Multiband balun

Abstract

To provide a multiband balun with a small area and variable bandwidth.SOLUTION: A multiband balun includes: two balanced lines, one end of each balanced line being grounded and the other end thereof being connected to a balanced terminal connected to a balanced circuit; an unbalanced line, one end thereof being connected to an unbalanced terminal connected to an unbalanced circuit; and a first switch, where the first switch switches a state of an unbalanced termination to one of an open state and a ground state, and the unbalanced termination is one end of the unbalanced line opposite the one end connected to the unbalanced terminal.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to multi-band baluns. [Background technology]

[0002] There are baluns that connect balanced circuits and unbalanced circuits. A Marchand balun, which uses coupled lines, is a balun with a wide bandwidth and low loss. As shown in Figure 15(a), for example, a Marchand balun includes a first short stub SS1 and a second short stub SS2, each with a length equal to 1 / 4 of the wavelength λ used, which is the wavelength corresponding to the operating frequency, and an open stub OS with a length equal to 1 / 2 of the wavelength λ used.

[0003] As the fifth generation mobile communication system (5G) and its successor, Beyond 5G (also known as 6G), move to multi-bands will increase communication capacity and flexibility, which is driving a growing demand for multi-band baluns that can handle signals in multiple frequency bands.

[0004] As an example of a technique for varying the band of a circuit element made up of a coupled line, Patent Document 1 discloses a technique for obtaining a variable-bandwidth filter capable of varying the center frequency over a wide band. The technique disclosed in Patent Document 1 is a variable-bandwidth filter having a coupled line made up of two transmission lines, and further comprising at least one switching element connected to a portion of the transmission lines and capable of changing the center frequency by switching the length of the coupled line through on / off switching. The length of the coupled line can be switched by the switching operation of the switching element, making it easy to realize a variable-bandwidth filter capable of varying the center frequency over a wide band. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-124311 Summary of the Invention [Problem to be solved by the invention]

[0006] The following analysis was performed by the inventors of the present disclosure.

[0007] For example, by applying the technology of Patent Document 1 to a balun, that is, by making the coupling line length variable, a balun that can support multiple bands can be realized. However, according to the technology disclosed in Patent Document 1, in order to make the coupling line length variable, it is necessary to add a new coupling line ADD, as shown in FIG. 15(b). Therefore, the circuit area of ​​the balun increases accordingly. This does not meet the demand for miniaturization of equipment along with multi-bandization.

[0008] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a multi-band balun that has a small area and is capable of varying bands. [Means for solving the problem]

[0009] According to a first aspect of the present disclosure, Two balanced lines, one end of which is grounded and the other end of which is connected to a balanced terminal that connects to a balanced circuit; an unbalanced line having one end connected to an unbalanced terminal connected to the unbalanced circuit; a first switch; The first switch switches the state of the unbalanced termination, which is the end of the unbalanced line opposite to the end connected to the unbalanced terminal, between an open state and a grounded state, and a multiband balun is provided. [Effects of the Invention]

[0010] According to the present disclosure, a multi-band balun with a small area and variable bandwidth can be provided. [Brief explanation of the drawings]

[0011] [Figure 1] 1A is a schematic diagram of a Marchand balun according to the present disclosure, and FIGS. 1B and 1C are schematic diagrams of transformer baluns according to the present disclosure. [Figure 2] 1 is an explanatory diagram illustrating frequency characteristics of a Marchand balun and a transformer balun according to the present disclosure. FIG. [Figure 3] 1A to 1C are a schematic diagram of an example of a multi-band balun according to an embodiment of the present disclosure, an explanatory diagram illustrating an operation mode for each state of a format conversion switch, and a diagram illustrating the frequency characteristics of each operation mode, respectively. [Figure 4] 10A and 10B are explanatory diagrams illustrating an example of a control mode of a format conversion switch of the multi-band balun according to an embodiment of the present disclosure. [Figure 5] 6(a) to 6(d) are schematic configuration diagrams of examples of multi-band baluns according to other embodiments of the present disclosure. [Figure 6] 10A is a diagram showing the frequency characteristics of a multiband balun according to another embodiment of the present disclosure, and FIG. 10B is a diagram showing an example configuration for each operation mode of a multiband balun according to another embodiment of the present disclosure. [Figure 7] 10A to 10C are, respectively, a schematic configuration diagram of an example of a multi-band balun according to another embodiment of the present disclosure, an explanatory diagram illustrating the operation modes for each state of the format conversion switch, and a diagram illustrating the frequency characteristics of each operation mode. [Figure 8] 10A to 10C are, respectively, a schematic configuration diagram of an example of a multi-band balun according to another embodiment of the present disclosure, an explanatory diagram illustrating the operation modes for each state of the format conversion switch, and a diagram illustrating the frequency characteristics of each operation mode. [Figure 9] 10A to 10C are, respectively, a schematic configuration diagram of an example of a multi-band balun according to another embodiment of the present disclosure, an explanatory diagram illustrating the operation modes for each state of the format conversion switch, and a diagram illustrating the frequency characteristics of each operation mode. [Figure 10] 10A to 10C are, respectively, a schematic configuration diagram of an example of a multi-band balun according to another embodiment of the present disclosure, an explanatory diagram illustrating the operation modes for each state of the format conversion switch, and a diagram illustrating the frequency characteristics of each operation mode. [Figure 11]10A to 10C are, respectively, a schematic configuration diagram of an example of a multi-band balun according to another embodiment of the present disclosure, an explanatory diagram illustrating the operation modes for each state of the format conversion switch, and a diagram illustrating the frequency characteristics of each operation mode. [Figure 12] 10A to 10C are, respectively, a schematic configuration diagram of an example of a multi-band balun according to another embodiment of the present disclosure, an explanatory diagram illustrating the operation modes for each state of the format conversion switch, and a diagram illustrating the frequency characteristics of each operation mode. [Figure 13] 10A to 10C are, respectively, a schematic configuration diagram of an example of a multi-band balun according to another embodiment of the present disclosure, an explanatory diagram illustrating the operation modes for each state of the format conversion switch, and a diagram illustrating the frequency characteristics of each operation mode. [Figure 14] FIG. 10 is a schematic configuration diagram of an example of a multi-band balun according to a modified example of the present disclosure. [Figure 15] 1A and 1B are explanatory diagrams for explaining the schematic configuration and frequency adjustment of a conventional Marchand balun, respectively. DETAILED DESCRIPTION OF THE INVENTION

[0012] Prior to describing the embodiments to which the present disclosure is applied, a balun for connecting a balanced circuit and an unbalanced circuit will be described. The present disclosure is not limited to the following embodiments, and various modifications are possible within the scope of the present disclosure. The drawings are schematic, and the ratios of dimensions may differ from those of the actual devices. Specific dimensions should be determined with reference to the following description. The drawings also include portions where the dimensional relationships and ratios differ between the various devices. Reference symbols in the drawings are used for convenience to identify elements as an example to facilitate understanding, and are not intended to limit the present disclosure to the illustrated embodiments. Unidirectional arrows in the drawings, which indicate the flow of signals or the connection relationships between elements, simply indicate the direction of the flow of a signal or data, and do not exclude bidirectionality.

[0013] One type of balun is known as the Marchand balun 910. The Marchand balun is a balun that uses electromagnetic field coupling to enable mutual conversion between balanced and unbalanced signals.

[0014] An example of a Marchand balun 910 is shown in Figure 1(a). As shown in this figure, the Marchand balun 910 includes an open stub OS (coupled line), which is an unbalanced line with a length L3 equal to half the wavelength (λ / 2) of the wavelength λ corresponding to the operating frequency, and first and second short stubs SS1 and SS2 (coupled lines), which are balanced lines with lengths L1 and L2 equal to a quarter of the wavelength (λ / 4). When there is no need to distinguish between the two, they are referred to as short stubs SS. In the Marchand balun 910, the end (unbalanced termination) of the open stub OS, which is an unbalanced line, opposite the end connected to the input / output terminals is open.

