JP2009152861A - Switching circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching circuit which can improve an isolation characteristics, when an electronic switch of a series line is set to off and can operate at high speed. <P>SOLUTION: A switching circuit is constituted of a first electronic switch 4, connected between an input terminal 1 and an output terminal 2; a second electronic switch 8 and a mechanical switch 9, connected in parallel which mutually turn off, when the first electronic switch 4 turns on and turn on mutually, when the first electronic switch 4 turns OFF; and a shunt circuit 7 connected between the input terminal 1 and the output terminal 2 and connected to a ground 5. Thus, when the first electronic switch 4 is off, the second electronic switch 8 and the mechanical switch 9 of the shunt circuit 7 are turned off so that a leak current flows to the ground 5. Also, by switching the first electronic switch 4 at a high speed, the switch circuit is operated at a high speed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a switch circuit in which an electronic switch and a mechanical switch are combined.

  In an apparatus such as a millimeter wave radar sensor, for example, a switch that operates at high speed is required in order to generate a short pulse signal of 1 ns or less or to switch a receiving antenna at high speed. The switch also requires isolation characteristics. The isolation characteristic refers to insulation when the switch is off, and the smaller the amount of leakage in the off state, the better the isolation characteristic.

  Conventionally, electronic switches such as MOSFETs and diodes are known as switches. For example, in an electronic switch in which an N-type source region and a drain region are provided on a P-type semiconductor substrate and a gate electrode is provided on the semiconductor substrate via an insulating film, an on-state voltage is applied between the gate and the source. In this state, the P-type semiconductor substrate directly under the gate electrode is polarized to form an N-type channel layer, and the source-drain are all the same N-type conductor. Flowing. In this case, the electronic switch is equivalent to a circuit composed of one resistor.

  On the other hand, when the electronic switch is in an off state where no voltage is applied between the gate and the source, a channel layer is not formed immediately below the gate electrode, and an N-type-P-type-N-type conductor is formed between the source and drain. No current flows between the source and drain. In this case, the electronic switch is equivalent to a circuit in which a capacitor having an impedance of (1 / jωC) and a resistor are connected in parallel. The capacitance C of the capacitor in the electronic switch is typically about 1 pF, although it depends on the dielectric constant of the P-type semiconductor substrate.

  The electronic switch having such electrical characteristics does not involve physical operation, and thus operates as a switch at a high speed. On the other hand, when a high-frequency signal is input to the electronic switch when the electronic switch is in an off state, A leak occurs. Since the impedance of the capacitor is represented by (1 / jωC), when an electric signal having a high frequency ω is input, the impedance of the capacitor decreases. Therefore, when an electrical signal in a high frequency range of GHz order is input to the electronic switch, there is a problem that leakage current flows even when the electronic switch is in an off state, and isolation characteristics cannot be secured.

  As switches, mechanical switches such as MEMS (Micro Electro Mechanical Systems) switches are known. The mechanical switch is, for example, a switch configured by separating two electrodes from each other by a certain distance, and utilizes the fact that each electrode attracts and contacts each other by electrostatic attraction when a voltage is applied between the electrodes.

  Since the two electrodes are in contact with each other when the mechanical switch is on, the mechanical switch is equivalent to a circuit composed of one resistor. Further, since air is interposed between the two electrodes when the mechanical switch is OFF, this is equivalent to a circuit composed of one capacitor. The capacitance of the capacitor in the mechanical switch is typically about several tens of fF although it depends on the area of the electrode.

  Such a mechanical switch has a feature that it is small in size, has low loss, and has excellent isolation characteristics even in a signal in a high frequency region, but has a drawback that it is difficult to perform high-speed operation because it involves mechanical operation.

  Therefore, for example, Patent Document 1 proposes a switch circuit that compensates for the disadvantages of both. Patent Document 1 proposes a switch circuit in which a mechanical switch and an electronic switch are provided in parallel for both the series line and the shunt line. In this switch circuit, each switch of the shunt line is turned off to transmit a signal while turning on each switch of the series line, and each switch of the shunt line is turned on while turning off each switch of the series line. Is configured to flow to the ground.

In such a switch circuit, the electronic switch provided in parallel is turned on until the mechanical switch starts up, the signal waveform is adjusted, and after the mechanical switch starts up, the electronic switch is turned off to reduce the mechanical loss. Only the function is suppressed, the transmission loss is suppressed, and the isolation characteristic is improved.
US Pat. No. 6,940,363

  However, in the above-described conventional technology, the series line electronic switch is turned on only until the series line mechanical switch is fully opened and closed, so that it is not possible to transmit a signal faster than the time until the mechanical switch is opened and closed. There is.

  In addition, the electronic switch has a larger capacitance when turned off than the mechanical switch, and the impedance to the high-frequency signal is reduced in view of the impedance of (1 / jωC). For this reason, a leak may occur in the electronic switch of the shunt line that should be turned off. Accordingly, there is a problem that the isolation characteristics of the switch circuit are deteriorated.

  An object of the present invention is to provide a switch circuit that can improve the isolation characteristic when a series line electronic switch is OFF and operates at high speed.

