JP2006157423A - High-frequency switching circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable obtaining proper isolation characteristic, even when a high-frequency signal is inputted in which off-capacitance of a field effect transistor that becomes a problem. <P>SOLUTION: Inductors 41, 42 and an FET 11 are provided on a transmission path connecting a terminal X1 and a node Y0; and an FET 12, a DC cut capacitor 21 and an inductor 31 are provided on a shunt path, connecting this transmission path and the ground. The input/output impedance of a circuit, consisting of the inductors 31, 41, 42 and the FET 12 in an off state, is configured so as to match the characteristic impedance of the transmission path. The inductors 31, 41, 42 are each configured of a bonding wire, the lead of a lead frame, the wiring of a semiconductor package, the wiring of a printed board or an inductor formed on a semiconductor substrate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high-frequency switch circuit that controls the flow of a high-frequency signal between a plurality of terminals.

  High-frequency switch circuits that control the flow of high-frequency signals between a plurality of terminals are used in wireless communication devices such as mobile phones and wireless communication base stations. The high frequency switch circuit is configured by providing a switch element such as a field effect transistor (hereinafter abbreviated as FET) on a transmission path through which a high frequency signal flows. Further, the high frequency switch circuit is provided with a shunt circuit that allows a high frequency signal flowing through the transmission path to escape to the ground when the switch element is in a cut-off state.

  FIG. 8 is a diagram showing a configuration of a conventional high-frequency switch circuit. The high frequency switch circuit 9 shown in FIG. 8 includes FETs 91 to 94 and DC cut capacitors 95 and 96. The FET 91 is provided on the first transmission path connecting the terminal X1 and the node Y0, and the FET 93 is provided on the second transmission path connecting the terminal X2 and the node Y0. The FET 92 and the DC cut capacitor 95 are provided on the first shunt path connecting the first transmission path and the ground, and the FET 94 and the DC cut capacitor 96 are the second shunt connecting the second transmission path and the ground. Provided on the route.

  A control signal CTRL1 is applied to the control terminals of the FETs 11 and 14, and a control signal CTRL2 having a level opposite to that of the control signal CTRL1 is applied to the control terminals of the FETs 12 and 13. When the FETs 11 and 14 are in the on state and the FETs 12 and 13 are in the off state, the terminal X1 and the terminal X3 are electrically connected, and the terminal X2 and the terminal X3 are electrically disconnected. At this time, the high-frequency signal flowing through the second transmission path passes through the first shunt path and flows to the ground. On the other hand, when the FETs 12 and 13 are in the on state and the FETs 11 and 14 are in the off state, the terminal X2 and the terminal X3 are electrically connected, and the terminal X1 and the terminal X3 are electrically disconnected. At this time, the high-frequency signal flowing through the first transmission path passes through the second shunt path and flows to the ground.

  In general, an FET included in a high-frequency switch circuit is equivalent to a resistance element (on-resistance) having a resistance value Ron if the FET is in an on state, and equivalent to a capacitance element (off-capacitance) having a capacitance value Coff if the FET is off. It is. For example, when the first transmission path in the high-frequency switch circuit 9 is in a conductive state, an equivalent circuit of a portion on the terminal X1 side of the node Y0 is as shown in FIG. Further, since the resistance value Ron is sufficiently small and the capacitance value C95 of the DC cut capacitor 95 is extremely larger than the capacitance value Coff, the circuit shown in FIG. 9A should be approximated by the circuit shown in FIG. 9B. Can do.

  When the frequency of the high-frequency signal flowing through the first transmission path is f, the impedance of the shunt circuit included in the circuit shown in FIG. 9B is Z = 1 / (j × 2πf × Coff). For this reason, as the frequency f increases, the impedance of the shunt circuit decreases, and high-frequency signals easily flow through the shunt circuit. As described above, in the conventional high-frequency switch circuit, the amount of the high-frequency signal flowing through the shunt circuit controlled in the cut-off state increases when the frequency of the signal to be transmitted increases due to the off-capacitance of the FET in the shunt circuit. The isolation characteristic when the transmission path is in a conductive state is deteriorated.

