WO2015174138A1

WO2015174138A1 - Variable attenuator, attenuation adjustment circuit, and attenuation adjustment method

Info

Publication number: WO2015174138A1
Application number: PCT/JP2015/058159
Authority: WO
Inventors: 和田　靖
Original assignee: 日本電気株式会社
Priority date: 2014-05-15
Filing date: 2015-03-19
Publication date: 2015-11-19

Abstract

Provided is a variable attenuator whereby loss of high frequency signals can be reduced. This variable attenuator is provided with: a coupler, which distributes high frequency signals inputted from an input port, and which outputs the thus distributed high frequency signals from a first output port, a second output port, and a third output port; and an attenuation adjustment unit having at least two FETs between the second output port and a grounding terminal, and between the third output port and the grounding terminal, said at least two FETs being connected in series by having a source terminal and a drain terminal therebetween.

Description

Variable attenuator, attenuation adjustment circuit, and attenuation adjustment method

The present invention relates to a variable attenuator, an attenuation adjustment circuit, and an attenuation adjustment method.

With the recent increase in the amount of communication traffic, attention has been focused on the millimeter wave band and the terahertz band, which have a wide range of usable frequencies. In such a microwave monolithic integrated circuit (MMIC: Monolithic Microwave Integrated Circuit) having a variable attenuation function of a high-frequency signal, the gain control function is required to have a wide frequency band. Therefore, the MMIC generally performs high-frequency signal level control by the following two methods.
Method 1. 1. Gain control method by drain current control of field effect transistor (FET) constituting amplifier. Gain control by attenuation circuit using FET impedance control The control method listed in Method 1 is widely used because it can have both functions of an amplifier and an attenuator. Since it is necessary to lower the drain current, the operating point of the amplifier approaches a class AB operation, and the distortion characteristics may deteriorate.
On the other hand, in the control method listed in Method 2, the FET is inserted between the high-frequency transmission line and the ground terminal, the drain terminal and the source terminal of the FET are connected to the high-frequency transmission line and the ground terminal, respectively, and the gate voltage input separately is used. Gain control is performed by changing the impedance of the FET (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 06-232607

In the case of Method 2, it is necessary to sufficiently reduce the parasitic capacitance Cds generated between the drain terminal and the source terminal of the FET in order to suppress the high-frequency signal passing loss. Therefore, an FET with a small gate width is used so that the area where the parasitic capacitance Cds is formed is reduced. However, an FET with a small gate width has a poor high-frequency distortion characteristic and may distort the signal.
As described above, the variable attenuator using the FET as the variable attenuating element has a trade-off relationship between the passage loss of the high frequency signal and the distortion characteristic.

The present invention has been made in view of the above problems, and an object thereof is to provide a variable attenuator, an attenuation adjustment circuit, and an attenuation adjustment method in which loss and distortion characteristics of a high-frequency signal to be transmitted are improved. It is in.

According to one aspect of the present invention, a coupler that distributes a high-frequency signal input from an input port and outputs a high-frequency signal distributed from each of the first output port, the second output port, and the third output port; An attenuation adjustment unit having at least two FETs connected in series via a source terminal and a drain terminal between the output port and the ground terminal and between the third output port and the ground terminal, respectively. And a variable attenuator.

According to an aspect of the present invention, the second output of the coupler that distributes a high-frequency signal input from an input port and outputs a high-frequency signal distributed from each of the first output port, the second output port, and the third output port. Attenuation amount having at least two FETs connected in series via a source terminal and a drain terminal between a port and a ground terminal and between the third output port of the coupler and the ground terminal, respectively. It is an adjustment circuit.

In one embodiment of the present invention, a high-frequency signal is input to the input port of a coupler having an input port, a first output port, a second output port, and a third output port, and the second output port and a ground terminal And an attenuation adjustment method for applying a voltage to the gate terminals of at least two FETs connected in series via a source terminal and a drain terminal, respectively, between the third output port and the ground terminal It is.

According to the above-described variable attenuator, attenuation adjustment circuit, and attenuation adjustment method, it is possible to improve the loss and distortion characteristics of the transmitted high-frequency signal.

It is a figure which shows the whole structure of the variable attenuator which concerns on 1st Embodiment. It is a figure which shows the whole structure of the variable attenuator which concerns on contrast. It is the 1st figure explaining the operation effect of the variable attenuator concerning a 1st embodiment. It is the 1st figure explaining the operation effect of the variable attenuator concerning a 1st embodiment. It is the 2nd figure explaining the operation effect of the variable attenuator concerning a 1st embodiment. It is the 2nd figure explaining the operation effect of the variable attenuator concerning a 1st embodiment. It is a 3rd figure explaining the effect of the variable attenuator which concerns on 1st Embodiment. It is the 4th figure explaining the operation effect of the variable attenuator concerning a 1st embodiment. It is a figure which shows the function structure of the variable attenuator 1 which concerns on other embodiment.