  In order to achieve the above object, according to the first aspect of the present invention, the first terminal connected between the input terminal (1) for inputting a signal from the outside and the output terminal (2) for outputting a signal to the outside. The second electronic switch (8) and the mechanical switch (9) which are turned off when the electronic switch (4) and the first electronic switch (4) are turned on, and turned on when the first electronic switch (4) is turned off. And a shunt circuit (7) connected between the input terminal (1) and the output terminal (2) and between the ground (5). .

  Thereby, even if the first electronic switch (4) leaks while the first electronic switch (4) is off, the second electronic switch (8) and the mechanical switch (9) of the shunt circuit (7). By turning on, a leakage current can flow to the ground (5). In this case, in the shunt circuit (7), the second electronic switch (8) can be used as a bypass line from when the mechanical switch (9) is turned on until the mechanical switch (9) is completely turned on. Therefore, when the first electronic switch (4) is off, it is possible to prevent leakage current from flowing to the output terminal (2), and thus the isolation characteristics can be improved.

  In addition, since the input terminal (1) and the output terminal (2) are switched only by the semiconductor switch (4), the switch circuit can be operated at high speed. As described above, the isolation characteristics can be improved and the device can be operated at high speed.

  The invention according to claim 2 is characterized in that the shunt circuit (7) is connected between the input terminal (1) and the first electronic switch (4) and between the ground (5). .

  Thus, when it is desired to turn off the output from the input terminal (1) to the output terminal (2), the first electronic switch (4) is turned off, and each switch of the shunt circuit (7) is turned on. The current can be passed to the ground (5) via the shunt circuit (7) without passing the signal to 4), and the isolation characteristic can be improved.

  The invention according to claim 3 is characterized in that the shunt circuit (7) is connected between the second electronic switch (4) and the output terminal (2) and between the ground (5). .

  Thereby, before the leakage current which passed the 1st electronic switch (4) is output outside from an output terminal (2), it can be sent through a shunt circuit (7) to a ground (5).

  In a fourth aspect of the invention, the second electronic switch (8) includes a first impedance element (10) connected in series to the ground (5) side of the second electronic switch (8). And

  Thereby, even if a leak occurs in the second electronic switch (8) when the second electronic switch (8) is off, the leakage current flows to the ground (5) by the first impedance element (10). Can be suppressed. Therefore, transmission loss between the input terminal (1) and the output terminal (2) can be suppressed.

  The invention according to claim 5 is characterized in that the second impedance element (15) is connected in series to the mechanical switch (9) on the ground (5) side of the mechanical switch (9).

  Thereby, in the shunt circuit (7), the impedance ratio between the path passing through the mechanical switch (9) and the path passing through the second electronic switch (8) can be changed, and the leak flowing through the shunt circuit (7). The current path can be arbitrarily selected. That is, by making the impedance of the path passing through the mechanical switch (9) higher than the impedance of the path passing through the second electronic switch (8), it is positive when the first electronic switch (4) is off. In addition, a leakage current can be passed to the ground (5) via the second electronic switch (8). On the other hand, when the impedance of the path through the mechanical switch (9) is made lower than the impedance of the path through the second electronic switch (8), the first electronic switch (4) is turned off. It is also possible to positively flow a leakage current to the ground (5) via the mechanical switch (9).

  The invention according to claim 6 is characterized in that a third impedance element (16) is connected in parallel to the first impedance element (10).

  Thereby, in the shunt circuit (7), a path passing through the second electronic switch (8) and the third impedance element (16) can be formed. For this reason, the impedance of the path through the second electronic switch (8) and the third impedance element (16) is made smaller than the path through the second electronic switch (8) and the first impedance element (10). After the first electronic switch (4) is turned off, the leakage current is grounded via the second electronic switch (8) and the third impedance element (16) until the mechanical switch (9) is completely turned on. (5). If the mechanical switch (9) is completely conductive, a leakage current can be passed to the ground (5) via the mechanical switch (9).

  In the case where the second impedance element (15) is connected to the subsequent stage of the mechanical switch (9), the path passing through the second electronic switch (8) and the first impedance element (10), the second electronic switch (8) And a path through the third impedance element (16) and the second impedance element (15), and a path through the mechanical switch (9) and the second impedance element (15) can be formed, The path through which the leak current flows can be arbitrarily selected.

  As in the seventh aspect of the invention, a capacitor (11) for preventing leakage of the second electronic switch (8) can be used as the first impedance element (10).

  As in the invention described in claim 8, as the first impedance element (10), a variable capacitance capacitor for adjusting the impedance of the path passing through the second electronic switch (8) and the first impedance element (10) ( 12) can be used.

  As in the invention described in claim 9, a mechanical switch (13) for preventing leakage of the second electronic switch (8) can be used as the first impedance element (10).

  As in the tenth aspect, an impedance variable element (14) capable of changing impedance can be used as the first impedance element (10).

  As in the invention described in claim 11, a capacitor (11) for preventing leakage of the mechanical switch (9) can be used as the second impedance element (15).

  As in the invention described in claim 12, as the second impedance element (15), a variable capacitance capacitor (12) for adjusting the impedance of a path passing through the mechanical switch (9) and the second impedance element (15) Can be used.