Conventionally, various methods have been devised to improve the isolation characteristics of a high-frequency switch circuit. Patent Document 1 describes a method in which a capacitor element that resonates in series with an inductance component existing between a source terminal of an FET in the shunt circuit and the ground is provided in the shunt circuit. Further, Patent Document 2 includes a plurality of shunt circuits including FETs and impedance elements, and these shunt circuits are parallel resonant circuits when the FET is in an on state, and series resonant circuits when the FET is in an off state. The method of making it operate | move is described.
Japanese Patent Laid-Open No. 10-13204 JP 2004-72362 A

  In order to eliminate the influence of the off-capacitance of the FET in the shunt circuit, the gate width of the FET may be narrowed. However, reducing the gate width of the FET increases the on-resistance of the FET. For this reason, when the transmission path is in the cut-off state, the on-resistance of the FET in the shunt circuit that is controlled to be conductive is increased, so that the amount of the high-frequency signal flowing through the shunt circuit is reduced. Thus, if the gate width of the FET is narrowed in order to improve the isolation characteristic when the transmission path is in a conductive state, the isolation characteristic when the transmission path is in a cutoff state is deteriorated.

  Further, according to the method described in Patent Document 1, the isolation characteristic when the transmission path is in the cut-off state can be improved, but the isolation characteristic when the transmission path is in the conductive state cannot be improved. In the method described in Patent Document 2, it is necessary to add at least two FETs each time a shunt circuit is provided. For this reason, there is a problem that as the number of transmission paths increases, the area of the FET on the chip increases and the chip size increases.

  Therefore, an object of the present invention is to provide a high-frequency switch circuit having good isolation characteristics even when a high-frequency signal in which the off-capacitance of a field effect transistor is a problem is input.

  The first high-frequency switch circuit of the present invention is a first switch section provided on a transmission path connecting the first terminal and the second terminal in order to control the flow of a high-frequency signal between the two terminals. A second switch unit provided on the shunt path connecting the transmission path and the ground, a reactance element provided on the ground side end of the shunt path, and the transmission path and the shunt path on the transmission path. First and second circuit elements provided on the first terminal side and the second terminal side, respectively, across the connection point.

  The first high-frequency switch circuit is configured so that the input / output impedance of the circuit including the first and second circuit elements, the second switch unit in the off state, and the reactance element matches the characteristic impedance of the transmission path. It is preferable that

  Further, the first and second circuit elements or reactance elements are constituted by bonding wires, lead frame leads, semiconductor package wiring, printed circuit board wiring, and inductors formed on the semiconductor substrate. Also good.

  The second high-frequency switch circuit according to the present invention includes a first high-frequency switch circuit provided on a first transmission path that connects the first terminal and a predetermined node to control a flow of a high-frequency signal between the three terminals. A switch unit; a second switch unit provided on a first shunt path connecting the first transmission path and ground; and a first reactance element provided at an end of the ground side of the first shunt path And a first transmission line and a second connection point provided on the first transmission path, with the connection point between the first transmission path and the first shunt path interposed therebetween, respectively. Provided on a second shunt path connecting the second transmission path and ground, and a third switch section provided on the second transmission path connecting the circuit element, the second terminal and the node. A fourth switch portion and a second rear portion provided at the ground side end of the second shunt path A third element and a second element provided on the second terminal side and the nodal point side, respectively, across the connection point between the second transmission path and the second shunt path on the transformer element and the second transmission path. 4 circuit elements, and a third transmission path connecting the third terminal and the node.

  The second high-frequency switch circuit is configured such that the input / output impedance of the circuit including the first and second circuit elements, the second switch unit in the off state, and the first reactance element is the characteristic impedance of the first transmission path. And the input / output impedance of the circuit composed of the third and fourth circuit elements, the fourth switch unit in the off state, and the second reactance element matches the characteristic impedance of the second transmission path. It is preferable that it is comprised.

  Further, the first to fourth circuit elements or reactance elements are constituted by bonding wires, lead frame leads, semiconductor package wiring, printed circuit board wiring, or inductors formed on the semiconductor substrate. Also good. The second high frequency switch circuit may further include a third reactance element on the third transmission path.

