may be configured to, when the first connection mode is achieved by the first switch and the fourth switch, switch connection of the first switch and the coupling terminal to the shorted state.

With this configuration, a detected current communicated through the first sub-line is outputted from the coupling terminal.

For example, in the directional coupler according to an aspect of the present invention, the first switching circuit may be formed by a combination of the third switch and the fourth switch.

This configuration eliminates switches for controlling the shorted state of both ends of a corresponding sub-line not used for detection, thereby reducing the circuit size. Furthermore, the number of switches coupled to sub-lines but not used directly to switch outputs of detected signals is decreased. As a result, the degree of coupling in a desired frequency band is increased, and the effect of reducing transfer loss of the main line is improved.

For example, in the directional coupler according to an aspect of the present invention, the second switching circuit may include a sixth switch configured to switch connection of the third switch and the fourth switch, and the termination circuit, between the shorted state and the open state.

This configuration can inhibit adverse effects such as power leakage to the coupling terminal and adverse effects caused by other circuits coupled to the coupling terminal, and as a result, desired characteristics are easily achieved.

For example, in the directional coupler according to an aspect of the present invention, the sixth switch may be configured to, when the third connection mode is achieved by the third switch and the fourth switch, switch connection of the third switch and the fourth switch, and the coupling terminal, to the open state.

With this configuration, the sub-line with ends shorted is not coupled to the coupling terminal, and thus, impedance matching between the sub-line outputting a detected signal and the coupling terminal is more effectively provided.

For example, in the directional coupler according to an aspect of the present invention, the sixth switch may be configured to, when the second connection mode is achieved by the second switch and the third switch, switch connection of the third switch and the coupling terminal to the shorted state.

With this configuration, a detected current communicated through the first sub-line is outputted from the coupling terminal.

The following describes directional couplers according to embodiments of the present invention in detail with reference to the drawings. It should be noted that the embodiments described below each represent one specific example of the present invention. Thus, the specifics including numerical values, shapes, materials, constituent elements, arrangements of the constituent elements, modes of connection of the constituent elements, steps, and the order of the steps given in the following embodiments are mere instances and are not intended to limit the present invention. Among the constituent elements in the following embodiments, constituent elements not recited in any of the independent claims are described as arbitrary constituent elements.

Further, the drawings are schematic drawings and are not necessarily depicted in an exact manner.

Thus, for example, the drawings are not consistent in terms of scale. Like reference symbols are used to denote substantially like configurations in the drawings, and redundant descriptions thereof are omitted or simplified.

First Embodiment

A directional coupler according to a first embodiment of the present invention will be described with reference to the drawings.FIG.1is a configuration diagram of the directional coupler according to the first embodiment.FIG.2is an equivalent circuit diagram of the directional coupler according to the first embodiment.

As illustrated inFIG.1, a directional coupler10includes a main line20, sub-lines31and32, switching circuits41and42, switches SW91and SW92, input-output terminals P21and P22, a coupling terminal Pcp, and a termination circuit80.

The main line20and the sub-lines31and32are formed by, for example, conductor patterns formed at an insulating substrate. The switching circuits41and42, the switches SW91and SW92, and the termination circuit80are formed by, for example, mounting electronic components mounted at the insulating substrate and conductor patterns formed at the insulating substrate. The input-output terminals P21and P22and the coupling terminal Pcpare formed by, for example, terminal conductor patterns formed at the insulating substrate.

The main line20is elongated in a particular direction (for example, elongated linearly). One end of the main line20is coupled to the input-output terminal P21, and the other end of the main line20is coupled to the input-output terminal P22.

The sub-line31is located at a position that enables the sub-line31to be electromagnetically coupled to the main line20. For example, the sub-line31is elongated in the direction along the main line20, spaced apart by a particular distance from the main line20. At this time, the shape of the sub-line31and the position of the sub-line31relative to the main line20are determined such that a desired degree of coupling with the main line20is achieved in a first frequency band.

The sub-line32is located at a position that enables the sub-line32to be electromagnetically coupled to the main line20. For example, the sub-line32is elongated in the direction along the main line20, spaced apart by a particular distance from the main line20. At this time, the shape of the sub-line32and the position of the sub-line32relative to the main line20are determined such that a desired degree of coupling with the main line20is achieved in a second frequency band.

The second frequency band does not completely coincide with the first frequency band. In other words, the second frequency band is different from the first frequency band. For example, the second frequency band may be a frequency band on the high frequency side with respect to the first frequency band. In this case, as illustrated inFIG.1, the length of the sub-line32along the main line20is shorter than the length of the sub-line31along the main line20. For example, the second frequency band may be a frequency band including 1.5 [GHz] or higher, of a particular frequency band width; the first frequency band may be a frequency band below 1.5 [GHz], of a particular frequency band width. The first frequency band and the second frequency band are merely an example, and this should not be interpreted as limiting.

The sub-line31has an end portion311at one end in the length direction and an end portion312at the other end in the length direction. The sub-line32has an end portion321at one end in the length direction and an end portion322at the other end in the length direction. One of the sub-lines31and32corresponds to a “first sub-line” of the present invention, and the other of the sub-lines31and32corresponds to a “second sub-line” of the present invention. When the sub-line31is the first sub-line, the end portion311corresponds to a “first end” of the present invention, and the end portion312corresponds to a “second end” of the present invention. When the sub-line32is the first sub-line, the end portion321corresponds to the “first end” of the present invention, and the end portion322corresponds to the “second end” of the present invention. When the sub-line31is the first sub-line, the end portion312may correspond to the “first end” of the present invention, and the end portion311may correspond to the “second end” of the present invention. When the sub-line32is the first sub-line, the end portion322may correspond to the “first end” of the present invention, and the end portion321may correspond to the “second end” of the present invention.

The switching circuit41includes switches SW11, SW12, SW13, and SW14. The switch SW11is coupled between the end portion311of the sub-line31and the coupling terminal Pcp. The switch SW11switches connection of the end portion311and the coupling terminal Pcpbetween a shorted state and an open state. The switch SW12is coupled between the end portion312of the sub-line31and the coupling terminal Pcp. The switch SW12switches connection of the end portion312and the coupling terminal Pcpbetween the shorted state and the open state. The switch SW13is coupled between the end portion311of the sub-line31and the termination circuit80. The switch SW13switches connection of the end portion311and the termination circuit80between the shorted state and the open state. The switch SW14is coupled between the end portion312of the sub-line31and the termination circuit80. The switch SW14switches connection of the end portion312and the termination circuit80between the shorted state and the open state.

A coupling terminal Pcpside of the switch SW11and a coupling terminal Pcpside of the switch SW12are coupled to each other. A termination circuit80side of the switch SW13and a termination circuit80side of the switch SW14are coupled to each other. When the sub-line31is the “first sub-line”, the switches SW11, SW12, SW13, and SW14respectively correspond to a “first switch”, a “second switch”, a “third switch”, and a “fourth switch” of the present invention.

The switching circuit42includes switches SW21, SW22, SW23, and SW24. The switch SW21is coupled between the end portion321of the sub-line32and the coupling terminal Pcp. The switch SW21switches connection of the end portion321and the coupling terminal Pcpbetween the shorted state and the open state. The switch SW22is coupled between the end portion322of the sub-line31and the coupling terminal Pcp. The switch SW22switches connection of the end portion322and the coupling terminal Pcpbetween the shorted state and the open state. The switch SW23is coupled between the end portion321of the sub-line32and the termination circuit80. The switch SW23switches connection of the end portion321and the termination circuit80between the shorted state and the open state. The switch SW24is coupled between the end portion322of the sub-line32and the termination circuit80. The switch SW24switches connection of the end portion322and the termination circuit80between the shorted state and the open state.

A coupling terminal Pcpside of the switch SW21and a coupling terminal Pcpside of the switch SW22are coupled to each other. A termination circuit80side of the switch SW23and a termination circuit80side of the switch SW24are coupled to each other. When the sub-line32is the “first sub-line”, the switches SW21, SW22, SW23, and SW24respectively correspond to the “first switch”, the “second switch”, the “third switch”, and the “fourth switch” of the present invention.

In the directional coupler10, the “first switch”, the “second switch”, the “third switch”, and the “fourth switch” are provided for each of the sub-lines31and32, but the “first switch”, the “second switch”, the “third switch”, and the “fourth switch” may be provided for only either the sub-line31or32. The switching circuits41and42correspond to a “second switching circuit” of the present invention.

The switch SW91is coupled between the end portions311and312of the sub-line31. The switch SW91switches connection of the end portions311and312between the shorted state and the open state. When the sub-line31is the “first sub-line”, the switch SW91corresponds to a “first switching circuit” of the present invention.

The switch SW92is coupled between the end portions321and322of the sub-line32. The switch SW92switches connection of the end portions321and322between the shorted state and the open state. When the sub-line32is the “first sub-line”, the switch SW92corresponds to the “first switching circuit” of the present invention.

In the directional coupler10, the “first switching circuit” is provided for each of the sub-lines31and32, but the “first switching circuit” may be provided for only either the sub-line31or32.