  As in the thirteenth aspect of the present invention, a mechanical switch (13) for preventing leakage of the second electronic switch (8) can be used as the second impedance element (15).

  As in the invention described in claim 14, an impedance variable element (14) capable of changing impedance can be used as the second impedance element (15).

  As in the invention described in claim 15, a capacitor (11) for preventing leakage of the second electronic switch (8) can be used as the third impedance element (16).

  As in the invention described in claim 16, as the third impedance element (16), a variable capacitance capacitor for adjusting the impedance of the path passing through the second electronic switch (8) and the third impedance element (16) ( 12) can be used.

  As in the invention described in claim 17, a mechanical switch (13) for preventing leakage of the second electronic switch (8) can be used as the third impedance element (16).

  As in the eighteenth aspect, an impedance variable element (14) capable of changing impedance can be used as the third impedance element (16).

  As in the invention described in claim 19, a MEMS switch can be used as the mechanical switch (9, 13). Thereby, a mechanical switch (9, 13) can be reduced in size.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The switch circuit shown in the present embodiment is used, for example, as a switch for receiving antennas for receiving signals when receiving signals transmitted from the outside with a plurality of receiving antennas. In particular, it is suitable for a device that handles a high frequency of GHz order.

  FIG. 1 is a circuit diagram of a switch circuit according to the first embodiment of the present invention. A series line 3 is formed between an input terminal 1 to which a transmission signal is input from the outside of the switch circuit and an output terminal 2 from which the transmission signal is output to the outside of the switch circuit.

  The series line 3 is provided with a first electronic switch 4. The first electronic switch 4 is a semiconductor switching element having no movable part such as a MOSFET or a diode. In the present embodiment, an n-channel MOSFET is employed as the first electronic switch 4. As shown in FIG. 1, the drain of the first electronic switch 4 is connected to the input terminal 1 and the source is connected to the output terminal 2.

  A shunt line 6 is provided between the series line 3 and the ground 5. The shunt line 6 is provided with a shunt circuit 7. The shunt circuit 7 is configured by connecting a second electronic switch 8 and a mechanical switch 9 in parallel. That is, in the present embodiment, both the route via the second electronic switch 8 and the route via the mechanical switch 9 are the shunt line 6 between the series line 3 and the ground 5.

  The second electronic switch 8 is a semiconductor switching element like the first electronic switch 4 and adopts a MOSFET. The mechanical switch 9 is a switch having a movable part. In the present embodiment, a mechanical switch 9 formed by MEMS technology is employed.

  As the mechanical switch 9 by MEMS, for example, a buffer layer is formed on a substrate, one electrode is provided on the buffer layer, a column is formed on the buffer layer, and the other electrode is supported by this column. Thus, it is possible to adopt a structure in which the two electrodes are arranged to face each other with air interposed therebetween. A voltage is applied to each electrically separated electrode, and each electrode functions as a switch by attracting and contacting each other by electrostatic attraction.

  In the switch circuit having such a configuration, the first electronic switch 4 provided on the series line 3 and the mechanical switch 9 and the second electronic switch 8 provided on the shunt line 6 are on / off controlled opposite to each other. The For example, the mechanical switch 9 and the second electronic switch 8 of the shunt circuit 7 are turned off when the first electronic switch 4 is on, and the mechanical switch 9 and the second electronic switch 8 of the shunt circuit 7 are turned off when the first electronic switch 4 is off. The two electronic switches 8 are turned on each other.

  The first electronic switch 4, the second electronic switch 8, and the mechanical switch 9 are controlled by a control circuit (not shown) provided outside the switch circuit. That is, the first and second electronic switches 4 and 8 are on / off controlled by a switching signal input from the control circuit to the gate, and the mechanical switch 9 is applied with a voltage from the control circuit. ON / OFF controlled. The above is the overall configuration of the switch circuit according to the present embodiment.

  Next, the operation of the switch circuit shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a time chart showing the contents of the operation of the switch circuit shown in FIG. The horizontal axis indicates time, and the vertical axis indicates the current magnitude.

  First, the first electronic switch 4 provided in the series line 3 is turned off, and the mechanical switch 9 and the second electronic switch 8 of the shunt circuit 7 provided in the shunt line 6 are both turned on. In this state, even if a transmission signal is input to the input terminal 1, the transmission signal is not transmitted to the output terminal 2 because the series line 3 is blocked by the first electronic switch 4.

  Since the first electronic switch 4 is a semiconductor switching element, even when the first electronic switch 4 is turned off, when the high-frequency transmission signal is input to the first electronic switch 4 as described above, the first electronic switch 4 As a result, the leakage current flows through the series line 3.

  However, since the mechanical switch 9 and the second electronic switch 8 of the shunt circuit 7 are both turned on, the leakage current flowing through the series line 3 passes through the shunt line 6 and the second electronic switch 8 that pass through the mechanical switch 9. The shunt line 6 flows to the ground 5. Thereby, the league current is not output to the outside from the output terminal 2, and the isolation characteristic of the switch circuit can be improved.

