JP2006238058A - High frequency switch circuit - Google Patents

Abstract

An object of the present invention is to provide a high-frequency switch circuit capable of reducing high-frequency signal leakage of a semiconductor switch section in an off state.
By applying a voltage complementary to a control voltage applied to open and close a semiconductor switch part to high-frequency signal input / output terminals 2 and 3 via DC potential transmission parts 13 and 14, High frequency signal leakage is reduced by increasing Vgs of the semiconductor switch portion on the side to the plus side and increasing Vgs of the semiconductor switch portion on the off side to the minus side.
[Selection] Figure 1

Description

  The present invention relates to a high-frequency switch circuit used for high-frequency communication such as a cellular phone and a wireless LAN.

FIG. 12 shows an example of a conventional high-frequency switch circuit using a field effect transistor.
In FIG. 12, 61 is a common terminal, 62 is a first high-frequency signal input / output terminal, 63 is a second high-frequency signal input / output terminal, 69 and 70 are semiconductor switch portions composed of field-effect transistors, 64 and 65 Is a voltage control terminal for applying a voltage for controlling opening and closing of the semiconductor switch portions 69 and 70.

  The drains of the semiconductor switch portions 69 and 70 are connected to each other and connected to the common terminal 61 via the coupling capacitor 66. The gates of the semiconductor switch sections 69 and 70 are connected to voltage control terminals 64 and 65 via resistance elements 71 and 72, respectively. The source of the semiconductor switch unit 69 is connected to the first high-frequency signal input / output terminal 62 via a coupling capacitor 67. The source of the semiconductor switch unit 70 is connected to the second high-frequency signal input / output terminal 63 via a coupling capacitor 68.

  73 is a resistance element arranged to connect the drain and the source of the semiconductor switch unit 69 so that the potential of the DC potential evaluation point J is equal to the potential of the DC potential evaluation point K, and 74 is the resistance of the semiconductor switch unit 70. This is a resistance element arranged to connect the drain and the source so that the potential at the DC potential evaluation point J is equal to the potential at the DC potential evaluation point L.

  Voltages at opposite levels are input to the voltage control terminals 64 and 65. When a voltage at a level higher than that of the voltage control terminal 65 is applied to the voltage control terminal 64, the semiconductor switch unit 69 is turned on, and the semiconductor switch unit 70 is turned on. Is switched off, and the common terminal 61 and the first high-frequency signal output terminal 62 are in a conductive state.

  Conversely, when a voltage having a level higher than that of the voltage control terminal 64 is applied to the voltage control terminal 65, the semiconductor switch unit 70 is turned on, the semiconductor switch unit 69 is turned off, and the common terminal 61 and the second high-frequency signal are turned on. A conduction state is established between the output terminals 63.

  FIG. 13 shows a DC potential evaluation point when applying 3 volts to the voltage control terminal 64 and 0 volt to the voltage control terminal 65, turning on the semiconductor switch 69 and turning off the semiconductor switch 70 in the prior art of FIG. The DC potential state of J-L is shown.

Hereinafter, the DC potential state at the DC potential evaluation points J to L in the prior art will be described with reference to FIGS. 12 and 13.
In FIG. 12, coupling capacitors 66 to 68 for preventing leakage of direct current are arranged in series between the high-frequency signal input / output terminal and the switch unit. It will flow. As shown in FIG. 13, the DC potential state at the DC potential evaluation point J includes the current I69 flowing from the gate to the drain of the field effect transistor constituting the semiconductor switch unit 69 and the current effect transistor constituting the semiconductor switch unit 70. It is uniquely determined so that the leakage current I70 from the drain to the gate becomes equal and the potential difference between the voltage control terminals 64 and 65 is 3 volts. Further, since the DC potential evaluation point J and the DC potential evaluation points K and L are connected in a DC manner via the resistance elements 73 and 74, the DC potential at the DC potential evaluation points K and L is evaluated as the DC potential. The value is almost the same as point J.
JP 2000-277703 A JP 2002-232278 A