The termination circuit80includes a variable resistor Rtand a variable capacitor Ct. A parallel circuit of the variable resistor Rtand the variable capacitor Ctcouples the switches SW13, SW14, SW23, and SW24to a reference potential.

In this configuration, as illustrated inFIG.2, a coupling capacitance C231is generated between the main line20(an inductance L20) and the sub-line31(an inductance L31). Also, a coupling capacitance C232is generated between the main line20(the inductance L20) and the sub-line32(an inductance L32). In other words, in the directional coupler10, the degree of electromagnetic coupling between the main line20and the sub-line31is controlled by changing the coupling capacitance C231, and as a result, a coupling signal of a desired level can be obtained in the first sub-line31. Similarly, in the directional coupler10, the degree of electromagnetic coupling between the main line20and the sub-line32is controlled by changing the coupling capacitance C232, and as a result, a coupling signal of a desired level can be obtained in the second sub-line32.

Connection Configuration of Directional Coupler10

The directional coupler10configured as described above outputs a detected signal corresponding to a radio-frequency signal communicated through the main line20from the coupling terminal Pcpalong various connection configurations described below.

(1-1) Configuration for Outputting Detected Signal Communicated from End Portion322Side to End Portion321Side of Sub-line32from Coupling Terminal Pcp

FIG.3is a state diagram illustrating a first connection configuration of the directional coupler according to the first embodiment.

As illustrated inFIG.3, the switches SW21and SW24of the switching circuit42are in the shorted state. The switches SW22and SW23of the switching circuit42are in the open state. As a result, the end portion321of the sub-line32is coupled to the coupling terminal Pcpbut not coupled to the termination circuit80. The end portion322of the sub-line32is coupled to the termination circuit80but not coupled to the coupling terminal Pcp. The switch SW92is in the open state.

The switches SW11, SW12, SW13, and SW14of the switching circuit41are in the open state.

With this configuration, the directional coupler10outputs from the coupling terminal Pcpa detected signal induced in the sub-line32and communicated from the end portion322side to the end portion321side. At this time, a detected signal induced in the sub-line32and communicated from the end portion322side to the end portion321side is a signal corresponding to a radio-frequency signal communicated from the input-output terminal P21side to the input-output terminal P22side in the main line20.

At this time, the switch SW91is in the shorted state. As a result, the end portions311and312of the sub-line31are coupled to each other. By implementing this configuration, the effect of the inductance L31of the sub-line31is reduced, and as a result, the capacitance component of the sub-line31coupled to the main line20in the equivalent circuit is changed, as compared to a configuration (a known configuration) in which the end portions311and312of the sub-line31are not coupled to each other.

Accordingly, the frequency of parallel resonance of the inductance L20of the main line20and the capacitance component of the sub-line31is changed. In this manner, it is possible to change the position of the attenuation pole in the transfer characteristic of the main line20at a particular frequency.

FIG.4is a graph illustrating an example of a simulation result of the transfer characteristic of the main line (S21). InFIG.4, a solid line indicates the characteristic of the configuration of the present application, and a dashed line indicates the characteristic of a first comparative configuration. The comparative configuration is a configuration without the switch SW91according to the invention of the present application.

As illustrated inFIG.4, as the result of making the end portions311and312of the sub-line31shorted by the switch SW91, the attenuation pole of the main line at a particular frequency (in the case inFIG.4, about 5.2 [GHz]) is shifted to the high frequency side (in the case inFIG.4, the frequency side higher than 7.0 [GHz]).

As a result, it is possible to suppress significant degradation of the transfer characteristic of the main line20over a wider frequency band and thus achieve a transfer characteristic with low loss. Consequently, while suppressing transfer loss of radio-frequency signals flowing through the main line20over a wider frequency band, the directional coupler10can obtain a detected signal in a desired frequency band.

With this configuration, the coupling capacitance of the sub-line31side to the main line20can be changed by turning the switch SW91into the shorted state. It is not easy to change the degree of coupling between the sub-line31not outputting a detected signal and the main line20in a physical manner. When the main line20and the sub-line31are formed at the same insulating substrate, changing the degree of coupling is more difficult. However, by using this configuration, the coupling capacitance of the sub-line31side to the main line20can be changed without changing, for example, the physical positional relationship between the main line20and the sub-line31.

(1-2) Mode for Outputting Detected Signal Communicated from End Portion321Side to End Portion322Side of Sub-line32from Coupling Terminal Pcp

FIG.5is a state diagram illustrating a second connection configuration of the directional coupler according to the first embodiment.

The switches SW22and SW23of the switching circuit42are in the shorted state. The switches SW21and SW24of the switching circuit42are in the open state. As a result, the end portion322of the sub-line32is coupled to the coupling terminal Pcpbut not coupled to the termination circuit80. The end portion321of the sub-line32is coupled to the termination circuit80but not coupled to the coupling terminal Pcp. The switch SW92is in the open state.

The switches SW11, SW12, SW13, and SW14of the switching circuit41are in the open state.

With this configuration, the directional coupler10outputs from the coupling terminal Pcpa detected signal induced in the sub-line32and communicated from the end portion321side to the end portion322side. At this time, a detected signal induced in the sub-line32and communicated from the end portion321side to the end portion322side is a signal corresponding to a radio-frequency signal communicated from the input-output terminal P22side to the input-output terminal P21side in the main line20(a reflected signal of a radio-frequency signal communicated from the input-output terminal P21side to the input-output terminal P22side in the main line20).

At this time, the switch SW91is in the shorted state. As a result, the end portions311and312of the sub-line31are coupled to each other. By implementing this configuration, similarly to the mode (1-1), it is possible to suppress significant degradation of the transfer characteristic of the main line20over a wider frequency band and thus achieve a transfer characteristic with low loss.

The directional coupler10switches between the mode (1-1) and the mode (1-2). As a result, the directional coupler10can output from the coupling terminal Pcpa detected current flowing through the sub-line32in any direction. In other words, the directional coupler10can output detected signals of both a radio-frequency signal communicated from the input-output terminal P21to the input-output terminal P22in the main line20and a radio-frequency signal communicated from the input-output terminal P22to the input-output terminal P21in the main line20of a frequency band detectable in the sub-line32. At the same time, as described above, the directional coupler10can achieve a transfer characteristic with low loss over a wide frequency band.

(1-3) Mode for Outputting Detected Signal Communicated from End Portion312Side to End Portion311Side of Sub-line31from the Coupling Terminal Pcp

FIG.6is a state diagram illustrating a third connection configuration of the directional coupler according to the first embodiment.

The switches SW11and SW14of the switching circuit41are in the shorted state. The switches SW12and SW13of the switching circuit41are in the open state. As a result, the end portion311of the sub-line31is coupled to the coupling terminal Pcpbut not coupled to the termination circuit80. The end portion312of the sub-line31is coupled to the termination circuit80but not coupled to the coupling terminal Pcp. The switch SW91is in the open state.

The switches SW21, SW22, SW23, and SW24of the switching circuit42are in the open state.

With this configuration, the directional coupler10outputs from the coupling terminal Pcpa detected signal induced in the sub-line31and communicated from the end portion312side to the end portion311side. At this time, a detected signal induced in the sub-line31and communicated from the end portion312side to the end portion311side is a signal corresponding to a radio-frequency signal communicated from the input-output terminal P21side to the input-output terminal P22side in the main line20.

At this time, the switch SW92is in the shorted state. As a result, the end portions321and322of the sub-line32are coupled to each other. By implementing this configuration, similarly to the modes (1-1) and (1-2), it is possible to suppress significant degradation of the transfer characteristic of the main line20over a wider frequency band and thus achieve a transfer characteristic with low loss.

(1-4) Mode for Outputting Detected Signal Communicated from end portion311Side to end Portion312side of Sub-line31from the Coupling Terminal Pcp

FIG.7is a state diagram illustrating a fourth connection configuration of the directional coupler according to the first embodiment.

The switches SW12and SW13of the switching circuit41are in the shorted state. The switches SW11and SW14of the switching circuit41are in the open state. As a result, the end portion312of the sub-line31is coupled to the coupling terminal Pcpbut not coupled to the termination circuit80. The end portion311of the sub-line31is coupled to the termination circuit80but not coupled to the coupling terminal Pcp. The switch SW91is in the open state.

The switches SW21, SW22, SW23, and SW24of the switching circuit42are in the open state.

With this configuration, the directional coupler10outputs from the coupling terminal Pcpa detected signal induced in the sub-line31and communicated from the end portion311side to the end portion312side. At this time, a detected signal induced in the sub-line31and communicated from the end portion311side to the end portion312side is a signal corresponding to a radio-frequency signal communicated from the input-output terminal P22side to the input-output terminal P21side in the main line20(a reflected signal of a radio-frequency signal communicated from the input-output terminal P21side to the input-output terminal P22side in the main line20).

At this time, the switch SW92is in the shorted state. As a result, the end portions321and322of the sub-line32are coupled to each other. By implementing this configuration, similarly to the modes (1-1), (1-2), and (1-3), it is possible to suppress significant degradation of the transfer characteristic of the main line20over a wider frequency band and thus achieve a transfer characteristic with low loss.