[0015] The open stub OS and the short stub SS are formed of, for example, wiring metal. Therefore, the short stub SS is also called the upper layer metal, and the open stub OS is called the lower layer metal. In FIG. 1(a), W1 and W3 are the line widths of the short stub SS and the open stub OS, respectively. Furthermore, L1, L2, and L3 are the line lengths of the first short stub SS1, the second short stub SS2, and the open stub OS, respectively. Furthermore, S is the distance between the coupled lines.

[0016] Another type of balun is the transformer-type balun 920. The transformer-type balun 920 is a balun that can mutually convert balanced and unbalanced signals by magnetic coupling between the primary coil and the secondary coil.

[0017] An example of a transformer balun 920 is shown in Figure 1(b). As shown in this figure, the transformer balun 920 includes a primary coil FC (unbalanced line: lower layer metal) and a secondary coil SC (balanced line: upper layer metal). Figure 1(c) is a schematic diagram showing the configuration of this transformer balun 920, similar to the Marchand balun 910. As shown in this figure, in the transformer balun 920, the termination (unbalanced termination), which is the end of the primary coil FC, which is an unbalanced line, opposite to the end connected to the input / output terminal, is grounded (GND).

[0018] As can be seen from FIGS. 1(a) and 1(c), the only difference in configuration between the Marchand balun 910 and the transformer balun 920 is whether the unbalanced termination of the unbalanced line is open or grounded.

[0019] However, when a Marchand balun 910 and a transformer balun 920 are fabricated with the same line length and their insertion losses (dB) are compared, their peak frequencies are different. Specifically, for example, when L1 and L2 are fabricated with lengths of 520 μm and L3 is fabricated with lengths of 1040 μm, frequency characteristics 911 of the Marchand balun 910 and frequency characteristics 921 of the transformer balun 920 are shown in Figure 2. As shown in this figure, the peak frequency fM (GHz) of the Marchand balun 910 is higher than the peak frequency fT (GHz) of the transformer balun 920.

[0020] Hereinafter, the frequency at the peak of the frequency characteristics will be referred to as the center frequency. The center frequency is uniquely determined by conditions such as the line lengths L1, L2, and L3, the line widths W1 and W2, and the coupled line spacing S. The center frequency is also the passband frequency of each balun. As mentioned above, when designed with the same dimensions, the center frequency fT (GHz) of the transformer balun 920 is lower than the center frequency fM (GHz) of the Marchand balun 910. In other words, the passband frequency differs depending on the type of balun.

[0021] This disclosure utilizes this to realize a multiband balun that can accommodate multiple different center frequencies (passband frequencies). Specifically, the unbalanced termination state of the unbalanced line is configured to be changeable between an open state and a grounded state. Then, by operating it as a Marchand balun and a transformer-type balun, a multiband balun that can accommodate signals in multiple different frequency bands is realized.

[0022] <<First Embodiment>> A first embodiment of a multiband balun to which the present disclosure is applied will be described with reference to the drawings. The multiband balun 110 of this embodiment is configured so that the termination state of the unbalanced line can be changed between an open state and a grounded state, and operates as a Marchand balun and a transformer balun. This allows the multiband balun 110 to handle signals in two different frequency bands.

[0023] [composition] 3(a) is a schematic configuration diagram of the multiband balun 110 of this embodiment. As shown in this figure, the multiband balun 110 of this embodiment includes a first balanced line 210, a second balanced line 220, an unbalanced line 310, an unbalanced terminal 311, a first balanced terminal 211, a second balanced terminal 221, and a format conversion switch (first switch) SW0.

[0024] The first balanced line 210 and the second balanced line 220 have one end grounded and the other end connected to a first balanced terminal 211 and a second balanced terminal 221 that are connected to the balanced circuit, respectively.

[0025] One end of the unbalanced line 310 is connected to an unbalanced terminal 311 that is connected to the unbalanced circuit. Note that a format conversion switch SW0 is connected to an unbalanced termination 312, which is the end of the unbalanced line 310 opposite to the end connected to the unbalanced terminal 311.

[0026] The multiband balun 110 of this embodiment converts an unbalanced input signal input from the unbalanced terminal 311 into a balanced output signal that passes a desired frequency component, and outputs the balanced output signal from the first balanced terminal 211 and the second balanced terminal 221. In addition, the multiband balun 110 converts a balanced input signal input from the first balanced terminal 211 and the second balanced terminal 221 into an unbalanced output signal, and outputs the unbalanced output signal from the unbalanced terminal 311.

[0027] The format conversion switch SW0 switches the state of the unbalanced termination 312 between an open state and a grounded state as seen from the high-frequency signal, i.e., switches the format of the multiband balun 110 between the merchant format and the transformer format.

[0028] Specifically, format conversion switch SW0 has a grounded terminal (ground terminal) 401. Then, in response to a control signal from control unit 490, unbalanced termination 312 is switched between a state in which it is connected to ground terminal 401 and a state in which it is not connected to ground terminal 401 (open state). Note that the state in which format conversion switch SW0 is connected to ground terminal 401 is called a short, and the state in which format conversion switch SW0 is not connected to ground terminal 401 is called an open.

[0029] The control unit 490 operates the format conversion switch SW0 by transmitting a control signal to the format conversion switch SW0, thereby switching the operation mode of the multiband balun 110 of this embodiment.

[0030] Here, the line lengths of the first balanced line 210, the second balanced line 220, and the unbalanced line 310 are defined as L1, L2, and L3, respectively. The line width of the first balanced line 210 is defined as W1, the line width of the second balanced line 220 is defined as W2, and the line width of the unbalanced line 310 is defined as W3. The spacing between the first balanced line 210 and the second balanced line 220 and the unbalanced line 310, i.e., the coupled line spacing, is defined as S. Note that the line widths W1, W2, and W3 may be the same or different. The line lengths L1 and L2 may be the same or different.

[0031] [Operation] Below, we will explain each operation mode that is realized by operating the format conversion switch SW0 under the control of the control unit 490. Fig. 3(b) shows the operation mode of the multiband balun 110 for each state of the format conversion switch SW0. Fig. 3(c) shows the frequency characteristics of the multiband balun 110 in each operation mode.

[0032] The operating mode when the format conversion switch SW0 is connected (short-circuited) to the ground terminal 401 and the unbalanced termination 312 of the unbalanced line 310 is grounded is called mode (MODE) 1. In this state, the multiband balun 110 operates as a transformer-type balun capable of converting signals between balanced and unbalanced states due to magnetic coupling between the primary and secondary coils. Specifically, the first balanced line 210 and the second balanced line 220 function as center-tapped primary coils with a line length of L1+L2. The unbalanced line 310 functions as a secondary coil with a line length of L3. When the operating mode is mode 1, the multiband balun 110 has frequency characteristics as shown in FIG. 3(c), with a center frequency of fT1 (GHz) (units will be omitted hereinafter). Note that this center frequency fT1 is uniquely determined by dimensional conditions such as the line lengths L1, L2, and L3, the line widths W1, W2, and W3, and the coupled line spacing S.

[0033] Furthermore, the operating mode in which the format conversion switch SW0 is not connected (open) to the ground terminal 401 and the unbalanced termination 312 of the unbalanced line 310 is open is called mode (MODE) 2. In this state, the multiband balun 110 operates as a Marchand balun, which can convert signals between balanced and unbalanced states using the coupled lines. Specifically, the first balanced line 210 and the second balanced line 220 function as short stubs with line lengths L1 and L2, respectively. The unbalanced line 310 functions as an open stub with line length L3. The frequency characteristics of the multiband balun 110 in mode 2 are as shown in FIG. 3(c), and the center frequency is fM1. Note that this center frequency fM1 is uniquely determined by dimensional conditions such as line lengths L1, L2, and L3, line widths W1, W2, and W3, and the coupled line spacing S.

[0034] Note that, for example, a field effect transistor (FET) 402 is used for the mode conversion switch SW0. A configuration example in which the FET 402 is used for the mode conversion switch SW0 is shown in FIG. 4. In this case, the control signal from the control unit 490 is a voltage (gate bias voltage).

[0035] The FET 402 becomes ON when the applied gate bias voltage exceeds the threshold value. That is, the mode conversion switch SW0 becomes short-circuited, and the unbalanced termination 312 of the unbalanced line 310 becomes grounded. Also, the FET 402 becomes OFF when the applied gate bias voltage is lower than the threshold value. That is, the mode conversion switch SW0 becomes open, and the unbalanced termination 312 of the unbalanced line 310 becomes open.