  The state of the DC potential of the switch circuit shown in the conventional example is as follows. The potential at the DC potential evaluation point J depends on the voltage-current characteristics Vgd-Igd characteristics between the gate and drain of the field effect transistors constituting the semiconductor switch sections 69 and 70 and the voltage applied to the voltage control terminals 64 and 65. The potentials of the DC potential evaluation points K and L are uniquely determined, and the resistance values of the resistance components between the source and drain of the field effect transistors constituting the semiconductor switch portions 69 and 70 and the resistance values of the resistance elements 73 and 74 are determined. And is substantially equal to the potential of the DC potential evaluation point J regardless of the open / closed state of the semiconductor switch portions 69 and 70.

  Therefore, in the conventional switch circuit, the drain potential and source potential of the field effect transistors constituting the respective semiconductor switch sections 69 and 70 are substantially the same regardless of the DC potential state of the gate and the open / close state of the switch. It becomes.

  For this reason, the gate potential in the on-side field effect transistor is not sufficiently higher than the source potential, and the insertion loss cannot be sufficiently reduced. In addition, in the off-side field effect transistor, the source potential is compared with the gate potential. There is a problem that it is not sufficiently large and leakage of high-frequency signals cannot be sufficiently prevented.

  An object of the present invention is to provide a high-frequency switch circuit that can reduce high-frequency signal leakage in an off-state switch section.

  A high-frequency switch circuit according to claim 1 of the present invention includes a plurality of high-frequency signal input / output terminals for inputting and outputting a high-frequency signal, and a plurality of semiconductor switch portions for opening and closing the high-frequency signal input / output terminals. In a high-frequency switch circuit, a voltage complementary to a control voltage applied to open and close the semiconductor switch unit is applied to at least one of the semiconductor switch unit on the input terminal side and / or the output terminal side A DC potential transmission unit is provided.

  Here, “a voltage complementary to the control voltage applied to open and close the switch unit” means that when the control voltage that turns the switch unit on is applied, the switch unit is turned off. It is a voltage, and is a voltage at which the switch unit is turned on when a control voltage that turns the switch unit off is applied.

  The high-frequency switch circuit according to claim 2 of the present invention includes a plurality of high-frequency signal input / output terminals for inputting and outputting a high-frequency signal, and a plurality of semiconductor switch portions for opening and closing the high-frequency signal input / output terminals. In the high-frequency switch circuit, the semiconductor switch unit includes an FET having a drain electrode and a source electrode connected to the high-frequency signal input / output terminal, or a plurality of FETs in which the drain electrode and the source electrode are connected in series. A DC potential transmission unit is provided that applies a voltage complementary to a control voltage applied to open / close the unit to at least one of the semiconductor switch units.

  According to this configuration, the voltage complementary to the control voltage applied to open and close the semiconductor switch unit is applied to at least one of the high-frequency signal input side and the output side via the DC potential transmission unit. Since the source potential of the semiconductor switch part in the on state is smaller than the gate potential and the source potential of the semiconductor switch part in the off state is larger than the gate potential, the insertion loss of the semiconductor switch part in the on state is reduced. It becomes possible to reduce the high-frequency signal leakage of the semiconductor switch part in the off state.

A high-frequency switch circuit according to a third aspect of the present invention is characterized in that, in the first aspect, the direct-current potential transmission portion is constituted by a resistance element.
According to a fourth aspect of the present invention, there is provided the high-frequency switch circuit according to the first aspect, wherein the direct current potential transmission section is constituted by a diode element.

  According to a fifth aspect of the present invention, the high-frequency switch circuit according to the first aspect is characterized in that the direct-current potential transmission section is constituted by a series connection of a diode element or a resistance element and an inductor element.