The directional coupler10switches between the mode (1-3) and the mode (1-4). As a result, the directional coupler10can output from the coupling terminal Pcpa detected current flowing through the sub-line31in any direction. In other words, the directional coupler10can output detected signals of both a radio-frequency signal communicated from the input-output terminal P21to the input-output terminal P22in the main line20and a radio-frequency signal communicated from the input-output terminal P22to the input-output terminal P21in the main line20of a frequency band detectable in the sub-line31. At the same time, as described above, the directional coupler10can achieve a transfer characteristic with low loss over a wide frequency band.

Further, the directional coupler10switches among the modes (1-1), (1-2), (1-3), and (1-4). As a result, the directional coupler10can obtain bidirectional detected signals in the plurality of sub-lines31and32from the main line20and output the bidirectional detected signals from the coupling terminal Pcp.

As described above, the sub-lines31and32differ from each other in the frequency band of detected signal. Thus, the directional coupler10can suppress degradation of the transfer characteristic of the main line20, while obtaining detected signals of a wider frequency bands.

Here, for example, it is assumed that the frequency bands detected in the sub-lines31and32are covered by a single sub-line. In this case, the degree of coupling cannot constantly reach close to a desired value over a wide frequency band. Specifically, the amount of coupling between the main line and the sub-line can be greater or smaller than a desired value at particular frequencies; otherwise, the amount of coupling between the main line and the sub-line can be relatively small over the entire detected frequency band.

However, the directional coupler10uses the plurality of sub-lines31and32covering different frequencies. As a result, the directional coupler10constantly reaches close to a desired value with respect to the degree of coupling over a wide frequency band that cannot be covered by a single sub-line.

At this time, increasing the number of sub-lines increases the coupling capacitance to the main line20; and due to the effect of parallel resonance of the sub-lines and the main line20, as described above, transfer loss of the main line20can increase at a particular frequency. However, in the directional coupler10, as described above, the coupling capacitance is changed by making both ends of the sub-line not used to output detected signals shorted, and this shifts the frequency at which transfer loss of the main line20is degraded. As a result, the directional coupler10can reduce transfer loss of the main line20, while constantly reaching a desired value or greater with respect to the degree of coupling over a wide frequency band.

Second Embodiment

A directional coupler according to a second embodiment of the present invention will be described with reference to the drawings.FIG.8is a configuration diagram of the directional coupler according to the second embodiment.

A directional coupler10A according to the second embodiment differs from the directional coupler10according to the first embodiment in that switching circuits41A and42A are included and the switches SW91and SW92are physically removed. Basically, in the directional coupler10A, the switching circuit41A additionally implements the function of the switch SW91, and the switching circuit42A additionally implements the function of the switch SW92. Other configurations of the directional coupler10A are the same as the directional coupler10, and descriptions of the same configurations are not repeated.

The switching circuit41A includes the switches SW11, SW12, SW13, and SW14. The switch SW11is coupled between the end portion311of the sub-line31and the coupling terminal Pcp. The switch SW11switches connection of the end portion311and the coupling terminal Pcpbetween the shorted state and the open state. The switch SW12is coupled between the end portion312of the sub-line31and the coupling terminal Pcp. The switch SW12switches connection of the end portion312and the coupling terminal Pcpbetween the shorted state and the open state. The switch SW13is coupled between the end portion311of the sub-line31and the termination circuit80. The switch SW13switches connection of the end portion311and the termination circuit80between the shorted state and the open state. The switch SW14is coupled between the end portion312of the sub-line31and the termination circuit80. The switch SW14switches connection of the end portion312and the termination circuit80between the shorted state and the open state.

A coupling terminal Pcpside of the switch SW11and a coupling terminal Pcpside of the switch SW12are coupled to each other. A termination circuit80side of the switch SW13and a termination circuit80side of the switch SW14are coupled. When the sub-line31is the “first sub-line”, the switches SW11, SW12, SW13, and SW14respectively correspond to the “first switch”, the “second switch”, the “third switch”, and the “fourth switch” of the present invention.

The switching circuit42A includes the switches SW21, SW22, SW23, and SW24. The switch SW21is coupled between the end portion321of the sub-line32and the coupling terminal Pcp. The switch SW21switches connection of the end portion321and the coupling terminal Pcpbetween the shorted state and the open state. The switch SW22is coupled between the end portion322of the sub-line31and the coupling terminal Pcp. The switch SW22switches connection of the end portion322and the coupling terminal Pcpbetween the shorted state and the open state. The switch SW23is coupled between the end portion321of the sub-line32and the termination circuit80. The switch SW23switches connection of the end portion321and the termination circuit80between the shorted state and the open state. The switch SW24is coupled between the end portion322of the sub-line32and the termination circuit80. The switch SW24switches connection of the end portion322and the termination circuit80between the shorted state and the open state.

A coupling terminal Pcpside of the switch SW21and a coupling terminal Pcpside of the switch SW22are coupled to each other. A termination circuit80side of the switch SW23and a termination circuit80side of the switch SW24are coupled. When the sub-line32is the “first sub-line”, the switches SW21, SW22, SW23, and SW24respectively correspond to the “first switch”, the “second switch”, the “third switch”, and the “fourth switch” of the present invention.

Connection Configuration of Directional Coupler10A

The directional coupler10A configured as described above outputs a detected signal corresponding to a radio-frequency signal communicated through the main line20from the coupling terminal Pcpalong various connection configurations described below.

(2-1) Configuration in Which Both Ends of Sub-line are Shorted by Controlling Switch Coupled to Coupling Terminal Pcp

FIG.9is a state diagram illustrating a first connection configuration of the directional coupler according to the second embodiment.FIG.9indicates a configuration for outputting a detected signal communicated from the end portion322side to the end portion321side of the sub-line32from the coupling terminal Pcp.

As illustrated inFIG.9, the switches SW21and SW24of the switching circuit42A are in the shorted state. The switches SW22and SW23of the switching circuit42A are in the open state. As a result, the end portion321of the sub-line32is coupled to the coupling terminal Pcpbut not coupled to the termination circuit80. The end portion322of the sub-line32is coupled to the termination circuit80but not coupled to the coupling terminal Pcp.

With this configuration, the directional coupler10A outputs from the coupling terminal Pcpa detected signal induced in the sub-line32and communicated from the end portion322side to the end portion321side.

The switches SW11and SW12of the switching circuit41A are in the shorted state. The switches SW13and SW14of the switching circuit41A are in the open state.

With this configuration, the end portions311and312of the sub-line31are coupled. This means that a circuit similar to the circuit in which the switch SW91is in the shorted state in the first embodiment (which corresponds to the mode (1-1) of the first embodiment) is formed.

Similarly, the mode for outputting a detected signal communicated from the end portion321side to the end portion322side of the sub-line32from the coupling terminal Pcp(which corresponds to the mode (1-2) of the first embodiment), the mode for outputting a detected signal communicated from the end portion312side to the end portion311side of the sub-line31from the coupling terminal Pcp(which corresponds to the mode (1-3) of the first embodiment), and the mode for outputting a detected signal communicated from the end portion311side to the end portion312side of the sub-line31from the coupling terminal Pcp(which corresponds to the mode (1-4) of the first embodiment) are formed by making both ends of the sub-line31or both ends of the sub-line32shorted using the switching circuit41A or42A, but detailed descriptions and illustrations thereof are omitted.

As a result, the directional coupler10A can reduce transfer loss of the main line20, while constantly reaching close to a desired value with respect to the degree of coupling over a wide frequency band.

Further, the directional coupler10A eliminates switches for controlling the shorted state of both ends of a corresponding sub-line not used for detection, thereby reducing the circuit size. Furthermore, the number of switches coupled to sub-lines but not used directly to switch outputs of detected signals is decreased. As a result, the degree of coupling in a desired frequency band is increased, and the effect of reducing transfer loss of the main line20is improved.

In the mode (2-1), the sub-line with ends shorted is not coupled to the termination circuit80. With this configuration, the directional coupler10A can inhibit adverse effects caused because the termination circuit80is coupled to the sub-line with ends shorted, such as power leakage to the termination circuit80, and thus, desired characteristics are easily achieved.

(2-2) Configuration in Which Both Ends of Sub-line are Shorted by Controlling Switch Coupled to Termination Circuit80

FIG.10is a state diagram illustrating a second connection configuration of the directional coupler according to the second embodiment. Similarly toFIG.9,FIG.10indicates a configuration for outputting a detected signal communicated from the end portion322side to the end portion321side of the sub-line32from the coupling terminal Pcp.

As illustrated inFIG.10, the switches SW21and SW24of the switching circuit42A are in the shorted state. The switches SW22and SW23of the switching circuit42A are in the open state. As a result, the end portion321of the sub-line32is coupled to the coupling terminal Pcpbut not coupled to the termination circuit80. The end portion322of the sub-line32is coupled to the termination circuit80but not coupled to the coupling terminal Pcp.

With this configuration, the directional coupler10outputs from the coupling terminal Pcpa detected signal induced in the sub-line32and communicated from the end portion322side to the end portion321side.

The switches SW13and SW14of the switching circuit41A are in the shorted state. The switches SW11and SW12of the switching circuit41A are in the open state.