[0036] As described above, the multi-band balun 110 of the present embodiment includes a mode conversion switch SW0 capable of switching the state of the unbalanced termination 312 of the unbalanced line 310 between an open state and a grounded state. By switching the mode conversion switch SW0 according to the control signal from the control unit 490, the multi-band balun 110 can be operated as either a transformer-type balun or a merchant balun.

[0037] As described above, generally, in a transformer-type balun and a merchant balun manufactured using the same line length, line width, and coupled line interval, the center frequency fT1 of the former is lower (fT1 < fM1) than the center frequency fM1 of the latter. That is, the center frequencies fT1 and fM1 of both are different.

[0038] Therefore, by having the mode conversion switch SW0 and switching it with the control signal from the control unit 490, the multi-band balun 110 of the present embodiment can change its center frequency. That is, it can correspond to two different passband frequencies.

[0039] Furthermore, the multiband balun 110 of this embodiment does not increase the circuit area because the circuit configuration simply requires adding a format conversion switch SW0 to the unbalanced termination 312 of the unbalanced line 310. Therefore, according to this embodiment, a small-area, band-variable multiband balun can be realized.

[0040] <<Other embodiments>> Generally, the shorter the line length of a balun, the higher the center frequency. In other words, the center frequency changes depending on the line length. In the following embodiments, this characteristic is also combined to configure a multi-band balun that can accommodate multiple passband frequencies. In the following embodiments, the line length is changed between the originally designed line length (first line length) and a second line length that is shorter than the first line length. This makes it possible to accommodate signals in multiple frequency bands without adding new line lengths.

[0041] First, possible operation modes of the multi-band balun of each of the following embodiments will be described with reference to FIGS. 5(a) to 5(d) and 6(a) and 6(b).

[0042] In the following embodiments, as shown in these figures, in addition to converting the system, the system line length conversion switch changes the line length of the unbalanced line 310 between a first line length L3 and a second line length L4 that is shorter than the first line length L3. At this time, the line length of the first balanced line 210 is changed accordingly between L1 and L6 that is shorter than L1. Note that the second line length L4 is L4 <L3である。

[0043] As shown in FIG. 5(a), the operating mode in which the line length of the unbalanced line 310 is the first line length L3 and the unbalanced termination 312 of the unbalanced line 310 is grounded is called mode 1. This is the same configuration as mode 1 in the first embodiment. In this operating mode, the balun operates as a transformer-type balun. A balun operating in this operating mode is called a first line length transformer-type balun. The center frequency of the frequency characteristics of the first line length transformer-type balun (MODE 1) is set to fT1, as shown in FIG. 6(a).

[0044] As shown in FIG. 5(b), the operating mode in which the line length of the unbalanced line 310 is the first line length L3 and the unbalanced termination 312 is in an open state is called mode 2. This is the same configuration as mode 2 in the first embodiment. In this operating mode, it operates as a Marchand balun. A balun operating in this operating mode is called a first line length Marchand balun. The center frequency of the frequency characteristics of the first line length Marchand balun (MODE 2) is set to fM1, as shown in FIG. 6(a). As described in the first embodiment, fM1>fT1.

[0045] 5(c), the operating mode in which the line length of the unbalanced line 310 is the second line length L4 (<the first line length L3) and the unbalanced termination 312 is grounded is called mode 3. A balun operating in this operating mode is called a second line length transformer balun. The center frequency of the frequency characteristics of the second line length transformer balun (MODE 3) is set to fT2 as shown in FIG. 6(a). As described above, since the second line length L4 is shorter than the first line length L3, fT2 > fT1.

[0046] Furthermore, as shown in FIG. 5(d), the operating mode in which the line length of the unbalanced line 310 is the second line length L4 and the unbalanced termination 312 is in an open state is called mode 4. A balun operating in this operating mode is called a second line length Marchand balun. The center frequency of the frequency characteristics of the second line length Marchand balun (MODE 4) is set to fM2, as shown in FIG. 6(a). As described above, since the second line length L4 is shorter than the first line length L3, fM2 > fM1.

[0047] FIG. 6(b) shows the termination state of the unbalanced line 310, the balun type during operation, the line length, and the center frequency (GHz) for each operation mode.

[0048] In each of the following embodiments, the second line length L4 is determined such that the center frequencies of the respective operation modes are fT1 < fT2 < fM1 < fM2 as shown in FIG. 6(a). As described above, the shorter the second line length L4 is, the higher the center frequency becomes. In the following embodiments, it is only necessary that fT2 and fM1 are different. For example, the second line length L4 may be determined such that fT1 < fM1 < fT2 < fM2.

[0049] <<Second Embodiment>> Next, a second embodiment to which the present disclosure is applied will be described. In this embodiment, a method line length conversion switch 410 is inserted in the middle of the unbalanced line 310 and the first balanced line 210 of the multi-band balun 110 of the first embodiment, and the state of the unbalanced termination is switched between the grounded state and the open state, and the line length of the coupling line is also changed. In the second embodiment, the operation mode of the multi-band balun 120 is switched between the above-described mode 1 and mode 4 by the method line length conversion switch 410, enabling the multi-band balun 120 to support a plurality of band frequencies.

[0050] A schematic configuration diagram of the multi-band balun 120 according to the second embodiment for realizing this is shown in FIG. 7(a). In this embodiment, the components having the same names as those in the first embodiment basically have the same functions as those in the first embodiment. Hereinafter, this embodiment will be described focusing on the differences from the first embodiment.

[0051] As shown in this figure, the multi-band balun 120 of this embodiment includes a first balanced line 210, a second balanced line 220, an unbalanced line 310, an unbalanced terminal 311, a first balanced terminal 211, a second balanced terminal 221, and a method line length conversion switch 410.

[0052] Also, similar to the first embodiment, one end of each of the first balanced line 210 and the second balanced line 2^ is grounded, and the other end is connected to the first balanced terminal 211 and the second balanced terminal 221 that are connected to the balanced circuit. The line length of the first balanced line 210 is L1. And the first balanced line 210 includes a divided first balanced line 230 and a first adjustment line 240.

[0053] The unbalanced line 310 has one end connected to an unbalanced terminal 311 that connects to the unbalanced circuit. The unbalanced line 310 has a first line length L3. The unbalanced line 310 includes a split unbalanced line 330 and a second adjustment line 340.

[0054] The type line length conversion switch 410 includes a first switch SW1 and a second switch SW2.

[0055] The divided first balanced line 230 is a portion of the first balanced line 210 with a line length L6 on the side connected to the first balanced terminal 211. The end of the divided first balanced line 230 opposite to the side connected to the first balanced terminal 211 is connected to the second switch SW2 of the line length conversion switch 410. That is, the second switch SW2 is arranged to divide the first balanced line 210.

[0056] Moreover, the unbalanced line 310 of this embodiment includes a split unbalanced line 330 and a second adjustment line 340. The split unbalanced line 330 is a portion of the unbalanced line 310 that is connected to the unbalanced terminal 311 and has a second line length L4. Furthermore, a termination 314 (unbalanced termination), which is an end of the split unbalanced line 330 opposite to the end that is connected to the unbalanced terminal 311, is connected to a first switch SW1 of the line length conversion switch 410. That is, the first switch SW1 is arranged to split the unbalanced line 310.

[0057] Hereinafter, when there is no need to particularly distinguish between the split first balanced line 230 and the second balanced line 220, they will be collectively referred to as balanced lines. Similarly, when there is no need to particularly distinguish between the first adjustment line 240 and the second adjustment line 340, they will be collectively referred to as adjustment line 420. Furthermore, when there is no need to particularly distinguish between the split unbalanced line 330, the balanced line, and the adjustment line 420, they will be collectively referred to as coupled lines.

[0058] In addition, in each of the following embodiments, for ease of viewing the drawings, the control unit is not shown. The function of the control unit is the same as in the first embodiment, and it transmits a control signal to each switch to switch the state of the switch.