  Subsequently, the first electronic switch 4 is turned on at the time point T 2, and the transmission signal input to the input terminal 1 is output from the output terminal 2. In this case, both the mechanical switch 9 and the second electronic switch 8 of the shunt circuit 7 are turned off. However, since the mechanical switch 9 has a time delay in operation, the mechanical switch 9 starts to be turned off at a time T1 earlier than the time T2. It is completely turned off at time T2. The second electronic switch 8 is turned off at the same time as the first electronic switch 4 is turned on.

  In such an intermediate state between the time point T1 and the time point T2, the mechanical switch 9 is about to be turned off, but the second electronic switch 8 is kept on. For this reason, even in the intermediate state, a bypass line by the second electronic switch 8 is secured, and a leak current can flow to the ground 5 via the shunt line 6 passing through the second electronic switch 8. Thereby, the fall of the isolation characteristic between the time T1 and the time T2 can be prevented.

  At time T2, the first electronic switch 4 is turned on, and the mechanical switch 9 and the second electronic switch 8 of the shunt circuit 7 are turned off. As a result, the transmission signal input to the input terminal 1 is output to the outside from the output terminal 2 via the series line 3.

  Thereafter, at time T3, the first electronic switch 4 is turned off, and transmission of the transmission signal is stopped. When the first electronic switch 4 is turned off, both the mechanical switch 9 and the second electronic switch 8 of the shunt circuit 7 are turned on. In this case, since there is a time delay in the operation of the mechanical switch 9, the mechanical switch 9 cannot be completely turned on until the time T4, but the second electronic switch 8 can be turned on simultaneously with the turning off of the first electronic switch 4. For this reason, in an intermediate state between the time point T3 and the time point T4, the leakage current flowing through the series line 3 can be supplied to the ground 5 by the shunt line 6 passing through the second electronic switch 8. Thereby, the fall of the isolation characteristic between the time T3 and the time T4 can be prevented.

  At time T4, since the mechanical switch 9 is completely turned on, the leakage current can be supplied to the ground 5 through both the shunt line 6 passing through the mechanical switch 9 and the shunt line 6 passing through the second electronic switch 8. it can.

  As described above, the shunt circuit 7 is a parallel circuit of the mechanical switch 9 and the second electronic switch 8. However, the mechanical switch 9 is physically contacted / separated and has a low resistance when turned on. In the state where the switch 9 is completely turned on, the leakage current flows to the ground 5 mainly through the shunt line 6 passing through the mechanical switch 9. However, since the operation delay occurs in the mechanical switch 9, the operation delay of the mechanical switch 9 can be supplemented by providing the shunt circuit 7 with the second electronic switch 8 that can follow the on / off of the first electronic switch 4. It has become. Further, when the mechanical switch 9 is completely turned on, a leak current can be supplied to the ground 5 through the low-resistance mechanical switch 9. Therefore, it can be said that the second electronic switch 8 and the mechanical switch 9 operate in a complementary manner.

  As described above, in the present embodiment, the first electronic switch 4 is provided in the series line 3, and the shunt circuit 7 in which the mechanical switch 9 and the second electronic switch 8 are connected in parallel between the series line 3 and the ground 5. It is characterized by connecting.

  As a result, even if the first electronic switch 4 leaks when the first electronic switch 4 is turned off, the mechanical switch 9 and the second electronic switch 8 of the shunt circuit 7 are turned on, so that the current flows through the series line 3. Leakage current can be passed to the ground 5. Therefore, the overall isolation characteristics between the input terminal 1 and the output terminal 2 can be improved.

  In the shunt circuit 7, the shunt line 6 passing through the second electronic switch 8 can be used as a bypass line until the mechanical switch 9 is completely turned on. Therefore, since the operation delay of the mechanical switch 9 can be compensated for by the second electronic switch 8, even if the first electronic switch 4 is operated at high speed, the transmission signal can be transmitted without degrading the isolation characteristics. it can.

  And since what was formed by MEMS as the mechanical switch 9 is used, the mechanical switch 9 itself can be reduced in size. Thereby, it is possible to avoid an increase in size of the switch circuit and to provide a compact switch circuit.

(Second Embodiment)
In the present embodiment, only different parts from the first embodiment will be described. The present embodiment is characterized in that an impedance element is provided on the shunt line 6 provided with the second electronic switch 8.

  FIG. 3 is a circuit diagram of the switch circuit according to the present embodiment. As shown in this figure, in the shunt circuit 7, the first impedance element 10 is connected in series on the subsequent stage of the second electronic switch 8, that is, on the ground 5 side. The subsequent stage of the second electronic switch 8 refers to the source of the second electronic switch 8.

  In the present embodiment, a capacitor 11 is employed as the first impedance element 10. The capacitor 11 serves as a resistor from the viewpoint of high frequency, and is used to prevent leakage of the second electronic switch 8. That is, when the first electronic switch 4 is on, the second electronic switch 8 is off, but even if a leak occurs in the second electronic switch 8, the capacitor 11 causes the second electronic switch 8 to Leakage current is prevented. Thereby, it is possible to prevent a transmission signal from flowing from the series line 3 to the shunt line 6 and to reduce transmission loss.