  According to the first high-frequency switch circuit, it is possible to cancel the influence of the off-capacitance of the second switch section and match the impedance between the input and output of the shunt circuit at the frequency of the signal to be transmitted. Thereby, even when a high frequency signal whose off-capacitance of the second switch section is a problem is input, good isolation characteristics can be obtained.

  According to the second high-frequency switch circuit, the influence of the off-capacitance of the second and fourth switch sections is canceled, and the impedance between the input and output of each shunt circuit is individually matched at the frequency of the signal flowing through each transmission path. Can be made. Thereby, in a high-frequency switch circuit having a plurality of transmission paths, good isolation characteristics can be obtained even when a high-frequency signal whose FET off-capacity is a problem is input.

  In the first and second high-frequency switch circuits, the switch unit and the reactance element are configured by inductors formed on the semiconductor substrate, so that the input / output impedance of the target circuit is high in the characteristic impedance of the transmission path. It is possible to increase the effect of improving isolation characteristics by matching with accuracy. In addition, the isolation characteristic can be improved without increasing the chip size by configuring the switch unit and the reactance element with a bonding wire or the like.

(First embodiment)
FIG. 1 is a circuit diagram showing a configuration of a high-frequency switch circuit according to a first embodiment of the present invention. The high-frequency switch circuit 1 shown in FIG. 1 includes FETs 11 and 12, a DC cut capacitor 21, and inductors 31, 41 and 42, and controls the flow of a high-frequency signal between the terminals X1 and X2. In the high-frequency switch circuit 1, the FETs 11 and 12 function as first and second switch sections, respectively. The inductor 31 functions as a reactance element, and the inductors 41 and 42 function as first and second circuit elements, respectively.

  In FIG. 1, a path connecting the terminal X1 and the terminal X2 is called a transmission path P, and a path connecting the connection point Y1 on the transmission path P and the ground is called a shunt path S. The high frequency signal flows in the direction from the terminal X1 to the terminal X2 or in the opposite direction. In the following, it is assumed that the high-frequency signal flows in a direction from the terminal X1 toward the terminal X2.

  As shown in FIG. 1, an inductor 41, an inductor 42, and an FET 11 are provided on the transmission path P in this order from the terminal X1 side. One end of the inductor 41 is connected to the terminal X1, and the other end is connected to the connection point Y1. One end of the inductor 42 is connected to the connection point Y1, and the other end is connected to one conduction terminal of the FET 11. The other conduction terminal of the FET 11 is connected to the terminal X2. As described above, the FETs 11 and 12 are provided on the transmission path P on the terminal X1 side and the terminal X2 side, respectively, with the connection point Y1 between the transmission path P and the shunt path S interposed therebetween. The position where the FET 11 is provided may be between the terminal X1 and the inductor 41, between the inductor 41 and the connection point Y1, or between the connection point Y1 and the inductor 42.

  On the shunt path S, an FET 12, a DC cut capacitor 21, and an inductor 31 are provided in this order from the connection point Y1 side. One conduction terminal of the FET 12 is connected to the connection point Y 1, and the other conduction terminal is connected to one electrode of the DC cut capacitor 21. The other electrode of the DC cut capacitor 21 is connected to one end of the inductor 31, and the other end of the inductor 31 is grounded. In this manner, the inductor 31 is provided at the ground side end of the shunt path S. The FET 12, the DC cut capacitor 21, and the inductor 31 connected as described above function as a shunt circuit.

  A control signal CTRL1 that is switched between a high level and a low level is applied to the control terminal of the FET 11. A second control signal CTRL2 having a level opposite to that of the control signal CTRL1 is applied to the control terminal of the FET 12. As a result, the transmission path P is switched between a conductive state (a state in which a high-frequency signal is transmitted) and a cutoff state (a state in which a high-frequency signal is not transmitted). In addition, the shunt path S has a function of releasing a high-frequency signal flowing through the transmission path P to the ground when the transmission path P is in a cutoff state. Specifically, when the FET 11 is on and the FET 12 is off, the high-frequency signal input from the terminal X1 reaches the terminal X2 via the FET 11. On the other hand, when the FET 11 is in the off state and the FET 12 is in the on state, the high frequency signal input from the terminal X1 flows to the ground via the shunt circuit including the FET 12 and the like.