[0059] In this embodiment, as described above, the first switch SW1 is arranged by disconnecting the unbalanced line 310 of the first embodiment. Specifically, as shown in this figure, the unbalanced line 310 is disconnected at a position of line length L4 (L4 < L3) from the end on the unbalanced terminal 311 side, and is inserted into its terminal 314. That is, the divided unbalanced line 330 is the part of the divided unbalanced line 310 on the unbalanced terminal 311 side, and the second adjustment line 340 is the other part. The line length L5 of the second adjustment line 340 is L5 = L3 - L4.

[0060] The second switch SW2 is arranged by disconnecting the first balanced line 210 of the first embodiment. In this embodiment, the first balanced line 210 is disconnected at a position of L6 from the end on the first balanced terminal 211 side, and the second switch SW2 is arranged there. That is, the divided first balanced line 230 is the part of the divided first balanced line 210 on the first balanced terminal 211 side, and the first adjustment line 240 is the other part. The line length of the first adjustment line 240 is L5, and L5 = L1 - L6.

[0061] The second adjustment line 340 has a terminal 341 on the first switch SW1 side. The terminal 313 at the end on the side opposite to the terminal 341 is grounded.

[0062] The first adjustment line 240 has a terminal TM2 on the second switch SW2 side, and the end on the opposite side is grounded.

[0063] The first switch SW1 operates according to a control signal from the control unit, and switches the state of the terminal 314 between a state connected to the terminal 341 of the second adjustment line 340 and a state not connected to the terminal 341 (open state; open). Thereby, the state and the line length of the terminal on the unbalanced line side are changed (switched).

[0064] The second switch SW2 operates in accordance with a control signal from the control unit, and switches the line length of the divided first balanced line 230.

[0065] The sizes of the other components of the multiband balun 120 of this embodiment are the same as those of the multiband balun 110 of the first embodiment.

[0066] [Operation] Below, we will explain each operation mode that is realized by operating the first switch SW1 and the second switch SW2 under the control of the control unit. Figure 7(b) shows the operation modes that are realized for each state of the first switch SW1 and the second switch SW2 of the multiband balun 120. Also, Figure 7(c) shows the frequency characteristics of the multiband balun 120 in each operation mode.

[0067] When the first switch SW1 is connected to the terminal 341, the split unbalanced line 330 and the second adjustment line 340 are connected. At this time, the second switch SW2 is connected to the terminal TM2. In this case, the total line length of the unbalanced line is L3 (first line length), and the unbalanced termination 312 (see FIGS. 5(a) to 5(d), the same applies below) is the termination 313 of the second adjustment line 340. The termination 313 is grounded. Therefore, the multiband balun 120 operates as a transformer-type balun with a line length of the first line length. That is, it operates in the above-mentioned mode 1. Its center frequency is fT1, as shown in FIG. 7(c).

[0068] On the other hand, when the first switch SW1 is in an open state, the split unbalanced line 330 is not connected to the second adjustment line 340. At this time, the second switch SW2 is connected to the terminal TM1. In this case, the line length of the unbalanced line is L4 (second line length), and the unbalanced termination 312 is the termination 314 of the split unbalanced line 330. The termination 314 is in an open state. Therefore, the multiband balun 120 operates as a Marchand balun with a line length of the second line length. That is, it operates in the above-mentioned mode 4. The center frequency is fM2, as shown in FIG. 7(c).

[0069] As described above, the multiband balun 120 of this embodiment includes the line length conversion switch 410. The line length conversion switch 410 can switch the state of the unbalanced termination on the unbalanced line side between an open state and a grounded state, and can switch the line length on the unbalanced line side between a first line length, which is the line length originally designed, and a second line length shorter than the first line length. By switching the line length conversion switch 410 in accordance with a control signal from the control unit, the multiband balun 120 can be operated as either a transformer-type balun with the first line length or a Marchand balun with a second line length shorter than the first line length (short line length Marchand balun).

[0070] As described above, the center frequencies fT1 and fM2 are different. Therefore, the multiband balun 120 of this embodiment can change its center frequency by switching the line length conversion switch 410 with a control signal from the control unit. In other words, it can accommodate two different passband frequencies.

[0071] Furthermore, the multiband balun 120 of this embodiment does not increase the circuit area because the circuit configuration simply requires adding the line length conversion switch 410 at a position that separates the unbalanced line 310 and the first balanced line 210. Therefore, according to this embodiment, a small-area, band-variable multiband balun can be realized.

[0072] <<Third Embodiment>> Next, a third embodiment to which the present disclosure is applied will be described. In this embodiment, as in the second embodiment, a line length conversion switch 410 is inserted between the unbalanced line 310 and the first balanced line 210 of the multiband balun 110 of the first embodiment, and the state of the unbalanced termination is switched between a grounded state and an open state, and the line length of the coupled line is also changed. In this embodiment, the line length conversion switch 410 switches the operation mode of the multiband balun 130 between the above-mentioned mode 3 and mode 2, allowing it to support multiple band frequencies.

[0073] A schematic configuration diagram of the multi-band balun 130 of this embodiment that achieves this is shown in Figure 8(a). Note that in this embodiment, components with the same names as those in the first embodiment basically have the same functions as those in the first embodiment. Below, this embodiment will be described, focusing on the differences from the first embodiment.

[0074] As shown in this figure, the multiband balun 130 of this embodiment includes a first balanced line 210, a second balanced line 220, an unbalanced line 310, an unbalanced terminal 311, a first balanced terminal 211, a second balanced terminal 221, and a line length conversion switch 410.

[0075] Similarly to the first embodiment, the first balanced line 210 and the second balanced line 220 have one end grounded and the other end connected to a first balanced terminal 211 and a second balanced terminal 221, which are connected to the balanced circuit. The line length of the first balanced line 210 is L1. The first balanced line 210 includes a decoupled first balanced line 230 and a first adjustment line 240.

[0076] The unbalanced line 310 has one end connected to an unbalanced terminal 311 that connects to the unbalanced circuit. The unbalanced line 310 has a first line length L3. The unbalanced line 310 includes a split unbalanced line 330 and a second adjustment line 340.

[0077] The type line length conversion switch 410 includes a first switch SW1 and a second switch SW2.

[0078] The divided first balanced line 230 is a portion of the first balanced line 210 with a line length L6 on the side connected to the first balanced terminal 211. The end of the divided first balanced line 230 opposite to the side connected to the first balanced terminal 211 is connected to the second switch SW2 of the line length conversion switch 410. That is, the second switch SW2 is arranged to divide the first balanced line 210.

[0079] Moreover, the unbalanced line 310 of this embodiment includes a split unbalanced line 330 and a second adjustment line 340. The split unbalanced line 330 is a portion of the unbalanced line 310 that is connected to the unbalanced terminal 311 and has a second line length L4. Furthermore, a termination 314, which is an end of the split unbalanced line 330 opposite to the end that is connected to the unbalanced terminal 311, is connected to a first switch SW1 of the line length conversion switch 410. That is, the first switch SW1 is arranged to split the unbalanced line 310.

[0080] The size, arrangement, and the like of each component are basically the same as those of the second embodiment. However, in this embodiment, the termination 313, which is the end of the second adjustment line 340, is in an open state. The first switch SW1 also includes a grounded terminal 411. The first switch SW1 switches the state of the termination 313 between a state in which it is connected to the terminal 341 of the second adjustment line 340 and a state in which it is connected to the terminal 411 and grounded, in accordance with a control signal from the control unit. This changes the state and line length of the termination on the unbalanced line side. That is, the line length on the unbalanced line side is switched between the first line length L1 and the second line length L2, and the state of the termination is switched between an open state and a grounded state.

[0081] [Operation] Below, we will explain each operation mode that is realized by operating the first switch SW1 and the second switch SW2 under the control of the control unit. Figure 8(b) shows the operation modes that are realized for each state of the first switch SW1 and the second switch SW2 of the multiband balun 130. Also, Figure 8(c) shows the frequency characteristics of the multiband balun 130 in each operation mode.

[0082] When the first switch SW1 is connected to the terminal 341, the split unbalanced line 330 and the second adjustment line 340 are connected. At this time, the second switch SW2 is connected to the terminal TM2. In this case, the total line length of the unbalanced line is L3 (first line length), and the unbalanced termination 312 is the termination 313 of the second adjustment line 340. The termination 313 is in an open state. Therefore, the multiband balun 130 operates as a Marchand balun with a line length of the first line length. That is, it operates in the above-mentioned mode 2. Its center frequency is fM1, as shown in FIG. 8(c).