  As described above, by providing the capacitor 11 as the first impedance element 10 at the subsequent stage of the second electronic switch 8, even if leakage occurs when the second electronic switch 8 is turned off, the capacitor 11 that functions as a resistor It is possible to suppress the leakage current from flowing to the ground 5.

(Third embodiment)
In the present embodiment, only different parts from the second embodiment will be described. FIG. 4 is a circuit diagram of the switch circuit according to the present embodiment. As shown in this figure, in this embodiment, a variable capacitance capacitor 12 is employed as the first impedance element 10.

  The capacity variable capacitor 12 can adjust the capacity. That is, the variable capacitor 12 adjusts the impedance of the shunt line 6 that passes through the second electronic switch 8 and the first impedance element 10.

  FIG. 5 is a time chart showing the contents of the operation of the switch circuit shown in FIG. FIG. 5 shows the change in impedance with respect to time for the variable capacitance capacitor 12.

  From time T1 when the mechanical switch 9 is turned off to time T2 when the mechanical switch 9 is actually switched to the off state, high-frequency leakage current flowing through the first electronic switch 4 in the off state is caused by the shunt line 6 via the second electronic switch 8. It flows to the ground 5 and the isolation characteristic is ensured.

  At time T2, the first electronic switch 4 is turned on, the mechanical switch 9 is completely turned off, and the second electronic switch 8 is turned off. Even if a leak occurs in the second electronic switch 8 after the time T2, the variable current capacitor 12 blocks the leak current by switching the variable capacitor 12 to the high impedance state.

  Thereafter, when the first electronic switch 4 is turned off at the time T3 and the mechanical switch 9 and the second electronic switch 8 are turned on, the leakage current is not increased until the time T4 when the mechanical switch 9 is completely turned on. Each of the shunt lines 6 flows through the second electronic switch 8 to ensure the isolation characteristics of the switch circuit.

  When the mechanical switch 9 is completely turned on at time T4, the leakage current flows mainly to the ground 5 through the shunt line 6 passing through the mechanical switch 9, so that the isolation characteristic of the switch circuit is ensured.

  As described above, the variable capacitance capacitor 12 can be used as the first impedance element 10.

(Fourth embodiment)
In the present embodiment, only different parts from the first embodiment will be described. FIG. 6 is a circuit diagram of the switch circuit according to the present embodiment. As shown in this figure, in this embodiment, a mechanical switch 13 for preventing leakage of the second electronic switch 8 is employed as the first impedance element 10. Since the mechanical switch 13 is a MEMS switch and is constituted by two electrodes as described above, it plays the same role as one capacitor. Thus, the mechanical switch 13 can be used as the first impedance element 10.

(Fifth embodiment)
In the present embodiment, only different parts from the first embodiment will be described. FIG. 7 is a circuit diagram of the switch circuit according to the present embodiment. As shown in this figure, in this embodiment, an impedance variable element 14 is employed as the first impedance element 10. The impedance variable element 14 has an impedance that increases as the frequency increases. For example, a chip resistor can be used. Thus, the impedance variable element 14 can be used as the first impedance element 10.

(Sixth embodiment)
In the present embodiment, only different portions from the above embodiments will be described. In the second embodiment, the capacitor 11 is provided as the first impedance element 10 at the subsequent stage of the second electronic switch 8 in the shunt circuit 7. However, in the present embodiment, an impedance element may be further provided at the subsequent stage of the mechanical switch 9. It is a feature.

  FIG. 8 is a circuit diagram of the switch circuit according to the present embodiment. As shown in this figure, the second impedance element 15 is connected in series to the ground 5 side of the mechanical switch 9. In the present embodiment, the variable capacitance capacitor 12 is employed as the second impedance element 15. The variable capacitance capacitor 12 is for adjusting the impedance of the shunt line 6 that passes through the mechanical switch 9 and the second impedance element 15.

  In such a shunt circuit 7, the impedance ratio between the shunt line 6 passing through the mechanical switch 9 and the shunt line 6 passing through the second electronic switch 8 can be changed. Thereby, the path of the leak current flowing through the shunt circuit 7 can be arbitrarily selected.

  For example, the impedance of the shunt line 6 passing through the mechanical switch 9 is made higher than that of the shunt line 6 passing through the second electronic switch 8. That is, the impedance of the shunt line 6 that passes through the mechanical switch 9 is increased using a capacitor having a large capacitance value. As a result, when the first electronic switch 4 is off, a leak current can be actively passed to the ground 5 through the shunt line 6 that passes through the second electronic switch 8.

  Similar to the time chart shown in FIG. 5, the impedance of the variable capacitance capacitor 12 is low impedance when the first electronic switch 4 is off, and high impedance when the first electronic switch 4 is on. As described above, the variable capacitor 12 can be provided as the second impedance element 15 in the shunt line 6 in which the mechanical switch 9 is provided so that the path through which the leakage current flows can be selected.

(Seventh embodiment)
In the present embodiment, only parts different from the sixth embodiment will be described. FIG. 9 is a circuit diagram of the switch circuit according to the present embodiment. As shown in this figure, in this embodiment, an impedance variable element 14 is used as the first impedance element 10.