With this configuration, the end portions311and312of the sub-line31are coupled. This means that a circuit similar to the circuit in which the switch SW91is in the shorted state in the first embodiment (which corresponds to the mode (1-1) of the first embodiment) is formed.

Similarly, the mode for outputting a detected signal communicated from the end portion321side to the end portion322side of the sub-line32from the coupling terminal Pcp(which corresponds to the mode (1-2) of the first embodiment), the mode for outputting a detected signal communicated from the end portion312side to the end portion311side of the sub-line31from the coupling terminal Pcp(which corresponds to the mode (1-3) of the first embodiment), and the mode for outputting a detected signal communicated from the end portion311side to the end portion312side of the sub-line31from the coupling terminal Pcp(which corresponds to the mode (1-4) of the first embodiment) are formed by making both ends of the sub-line31or both ends of the sub-line32shorted using the switching circuit41A or42A, but detailed descriptions and illustrations thereof are omitted.

As such, with the mode (2-2), the directional coupler10A can achieve the same effects and advantages as the mode (2-1) described above.

In the mode (2-2), the sub-line with ends shorted is not coupled to the coupling terminal Pcp. With this configuration, the directional coupler10A can inhibit adverse effects caused because the coupling terminal Pcpis coupled to the sub-line with ends shorted, such as power leakage to the coupling terminal Pcp, and adverse effects caused by other circuits coupled to the coupling terminal Pcp, and thus, desired characteristics are easily achieved. Further, in the mode (2-2), the sub-line with ends shorted is not coupled to the coupling terminal Pcp, and thus, impedance matching between the sub-line outputting a detected signal and the coupling terminal Pcpis more effectively provided.

Third Embodiment

A directional coupler according to a third embodiment of the present invention will be described with reference to the drawings.FIG.11is a configuration diagram of the directional coupler according to the third embodiment.

A directional coupler10B according to the third embodiment differs from the directional coupler10A according to the second embodiment in that a switching circuit491is added. Other configurations of the directional coupler10B are the same as the directional coupler10A, and descriptions of the same configurations are not repeated.

The switching circuit491is coupled between switching circuits41B and42B and the coupling terminal Pcp. The switching circuit41B is configured in the same manner as the switching circuit41A. The switching circuit42B is configured in the same manner as the switching circuit42A. The switching circuit491functions as a part of the “second switching circuit” of the present invention.

More specifically, the switching circuit491includes switches SW41and SW42. When the sub-line31is the “first sub-line”, the switch SW41corresponds to a “fifth switch” of the present invention. When the sub-line32is the “first sub-line”, the switch SW42corresponds to the “fifth switch” of the present invention.

The switch SW41is coupled between the switches SW11and SW12of the switching circuit41B and the coupling terminal Pcp. The switch SW41switches connection of the switches SW11and SW12and the coupling terminal Pcpbetween the shorted state and the open state. The switch SW42is coupled between the switches SW21and SW22of the switching circuit42B and the coupling terminal Pcp. The switch SW42switches connection of the switches SW21and SW22and the coupling terminal Pcpbetween the shorted state and the open state.

Connection Configuration of Directional Coupler10B

The directional coupler10B configured as described above outputs a detected signal corresponding to a radio-frequency signal communicated through the main line20from the coupling terminal Pcpalong various connection configurations described below.

(3-1) Configuration for Outputting Detected Signal communicated from End Portion322Side to End Portion321Side of Sub-line32from Coupling Terminal Pcp

FIG.12is a state diagram illustrating a first connection configuration of the directional coupler according to the third embodiment.

As illustrated inFIG.12, the switches SW21and SW24of the switching circuit42B are in the shorted state. The switches SW22and SW23of the switching circuit42B are in the open state. As a result, the end portion321of the sub-line32is coupled to the switch SW42of the switching circuit491but not coupled to the termination circuit80. The end portion322of the sub-line32is coupled to the termination circuit80but not coupled to the coupling terminal Pcp.

The switch SW42of the switching circuit491is in the shorted state. As a result, the end portion321of the sub-line32is coupled to the coupling terminal Pcpvia the switches SW21and SW42.

With this configuration, the directional coupler10B outputs from the coupling terminal Pcpa detected signal induced in the sub-line32and communicated from the end portion322side to the end portion321side.

The switches SW11and SW12of the switching circuit41B are in the shorted state. The switches SW13and SW14of the switching circuit41B are in the open state.

With this configuration, the end portions311and312of the sub-line31are coupled. This means that a circuit similar to the circuit in which the switch SW91is in the shorted state in the first embodiment (which corresponds to the mode (1-1) of the first embodiment) is formed.

The switch SW41of the switching circuit491is in the open state. As a result, the switches SW11and SW12of the switching circuit41B and also the sub-line31are not coupled to the coupling terminal Pcp.

Similarly, in the mode for outputting a detected signal communicated from the end portion321side to the end portion322side of the sub-line32from the coupling terminal Pcp(which corresponds to the mode (1-2) of the first embodiment), the end portions311and312of the sub-line31are coupled, but detailed descriptions and illustrations thereof are omitted.

As a result, the directional coupler10B can reduce transfer loss of the main line20, while constantly reaching a desired value or greater with respect to the degree of coupling over a wide frequency band.

In the mode (3-1), the sub-line31with ends shorted is not coupled to the coupling terminal Pcp. With this configuration, the directional coupler10B can inhibit adverse effects caused because the coupling terminal Pcpis coupled to the sub-line31with ends shorted, such as power leakage to the coupling terminal Pcp, and adverse effects caused by other circuits coupled to the coupling terminal Pcp, and thus, desired characteristics are easily achieved. Further, in the mode (3-1), the sub-line31with ends shorted is not coupled to the coupling terminal Pcp, and thus, impedance matching between the sub-line32outputting a detected signal and the coupling terminal Pcpis more effectively provided.

(3-2) Configuration for Outputting Detected Signal Communicated from End Portion312Side to End Portion311Side of Sub-line31from Coupling Terminal Pcp

FIG.13is a state diagram illustrating a second connection configuration of the directional coupler according to the third embodiment.

As illustrated inFIG.13, the switches SW11and SW14of the switching circuit41B are in the shorted state. The switches SW12and SW13of the switching circuit41B are in the open state. As a result, the end portion311of the sub-line31is coupled to the switch SW41of the switching circuit491but not coupled to the termination circuit80. The end portion312of the sub-line31is coupled to the termination circuit80but not coupled to the coupling terminal Pcp.

The switch SW41of the switching circuit491is in the shorted state. As a result, the end portion311of the sub-line31is coupled to the coupling terminal Pcpvia the switches SW11and SW41.

With this configuration, the directional coupler10B outputs from the coupling terminal Pcpa detected signal induced in the sub-line31and communicated from the end portion312side to the end portion311side.

The switches SW21and SW22of the switching circuit42B are in the shorted state. The switches SW23and SW24of the switching circuit42B are in the open state.

With this configuration, the end portions321and322of the sub-line32are coupled. This means that a circuit similar to the circuit in which the switch SW92is in the shorted state in the first embodiment (which corresponds to the mode (1-3) of the first embodiment) is formed.

The switch SW42of the switching circuit491is in the open state. As a result, the switches SW21and SW22of the switching circuit42B and also the sub-line32are not coupled to the coupling terminal Pcp.

Similarly, in the mode for outputting a detected signal communicated from the end portion311side to the end portion312side of the sub-line31from the coupling terminal Pcp(which corresponds to the mode (1-4) of the first embodiment), the end portions321and322of the sub-line32are coupled, but detailed descriptions and illustrations thereof are omitted.

As a result, the directional coupler10B can reduce transfer loss of the main line20, while constantly reaching a desired value or greater with respect to the degree of coupling over a wide frequency band.

In the mode (3-2), the sub-line32with ends shorted is not coupled to the coupling terminal Pcp. With this configuration, the directional coupler10B can inhibit adverse effects caused because the coupling terminal Pcpis coupled to the sub-line32with ends shorted, such as power leakage to the coupling terminal Pcp, and adverse effects caused by other circuits coupled to the coupling terminal Pcp, and thus, desired characteristics are easily achieved. Further, in the mode (3-2), the sub-line32with ends shorted is not coupled to the coupling terminal Pcp, and thus, impedance matching between the sub-line31outputting a detected signal and the coupling terminal Pcpis more effectively provided.

Fourth Embodiment

A directional coupler according to a fourth embodiment of the present invention will be described with reference to the drawings.FIG.14is a configuration diagram of the directional coupler according to the fourth embodiment.

A directional coupler10C according to the fourth embodiment differs from the directional coupler10A according to the second embodiment in that a switching circuit492is added. Other configurations of the directional coupler10C are the same as the directional coupler10A, and descriptions of the same configurations are not repeated.

The switching circuit492is coupled between switching circuits41C and42C and the termination circuit80. The switching circuit41C is configured in the same manner as the switching circuit41A. The switching circuit42C is configured in the same manner as the switching circuit42A. The switching circuit492functions as a part of the “second switching circuit” of the present invention.