[0083] On the other hand, when the first switch SW1 is connected to the terminal 411, the split unbalanced line 330 is not connected to the second adjustment line 340. At this time, the second switch SW2 is connected to the terminal TM1. In this case, the line length of the unbalanced line is L4 (second line length), and the unbalanced termination 312 is the termination 314 of the split unbalanced line 330. The termination 314 is grounded. Therefore, the multiband balun 130 operates as a transformer-type balun with a line length of the second line length. That is, it operates in the above-mentioned mode 3. The center frequency is fT2, as shown in FIG. 8(c).

[0084] As described above, the multiband balun 130 of this embodiment can be operated as either a Marchand balun with a first line length or a transformer balun with a second line length that is shorter than the first line length, using the line length conversion switch 410.

[0085] As described above, the center frequencies fT2 and fM1 are different. Therefore, the multiband balun 130 of this embodiment can change its center frequency by switching the line length conversion switch 410 with a control signal from the control unit. In other words, it can accommodate two different passband frequencies.

[0086] Furthermore, the multiband balun 130 of this embodiment does not increase the circuit area because the circuit configuration simply requires adding the line length conversion switch 410 at a position that separates the unbalanced line 310 and the first balanced line 210. Therefore, according to this embodiment, a small-area, band-variable multiband balun can be realized.

[0087] <<Fourth Embodiment>> Next, a fourth embodiment to which the present disclosure is applied will be described. In this embodiment, a terminal 411, which is terminated at a grounded terminal as viewed from a high-frequency signal, is added to the first switch SW1 of the second embodiment, thereby realizing a multi-band balun 140 that can support three different bands.

[0088] The present embodiment will be described below, focusing on the configuration that differs from the second embodiment.

[0089] 9(a) is a schematic diagram of the multiband balun 140 of this embodiment. As shown in this figure, the multiband balun 140 of this embodiment has the same configuration as the multiband balun 120 of the second embodiment.

[0090] However, as described above, the first switch SW1 of this embodiment further includes the terminal 411 whose termination is in a grounded state. Therefore, the first switch SW1 can switch the state of the termination 313 between a state where it is connected to the terminal 341, a state where it is connected to the grounded terminal 411, and an open state, in accordance with a control signal from the control unit. In other words, the first switch SW1 can take three states.

[0091] [Operation] Below, we will explain each operation mode that is realized by operating the first switch SW1 and the second switch SW2 under the control of the control unit. Figure 9(b) shows the operation modes that are realized for each state of the first switch SW1 and the second switch SW2 of the multiband balun 140. Also, Figure 9(c) shows the frequency characteristics of the multiband balun 140 in each operation mode.

[0092] When the first switch SW1 is connected to the terminal 341, the split unbalanced line 330 and the second adjustment line 340 are connected. At this time, the second switch SW2 is connected to the terminal TM2. In this case, the total line length of the unbalanced line is L3 (first line length), and its end 313 is grounded. Therefore, the multiband balun 140 operates as a transformer-type balun with a line length of the first line length. That is, it operates in the above-mentioned mode 1. Its center frequency is fT1, as shown in FIG. 9(c).

[0093] Furthermore, when the first switch SW1 is in an open state, the split unbalanced line 330 is not connected to the second adjustment line 340. At this time, the second switch SW2 is connected to the terminal TM1. In this case, the line length of the unbalanced line is L4 (second line length), and its termination 314 is in an open state. Therefore, the multiband balun 140 operates as a Marchand balun with a line length of the second line length. That is, it operates in the above-mentioned mode 4. Its center frequency is fM2, as shown in FIG. 9(c).

[0094] Furthermore, when the first switch SW1 is connected to the grounded terminal 411, the split unbalanced line 330 is not connected to the second adjustment line 340. At this time, the second switch SW2 is connected to the terminal TM1. In this case, the line length of the unbalanced line is L4 (second line length), and its termination 314 is grounded. Therefore, the multiband balun 140 operates as a transformer-type balun with the line length of the second line length. That is, it operates in the above-mentioned mode 3. Its center frequency is fT2, as shown in FIG. 9(c).

[0095] As described above, the multiband balun 140 of this embodiment can be operated as either a transformer balun with a first line length, a Marchand balun with a second line length, or a transformer balun with a second line length by using the line length conversion switch 410.

[0096] As described above, these center frequencies fT1, fT2, and fM2 are different. Therefore, the multiband balun 140 of this embodiment can change its center frequency by switching the line length conversion switch 410 with a control signal from the control unit. In other words, it can accommodate three different passband frequencies.

[0097] Furthermore, the circuit configuration of the multiband balun 140 of this embodiment does not increase the circuit area because the line length conversion switch 410 is simply added at a position that separates the unbalanced line 310 and the first balanced line 210. Therefore, according to this embodiment, a small-area, band-variable multiband balun can be realized.

[0098] <<Fifth Embodiment>> Next, a fifth embodiment to which the present disclosure is applied will be described. In this embodiment, a pattern is added to the first switch SW1 of the third embodiment to switch the state of the termination 314 of the split unbalanced line 330 to an open state when viewed from the perspective of a high-frequency signal. This realizes a multi-band balun 150 that can support three different bands.

[0099] The present embodiment will be described below, focusing on the configuration that differs from the third embodiment.

[0100] 10(a) is a schematic diagram of the multiband balun 150 of this embodiment. As shown in this figure, the multiband balun 150 of this embodiment has the same configuration as the multiband balun 130 of the third embodiment.

[0101] However, as described above, the first switch SW1 of this embodiment can also open the termination 314. Therefore, the first switch SW1 can switch the state of the termination 314 between a state where it is connected to the terminal 341, a state where it is connected to the terminal 411 in the ground state, and an open state, in accordance with a control signal from the control unit. In other words, the first switch SW1 can take three states.

[0102] [Operation] Below, we will explain each operation mode that is realized by operating the first switch SW1 and the second switch SW2 under the control of the control unit. Figure 10(b) shows the operation modes that are realized for each state of the first switch SW1 and the second switch SW2 of the multiband balun 150. Also, Figure 10(c) shows the frequency characteristics of the multiband balun 150 in each operation mode.

[0103] When the first switch SW1 is connected to the terminal 341, the split unbalanced line 330 and the second adjustment line 340 are connected. At this time, the second switch SW2 is connected to the terminal TM2. In this case, the total line length of the unbalanced line is L3 (first line length), and the termination 313 is in an open state. Therefore, the multiband balun 150 operates as a Marchand balun with a line length of the first line length. That is, it operates in the above-mentioned mode 2. Its center frequency is fM1, as shown in FIG. 10(c).

[0104] Furthermore, when the first switch SW1 is connected to the terminal 411, the split unbalanced line 330 is not connected to the second adjustment line 340. At this time, the second switch SW2 is connected to the terminal TM1. In this case, the line length of the unbalanced line is L4 (second line length), and its termination 314 is grounded. Therefore, the multiband balun 150 operates as a transformer-type balun with a line length of the second line length. That is, it operates in the above-mentioned mode 3. Its center frequency is fT2, as shown in FIG. 10(c).

[0105] Furthermore, when the first switch SW1 is in an open state, the split unbalanced line 330 is not connected to the second adjustment line 340. At this time, the second switch SW2 is connected to the terminal TM1. In this case, the line length of the unbalanced line is L4 (second line length), and its termination 314 is in an open state. Therefore, the multiband balun 150 operates as a Marchand balun with a line length of the second line length. That is, it operates in the above-mentioned mode 4. Its center frequency is fM2, as shown in FIG. 10(c).

[0106] As described above, the multiband balun 150 of this embodiment can be operated as either a Marchand balun with a first line length, a transformer balun with a second line length, or a Marchand balun with a second line length by using the line length conversion switch 410.

[0107] As described above, these center frequencies fT2, fM1, and fM2 are different. Therefore, the multiband balun 150 of this embodiment can change its center frequency by switching the line length conversion switch 410 with a control signal from the control unit. In other words, it can accommodate three different passband frequencies.