  FIG. 10 is a time chart showing the contents of the operation of the switch circuit shown in FIG. Until the time T2 when the second electronic switch 8 is switched from on to off, or after the time T3 when the second electronic switch 8 is switched from off to on, both the impedance variable element 14 and the variable capacitance capacitor 12 are set in the low impedance state. For this reason, each shunt line 6 of the shunt circuit 7 has a low impedance, and the isolation characteristics are improved.

  On the other hand, when the first electronic switch 4 is on, both the variable impedance element 14 and the variable capacitance capacitor 12 are switched to the high impedance state. For this reason, the impedance of each shunt line 6 rises together to prevent leakage current and improve transmission loss.

  As described above, the variable impedance element can be used as the first impedance element 10 and the variable capacitance capacitor 12 can be used as the second impedance element 15.

(Eighth embodiment)
In the present embodiment, only different parts from the second embodiment will be described. The present embodiment is characterized in that a third impedance element for connecting the shunt line 6 via the mechanical switch 9 and the shunt line 6 via the second electronic switch 8 is provided.

  FIG. 11 is a circuit diagram of the switch circuit according to the present embodiment. As shown in this figure, a third impedance element 16 is connected in parallel to a capacitor 11 that is the first impedance element 10. Here, since the third impedance element 16 is connected between the subsequent stage of the mechanical switch 9 and the subsequent stage of the second electronic switch 8, a bridge circuit is configured by the third impedance element 16 in the shunt circuit 7. In the present embodiment, a variable capacitance capacitor 12 for adjusting the impedance of the path passing through the second electronic switch 8 and the third impedance element 16 is employed as the third impedance element 16.

  FIG. 12 is a time chart showing the contents of the operation of the switch circuit shown in FIG. When the first electronic switch 4 is on, the variable capacitance capacitor 12 serving as a bridge component is in a high impedance state. For this reason, the leakage current from the second electronic switch 8 is blocked by the variable capacitance capacitor 12 and the capacitor 11, and the transmission loss is improved.

  On the other hand, when the first electronic switch 4 is off, the variable capacitance capacitor 12 serving as a bridge component is in a low impedance state. For this reason, the leakage current from the first electronic switch 4 flows to the ground 5 via the second electronic switch 8 and the variable capacitance capacitor 12.

  That is, the impedance of the path through the second electronic switch 8 and the variable capacitance capacitor 12 is made smaller than that of the shunt line 6 through the second electronic switch 8 and the first impedance element 10, so that the first electronic switch 4 is timed. After turning off at T3, the leakage current can flow to the ground 5 via the second electronic switch 8 and the variable capacitance capacitor 12 until the time T4 when the mechanical switch 9 is completely turned on. After the time T4 when the mechanical switch 9 is completely turned on, a leak current is passed to the ground 5 via the shunt line 6 passing through the mechanical switch 9. The same applies until the mechanical switch 9 is turned off at time T1 and completely turned off at time T2.

  As described above, by providing the variable capacitance capacitor 12 as the third impedance element 16 as the bridge component, the second electronic switch 8 and the variable capacitance capacitor 12 are passed until the mechanical switch 9 is completely turned on or off. A path can be formed, and a leakage current can flow to the ground 5. Thereby, the isolation characteristic can be improved.

(Ninth embodiment)
In the present embodiment, only parts different from the eighth embodiment will be described. FIG. 13 is a circuit diagram of the switch circuit according to the present embodiment. As shown in this figure, in the present embodiment, an impedance variable element 14 that can change the impedance is used as the third impedance element 16. The operation of the switch circuit shown in FIG. 13 is the same as that shown in FIG. Thus, the variable impedance element 14 can be used as the third impedance element 16.

(10th Embodiment)
In the present embodiment, only portions different from the eighth and ninth embodiments will be described. FIG. 14 is a circuit diagram of the switch circuit according to the present embodiment. As shown in this figure, in this embodiment, an impedance variable element 14 is used for each of the first and third impedance elements 10 and 16.

  FIG. 15 is a time chart showing the contents of the operation of the switch circuit shown in FIG. As shown in this figure, when the first electronic switch 4 is turned on at time T2, the impedance variable element 14 at the rear stage of the second electronic switch 8 and the impedance variable element 14 as a bridge component are both in a high impedance state. Therefore, the leakage current from the second electronic switch 8 is blocked by each impedance variable element 14, and the transmission loss is improved.

  On the other hand, when the first electronic switch 4 is turned off at the time T3 (or before the time T2), both the variable impedance elements 14 are in a low impedance state. Accordingly, the leakage current from the first electronic switch 4 flows to the ground 5 mainly through the shunt line 6 passing through the mechanical switch 9. As described above, the variable impedance element 14 can be used as each of the first and third impedance elements 10 and 16.

(Eleventh embodiment)
In the present embodiment, only parts different from the ninth embodiment will be described. FIG. 16 is a circuit diagram of the switch circuit according to the present embodiment. As shown in this figure, the switch circuit shown in FIG. 13 has a circuit configuration in which a second impedance element 15 is provided after the mechanical switch 9. In the present embodiment, the variable impedance element 14 is employed as the second impedance element 15.