  According to a sixth aspect of the present invention, there is provided a high frequency switch circuit comprising: a common terminal for inputting / outputting a high frequency signal; first and second high frequency signal input / output terminals for inputting / outputting a high frequency signal; the common terminal; A first FET that opens and closes between the first high-frequency signal input / output terminal; a second FET that opens and closes between the common terminal and the second high-frequency signal input / output terminal; and the second FET. A first DC potential transmission unit for transmitting a potential applied to the gate electrode of the first FET to the source electrode of the first FET, and a potential applied to the gate electrode of the first FET to the source electrode of the second FET. And a second direct-current potential transmission unit.

According to a seventh aspect of the present invention, the high-frequency switch circuit according to the sixth aspect is characterized in that the first and second direct-current potential transmission portions are constituted by resistance elements.
The high-frequency switch circuit according to an eighth aspect of the present invention is characterized in that, in the sixth aspect, the first and second DC potential transmission units are configured by diode elements.

  A high-frequency switch circuit according to a ninth aspect of the present invention is characterized in that, in the sixth aspect, the first and second DC potential transmission units are configured by a series connection of a diode element or a resistance element and an inductor element. .

  The present invention provides a low-loss, high-isolation high-frequency switch circuit by reducing the source potential relative to the gate potential of the on-side switch section and increasing the source potential relative to the gate potential of the off-side switch section. It becomes possible to provide.

Embodiments of the present invention will be described with reference to FIGS.
(First embodiment)
FIG. 1 shows a high-frequency switch circuit according to the first embodiment.

  In FIG. 1, 1 is a common terminal, 2 is a first high-frequency signal input / output terminal, 3 is a second high-frequency signal input / output terminal, 9 and 10 are semiconductor switch portions formed of field effect transistors, 4, 5 Is a voltage control terminal for applying a voltage for controlling opening and closing of the semiconductor switch sections 9 and 10.

  The drains of the semiconductor switch units 9 and 10 are connected to each other and connected to the common terminal 1 via the coupling capacitor 6. The gates of the semiconductor switch sections 9 and 10 are connected to the voltage control terminals 4 and 5 via the resistance elements 11 and 12, respectively. The source of the semiconductor switch unit 9 is connected to the first high-frequency signal input / output terminal 2 via the coupling capacitor 7. The source of the semiconductor switch unit 10 is connected to the second high-frequency signal input / output terminal 3 via the coupling capacitor 8. Reference numerals 13 and 14 denote resistance elements as DC potential transmission units arranged for applying a voltage complementary to the control voltage.

  Voltages at opposite levels are input to the voltage control terminals 4 and 5, and when a voltage having a level higher than that of the voltage control terminal 5 is applied to the voltage control terminal 4, the semiconductor switch unit 9 is turned on, and the semiconductor switch unit 10 Is switched off, and the common terminal 1 and the first high-frequency signal output terminal 2 are in a conductive state.

  Conversely, when a voltage having a level higher than that of the voltage control terminal 4 is applied to the voltage control terminal 5, the semiconductor switch unit 10 is turned on, the semiconductor switch unit 9 is turned off, and the common terminal 1 and the second high-frequency signal are turned on. A conduction state is established between the output terminals 3.

  Further, in this (first embodiment), the control voltages applied to the voltage control terminals 4 and 5 in order to open and close the semiconductor switch sections 9 and 10 are respectively applied to the source side (DC potential evaluation point) of the field effect transistor. C and B) are applied via resistance elements 13 and 14, respectively. For example, when a voltage larger than that of the voltage control terminal 5 is applied to the voltage control terminal 4, the semiconductor switch unit 9 is turned on, and the semiconductor switch unit 10 is turned off, the on-state DC potential evaluation point B is when the resistance element 13 is not present. The DC potential evaluation point C on the off side can be made higher compared to the case where the resistance element 14 is not provided.

  2 and 3, DC voltage evaluation points A to C when 3 V is applied to the voltage control terminal 4 and 0 V is applied to the voltage control terminal 5 to turn on the semiconductor switch 9 and turn off the semiconductor switch 10. Indicates the DC potential state. Hereinafter, the DC potential state at the DC potential evaluation points A to C will be described with reference to FIG.