[0108] Furthermore, the circuit configuration of the multiband balun 150 of this embodiment does not increase the circuit area because the line length conversion switch 410 is simply added at a position that separates the unbalanced line 310 and the first balanced line 210. Therefore, according to this embodiment, a small-area, band-variable multiband balun can be realized.

[0109] <<Sixth Embodiment>> Next, a sixth embodiment to which the present disclosure is applied will be described. In this embodiment, a second format conversion switch 430 capable of switching its state between an open state and a grounded state as viewed from a high-frequency signal is provided at the end 313 of the second adjustment line 340 of the second embodiment. This realizes a multiband balun 160 that can support three different bands.

[0110] The present embodiment will be described below, focusing on the configuration that differs from the second embodiment.

[0111] 11(a) is a schematic configuration diagram of the multiband balun 160 of this embodiment. As shown in this figure, the multiband balun 160 of this embodiment has basically the same configuration as the multiband balun 120 of the second embodiment. Furthermore, as described above, the second format conversion switch 430 is provided at the end 313 of the second adjustment line 340.

[0112] The second format conversion switch 430 includes a third switch SW3 that can switch the state of the termination 313 between a grounded state and an open state in response to a control signal from the control unit. The third switch SW3 includes a terminal 431 whose termination is in a grounded state.

[0113] [Operation] Below, we will explain each operation mode that is realized by operating the first switch SW1, the second switch SW2, and the third switch SW3 under the control of the control unit. Figure 11(b) shows the operation modes that are realized for each state of the first switch SW1, the second switch SW2, and the third switch SW3 of the multiband balun 160. Also, Figure 11(c) shows the frequency characteristics of the multiband balun 160 in each operation mode.

[0114] When the first switch SW1 is connected to the terminal 341, the split unbalanced line 330 and the second adjustment line 340 are connected. At this time, the second switch SW2 is connected to the terminal TM2. In this case, the total line length of the unbalanced line is L3 (first line length). Here, when the third switch SW3 is connected to the terminal 431, the end of the unbalanced line is grounded. Therefore, the multiband balun 160 operates as a transformer-type balun with a line length of the first line length. That is, it operates in the above-mentioned mode 1. Its center frequency is fT1, as shown in FIG. 11(c).

[0115] Furthermore, when the first switch SW1 is connected to the terminal 341, the second switch SW2 is connected to the terminal TM2, and the third switch SW3 is open, the unbalanced line has a line length of L3 (first line length) and the end is open. Therefore, the multiband balun 160 operates as a Marchand balun with a line length of the first line length. That is, it operates in the above-mentioned mode 2. Its center frequency is fM1, as shown in FIG. 11(c).

[0116] On the other hand, when the first switch SW1 is in an open state, the split unbalanced line 330 is not connected to the second adjustment line 340. At this time, the second switch SW2 is connected to the terminal TM1. In this case, the line length of the unbalanced line is L4 (second line length), and its termination 314 is in an open state. Therefore, the multiband balun 160 operates as a Marchand balun with a line length of the second line length. That is, it operates in the above-mentioned mode 4. Its center frequency is fM2, as shown in FIG. 11(c).

[0117] As described above, the multiband balun 160 of this embodiment can be operated as either a transformer-type balun with a first line length, a Marchand balun with a first line length, or a Marchand balun with a second line length, using the system line length conversion switch 410 and the second system conversion switch 430.

[0118] As described above, these center frequencies fT1, fM1, and fM2 are different. Therefore, the multiband balun 160 of this embodiment can change its center frequency by switching the system line length conversion switch 410 and the second system conversion switch 430 using a control signal from the control unit. In other words, it can accommodate three different passband frequencies.

[0119] Furthermore, the multiband balun 160 of this embodiment does not increase the circuit area because the circuit configuration simply requires the addition of the system line length conversion switch 410 and the second system conversion switch 430. Therefore, according to this embodiment, a small-area, band-variable multiband balun can be realized.

[0120] <<Seventh Embodiment>> Next, a seventh embodiment to which the present disclosure is applied will be described. In this embodiment, a second format conversion switch 430 capable of switching its state between an open state and a grounded state as viewed from a high-frequency signal is provided at the end 313 of the second adjustment line 340 of the third embodiment. This realizes a multiband balun 170 that can support three different bands.

[0121] The present embodiment will be described below, focusing on the configuration that differs from the third embodiment.

[0122] 12(a) is a schematic configuration diagram of the multiband balun 170 of this embodiment. As shown in this figure, the multiband balun 170 of this embodiment has basically the same configuration as the multiband balun 130 of the third embodiment. Furthermore, as described above, the second format conversion switch 430 is provided at the end 313 of the second adjustment line 340.

[0123] The second format conversion switch 430 includes a third switch SW3 that can switch the state of the termination 313 between a grounded state and an open state in response to a control signal from the control unit. The third switch SW3 includes a terminal 431 whose termination is in a grounded state.

[0124] [Operation] Below, we will explain each operation mode that is realized by operating the first switch SW1, the second switch SW2, and the third switch SW3 under the control of the control unit. Figure 12(b) shows the operation modes that are realized for each state of the first switch SW1, the second switch SW2, and the third switch SW3 of the multiband balun 170. Also, Figure 12(c) shows the frequency characteristics of the multiband balun 170 in each operation mode.

[0125] When the first switch SW1 is connected to the terminal 341, the split unbalanced line 330 and the second adjustment line 340 are connected. At this time, the second switch SW2 is connected to the terminal TM2. In this case, the total line length of the unbalanced line is L3 (first line length). Here, when the third switch SW3 is connected to the terminal 431, the end of the unbalanced line is grounded. Therefore, the multiband balun 170 operates as a transformer-type balun with a line length of the first line length. That is, it operates in the above-mentioned mode 1. Its center frequency is fT1, as shown in FIG. 12(c).

[0126] Furthermore, when the first switch SW1 is connected to the terminal 341, the second switch SW2 is connected to the terminal TM2, and the third switch SW3 is open, the unbalanced line has a line length of L3 (first line length) and the end is open. Therefore, the multiband balun 170 operates as a Marchand balun with a line length of the first line length. That is, it operates in the above-mentioned mode 2. Its center frequency is fM1, as shown in FIG. 12(c).

[0127] On the other hand, when the first switch SW1 is connected to the terminal 411, the split unbalanced line 330 is not connected to the second adjustment line 340. At this time, the second switch SW2 is connected to the terminal TM1. In this case, the line length of the unbalanced line is L4 (second line length), and its termination 314 is grounded. Therefore, the multiband balun 170 operates as a transformer-type balun with the line length of the second line length. That is, it operates in the above-mentioned mode 3. Its center frequency is fT2, as shown in FIG. 12(c).

[0128] As described above, the multiband balun 170 of this embodiment can be operated as either a transformer balun with a first line length, a Marchand balun with a first line length, or a transformer balun with a second line length, by using the system line length conversion switch 410 and the second system conversion switch 430.

[0129] As described above, these center frequencies fT1, fT2, and fM1 are different. Therefore, the multiband balun 170 of this embodiment can change its center frequency by switching the system line length conversion switch 410 and the second system conversion switch 430 using a control signal from the control unit. In other words, it can accommodate three different passband frequencies.

[0130] Furthermore, the multiband balun 170 of this embodiment does not increase the circuit area because the circuit configuration simply requires the addition of the system line length conversion switch 410 and the second system conversion switch 430. Therefore, according to this embodiment, a small-area, band-variable multiband balun can be realized.

[0131] <<Eighth Embodiment>> Next, an eighth embodiment to which the present disclosure is applied will be described. In this embodiment, a pattern for switching the state of the termination 314 of the split unbalanced line 330 to an open state as viewed from a high-frequency signal is added to the first switch SW1 of the seventh embodiment. As a result, this embodiment realizes a multi-band balun 180 that can support four different bands.

[0132] The present embodiment will be described below, focusing on the configuration that differs from the seventh embodiment.