  When the transmission path P is conductive, the FET 11 is equivalent to a resistance element (ON resistance) having a resistance value Ron, and the FET 12 is equivalent to a capacitance element having a capacitance value Coff. Therefore, an equivalent circuit of the high-frequency switch circuit 1 when the transmission path P is in a conductive state is as shown in FIG. Since the resistance value Ron of the on-resistance is sufficiently small and the capacitance value C21 of the DC cut capacitor 21 is extremely larger than the capacitance value Coff of the off-capacitance, the circuit shown in FIG. 2A is the circuit shown in FIG. Can be approximated by

  The high-frequency switch circuit 1 is configured so that the input / output impedance of the circuit including the inductors 31, 41, and 42 and the FET 12 in the off state (that is, the circuit shown in FIG. 2B) matches the characteristic impedance of the transmission path P. It is configured. Thereby, when the transmission path P is in the conductive state, the influence of the off-capacitance of the FET 12 can be canceled, and the impedance between the input and output of the shunt circuit can be matched at the frequency of the signal to be transmitted. Therefore, even when a high frequency signal in which the off-capacitance of the FET is a problem is input, good isolation characteristics can be obtained.

  Hereinafter, a configuration example of the inductors 31, 41, 42 will be described. All or part of the high-frequency switch circuit 1 is realized as a semiconductor chip. Therefore, the inductors 31, 41, and 42 can be configured by inductors (for example, spiral inductors) formed as circuit elements on a semiconductor substrate (first method). In addition, parasitic inductance components due to bonding wires, lead frame leads, and semiconductor package wiring are added to the terminals of the semiconductor chip, and parasitics due to the wiring of the printed circuit board are added to the terminals of the semiconductor chip mounted on the printed circuit board. An inductance component is added. Therefore, the inductors 31, 41, and 42 can be configured by parasitic inductance components added to the terminals of the semiconductor chip (second method). Further, by combining the first and second methods, the inductors 31, 41, and 42 can be configured by the parasitic inductance component added to the inductor formed on the semiconductor substrate and the terminal of the semiconductor chip (first). Method 3).

  A specific example of the second method will be described. One end of the shunt circuit of the high-frequency switch circuit 1 is grounded. For this reason, even if one electrode of the DC cut capacitor 21 is directly grounded in the circuit configuration, the operation of the high frequency switch circuit 1 is the same as when a predetermined inductor is provided between the DC cut capacitor 21 and the ground. Become. Therefore, instead of an inductor formed as a circuit element on a semiconductor substrate, one selected from bonding wires, lead frame leads, semiconductor package wirings, and printed circuit board wirings (hereinafter referred to as bonding wires). The inductor 31 can be configured by the above elements.

  The same can be said for the inductor 41. That is, when the terminal X1 is a terminal of a semiconductor chip, even if the terminal X1 and the node Y0 are directly connected due to the circuit configuration, the operation of the high-frequency switch circuit 1 is predetermined between the terminal X1 and the node Y0. This is the same as when an inductor is provided. Therefore, the inductor 41 can be configured by one or more elements selected from bonding wires and the like.

  With respect to the inductor 42, the same can be said for the inductors 31 and 41 if the connection order of the inductor 42 and the FET 11 is reversed. When the connection order of the inductor 42 and the FET 11 is as shown in FIG. 1 and the terminal X2 is a terminal of the semiconductor chip, the parasitic inductance component between the conduction terminal on the terminal X2 side of the FET 11 and the terminal X2 should be considered. Is preferred.

  When the first method is employed, the inductance component of each inductor can be matched with the design value with high accuracy. Therefore, the input / output impedance of the circuit shown in FIG. 2B can be matched with the characteristic impedance of the transmission path P with high accuracy, and the improvement effect of the isolation characteristic can be enhanced. When the second method is adopted, it is not necessary to newly provide an inductor on the chip. Therefore, the isolation characteristics can be improved without increasing the chip size.