More specifically, the switching circuit492includes switches SW43and SW44. When the sub-line31is the “first sub-line”, the switch SW43corresponds to a “sixth switch” of the present invention. When the sub-line32is the “first sub-line”, the switch SW44corresponds to the “sixth switch” of the present invention.

The switch SW43is coupled between the switches SW13and SW14of the switching circuit41C and the termination circuit80. The switch SW43switches connection of the switches SW13and SW14and the termination circuit80between the shorted state and the open state. The switch SW44is coupled between the switches SW23and SW24of the switching circuit42C and the termination circuit80. The switch SW44switches connection of the switches SW23and SW24and the termination circuit80between the shorted state and the open state.

(4-1) Configuration for Outputting Detected Signal Communicated from End Portion322Side to End Portion321Side of Sub-line32from Coupling Terminal Pcp

FIG.15is a state diagram illustrating a first connection configuration of the directional coupler according to the fourth embodiment.

As illustrated inFIG.15, the switches SW21and SW24of the switching circuit42C are in the shorted state. The switches SW22and SW23of the switching circuit42C are in the open state. As a result, the end portion321of the sub-line32is coupled to the coupling terminal Pcpbut not coupled to the switch SW44of the switching circuit492. The end portion322of the sub-line32is coupled to the switch SW44of the switching circuit492but not coupled to the coupling terminal Pcp.

The switch SW44of the switching circuit492is in the shorted state. As a result, the end portion322of the sub-line32is coupled to the termination circuit80via the switches SW24and SW44.

With this configuration, the directional coupler10C outputs from the coupling terminal Pcpa detected signal induced in the sub-line32and communicated from the end portion322side to the end portion321side.

The switches SW13and SW14of the switching circuit41C are in the shorted state.

With this configuration, the end portions311and312of the sub-line31are coupled. This means that a circuit similar to the circuit in which the switch SW91is in the shorted state in the first embodiment (which corresponds to the mode (1-1) of the first embodiment) is formed.

The switch SW43of the switching circuit492is in the open state. As a result, the switches SW13and SW14of the switching circuit41C and also the sub-line31are not coupled to the termination circuit80.

Also, the switches SW11and SW12of the switching circuit41C are in the open state. As a result, the sub-line31is not coupled to the coupling terminal Pcp.

Similarly, in the mode for outputting a detected signal communicated from the end portion321side to the end portion322side of the sub-line32from the coupling terminal Pcp(which corresponds to the mode (1-2) of the first embodiment), the end portions311and312of the sub-line31are coupled, but detailed descriptions and illustrations thereof are omitted.

As a result, the directional coupler10C can reduce transfer loss of the main line20, while constantly reaching a desired value or greater with respect to the degree of coupling over a wide frequency band.

In the mode (4-1), the sub-line31with ends shorted is not coupled to the termination circuit80. With this configuration, the directional coupler10C can inhibit adverse effects caused because the termination circuit80is coupled to the sub-line31with ends shorted, such as power leakage to the termination circuit80, and thus, desired characteristics are easily achieved.

(4-2) Configuration for Outputting Detected Signal Communicated from End Portion312Side to End Portion311Side of Sub-line31from Coupling Terminal Pcp

FIG.16is a state diagram illustrating a second connection configuration of the directional coupler according to the fourth embodiment.

As illustrated inFIG.16, the switches SW11and SW14of the switching circuit41C are in the shorted state. The switches SW12and SW13of the switching circuit41C are in the open state. As a result, the end portion311of the sub-line31is coupled to the coupling terminal Pcpbut not coupled to the termination circuit80. The end portion312of the sub-line31is coupled to the switch SW43of the switching circuit492but not coupled to the coupling terminal Pcp.

The switch SW43of the switching circuit492is in the shorted state. As a result, the end portion312of the sub-line31is coupled to the termination circuit80via the switches SW14and SW43.

With this configuration, the directional coupler10C outputs from the coupling terminal Pcpa detected signal induced in the sub-line31and communicated from the end portion312side to the end portion311side.

The switches SW23and SW24of the switching circuit42C are in the shorted state. With this configuration, the end portions321and322of the sub-line32are coupled. This means that a circuit similar to the circuit in which the switch SW92is in the shorted state in the first embodiment (which corresponds to the mode (1-3) of the first embodiment) is formed.

The switch SW44of the switching circuit492is in the open state. As a result, the switches SW23and SW24of the switching circuit42C and also the sub-line32are not coupled to the termination circuit80.

Also, the switches SW21and SW22of the switching circuit42C are in the open state. As a result, the sub-line32is not coupled to the coupling terminal Pcp.

Similarly, in the mode for outputting a detected signal communicated from the end portion311side to the end portion312side of the sub-line31from the coupling terminal Pcp(which corresponds to the mode (1-4) of the first embodiment), the end portions321and322of the sub-line32are coupled, but detailed descriptions and illustrations thereof are omitted.

As a result, the directional coupler10C can reduce transfer loss of the main line20, while constantly reaching a desired value or greater with respect to the degree of coupling over a wide frequency band.

In the mode (4-2), the sub-line32with ends shorted is not coupled to the termination circuit80. With this configuration, the directional coupler10C can inhibit adverse effects caused because the termination circuit80is coupled to the sub-line32with ends shorted, such as power leakage to the termination circuit80, and thus, desired characteristics are easily achieved. Further, in the mode (4-2), the sub-line32with ends shorted is not coupled to the coupling terminal Pcp, and thus, impedance matching between the sub-line31outputting a detected signal and the coupling terminal Pcpis more effectively provided.

Fifth Embodiment

A directional coupler according to a fifth embodiment of the present invention will be described with reference to the drawings.FIG.17is a configuration diagram of the directional coupler according to the fifth embodiment.

A directional coupler10D according to the fifth embodiment differs from the directional coupler10C according to the fourth embodiment in that the switching circuit492including the switches SW43and SW44, which correspond to the “sixth switch” of the present invention, is removed, and termination circuits are provided for the respective sub-lines. Other configurations of the directional coupler10D are the same as the directional coupler10C, and descriptions of the same configurations are not repeated.

As illustrated inFIG.17, the directional coupler 10D includes switching circuits41D and42D and termination circuits81and82. The switching circuit41D is configured in the same manner as the switching circuit41C. The switching circuit42D is configured in the same manner as the switching circuit42C.

The termination circuit81is coupled to the switching circuit41D. More specifically, the termination circuit81is coupled to the switches SW13and SW14of the switching circuit41D. The termination circuit81includes a variable resistor Rt1and a variable capacitor Ct1. A parallel circuit of the variable resistor Rt1and the variable capacitor Ct1couples the switches SW13and SW14to a reference potential. The termination circuit81is configured to achieve impedance matching in a frequency band of radio-frequency signal detected in the sub-line31.

The termination circuit82is coupled to the switching circuit42D. More specifically, the termination circuit82is coupled to the switches SW23and SW24of the switching circuit42D. The termination circuit82includes a variable resistor Rt2and a variable capacitor Ct2. A parallel circuit of the variable resistor Rt2and the variable capacitor Ct2couples the switches SW23and SW24to a reference potential. The termination circuit82is configured to achieve impedance matching in a frequency band of radio-frequency signal detected in the sub-line32.

(5-1) Configuration for Outputting Detected Signal Communicated from End Portion322Side to End Portion321Side of Sub-line32from Coupling Terminal Pcp

FIG.18is a state diagram illustrating a first connection configuration of the directional coupler according to the fifth embodiment.

As illustrated inFIG.18, the switches SW21and SW24of the switching circuit42D are in the shorted state. The switches SW22and SW23of the switching circuit42D are in the open state. As a result, the end portion321of the sub-line32is coupled to the coupling terminal Pcpbut not coupled to the termination circuit82. The end portion322of the sub-line32is coupled to the termination circuit82but not coupled to the coupling terminal Pcp.

With this configuration, the directional coupler 10D outputs from the coupling terminal Pcpa detected signal induced in the sub-line32and communicated from the end portion322side to the end portion321side.

The switches SW13and SW14of the switching circuit41D are in the shorted state.

With this configuration, the end portions311and312of the sub-line31are coupled. This means that a circuit similar to the circuit in which the switch SW91is in the shorted state in the first embodiment (which corresponds to the mode (1-1) of the first embodiment) is formed.

Similarly, in the mode for outputting a detected signal communicated from the end portion321side to the end portion322side of the sub-line32from the coupling terminal Pcp(which corresponds to the mode (1-2) of the first embodiment), the end portions311and312of the sub-line31are coupled, but detailed descriptions and illustrations thereof are omitted.

As a result, the directional coupler10D can reduce transfer loss of the main line20, while constantly reaching a desired value or greater with respect to the degree of coupling over a wide frequency band.

In the mode (5-1), the sub-line31with ends shorted is not coupled to the circuit on the sub-line32side. With this configuration, the directional coupler10D can inhibit adverse effects caused because the circuit on the sub-line32side is coupled to the sub-line31with ends shorted, and thus, desired characteristics are easily achieved.

Further, because the termination circuit82handling only the sub-line32is provided, it is possible to more effectively provide impedance matching of detected signals in the sub-line32without increasing the circuit size.