[0133] 13(a) is a schematic diagram of the multiband balun 180 of this embodiment. As shown in this figure, the multiband balun 180 of this embodiment has basically the same configuration as the multiband balun 170 of the seventh embodiment. Furthermore, as described above, the termination 314 can be set to an open state. Therefore, the first switch SW1 can switch the state of the termination 314 between a state in which it is connected to the terminal 341, a state in which it is connected to the terminal 411 in the ground state, and an open state in accordance with a control signal from the control unit. In other words, three states are possible.

[0134] The second format conversion switch 430 includes a third switch SW3 that can switch the state of the termination 313 between a grounded state and an open state in response to a control signal from the control unit. The third switch SW3 includes a terminal 431 whose termination is in a grounded state.

[0135] Therefore, when the first switch SW1 is connected to the terminal 341, the third switch SW3 can switch the state of the termination 313 between a state where it is connected to the terminal 431 in the grounded state and an open state.

[0136] [Operation] Below, we will explain each operation mode that is realized by operating the first switch SW1, the second switch SW2, and the third switch SW3 under the control of the control unit. Figure 13(b) shows the operation modes that are realized for each state of the first switch SW1, the second switch SW2, and the third switch SW3 of the multiband balun 180. Also, Figure 13(c) shows the frequency characteristics of the multiband balun 180 in each operation mode.

[0137] When the first switch SW1 is connected to the terminal 341, the split unbalanced line 330 and the second adjustment line 340 are connected. At this time, the second switch SW2 is connected to the terminal TM2. In this case, the total line length of the unbalanced line is L3 (first line length). Here, when the third switch SW3 is connected to the terminal 431, the end of the unbalanced line is grounded. Therefore, the multiband balun 180 operates as a transformer-type balun with a line length of the first line length. That is, it operates in the above-mentioned mode 1. Its center frequency is fT1, as shown in FIG. 13(c).

[0138] Furthermore, when the first switch SW1 is connected to the terminal 341, the second switch SW2 is connected to the terminal TM2, and the third switch SW3 is open, the unbalanced line has a line length of L3 (first line length) and the end is open. Therefore, the multiband balun 180 operates as a Marchand balun with a line length of the first line length. That is, it operates in the above-mentioned mode 2. Its center frequency is fM1, as shown in FIG. 13(c).

[0139] Furthermore, when the first switch SW1 is connected to the terminal 411, the split unbalanced line 330 is not connected to the second adjustment line 340. At this time, the second switch SW2 is connected to the terminal TM1. In this case, the line length of the unbalanced line is L4 (second line length), and its termination 314 is grounded. Therefore, the multiband balun 180 operates as a transformer-type balun with a line length of the second line length. That is, it operates in the above-mentioned mode 3. Its center frequency is fT2, as shown in FIG. 13(c).

[0140] Furthermore, when the first switch SW1 is in an open state, the split unbalanced line 330 is not connected to the second adjustment line 340. At this time, the second switch SW2 is connected to the terminal TM1. In this case, the line length of the unbalanced line is L4 (second line length), and its termination 314 is in an open state. Therefore, the multiband balun 180 operates as a Marchand balun with a line length of the second line length. That is, it operates in the above-mentioned mode 4. Its center frequency is fM2, as shown in FIG. 13(c).

[0141] As described above, the multiband balun 180 of this embodiment can be operated as any one of a transformer balun with a first line length, a Marchand balun with a first line length, a transformer balun with a second line length, and a Marchand balun with a second line length, by using the system line length conversion switch 410 and the second system conversion switch 430.

[0142] As described above, these center frequencies fT1, fT2, fM1, and fM2 are different. Therefore, the multiband balun 180 of this embodiment can change its center frequency by switching the system line length conversion switch 410 and the second system conversion switch 430 using a control signal from the control unit. In other words, it can accommodate four different passband frequencies.

[0143] Furthermore, the multiband balun 180 of this embodiment does not increase the circuit area because the circuit configuration simply requires the addition of the system line length conversion switch 410 and the second system conversion switch 430. Therefore, according to this embodiment, a small-area, band-variable multiband balun can be realized.

[0144] <Variation 1> In the above embodiments, each switch (first switch SW1, second switch SW2, and third switch SW3) is switchable by an applied voltage, for example, a FET 402 is used. However, the configuration for realizing each switch is not limited to this. There are no particular restrictions as long as it is switchable between two or three states. For example, a PIN diode or the like may be used. Furthermore, a current-driven transistor may be used.

[0145] <Variation 2> For ease of explanation, the above embodiments specify the upper and lower metal layers of the multi-band balun, but the structure is not limited to this. Any structure may be used as long as coupling is possible.

[0146] <Variation 3> In each of the above embodiments, the line length is adjusted on the balanced line side by disconnecting the first balanced line side and inserting the second switch SW2, but this is not limited to this. For example, the line length may be adjusted by inserting the second switch SW2 on the second balanced line side. Alternatively, the line length may be adjusted by inserting the second switch SW2 on both the first balanced line and the second balanced line.

[0147] <Variation 4> In each of the above embodiments, the unbalanced line 310 and the first balanced line 210 are each divided at one location, and a line length conversion switch 410 is inserted to adjust the line length. However, this is not limited to this. For example, as shown in FIG. 14, the unbalanced line 310 and the first balanced line 210 may be divided at multiple locations, and a line length conversion switch 410 may be inserted at each division location. Here, an example of the second embodiment is shown. The same applies to the other examples. This makes it possible to adjust the line length of each coupled line in a variety of ways, thereby increasing the number of frequency bands that can be supported.

[0148] Although the embodiments and modifications of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be modified in various ways that would be understandable to a person skilled in the art. Each embodiment and modification can be combined with other embodiments as appropriate. Furthermore, for example, the network configurations and element configurations shown in the drawings are examples intended to aid in understanding the present disclosure and are not limited to the configurations shown in these drawings.