  FIG. 3 is a diagram illustrating an example of the insertion loss characteristic of the high-frequency switch circuit 1. In FIG. 3, the horizontal axis represents the frequency of the signal to be transmitted, and the vertical axis represents the insertion loss (that is, the signal attenuation due to passing through the high-frequency switch circuit 1). FIG. 3 shows the insertion loss (solid line) of the high-frequency switch circuit 1 and the insertion loss (broken line) of the conventional high-frequency switch circuit in the range where the frequency of the input signal is up to several GHz. As shown in FIG. 3, the insertion loss of the conventional high-frequency switch circuit is minimized near the frequency f1, and increases as the frequency increases. For this reason, for example, when the frequency of the signal to be transmitted is f2, the attenuation amount of the signal reaches a considerable level. On the other hand, the insertion loss of the high-frequency switch circuit 1 is minimized in the vicinity of the frequency f1, but does not increase so much as the frequency increases. For this reason, even when the frequency of the signal to be transmitted is f2, the signal is not attenuated so much. As described above, according to the high-frequency switch circuit 1, it is possible to prevent the frequency characteristics of the insertion loss from being deteriorated due to the off-capacitance of the FET in the shunt circuit.

  By the way, in the high frequency switch circuit 1, if the input / output impedance of the circuit shown in FIG. 2B is perfectly matched with the characteristic impedance of the transmission path P, the improvement effect of the isolation characteristic is maximized. However, even if impedance matching is not perfect, the isolation characteristic is improved depending on the degree of matching. Therefore, as the high-frequency switch circuit according to the present embodiment, the input / output impedance of the circuit shown in FIG. 2B matches the characteristic impedance of the transmission path P under a predetermined condition (for example, plus the characteristic impedance of the transmission path P). A high frequency switch circuit (within a range of minus 50%) may be used.

  As described above, according to the high frequency switch circuit of the present embodiment, the influence of the off-capacitance of the FET in the shunt circuit is canceled, and the impedance between the input and output of the shunt circuit is matched at the frequency of the signal to be transmitted. Can do. Thereby, even when a high frequency signal in which the off-capacitance of the FET is a problem is input, good isolation characteristics can be obtained.

(Second Embodiment)
FIG. 4 is a circuit diagram showing a configuration of a high-frequency switch circuit according to the second embodiment of the present invention. The high frequency switch circuit 2 shown in FIG. 4 includes FETs 11 to 14, DC cut capacitors 21 and 22, and inductors 31 to 33 and 41 to 44, and controls the flow of a high frequency signal between the terminals X1 to X3. In the high-frequency switch circuit 2, the FETs 11 to 14 function as first to fourth switch sections, respectively. The inductors 31 to 33 function as first to third reactance elements, respectively, and the inductors 41 to 44 function as first to fourth circuit elements, respectively.

  In FIG. 4, the paths connecting the terminals X1 to X3 and the node Y0 are transmission paths P1 to P3, the path connecting the connection point Y1 on the transmission path P1 and the ground is the shunt path S1, and the connection point Y2 on the transmission path P2. A path connecting the ground and the ground is referred to as a shunt path S2. The high-frequency signal may flow in a direction from the terminal X1 toward the terminal X3 (or in the opposite direction) and may flow in a direction from the terminal X2 toward the terminal X3 (or in the opposite direction). In the following, it is assumed that the high frequency signal flows from the terminals X1 and X2 toward the terminal X3.

  As shown in FIG. 4, the high-frequency switch circuit 2 is the same circuit as the high-frequency switch circuit 1 (FIG. 1) according to the first embodiment on the terminal X1 side from the node Y0 and on the terminal X2 side from the node Y0. (Hereinafter referred to as X1-side switch unit and X2-side switch unit). In the X1-side switch unit, an inductor 41, an inductor 42, and an FET 11 are provided in order from the terminal X1 side on the transmission path P1, and an FET 12, a DC cut capacitor 21, and the like are sequentially provided on the shunt path S1 from the connection point Y1 side. An inductor 31 is provided. In the X2-side switch unit, an inductor 43, an inductor 44, and an FET 12 are provided in order from the terminal X2 side on the transmission path P2, and an FET 14 and a DC cut capacitor 22 are sequentially provided from the connection point Y2 side on the shunt path S2. , And an inductor 32 is provided. Furthermore, one end of the inductor 33 is connected to the terminal X3, and the other end is connected to the node Y0.