  FIG. 17 is a time chart showing the contents of the operation of the switch circuit shown in FIG. As shown in this figure, when the first electronic switch 4 is on, the capacitor 11 at the rear stage of the second electronic switch 8, the impedance variable element 14 at the rear stage of the mechanical switch 9, and all the n impedance variable elements 14 as bridge parts A high impedance state prevents leakage current.

  When the impedance variable element 14 is provided at the subsequent stage of the mechanical switch 9, the shunt line 6 passing through the second electronic switch 8 and the capacitor 11, the second electronic switch 8, and the impedance variable element 14 and the mechanical switch 9 as bridge parts are provided. It is possible to form a path that passes through the impedance variable element 14 at the subsequent stage and a shunt line 6 that passes through the mechanical switch 9 and the impedance variable element 14. Therefore, by adjusting the impedance of each path, the path through which the leak current flows can be arbitrarily selected.

(Twelfth embodiment)
In the present embodiment, only parts different from the eleventh embodiment will be described. FIG. 18 is a circuit diagram of the switch circuit according to the present embodiment. As shown in this figure, in this embodiment, an impedance variable element 14 is used as the first impedance element 10. The operation of the switch circuit shown in FIG. 18 is the same as that shown in FIG. Thus, the impedance variable element 14 can be used as the first impedance element 10.

(13th Embodiment)
In the present embodiment, only parts different from the tenth embodiment will be described. In the tenth embodiment, the variable impedance element 14 is used as the first impedance element 10, but in this embodiment, as shown in FIG. 19, a capacitor 11 is used as the first impedance element 10, and the mechanical switch is used. The second impedance element 15 is connected to the subsequent stage of 9. In addition, the variable impedance element 14 is used as the second and third impedance elements 15 and 16.

  FIG. 20 is a time chart showing the contents of the operation of the switch circuit shown in FIG. As shown in this figure, when the first electronic switch 4 is on between the time point T2 and the time point T3, the impedance variable element 14 at the rear stage of the mechanical switch 9 and the impedance variable element 14 connected in parallel to the capacitor 11 are used. Is in a high impedance state to prevent leakage current.

  As described above, in the circuit configuration using the first to third impedance elements 10, 15, and 16, the impedance variable element 14 is disposed after the mechanical switch 9, and the leakage current of the shunt line 6 that passes through the mechanical switch 9. Can be prevented.

(14th Embodiment)
In the present embodiment, only parts different from the thirteenth embodiment will be described. As shown in FIG. 21, in this embodiment, an impedance variable element 14 is used as the first impedance element 10.

  FIG. 22 is a time chart showing the contents of the operation of the switch circuit shown in FIG. As shown in this figure, when the first electronic switch 4 is on between the time point T2 and the time point T3, the impedance variable element 14 at the rear stage of the mechanical switch 9 and the rear stage of the second electronic switch 8 are connected in parallel. Further, by setting each impedance variable element 14 to a high impedance state, leakage current is prevented. Thus, in the switch circuit, a circuit configuration in which all of the first to third impedance elements 10, 15, and 16 are the impedance variable elements 14 may be used.

(Other embodiments)
In each of the above embodiments, the shunt circuit 7 is connected between the first electronic switch 4 and the output terminal 2 and the ground 5, that is, between the rear stage of the first electronic switch 4 and the ground 5. The shunt circuit 7 may be connected between the input terminal 1 and the first electronic switch 4, that is, between the previous stage of the first electronic switch 4 and the ground 5. In this case, the leak input to the input terminal 1 flows to the ground 5 through the shunt circuit 7 before flowing through the first electronic switch 4.

  In each of the above-described embodiments, the use of the one formed by MEMS as the mechanical switch 9 has been described. However, if the mechanical switch 9 is turned on / off by the mechanical operation of the movable portion, the one formed by MEMS is used. Not necessarily.

  In the sixth and seventh embodiments, the use of the variable capacitance capacitor 12 as the second impedance element 15 has been described. However, any one of the capacitor 11, the mechanical switch 13, and the impedance variable element 14 is used as the second impedance element 15. You can also

  In the eighth to fourteenth embodiments, the use of the variable capacitor 12 or the variable impedance element 14 as the third impedance element 16 has been described. However, either the capacitor 11 or the mechanical switch 13 is used as the third impedance element 16. You can also

  That is, as the first to third impedance elements 10, 15, and 16, a circuit configuration in which each of the capacitor 11, the variable capacitance capacitor 12, the mechanical switch 13, and the impedance variable element 14 can be combined. For example, a capacitor 11 for preventing leakage of the mechanical switch 9 can be used as the second impedance element 15, and a mechanical switch 13 can be used as the second impedance element 15. Further, as the third impedance element 16, a capacitor 11 or a mechanical switch 13 for preventing leakage of the second electronic switch 8 can be used.

  As the capacitance variable capacitor 12, for example, a capacitor whose capacitance value is manually changed when the switch circuit is manufactured or when the switch circuit is actually used may be used.

  In the above embodiments, single elements are used as the first to third impedance elements 10, 15, and 16. However, a plurality of elements may be combined in series or in parallel.