  As shown in FIG. 2, the DC potential state at the DC potential evaluation point B is such that the current I9 flowing from the gate to the drain of the switch unit 9 is equal to the current I13 flowing through the resistance element 13, and the voltage control terminals 4 and 5 The potential difference is determined to be 3 volts. The direct current potential state at the direct current potential evaluation point A is substantially equal to the direct current potential at the direct current potential evaluation point B because the switch unit 9 is on and is in a conductive state.

  As shown in FIG. 3, the DC potential state at the DC potential evaluation point C is such that the leakage current I10 from the source to the gate of the switch unit 10 is equal to the current I14 flowing through the resistance element 14, and the voltage control terminals 4 and 5 Is determined to be 3 volts.

  Therefore, by adjusting the resistance values of the resistance elements 13 and 14 and adjusting the current flowing through the resistance elements, the DC potential states at the DC potential evaluation points A to C can be set to desired values.

  More specifically, a current larger than the current value determined by the Vgd-Igd characteristic of the field effect transistor in a region of a voltage lower than the voltage Vgd where the Vgd-Igd characteristic of the field effect transistor shows a steep rise. By using the resistance elements 13 and 14 that can flow, it is possible to reduce the source potential with respect to the gate potential of the on-side switch section and to increase the source potential with respect to the gate potential of the off-side switch section. Become.

  6 to FIG. 11 show that, in the high-frequency switch circuit of FIG. 1, the semiconductor switch portions 9 and 10 are connected in series in two stages of field effect transistors with a gate width of 2 mm, the resistance elements 11 and 12 are 80 kΩ, and the voltage control terminal 4 In the prior art shown in FIG. 12, the potential state of the DC potential evaluation points A to C when 3 volts and 0 volts are applied to the voltage control terminal 5, the insertion loss, the isolation, and the second harmonic measured value, respectively. Similarly, the semiconductor switch portions 69 and 70 are connected in series in a two-stage field effect transistor having a gate width of 2 mm, the resistance elements 71 and 72 are 80 kΩ, the voltage control terminal 64 is 3 volts, and the voltage control terminal 65 is 0 volts. DC potential evaluation points J to L when applied, insertion loss, isolation, harmonics (2nd Harmonics) actual Shows a comparison of the value.

The measurement frequency was f = 1 GHz, the input power was insertion loss, Pin = 15 dBm during isolation evaluation, and Pin = 26 dBm during harmonic evaluation.
The resistance elements 13 and 14 in FIG. 1 have two resistance values of 510 kΩ and 910 kΩ, and the resistance values of the resistance elements 73 and 74 in the prior art in FIG. Six types were used.

  As shown in FIGS. 6 to 8, the source potential with respect to the gate potential of the on-side switch portion is about 2.65 volts in the prior art, whereas in this embodiment, 2.0 to 2.2. The source potential with respect to the gate potential of the switch part on the off side is 2.4 to 2.65 volts in the prior art, whereas in the present embodiment, the source potential is 2.7 to 2.5 volts. It was confirmed that it would be as large as 2.95 volts.

  Also, as shown in FIGS. 9 to 11, the first embodiment of the present invention achieves lower insertion loss, higher isolation, and lower second harmonic level, which is unnecessary radiation, in comparison with the prior art. Has been.

  In the above embodiment, the resistance elements 13 and 14 are provided, but one of them can be omitted. In this case, the source and drain of the omitted semiconductor switch portion are connected by resistance elements 73 and 74 as shown in FIG.