  A control signal CTRL1 that is switched between a high level and a low level is applied to the control terminals of the FETs 11 and 14. A second control signal CTRL2 having a level opposite to that of the control signal CTRL1 is applied to the control terminals of the FETs 12 and 13. As a result, the transmission path P1 is switched between a conduction state and a cutoff state, and the transmission path P2 is switched to a state opposite to the transmission path P1. Further, the shunt path S1 has a function of escaping a high-frequency signal flowing through the transmission path P1 to the ground when the transmission path P1 is in a cutoff state, and the shunt path S2 is when the transmission path P2 is in a cutoff state. It has a function of escaping the high-frequency signal flowing through the transmission path P2 to the ground.

  In the high-frequency switch circuit 2, the input / output impedance of the circuit composed of the inductors 31, 41, 42 and the off-state FET 12 matches the characteristic impedance of the transmission path P1, and the inductors 32, 43, 44, and the off-state The input / output impedance of the circuit composed of the FET 14 is matched with the characteristic impedance of the transmission path P2.

  Accordingly, in the X1 side switch unit, when the transmission path P1 is in a conducting state, the influence of the off-capacitance of the FET 12 is canceled, and the frequency of the signal flowing through the transmission path P1 is between the input and output of the shunt circuit in the X1 side switch unit. Can be matched. Similarly, in the X2-side switch section, when the transmission path P2 is in the conductive state, the influence of the off-capacitance of the FET 14 is canceled and the frequency of the signal flowing through the transmission path P2 is between the input and output of the shunt circuit in the X2-side switch section. Can be matched.

  In the high-frequency switch circuit 2, there are cases where the frequencies of the signals flowing in the transmission path P <b> 1 and the transmission path P <b> 2 are different, and the off capacitances are different between the FET 12 and the FET 14. Even in such a case, by using the suitable inductors 31, 32, 41 to 44, the impedance between the input and output of each shunt circuit can be individually matched at the frequency of the signal flowing through each transmission path. Therefore, in a high-frequency switch circuit having a plurality of transmission paths, good isolation characteristics can be obtained even when a high-frequency signal whose FET off-capacity is a problem is input.

  FIG. 5 is a diagram illustrating an implementation example of the high-frequency switch circuit 2. In the high-frequency switch circuit 200 shown in FIG. 5, the inductors 31 to 33 and 41 to 44 are realized by bonding wires 231 to 233 and 241 to 244, respectively. In the high frequency switch circuit 200, bonding wires are usually used at locations where wiring on a semiconductor substrate is used. Specifically, in the high-frequency switch circuit 200, the FET 11 and FET 12 are connected using a bonding wire 242 and the FET 13 and FET 14 are connected using a bonding wire 244. By realizing the inductors 42 and 44 using the bonding wires 242 and 244 as described above, the isolation characteristics can be improved without increasing the chip size.

  As described above, according to the high frequency switch circuit according to the present embodiment, the influence of the off-capacitance of the FET in each shunt circuit is canceled, and the frequency of the signal flowing through each transmission path is between the input and output of each shunt circuit. The impedance can be matched individually. Thereby, in a high-frequency switch circuit having a plurality of transmission paths, good isolation characteristics can be obtained even when a high-frequency signal whose FET off-capacity is a problem is input.

(Third embodiment)
FIG. 6 is a circuit diagram showing the configuration of the high-frequency switch circuit according to the third embodiment of the present invention. The high-frequency switch circuit 3 shown in FIG. 6 removes the inductor 33 from the high-frequency switch circuit 2 (FIG. 4) according to the second embodiment, and changes the connection order of the FET 11 and the inductor 42 and the connection order of the FET 13 and the inductor 44. Each is reversed. Since the detailed configuration and effect of the high-frequency switch circuit 3 are the same as those of the high-frequency switch circuit 2, the description thereof is omitted here.