(5-2) Configuration for Outputting Detected Signal Communicated from End Portion312Side to End Portion311Side of Sub-line31from Coupling Terminal Pcp

FIG.19is a state diagram illustrating a second connection configuration of the directional coupler according to the fifth embodiment.

As illustrated inFIG.19, the switches SW11and SW14of the switching circuit41D are in the shorted state. The switches SW12and SW13of the switching circuit41D are in the open state. As a result, the end portion311of the sub-line31is coupled to the coupling terminal Pcpbut not coupled to the termination circuit81. The end portion312of the sub-line31is coupled to the termination circuit81but not coupled to the coupling terminal Pcp.

With this configuration, the directional coupler10D outputs from the coupling terminal Pcpa detected signal induced in the sub-line31and communicated from the end portion312side to the end portion311side.

The switches SW23and SW24of the switching circuit42D are in the shorted state. With this configuration, the end portions321and322of the sub-line32are coupled. This means that a circuit similar to the circuit in which the switch SW92is in the shorted state in the first embodiment (which corresponds to the mode (1-3) of the first embodiment) is formed.

Also, the switches SW21and SW22of the switching circuit42D are in the open state. As a result, the sub-line32is not coupled to the coupling terminal Pcp.

Similarly, in the mode for outputting a detected signal communicated from the end portion311side to the end portion312side of the sub-line31from the coupling terminal Pcp(which corresponds to the mode (1-4) of the first embodiment), the end portions321and322of the sub-line32are coupled, but detailed descriptions and illustrations thereof are omitted.

As a result, the directional coupler10D can reduce transfer loss of the main line20, while constantly reaching close to a desired value with respect to the degree of coupling over a wide frequency band.

In the mode (5-2), the sub-line32with ends shorted is not coupled to the circuit on the sub-line31side. With this configuration, the directional coupler10D can inhibit adverse effects caused because the circuit on the sub-line31side is coupled to the sub-line32with ends shorted, and thus, desired characteristics are easily achieved.

Further, because the termination circuit81handling only the sub-line31is provided, it is possible to more effectively provide impedance matching of detected signals in the sub-line31without increasing the circuit size.

Further, the directional coupler10D includes the termination circuit81for the sub-line31and the termination circuit82for the sub-line32in an individual manner. With this configuration, impedance matching can be provided individually for the frequency band detected in the sub-line31and the frequency band detected in the sub-line32. As a result, without increasing the circuit size, the directional coupler10D can output detected signals of a wide frequency band with lower loss. Furthermore, with this configuration, the directional coupler10D inhibits adverse effects of the sub-lines31and32on the main line20effectively in an individual manner, thereby further suppressing degradation of the transfer characteristic of the main line20.

Sixth Embodiment

A directional coupler according to a sixth embodiment of the present invention will be described with reference to the drawings.FIG.20is a configuration diagram of the directional coupler according to the sixth embodiment.

A directional coupler10E according to the sixth embodiment differs from the directional coupler10A according to the second embodiment in that a coupling terminal is provided for each sub-line.

Other configurations of the directional coupler10E are the same as the directional coupler10A, and descriptions of the same configurations are not repeated.

As illustrated inFIG.20, the directional coupler10E includes switching circuits41E and42E and coupling terminals Pcp1and Pcp2.

The switching circuit41E is configured in the same manner as the switching circuit41A. The switching circuit42E is configured in the same manner as the switching circuit42A. In the directional coupler10E, no switch corresponds to the “fifth switch” of the present invention.

The coupling terminal Pcp1is coupled to the switching circuit41E. More specifically, the coupling terminal Pcp1is coupled to the switches SW11and W12.

The coupling terminal Pcp2is coupled to the switching circuit42E. More specifically, the coupling terminal Pcp2is coupled to the switches SW21and W22.

(6-1) Configuration for Outputting Detected Signal Communicated from End Portion322Side to End Portion321Side of Sub-line32from Coupling Terminal Pcp2

FIG.21is a state diagram illustrating a first connection configuration of the directional coupler according to the sixth embodiment.

As illustrated inFIG.21, the switches SW21and SW24of the switching circuit42E are in the shorted state. The switches SW22and SW23of the switching circuit42E are in the open state. As a result, the end portion321of the sub-line32is coupled to the coupling terminal Pcp2but not coupled to the termination circuit80. The end portion322of the sub-line32is coupled to the termination circuit80but not coupled to the coupling terminal Pcp2.

With this configuration, the directional coupler10E outputs from the coupling terminal Pcp2a detected signal induced in the sub-line32and communicated from the end portion322side to the end portion321side.

The switches SW11and SW12of the switching circuit41E are in the shorted state.

With this configuration, the end portions311and312of the sub-line31are coupled. This means that a circuit similar to the circuit in which the switch SW91is in the shorted state in the first embodiment (which corresponds to the mode (1-1) of the first embodiment) is formed.

Similarly, in the mode for outputting a detected signal communicated from the end portion321side to the end portion322side of the sub-line32from the coupling terminal Pcp2(which corresponds to the mode (1-2) of the first embodiment), the end portions311and312of the sub-line31are coupled, but detailed descriptions and illustrations thereof are omitted.

As a result, the directional coupler10E can reduce transfer loss of the main line20, while constantly reaching a desired value or greater with respect to the degree of coupling over a wide frequency band.

In the mode (6-1), the sub-line31with ends shorted is not coupled to the circuit on the sub-line32side. With this configuration, the directional coupler10E can inhibit adverse effects caused because the circuit on the sub-line32side is coupled to the sub-line31with ends shorted, and thus, desired characteristics are easily achieved.

(6-2) Configuration for Outputting Detected Signal Communicated from the End Portion312Side to the End Portion311Side of the Sub-line31from Coupling Terminal Pcp1

FIG.22is a state diagram illustrating a second connection configuration of the directional coupler according to the sixth embodiment.

As illustrated inFIG.22, the switches SW11and SW14of the switching circuit41E are in the shorted state. The switches SW12and SW13of the switching circuit41E are in the open state. As a result, the end portion311of the sub-line31is coupled to the coupling terminal Pcp1but not coupled to the termination circuit80. The end portion312of the sub-line31is coupled to the termination circuit80but not coupled to the coupling terminal Pcp1.

With this configuration, the directional coupler10E outputs from the coupling terminal Pcp1a detected signal induced in the sub-line31and communicated from the end portion312side to the end portion311side.

The switches SW21and SW22of the switching circuit42E are in the shorted state. With this configuration, the end portions321and322of the sub-line32are coupled. This means that a circuit similar to the circuit in which the switch SW92is in the shorted state in the first embodiment (which corresponds to the mode (1-3) of the first embodiment) is formed.

Also, the switches SW23and SW24of the switching circuit42E are in the open state. As a result, the sub-line32is not coupled to the termination circuit80.

Similarly, in the mode for outputting a detected signal communicated from the end portion311side to the end portion312side of the sub-line31from the coupling terminal Pcp1(which corresponds to the mode (1-4) of the first embodiment), the end portions321and322of the sub-line32are coupled, but detailed descriptions and illustrations thereof are omitted.

As a result, the directional coupler10E can reduce transfer loss of the main line20, while constantly reaching a desired value or greater with respect to the degree of coupling over a wide frequency band.

In the mode (6-2), the sub-line32with ends shorted is not coupled to the circuit on the sub-line31side. With this configuration, the directional coupler10E can inhibit adverse effects caused because the circuit on the sub-line31side is coupled to the sub-line32with ends shorted, and thus, desired characteristics are easily achieved.

Seventh Embodiment

A directional coupler according to a seventh embodiment of the present invention will be described with reference to the drawings.FIG.23is a configuration diagram of the directional coupler according to the seventh embodiment.

A directional coupler10F according to the seventh embodiment differs from the directional coupler10D according to the fifth embodiment in that a coupling terminal is provided for each sub-line.

This means that the directional coupler10F has a configuration in which the termination-circuit-side configuration of the directional coupler10D and the coupling-terminal-side configuration of the directional coupler10E are combined together. Other configurations of the directional coupler10F are the same as the directional couplers10D and10E, and descriptions of the same configurations are not repeated. Similarly to the directional coupler10E according to the sixth embodiment, in the directional coupler10F, no switch corresponds to the “fifth switch” of the present invention.

The directional coupler10F includes switching circuits41F and42F, the coupling terminals Pcp1and Pcp2, and the termination circuits81and82. The switching circuit41F is configured in the same manner as the switching circuits41D and41E. The switching circuit42F is configured in the same manner as the switching circuits42D and42E.

The coupling terminal Pcp1and the termination circuit81are coupled to the switching circuit41F. More specifically, the coupling terminal Pcp1is coupled to the switches SW11and SW12of the switching circuit41F. The termination circuit81is coupled to the switches SW13and SW14of the switching circuit41F.

The coupling terminal Pcp2and the termination circuit82are coupled to the switching circuit42F. More specifically, the coupling terminal Pcp2is coupled to the switches SW21and SW22of the switching circuit42F. The termination circuit82is coupled to the switches SW23and SW24of the switching circuit42F.

With this configuration, the directional coupler10F can reduce transfer loss of the main line20, while constantly reaching close to a desired value with respect to the degree of coupling over a wide frequency band.