(Second Embodiment)
FIG. 4 shows the high-frequency switch circuit of the (second embodiment).
In FIG. 1, the voltage control terminal 4 and the DC potential evaluation point C are connected by a resistance element 14 as a DC potential transmission unit, and the voltage control terminal 5 and the DC potential evaluation point B are connected as a resistance element as a DC potential transmission unit. In FIG. 4, the voltage control terminal 4 and the DC potential evaluation point C are connected by a diode element 34 as a DC potential transmission unit, and the voltage control terminal 5 and the DC potential evaluation point B are connected. 1 is different from FIG. 1 only in that a diode element 33 as a direct-current potential transmission unit is connected. The diode element 33 is connected with the voltage control terminal 5 side as an anode, and the diode element 34 is connected with the voltage control terminal 4 side as an anode. As the diode elements 33 and 34, diode elements capable of flowing a current that is larger in both positive and negative values than the current value determined by the Vgd-Igd characteristics of the field effect transistors constituting the semiconductor switch units 9 and 10 are used. .

  In the high-frequency switch circuit according to the second embodiment, the potential state of the DC / DC potential evaluation points A to C by adjusting the current value flowing through the diode element may be set to a desired value as in the first embodiment. Accordingly, the source potential with respect to the gate potential of the on-side switch unit can be made smaller, and the source potential with respect to the gate potential of the off-side switch unit can be made larger.

  In the above embodiment, the diode elements 33 and 34 are provided, but one of them can be omitted. In this case, the source and drain of the omitted semiconductor switch portion are connected by resistance elements 73 and 74 as shown in FIG.

(Third embodiment)
FIG. 5 shows the high-frequency switch circuit of the (third embodiment).
In FIG. 1, the voltage control terminal 4 and the DC potential evaluation point C are connected by a resistance element 14 as a DC potential transmission unit, and the voltage control terminal 5 and the DC potential evaluation point B are connected as a resistance element as a DC potential transmission unit. In FIG. 5, the voltage control terminal 4 and the DC potential evaluation point C are connected by a series circuit of a resistance element 54 and an inductor element 56 as a DC potential transmission unit. 1 is different from FIG. 1 only in that a direct current potential evaluation point B is connected by a series circuit of a resistance element 53 and an inductor element 55 as a direct current potential transmission section.

  In particular, the resistance elements 53 and 54 are arranged for applying a voltage complementary to the control voltage to the source electrode side, and the inductor elements 55 and 56 are the first high-frequency signal input / output terminal 2 and the second The high frequency signal at the high frequency signal input / output terminal 3 is prevented from leaking to the voltage control terminal side.

In the high-frequency switch circuit according to the third embodiment, the same effect as in the first and second embodiments can be obtained.
In the above embodiment, the series circuit of the resistor element 53 and the inductor element 55 and the series circuit of the resistor element 54 and the inductor element 56 are provided, but one of them can be omitted. In this case, the source and drain of the omitted semiconductor switch portion are connected by resistance elements 73 and 74 as shown in FIG.

  4, an inductor element 55 as shown in FIG. 5 is connected in series with the diode element 33 in order to prevent a high frequency signal from leaking to the voltage control terminal side, and in series with the diode element 34. An inductor element 56 as shown in FIG. 5 may be connected.

  In the (first embodiment), both of the two DC potential transmission units are configured by the resistance elements 13 and 14, and in the (second embodiment), both of the two DC potential transmission units are the diode elements 33. In the third embodiment, each of the two DC potential transmission units is composed of a series circuit of a resistance element 53 and an inductor element 55, and a series circuit of a resistance element 54 and an inductor element 56. However, one and the other of the DC potential transmission units can be configured by combining the embodiments. Specifically, the resistor element 14 of the (first embodiment) is replaced with the diode element 34 of the (second embodiment), or the resistor element 54 and the inductor element 56 of the (third embodiment) are connected in series. It can also be configured by replacing with a circuit. Further, the diode element 34 of the diode elements 33 and 34 of the (second embodiment) can be replaced with a series circuit of the resistor element 54 and the inductor element 56 of the (third embodiment).

  In each of the above-described embodiments, each semiconductor switch unit is configured by one field effect transistor. However, a plurality of field effect transistors may be connected in series.