  FIG. 7 is a diagram illustrating an implementation example of the high-frequency switch circuit 3. In the high-frequency switch circuit 300 shown in FIG. 7, the inductors 31, 32, 41 to 44 are realized by bonding wires 331, 332, 341 to 344, respectively. In the high frequency switch circuit 300, two bonding wires are usually used at a place where one bonding wire is used. Specifically, the terminal X3 is usually connected to a wiring on the semiconductor substrate that connects one conduction terminal of the FET 11 and one conduction terminal of the FET 13 by using one bonding wire. On the other hand, in the high-frequency switch circuit 300, one conduction terminal of the FET 11 and the terminal X3 are connected using the bonding wire 342, and separately, one conduction terminal of the FET 13 and the terminal X3 are connected to the bonding wire 344. Is connected using. By realizing the inductors 42 and 44 using the bonding wires 342 and 344 as described above, the isolation characteristics can be improved without increasing the chip size.

  As described above, according to the high frequency switch circuit according to the present embodiment, the same effect as the high frequency switch circuit according to the second embodiment can be obtained.

  The high-frequency switch circuit according to each of the embodiments described above is characterized in that a circuit element having an inductance component is provided on both sides of the connection point between the transmission path and the shunt path on the transmission path. As shown, high-frequency switch circuits according to various modifications having this feature can be configured.

  First, in each of the above embodiments, the high-frequency switch circuit that controls the flow of a high-frequency signal between two or three terminals has been described, but the number of input / output terminals may be four or more. Even if the number of input / output terminals is four or more, if circuit elements having an inductance component are provided on both sides of the connection point between the transmission path and the shunt path on each transmission path, the isolation characteristics Can be improved.

  In each of the above embodiments, the first to fourth switch units are configured using one FET. However, a plurality of FETs (field effect transistor stages) connected in series or in parallel are used. You may comprise the 1st-4th switch part.

  Also, in the second and third embodiments, similarly to the first embodiment, a circuit including two circuit elements on the transmission path, an off-capacitance on the shunt path, and a reactance element on the shunt path. A high-frequency switch circuit in which the input / output impedance matches the characteristic impedance of the transmission path under a predetermined condition may be configured.

  Moreover, the high frequency switch circuit which has various structures can be comprised by combining arbitrarily the high frequency switch circuit which concerns on each said embodiment, and the high frequency switch circuit which concerns on each said modification.

  The high-frequency switch circuit of the present invention has an effect that a good isolation characteristic can be obtained even when a high-frequency signal in which the off-capacitance of the field effect transistor is a problem is input. It can be used for various wireless communication devices.

1 is a circuit diagram showing a configuration of a high-frequency switch circuit according to a first embodiment of the present invention. The figure which shows the equivalent circuit of the high frequency switch circuit which concerns on the 1st Embodiment of this invention The figure which shows the insertion loss characteristic of the high frequency switch circuit which concerns on the 1st Embodiment of this invention A circuit diagram showing composition of a high frequency switch circuit concerning a 2nd embodiment of the present invention. The figure which shows the implementation example of the high frequency switch circuit which concerns on the 2nd Embodiment of this invention. A circuit diagram showing composition of a high frequency switch circuit concerning a 3rd embodiment of the present invention. The figure which shows the implementation example of the high frequency switch circuit which concerns on the 3rd Embodiment of this invention. Diagram showing a conventional high-frequency switch circuit The figure which shows the equivalent circuit of the conventional high frequency switch circuit

Explanation of symbols

1-3, 200, 300 ... high frequency switch circuits 11-14 ... FET
21, 22 ... DC cut capacitors 31 to 33, 41 to 44 ... inductors 231 to 233, 241 to 244, 331 to 332, 341 to 344 ... bonding wires

Claims (15)