1 is a circuit diagram of a switch circuit according to a first embodiment of the present invention. It is the time chart which showed the content of the action | operation of the switch circuit shown by FIG. It is a circuit diagram of a switch circuit concerning a 2nd embodiment of the present invention. It is a circuit diagram of a switch circuit concerning a 3rd embodiment of the present invention. FIG. 5 is a time chart showing the contents of operation of the switch circuit shown in FIG. 4. FIG. It is a circuit diagram of the switch circuit concerning a 4th embodiment of the present invention. It is a circuit diagram of a switch circuit concerning a 5th embodiment of the present invention. It is a circuit diagram of the switch circuit concerning a 6th embodiment of the present invention. It is a circuit diagram of a switch circuit concerning a 7th embodiment of the present invention. 10 is a time chart showing the contents of the operation of the switch circuit shown in FIG. 9. It is a circuit diagram of a switch circuit concerning an 8th embodiment of the present invention. 12 is a time chart showing the contents of the operation of the switch circuit shown in FIG. It is a circuit diagram of the switch circuit concerning a 9th embodiment of the present invention. It is a circuit diagram of the switch circuit concerning a 10th embodiment of the present invention. It is the time chart which showed the content of the action | operation of the switch circuit shown by FIG. It is a circuit diagram of a switch circuit concerning an 11th embodiment of the present invention. FIG. 17 is a time chart showing the contents of the operation of the switch circuit shown in FIG. 16. It is a circuit diagram of a switch circuit concerning a 12th embodiment of the present invention. It is a circuit diagram of a switch circuit concerning a 13th embodiment of the present invention. It is the time chart which showed the content of the action | operation of the switch circuit shown by FIG. It is a circuit diagram of the switch circuit concerning a 14th embodiment of the present invention. It is the time chart which showed the content of the action | operation of the switch circuit shown by FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input terminal 2 Output terminal 4 1st electronic switch 5 Ground 7 Shunt circuit 8 2nd electronic switch 9, 13 Mechanical switch 10 1st impedance element 11 Capacitor 12 Capacitance variable capacitor 14 Impedance variable element 15 2nd impedance element 16 3rd impedance element

Claims (19)

A first electronic switch (4) connected between an input terminal (1) for inputting a signal from the outside and an output terminal (2) for outputting a signal to the outside;
A second electronic switch (8) and a mechanical switch (9) that are turned off when the first electronic switch (4) is turned on and turned on when the first electronic switch (4) is turned off are connected in parallel. And a shunt circuit (7) connected between the input terminal (1) and the output terminal (2) and between the ground (5).   The shunt circuit (7) is connected between the input terminal (1) and the first electronic switch (4) and between the ground (5). Switch circuit.   The shunt circuit (7) is connected between the second electronic switch (4) and the output terminal (2) and between the ground (5).   A first impedance element (10) is connected to the second electronic switch (8) in series on the ground (5) side of the second electronic switch (8). The switch circuit according to any one of the above.   The switch circuit according to claim 4, wherein a second impedance element (15) is connected to the mechanical switch (9) in series on the ground (5) side of the mechanical switch (9).   The switch circuit according to claim 4 or 5, wherein a third impedance element (16) is connected in parallel to the first impedance element (10).   The capacitor (11) for preventing leakage of the second electronic switch (8) is used as the first impedance element (10), according to any one of claims 4 to 6. Switch circuit.   As the first impedance element (10), a variable capacitance capacitor (12) for adjusting an impedance of a path passing through the second electronic switch (8) and the first impedance element (10) is used. The switch circuit according to any one of claims 4 to 6.   The mechanical switch (13) for preventing the leakage of the second electronic switch (8) is used as the first impedance element (10), according to any one of claims 4 to 6. Switch circuit.   The switch circuit according to any one of claims 4 to 6, wherein an impedance variable element (14) capable of changing an impedance is used as the first impedance element (10).   The switch circuit according to claim 5, wherein a capacitor (11) for preventing leakage of the mechanical switch (9) is used as the second impedance element (15).   As the second impedance element (15), a variable capacitance capacitor (12) for adjusting the impedance of a path passing through the mechanical switch (9) and the second impedance element (15) is used. The switch circuit according to claim 5.   The switch circuit according to claim 5, wherein a mechanical switch (13) for preventing leakage of the second electronic switch (8) is used as the second impedance element (15).   The switch circuit according to claim 5, wherein an impedance variable element (14) capable of changing an impedance is used as the second impedance element (15).   The switch circuit according to claim 6, wherein a capacitor (11) for preventing leakage of the second electronic switch (8) is used as the third impedance element (16).   As the third impedance element (16), a variable capacitance capacitor (12) for adjusting the impedance of a path passing through the second electronic switch (8) and the third impedance element (16) is used. The switch circuit according to claim 6.   The switch circuit according to claim 6, wherein a mechanical switch (13) for preventing leakage of the second electronic switch (8) is used as the third impedance element (16).   The switch circuit according to claim 6, wherein an impedance variable element (14) capable of changing impedance is used as the third impedance element (16).   10. The switch circuit according to claim 1, wherein the mechanical switch (9, 13) is a MEMS switch.

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