  The present invention is useful in the design method of a high frequency switch with low insertion loss and high isolation.

Configuration diagram of a high-frequency switch circuit according to the first embodiment of the present invention Source potential state diagram of on-side field effect transistor of same embodiment Source potential state diagram of off-side field effect transistor of same embodiment The block diagram of the switch circuit for high frequency in (2nd Embodiment) of this invention The block diagram of the switch circuit for high frequency in (3rd Embodiment) of this invention Measured result diagram of drain side DC potential state of field effect transistor in (first embodiment) of the present invention Measured result diagram of source side DC potential state of on-side field effect transistor in (first embodiment) of the present invention Measured result diagram of source-side DC potential state of off-side field effect transistor in (first embodiment) of the present invention Measured result diagram of insertion loss characteristics in (first embodiment) of the present invention Measured result diagram of isolation characteristics in (first embodiment) of the present invention Measured result diagram of second harmonic radiation level in (first embodiment) of the present invention Configuration diagram of conventional high-frequency switch circuit The figure which shows the DC potential state of the source electrode and drain electrode of the field effect transistor of the conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Common terminal 2 1st high frequency signal input / output terminal 3 2nd high frequency signal input / output terminal 4, 5 Voltage control terminal 6, 7, 8 Coupling capacitor 9, 10 Semiconductor switch part 11, 12 Resistance element 13, 14 Resistance Element (DC potential transmission part)
33, 34 Diode element (DC potential transmission part)
53, 55 Resistive element and inductor elements 54, 56 constituting the DC potential transmission part Resistance element and inductor element constituting the DC potential transmission part

Claims (9)

In a high-frequency switch circuit comprising a plurality of high-frequency signal input / output terminals for inputting and outputting a high-frequency signal, and a plurality of semiconductor switch sections for opening and closing these high-frequency signal input / output terminals,
A high-frequency switch circuit provided with a DC potential transmission unit that applies a voltage complementary to a control voltage applied to open and close the semiconductor switch unit to at least one of the semiconductor switch units. In a high-frequency switch circuit comprising a plurality of high-frequency signal input / output terminals for inputting and outputting a high-frequency signal, and a plurality of semiconductor switch sections for opening and closing these high-frequency signal input / output terminals,
The semiconductor switch part is
The FET comprises a drain electrode and a source electrode connected to the high-frequency signal input / output terminal, or a plurality of FETs in which a drain electrode and a source electrode are connected in series.
A high-frequency switch circuit provided with a DC potential transmission unit that applies a voltage complementary to a control voltage applied to open and close the semiconductor switch unit to at least one of the semiconductor switch units. The high-frequency switch circuit according to claim 1, wherein the direct-current potential transmission portion is constituted by a resistance element. The high-frequency switch circuit according to claim 1, wherein the DC potential transmission unit is configured by a diode element. The high-frequency switch circuit according to claim 1, wherein the DC potential transmission unit is configured by connecting a diode element or a resistance element and an inductor element in series. A common terminal for inputting and outputting high-frequency signals;
First and second high-frequency signal input / output terminals for inputting and outputting high-frequency signals;
A first FET that opens and closes between the common terminal and the first high-frequency signal input / output terminal;
A second FET that opens and closes between the common terminal and the second high-frequency signal input / output terminal;
A first DC potential transmission unit for transmitting a potential applied to the gate electrode of the second FET to the source electrode of the first FET;
A high-frequency switch circuit comprising: a second DC potential transmission unit for transmitting a potential applied to the gate electrode of the first FET to a source electrode of the second FET. 7. The high frequency switch circuit according to claim 6, wherein the first and second DC potential transmission units are constituted by resistance elements. 7. The high-frequency switch circuit according to claim 6, wherein the first and second DC potential transmission units are constituted by diode elements. 7. The high-frequency switch circuit according to claim 6, wherein the first and second DC potential transmission units are configured by series connection of a diode element or a resistance element and an inductor element.

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