[0149] Finally, preferred embodiments of the present disclosure will be summarized. Some or all of the above-described embodiments can be described as, but are not limited to, the following supplementary notes. (Appendix 1) The multi-band balun consists of two balanced lines, one end of which is grounded and the other end of which is connected to a balanced terminal that connects to a balanced circuit. an unbalanced line having one end connected to an unbalanced terminal connected to the unbalanced circuit; a first switch; The first switch switches the state of an unbalanced termination, which is an end of the unbalanced line opposite to the end connected to the unbalanced terminal, between an open state and a grounded state. (Appendix 2) In the multi-band balun described in Appendix 1, the unbalanced line has a first line length, It is desirable that the first switch further switches the line length of the unbalanced line between the first line length and a second line length that is shorter than the first line length. (Appendix 3) In the multi-band balun described in Supplementary Note 2, the unbalanced line includes: a split unbalanced line that is connected to the unbalanced terminal and has a second line length that is shorter than the first line length; and an adjustment line that has a length that is equal to or shorter than the difference between the first line length and the second line length, One end of the adjustment line on the split unbalanced line side is connected to a first terminal, and the other end is grounded; It is desirable that the first switch switches the state of the unbalanced termination between the open state and the grounded state by switching the state of one end of the split unbalanced line opposite to the end connected to the unbalanced terminal between a connected state to the first terminal and an open state. (Appendix 4) In the multi-band balun described in Appendix 2, the unbalanced line includes a split unbalanced line that is connected to the unbalanced terminal and has a second line length that is shorter than the first line length, and an adjustment line that has a length that is equal to or shorter than the difference between the first line length and the second line length, One end of the adjustment line on the split unbalanced line side is connected to a first terminal, and the other end is in an open state; It is desirable that the first switch switches the state of the unbalanced termination between the open state and the grounded state by switching the state of one end of the split unbalanced line opposite to the end connected to the unbalanced terminal between a connected state to the first terminal and a grounded state. (Appendix 5) In the multi-band balun described in Supplementary Note 3, It is desirable that the first switch be capable of switching the state of one end of the split unbalanced line opposite to the one end connected to the unbalanced terminal, between the other end and a grounded state. (Appendix 6) In the multi-band balun described in Supplementary Note 4, It is desirable that the first switch be capable of switching the state of one end of the split unbalanced line opposite to the end connected to the unbalanced terminal between an open state and an open state. (Appendix 7) In the multi-band balun according to Supplementary Note 3 or 5, It is preferable to further include a second mode conversion switch connected to the other end of the adjustment line, for switching the state of the other end to either an open state or a grounded state. (Appendix 8) In the multi-band balun according to Supplementary Note 4 or 6, It is preferable to further include a second mode conversion switch connected to the other end of the adjustment line, for switching the state of the other end to either an open state or a grounded state. (Appendix 9) 9. The multi-band balun according to claim 7, It is desirable that the first switch be capable of switching the state of one end of the split unbalanced line opposite to the end connected to the unbalanced terminal between a connected state to the first terminal, an open state, and a grounded state. (Appendix 10) 10. The multi-band balun according to any one of Supplementary Notes 1 to 9, It is desirable that the first switch operates in accordance with a control signal from a control unit. (Appendix 11) 10. The multi-band balun according to any one of Supplementary Notes 7 to 9, It is desirable that the second format conversion switch operates in accordance with a control signal from a control unit. (Appendix 12) In the multi-band balun described in Supplementary Note 2, Further comprising a second switch; It is desirable that the second switch be switched so that the sum of the line lengths of the two balanced lines corresponds to the line length of the unbalanced line. (Appendix 13) In the multi-band balun according to Supplementary Note 2 or 12, the first switch switches the unbalanced line between at least one of a first state and a third state and at least one of a second state and a fourth state; the first state is a state in which the line length of the unbalanced line is the first line length and a state of the unbalanced termination is the grounded state; the second state is such that the line length of the unbalanced line is the first line length and the state of the unbalanced termination is the open state; the third state is a state in which the line length of the unbalanced line is the second line length and the state of the unbalanced termination is the grounded state; In the fourth state, it is desirable that the line length of the unbalanced line is the second line length and the state of the unbalanced termination is the open state. (Appendix 14) In the multi-band balun described in Appendix 1, The first switch is preferably connected to the unbalanced termination. (Appendix 15) The multi-band balun consists of two balanced lines, one end of which is grounded and the other end of which is connected to a balanced terminal that connects to a balanced circuit. an unbalanced line having one end connected to an unbalanced terminal connected to the unbalanced circuit; a line length conversion switch; the unbalanced line includes: a split unbalanced line that is connected to the unbalanced terminal and has a second line length that is shorter than the first line length; and an adjustment line that has a length that is equal to or shorter than the difference between the first line length and the second line length, One end of the adjustment line on the split unbalanced line side is connected to a first terminal, and the other end is grounded; The line length conversion switch is connected to one end of the split unbalanced line on the split unbalanced line side, and is capable of switching the state of the one end between a connected state to the first terminal and an open state. (Appendix 16) The multi-band balun consists of two balanced lines, one end of which is grounded and the other end of which is connected to a balanced terminal that connects to a balanced circuit. an unbalanced line having one end connected to an unbalanced terminal connected to the unbalanced circuit; a line length conversion switch; the unbalanced line includes a split unbalanced line that is connected to the unbalanced terminal and has a second line length that is shorter than the first line length, and an adjustment line that has a length that is equal to or shorter than the difference between the first line length and the second line length, One end of the adjustment line on the split unbalanced line side is connected to a first terminal, and the other end is in an open state; It is desirable that the line length conversion switch is connected to one end of the split unbalanced line opposite to the end connected to the unbalanced terminal, and that the state of the one end is switched between a connection state to the first terminal and a grounded state, thereby switching the state of the unbalanced termination to either the open state or the grounded state. (Appendix 17) 9. The multi-band balun according to claim 7, The second format conversion switch is preferably connected to the other end of the adjustment line.

[0150] The disclosures of the above-mentioned patent documents, etc. are incorporated herein by reference. Modifications and adjustments of the embodiments and variations are possible within the scope of the entire disclosure (including the claims), and further based on the basic technical concepts thereof. Furthermore, various combinations and selections of the various disclosed elements (including each element of each claim, each element of each embodiment or variation, each element of each drawing, etc.) are possible within the scope of the disclosure of the present disclosure. In other words, the present disclosure naturally includes various modifications and alterations that would be possible by a person skilled in the art in accordance with the entire disclosure, including the claims, and the technical concepts thereof. In particular, with regard to the numerical ranges set forth herein, any numerical value or subrange included within the range should be construed as specifically set forth, even if not otherwise specified. [Explanation of symbols]

[0151] 110: Multiband balun, 120: Multiband balun, 130: Multiband balun, 140: Multiband balun, 150: Multiband balun, 160: Multiband balun, 170: Multiband balun, 180: Multiband balun, 210: first balanced line, 211: first balanced terminal, 220: second balanced line, 221: second balanced terminal, 230: split first balanced line, 240: first adjustment line, 310: unbalanced line, 311: unbalanced terminal, 312: unbalanced termination, 313: termination, 314: termination, 330: split unbalanced line, 340: second adjustment line, 341: terminal, 401: Ground terminal, 402: FET, 410: System line length conversion switch, 411: Terminal, 420: Adjustment line, 430: Second system conversion switch, 431: Terminal, 490: Control unit, 910: Marchand balun, 911: Frequency characteristics, 920: Transformer type balun, 921: Frequency characteristics, ADD: coupled line, FC: primary coil, L1: line length, L2: line length, L3: line length (first line length), L4: line length (second line length), L5: line length, L6: line length, OS: open stub, S: coupled line spacing, SC: secondary coil, SS: short stub, SS1: first short stub, SS2: second short stub, SW0: format conversion switch, SW1: first switch, SW2: second switch, SW3: third switch, TM1: terminal, TM2: terminal, W1: line width, W2: line width, W3: line width, fM: center frequency, fM1: center frequency, fM2: center frequency, fT: center frequency, fT1: center frequency, fT2: center frequency, λ: wavelength used

Claims

1. Two balanced lines, one end of which is grounded and the other end of which is connected to a balanced terminal that is connected to a balanced circuit; an unbalanced line having one end connected to an unbalanced terminal connected to the unbalanced circuit; a first switch; The first switch switches the state of the unbalanced termination, which is the end of the unbalanced line opposite to the end connected to the unbalanced terminal, between an open state and a grounded state.

2. 2. The multi-band balun of claim 1, the unbalanced line has a first line length, The first switch further switches the line length of the unbalanced line between the first line length and a second line length that is shorter than the first line length.

3. 3. The multi-band balun according to claim 2, the unbalanced line includes: a split unbalanced line that is connected to the unbalanced terminal and has a second line length that is shorter than the first line length; and an adjustment line that has a length that is equal to or shorter than the difference between the first line length and the second line length, One end of the adjustment line on the split unbalanced line side is connected to a first terminal, and the other end is grounded; The first switch switches the state of the unbalanced termination between the open state and the grounded state by switching the state of one end of the split unbalanced line opposite to the end connected to the unbalanced terminal between a connected state to the first terminal and an open state.

4. 3. The multi-band balun according to claim 2, the unbalanced line includes a split unbalanced line that is connected to the unbalanced terminal and has a second line length that is shorter than the first line length, and an adjustment line that has a length that is equal to or shorter than the difference between the first line length and the second line length, One end of the adjustment line on the split unbalanced line side is connected to a first terminal, and the other end is in an open state; The first switch switches the state of the unbalanced termination between the open state and the grounded state by switching the state of one end of the split unbalanced line opposite to the end connected to the unbalanced terminal between a connected state to the first terminal and a grounded state.

5. 4. The multi-band balun according to claim 3, The first switch is capable of switching the state of one end of the split unbalanced line opposite to the one end connected to the unbalanced terminal between a grounded state and a grounded state.

6. 5. The multi-band balun according to claim 4, The first switch is capable of switching the state of one end of the split unbalanced line opposite to the one end connected to the unbalanced terminal between an open state and an open state.

7. 4. The multi-band balun according to claim 3, The multiband balun further includes a second format conversion switch that switches the state of the other end of the adjustment line between an open state and a grounded state.

8. 5. The multi-band balun according to claim 4, The multiband balun further includes a second format conversion switch that switches the state of the other end of the adjustment line between an open state and a grounded state.

9. 9. The multi-band balun according to claim 8, The first switch is capable of switching the state of one end of the split unbalanced line opposite to the one end connected to the unbalanced terminal between an open state and an open state.

10. 2. The multi-band balun of claim 1, The first switch operates in accordance with a control signal from a control unit.

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