Eighth Embodiment

A directional coupler according to an eighth embodiment of the present invention will be described with reference to the drawings.FIG.24is a configuration diagram of the directional coupler according to the eighth embodiment.

A directional coupler10G according to the eighth embodiment differs from the directional coupler10according to the first embodiment in that a coupling terminal and a termination circuit are provided for each sub-line. Other configurations of the directional coupler10G are the same as the directional coupler10, and descriptions of the same configurations are not repeated.

The directional coupler10G includes the coupling terminals Pcp1and Pcp2and the termination circuits81and82.

The coupling terminal Pcp1and the termination circuit81are coupled to the switching circuit41. More specifically, the coupling terminal Pcp1is coupled to the switches SW11and SW12of the switching circuit41. The termination circuit81is coupled to the switches SW13and SW14of the switching circuit41.

The coupling terminal Pcp2and the termination circuit82are coupled to the switching circuit42. More specifically, the coupling terminal Pcp2is coupled to the switches SW21and SW22of the switching circuit42. The termination circuit82is coupled to the switches SW23and SW24of the switching circuit42.

With this configuration, the directional coupler10G can reduce transfer loss of the main line20, while constantly reaching close to a desired value with respect to the degree of coupling over a wide frequency band.

Ninth Embodiment

A directional coupler according to a ninth embodiment of the present invention will be described with reference to the drawings.FIG.25is a configuration diagram of the directional coupler according to the ninth embodiment.

A directional coupler10H according to the ninth embodiment has a configuration in which the directional couplers10B and10C according to the third and fourth embodiments are combined together. More specifically, the directional coupler10H includes the switching circuit491of the directional coupler10B and the switching circuit492of the directional coupler10C. Other configurations of the directional coupler10H are the same as the directional couplers10B and10C, and descriptions of the same configurations are not repeated.

The directional coupler10F includes switching circuits41H and42H and the switching circuits491and492. The switching circuit41H is configured in the same manner as the switching circuits41B and41C. The switching circuit42H is configured in the same manner as the switching circuits42B and42C.

The switching circuit491is coupled between the coupling terminal Pcpand the switching circuits41H and42H. The switching circuit492is coupled between the termination circuit80and the switching circuits41H and42H.

With this configuration, the directional coupler10F can reduce transfer loss of the main line20, while constantly reaching close to a desired value with respect to the degree of coupling over a wide frequency band.

Tenth Embodiment

A directional coupler according to a tenth embodiment of the present invention will be described with reference to the drawings.FIG.26is a configuration diagram of the directional coupler according to the tenth embodiment.

As illustrated inFIG.26, a directional coupler10I according to the tenth embodiment differs from the directional coupler10according to the first embodiment in that three sub-lines are included. Other configurations of the directional coupler10I are the same as the directional coupler10, and descriptions of the same configurations are not repeated.

The directional coupler10I includes a sub-line33, a switching circuit43, and a switch SW93.

The sub-line33is located at a position that enables the sub-line33to be electromagnetically coupled to the main line20. For example, the sub-line33is elongated in the direction along the main line20, spaced apart by a particular distance from the main line20. At this time, the shape of the sub-line33and the position of the sub-line33relative to the main line20are determined such that a desired degree of coupling with the main line20is achieved in a third frequency band.

The third frequency band does not completely coincide with the first and second frequency bands. In other words, the third frequency band is different from the second frequency band and the first frequency band. The third frequency band is, for example, a frequency band higher than the first frequency band and the second frequency band. The third frequency band may be a frequency band including 3.3 GHz and higher.

The sub-line33has an end portion331at one end in the length direction and an end portion332at the other end in the length direction. Two of the sub-lines31,32, and33correspond to the “first sub-line” of the present invention, and the other of the sub-lines31,32, and33corresponds to the “second sub-line” of the present invention. When the sub-line31is the first sub-line, the end portion311corresponds to the “first end” of the present invention, and the end portion312corresponds to the “second end” of the present invention. When the sub-line32is the first sub-line, the end portion321corresponds to the “first end” of the present invention, and the end portion322corresponds to the “second end” of the present invention. When the sub-line33is the first sub-line, the end portion331corresponds to the “first end” of the present invention, and the end portion332corresponds to the “second end” of the present invention.

The switching circuit43includes switches SW31, SW32, SW33, and SW34. The switch SW31is coupled between the end portion331of the sub-line33and the coupling terminal Pcp. The switch SW31switches connection of the end portion331and the coupling terminal Pcpbetween the shorted state and the open state. The switch SW32is coupled between the end portion332of the sub-line33and the coupling terminal Pcp. The switch SW32switches connection of the end portion332and the coupling terminal Pcpbetween the shorted state and the open state. The switch SW33is coupled between the end portion331of the sub-line33and the termination circuit80. The switch SW33switches connection of the end portion331and the termination circuit80between the shorted state and the open state. The switch SW34is coupled between the end portion332of the sub-line33and the termination circuit80. The switch SW34switches connection of the end portion332and the termination circuit80between the shorted state and the open state. The switching circuit43is a part of the “second switching circuit” of the present invention.

A coupling terminal Pcpside of the switch SW31and a coupling terminal Pcpside of the switch SW32are coupled. A termination circuit80side of the switch SW33and a termination circuit80side of the switch SW34are coupled. When the sub-line33is the “first sub-line”, the switches SW31, SW32, SW33, and SW34respectively correspond to the “first switch”, the “second switch”, the “third switch”, and the “fourth switch” of the present invention.

The switch SW93is coupled between the end portions331and332of the sub-line33. The switch SW93switches connection of the end portions331and332between the shorted state and the open state. When the sub-line33is the “first sub-line”, the switch SW93corresponds to the “first switching circuit” of the present invention.

FIG.27is a graph illustrating an example of a simulation result of the transfer characteristic of the main line (S21). InFIG.27, a solid line indicates the characteristic of the configuration of the present application, a dashed line indicates the characteristic of the first comparative configuration, and a dot-dash line indicates the characteristic of a second comparative configuration. The first and second comparative configurations indicate configurations in which sub-lines not outputting detected signals are not in the shorted state; the first comparative configuration indicates a configuration with two sub-lines; the second comparative configuration indicates a configuration with three sub-lines.

As illustrated inFIG.27, as the number of sub-lines increases, the frequency of attenuation pole is shifted to the lower side. For example, in the cases inFIG.27, the frequency of attenuation pole with two sub-lines is about 5.2 [GHz], whereas the frequency of attenuation pole with three sub-lines is decreased to about 4.8 [GHz]. This means that more adverse effects occur in the frequency band of radio-frequency signals communicated in the main line20of the directional coupler10I.

However, because the directional coupler10I has the configuration described above, the attenuation pole is shifted to the high frequency side (in the case inFIG.27, the high frequency side higher than 7.0 [GHz]).

As a result, it is possible to suppress significant degradation of the transfer characteristic of the main line20over a wider frequency band and thus achieve a transfer characteristic with low loss. Consequently, the directional coupler10I can obtain a detected signal in a desired frequency band, while suppressing transfer loss of radio-frequency signals flowing through the main line20over an even wider frequency band.

In particular, because three sub-lines are used in the directional coupler10I, the directional coupler10I can be used to detect waves of a frequency band wider than when two sub-lines are used. Also in this case, it is possible to obtain detected signals in a desired frequency band, while reducing transfer loss of radio-frequency signals communicated in the main line20.

Although the case of three sub-lines is presented, the number of sub-lines may be four or more. Also in these cases, one of the sub-lines is used to output a detected signal, and both ends of the other sub-lines are shorted.

Eleventh Embodiment

A directional coupler according to an eleventh embodiment of the present invention will be described with reference to the drawings.FIG.28is a configuration diagram of the directional coupler according to the eleventh embodiment.

As illustrated inFIG.28, a directional coupler10J according to the eleventh embodiment differs from the directional coupler10according to the first embodiment in that SP3T switches are used. Other configurations of the directional coupler10J are the same as the directional coupler10, and descriptions of the same configurations are not repeated.

The directional coupler10J includes switching circuits41J and42J. The switching circuits41J and42J correspond to the “second switching circuit” of the present invention.

Of the switch SW113, a single-pole-side terminal is coupled to the coupling terminal Pcp; a triple-throw-side terminal is coupled to the end portion311of the sub-line31; another triple-throw-side terminal is coupled to the end portion312of the sub-line31; and the other triple-throw-side terminal is a floating terminal not coupled to anywhere. Of the switch SW123, a single-pole-side terminal is coupled to the termination circuit80; a triple-throw-side terminal is coupled to the end portion311of the sub-line31; another triple-throw-side terminal is coupled to the end portion312of the sub-line31; and the other triple-throw-side terminal is a floating terminal not coupled to anywhere.

Of the switch SW213, a single-pole-side terminal is coupled to the coupling terminal Pcp; a triple-throw-side terminal is coupled to the end portion321of the sub-line32; another triple-throw-side terminal is coupled to the end portion322of the sub-line32; and the other triple-throw-side terminal is a floating terminal not coupled to anywhere. Of the switch SW223, a single-pole-side terminal is coupled to the termination circuit80; a triple-throw-side terminal is coupled to the end portion321of the sub-line32; another triple-throw-side terminal is coupled to the end portion322of the sub-line32; and the other triple-throw-side terminal is a floating terminal not coupled to anywhere.