A high-frequency switch circuit that controls the flow of a high-frequency signal between two terminals,
A first switch unit provided on a transmission path connecting the first terminal and the second terminal;
A second switch unit provided on a shunt path connecting the transmission path and the ground;
A reactance element provided at a grounded end of the shunt path;
First and second circuit elements respectively provided on the first terminal side and the second terminal side across the connection point between the transmission path and the shunt path on the transmission path. Equipped with a high frequency switch circuit.   The input / output impedance of the circuit including the first and second circuit elements, the second switch unit in the off state, and the reactance element is configured to match the characteristic impedance of the transmission path. The high frequency switch circuit according to claim 1, wherein:   At least one of the first and second circuit elements is composed of one or more elements selected from a bonding wire, a lead frame lead, a semiconductor package wiring, and a printed circuit board wiring. The high frequency switch circuit according to claim 1, wherein:   2. The high-frequency switch circuit according to claim 1, wherein at least one of the first and second circuit elements is configured by an inductor formed on a semiconductor substrate.   At least one of the first and second circuit elements is one or more elements selected from a bonding wire, a lead frame lead, a semiconductor package wiring, and a printed circuit board wiring, and a semiconductor substrate. The high-frequency switch circuit according to claim 1, wherein the high-frequency switch circuit is configured by an inductor formed on the substrate.   2. The high frequency device according to claim 1, wherein the reactance element includes at least one element selected from a bonding wire, a lead frame lead, a semiconductor package wiring, and a printed circuit board wiring. Switch circuit.   The reactance element is composed of one or more elements selected from bonding wires, lead frame leads, semiconductor package wiring, printed circuit board wiring, and an inductor formed on the semiconductor substrate. The high-frequency switch circuit according to claim 1, wherein the high-frequency switch circuit is characterized. A high-frequency switch circuit that controls the flow of a high-frequency signal between three terminals,
A first switch unit provided on a first transmission path connecting the first terminal and a predetermined node;
A second switch unit provided on a first shunt path connecting the first transmission path and ground;
A first reactance element provided at a ground side end of the first shunt path;
First and second terminals respectively provided on the first terminal side and the node side on the first transmission path across a connection point between the first transmission path and the first shunt path. Two circuit elements;
A third switch unit provided on a second transmission path connecting the second terminal and the node;
A fourth switch unit provided on a second shunt path connecting the second transmission path and the ground;
A second reactance element provided at a ground-side end of the second shunt path;
Third and second terminals provided on the second terminal side and the node side, respectively, on the second transmission path with a connection point between the second transmission path and the second shunt path interposed therebetween. 4 circuit elements;
A high-frequency switch circuit comprising a third transmission path connecting a third terminal and the node. The input / output impedance of the circuit including the first and second circuit elements, the second switch unit in the off state, and the first reactance element matches the characteristic impedance of the first transmission path, And,
The input / output impedance of the circuit including the third and fourth circuit elements, the fourth switch unit in the off state, and the second reactance element is matched with the characteristic impedance of the second transmission path. 9. The high frequency switch circuit according to claim 8, wherein the high frequency switch circuit is configured as follows.   At least one of the first to fourth circuit elements is composed of one or more elements selected from bonding wires, lead frame leads, semiconductor package wiring, and printed circuit board wiring. The high-frequency switch circuit according to claim 8, wherein:   9. The high frequency switch circuit according to claim 8, wherein at least one of the first to fourth circuit elements is constituted by an inductor formed on a semiconductor substrate.   At least one of the first to fourth circuit elements includes at least one element selected from a bonding wire, a lead frame lead, a semiconductor package wiring, and a printed circuit board wiring, and a semiconductor substrate. The high-frequency switch circuit according to claim 8, wherein the high-frequency switch circuit is configured by an inductor formed on the substrate.   At least one of the first and second reactance elements is constituted by one or more elements selected from a bonding wire, a lead frame lead, a semiconductor package wiring, and a printed circuit board wiring. The high-frequency switch circuit according to claim 8.   At least one of the first and second reactance elements is formed on one or more elements selected from a bonding wire, a lead frame lead, a semiconductor package wiring, and a printed circuit board wiring, and the semiconductor substrate. The high-frequency switch circuit according to claim 8, wherein the high-frequency switch circuit is configured by an inductor that is formed.   The high frequency switch circuit according to claim 8, further comprising a third reactance element on the third transmission path.

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