For example, when a detected signal communicated from the end portion322side to the end portion321side of the sub-line32is outputted from the coupling terminal Pcp, the terminal coupled to the end portion321of the sub-line32is selected from the triple-throw-side terminals of the switch SW213, and the terminal coupled to the end portion322of the sub-line32is selected from the triple-throw-side terminals of the switch SW223. Of the switches SW91and SW92, the switch SW91is in the shorted state, and the switch SW92is in the open state. Of each of the switches SW113and SW123, the floating terminal is selected from the triple-throw-side terminals.

With this configuration, similarly to the directional coupler10according to the first embodiment, the directional coupler10J can obtain a detected signal in a desired frequency band, while suppressing transfer loss of radio-frequency signals flowing through the main line20over a wide frequency band. When of the sub-lines31and32, a sub-line not coupled to the coupling terminal Pcpand the termination circuit80(for example, the sub-line31) is in the shorted state, the floating terminal of the switching circuit41J is selected so that coupling the sub-line31to the sub-line32is avoided. This can reduce adverse effects caused when the sub-line31is coupled to the sub-line32.

Twelfth Embodiment

A directional coupler according to a twelfth embodiment of the present invention will be described with reference to the drawings.FIG.29is a configuration diagram of the directional coupler according to the twelfth embodiment.

As illustrated inFIG.29, a directional coupler10K according to the twelfth embodiment differs from the directional coupler10H according to the ninth embodiment in that SPDT switches are used. Other configurations of the directional coupler10K are the same as the directional coupler10H, and descriptions of the same configurations are not repeated.

Of the switch SW112, a single-pole-side terminal is coupled to the switching circuit491K; a double-throw-side terminal is coupled to the end portion311of the sub-line31; and the other double-throw-side terminal is coupled to the end portion312of the sub-line31. Of the switch SW122, a single-pole-side terminal is coupled to the switching circuit492K; a double-throw-side terminal is coupled to the end portion311of the sub-line31; and the other double-throw-side terminal is coupled to the end portion312of the sub-line31.

Of the switch SW212, a single-pole-side terminal is coupled to the switching circuit491K; a double-throw-side terminal is coupled to the end portion321of the sub-line32; and the other double-throw-side terminal is coupled to the end portion322of the sub-line32. Of the switch SW222, a single-pole-side terminal is coupled to the switching circuit492K; a double-throw-side terminal is coupled to the end portion321of the sub-line32; and the other double-throw-side terminal is coupled to the end portion322of the sub-line32.

The switching circuit491K is a single-pole double-throw (SPDT) switch element. Of the switching circuit491K, a single-pole-side terminal is coupled to the coupling terminal Pcp; a double-throw-side terminal is coupled to the switch SW112of the switching circuit41K; and the other double-throw-side terminal is coupled to the switch SW212of the switching circuit42K.

The switching circuit492K is a single-pole double-throw (SPDT) switch element. Of the switching circuit492K, a single-pole-side terminal is coupled to the terminationcircuit80; a double-throw-side terminal is coupled to the switch SW122of the switching circuit41K; and the other double-throw-side terminal is coupled to the switch SW222of the switching circuit42K.

With this configuration, similarly to the directional coupler10H according to the ninth embodiment, the directional coupler10K can obtain a detected signal in a desired frequency band, while suppressing transfer loss of radio-frequency signals flowing through the main line20over a wide frequency band.

As indicated in the directional couplers10J and10K, switching circuits are not limited to single-pole single-throw (SPST) switches; switching circuits are implemented by m-pole n-throw (mPnT: m and n are positive integers) switches.

Thirteenth Embodiment

A directional coupler according to a thirteenth embodiment of the present invention will be described with reference to the drawings.FIGS.30A,30B, and30Care plan views of a main line and sub-lines of a directional coupler according to the thirteenth embodiment.FIGS.30A and30Cillustrate sub-lines, andFIG.30Billustrates a main line.FIG.31is a sectional view schematically illustrating a structure of the directional coupler according to the thirteenth embodiment.FIG.31illustrates a section taken along line A-A inFIGS.30A,30B, and30C.

A directional coupler10L according to the thirteenth embodiment realizes one structure of the directional coupler10according to the first embodiment. The circuit configuration of the directional coupler10L is the same as the circuit configuration of the directional coupler10, and descriptions of the circuit configuration is omitted.

As illustrated inFIGS.30A,30B,30C, and31, the directional coupler10L includes a multilayer body100. The multilayer body100includes a plurality of insulator layers stacked. For example, the multilayer body100is formed by stacking a plurality of prepreg layers on both side of a core material layer.

As illustrated inFIG.30B, the main line20is a conductor elongated in a particular shape. More specifically, the main line20is shaped as a loop with an almost single turn. A loop of the present invention is not necessarily a complete ring, and a loop has at least a portion of a ring.

As illustrated inFIG.31, the sub-line31is disposed on one side with respect to the main line20in the thickness direction of the multilayer body100. As illustrated inFIG.30A, the sub-line31is a conductor elongated in a particular shape. More specifically, the sub-line31is shaped as a loop with almost two turns. The sub-line31is elongated parallel to the main line20for the almost entire length. As a result, the sub-line31can be electromagnetically coupled to the main line20to a particular degree of coupling.

As illustrated inFIG.31, the sub-line32is disposed on the other side with respect to the main line20in the thickness direction of the multilayer body100. As illustrated inFIG.30C, the sub-line32is a conductor elongated in a particular shape. More specifically, the sub-line32is shaped as a loop with an almost single turn. The sub-line32is elongated parallel to the main line20for the almost entire length. As a result, the sub-line32can be electromagnetically coupled to the main line20to a particular degree of coupling.

The length of the loop of the sub-line31is longer than the length of the loop of the sub-line32. As a result, the frequency band that can be coupled in the sub-line31is lower than the frequency band that can be coupled in the sub-line32.

As illustrated inFIG.30A, the end portions311and312of the sub-line31are close to each other. As used herein, the term “close” indicates, for example, the arrangement in which the distance between the end portions311and312is shorter than one shorter side determining the ring-like central open space formed by the sub-line31(the diameter when the ring-like shape is circular) as illustrated inFIG.30A, and more preferably, the arrangement in which the distance between the end portions311and312is ½ of the one shorter side or shorter, or ¼ of the one shorter side or shorter.

With this structure, the connection distance between the end portions311and312and the switch SW91is made short. As a result, when the switch SW91is in the shorted state, the inductance in the path including the switch SW91is low. This suppresses a decrease in how much the resonant frequency is shifted due to the effect of the switch SW91in the shorted state. As such, the effect of the switch SW91in the shorted state becomes more effective.

Similarly, as illustrated inFIG.30C, the end portions321and322of the sub-line32are close to each other. As used herein, the term “close” indicates, for example, the arrangement in which the distance between the end portions321and322is shorter than one shorter side determining the ring-like central open space formed by the sub-line32(the diameter when the ring-like shape is circular) as illustrated inFIG.30C, and more preferably, the arrangement in which the distance between the end portions321and322is ½ of the one shorter side or shorter, or ¼ of the one shorter side or shorter.

With this structure, the connection distance between the end portions321and322and the switch SW92is made short. As a result, when the switch SW92is in the shorted state, the inductance in the path including the switch SW92is low. This suppresses a decrease in how much the resonant frequency is shifted due to the effect of the switch SW92in the shorted state. As such, the effect of the switch SW92in the shorted state becomes more effective.

This embodiment is not to be interpreted as limiting. The above describes a mode in which the switch SW91(a switch for bringing a low-frequency-side sub-line in the shorted state) and the switch SW92(a switch for bringing a high-frequency-side sub-line in the shorted state) are both provided, but it is sufficient that either the switch SW91(a switch for bringing a low-frequency-side sub-line in the shorted state) or the switch SW92(a switch for bringing a high-frequency-side sub-line in the shorted state) be provided. In this case, the higher the frequency band is, the more the effect on the attenuation pole is. For this reason, it is preferable that the directional coupler include at least the switch SW91(a switch for bringing a low-frequency-side sub-line in the shorted state).

Fourteenth Embodiment

A directional coupler according to a fourteenth embodiment of the present invention will be described with reference to the drawings.FIG.32is a configuration diagram of the directional coupler according to the fourteenth embodiment.

A directional coupler10X according to the fourteenth embodiment has a configuration in which the switching circuits41and42are removed from the directional coupler10G according to the eighth embodiment. Other configurations of the directional coupler10X are the same as the directional coupler10G, and descriptions of the same configurations are not repeated.

In this configuration, although only coupling signals in one direction are obtained in the sub-lines31and32, similarly to the directional coupler10G according to the eighth embodiment, the directional coupler10X can obtain a detected signal in a desired frequency band, while suppressing transfer loss of radio-frequency signals flowing through the main line20over a wide frequency band.

The configurations of the embodiments may be combined in any appropriate manner, and it is possible to achieve effects and advantages corresponding to individual combinations thereof.