<First Embodiment>
The variable attenuator according to the first embodiment will be described below with reference to the drawings.
FIG. 1 is a diagram illustrating an overall configuration of a variable attenuator according to the first embodiment.
As shown in FIG. 1, the variable attenuator 1 according to this embodiment includes a Lange coupler 10 (coupler), an attenuation adjustment unit 11 (an attenuation adjustment circuit), and a variable voltage source 13.
The Lange coupler 10 distributes a high frequency signal (RFin) input from the input port Pin, and outputs the distributed high frequency signal from each of the first output port Pout1, the second output port Pout2, and the third output port Pout3. The Lange coupler 10 includes a first coupled line 100 that connects the input port Pin and the second output port Pout2, and a second coupled line 101 that connects the first output port Pout1 and the third output port Pout3. .
The first coupled line 100 and the second coupled line 101 are arranged in parallel with a coupled line length L. The coupling line length L is set to a length (specifically, 1/4 of the wavelength λ of the high frequency signal) according to the frequency (wavelength) of the high frequency signal input from the input port Pin. As a result, the high-frequency signal input from the input port Pin is connected to each of the first output port Pout1, the second output port Pout2, and the third output port Pout3 by electromagnetic coupling between the first coupling line 100 and the second coupling line 101. Distributed to. The distribution ratio to each of the first output port Pout1, the second output port Pout2, and the third output port Pout3 is determined according to the impedance of the element connected to the tip of each output port.
Note that the variable attenuator 1 according to the present embodiment is a variable attenuator applied to a high-frequency signal in the 75 to 110 GHz frequency band that is a millimeter wave band. In this case, the coupled line length L in the Lange coupler 10 is, for example, 300 μm, which is a quarter wavelength of 90 GHz, which is substantially the center frequency of the frequency band (75 to 110 GHz). However, the variable attenuator according to another embodiment is not limited to the above-described aspect, and for example, the coupled line length L may be set to a length optimized for a frequency band other than the millimeter wave band.

The attenuation adjustment unit 11 includes a terminal connected to the second output port Pout2 and the third output port Pout3 of the Lange coupler 10, a ground terminal GND connected to a potential line that applies a ground potential (0V), and a variable voltage source 13. And a control terminal C connected to the.
Further, the attenuation adjustment unit 11 includes a first FET 120, a second FET 121, and a second FET 121 that are connected in series via the source terminal S and the drain terminal D between the second output port Pout2 of the Lange coupler 10 and the ground terminal GND. ,have. The attenuation adjustment unit 11 includes a third FET 122, a fourth FET 123, and a third FET 122 connected in series via the source terminal S and the drain terminal D between the third output port Pout3 of the Lange coupler 10 and the ground terminal GND. ,have.
More specifically, the second output port Pout2 and the drain terminal D of the first FET 120 are connected, the source terminal S of the first FET 120 and the drain terminal D of the second FET 121 are connected, and the source terminal S of the second FET 121 and the ground. Terminal GND is connected.
Similarly, the third output port Pout3 and the drain terminal D of the third FET 122 are connected, the source terminal S of the third FET 122 and the drain terminal D of the fourth FET 123 are connected, and the source terminal S of the fourth FET 123 and the ground terminal GND are connected. Connected.
In the present embodiment, each of the first FET 120 to the fourth FET 123 is an FET made of GaAs (gallium arsenide) generally used for millimeter wave band MMICs. Further, the gate width W of each of the first FET 120 to the fourth FET 123 (the width of the gate terminal in the direction orthogonal to the direction in which current flows between the source and drain) is formed to be about 25 μm, for example. However, in other embodiments, the present invention is not limited to this mode, and the first FET 120 to the fourth FET 123 may be formed of FETs made of Si (silicon), for example.

As shown in FIG. 1, the attenuation adjustment unit 11 further includes resistance elements R1 to R4.
One end of the resistance element R1 is connected to the gate terminal G of the first FET 120, and the other end is connected to the control terminal C. Similarly, one end of the resistor element R2 is connected to the gate terminal G of the second FET 121, one end of the resistor element R3 is connected to the gate terminal G of the third FET 122, and one end of the resistor element R4 is connected to the gate terminal G of the fourth FET 123. The other ends of the resistance elements R2 to R4 are all connected to the control terminal C. That is, the control terminal C is connected to all the gate terminals G of the first FET 120 to the fourth FET 123 via the resistance elements R1 to R4. Each of the resistance elements R1 to R4 is provided so that the variable voltage source 13 stably controls the DC (direct current) voltage applied to the gate terminals G of the first FET 120 to the fourth FET 123. Each of the resistance elements R1 to R4 has a resistance value of, for example, about 1 kΩ.

The variable voltage source 13 is connected to the control terminal C and applies a predetermined DC voltage to the control terminal C. The variable voltage source 13 can change the DC voltage applied to the control terminal C as desired within a certain range (for example, ± 1 V).

The variable attenuator 1 having the above configuration operates, for example, as follows.
When the variable voltage source 13 applies an off voltage (for example, −1V) to the gate terminals G of the first FET 120 to the fourth FET 123, the first FET 120 to the fourth FET 123 are in an off state (a state where the impedance is high). No current flows between the source and drain. Accordingly, the second output port Pout2 and the third output port Pout3 are opened.
Then, the high frequency signal RFin input from the input terminal Pin is substantially totally reflected at the second output port Pout2 and the third output port Pout3, and is output from the first output terminal Pout1 as a high frequency signal RFout without being attenuated.

On the other hand, when the variable voltage source 13 applies an on voltage (for example, +1 V) to the gate terminals G of the first FET 120 to the fourth FET 123, the first FET 120 to the fourth FET 123 are in an on state (low impedance state). A current flows between the source and drain. Therefore, the strength of the high frequency signal transmitted from the second output port Pout2 and the third output port Pout3 to the ground terminal GND increases, and as a result, the high frequency signal RFout output from the first output port Pout1 is attenuated.
In the variable attenuator 1 using the Lange coupler 10, in order to appropriately attenuate the high-frequency signal RFin input to the first output port Pout1 based on the impedance at the second output port Pout2 or the third output port Pout3. The impedances of the FETs connected to the second output port Pout2 and the third output port Pout3 need to be changed while being uniform.

As described above, the variable attenuator 1 adjusts the DC voltage applied to the control terminal C (that is, each gate terminal G) by the variable voltage source 13 to change the impedance of the first FET 120 to the fourth FET 123, thereby changing the high frequency. The amount of signal attenuation can be changed.

FIG. 2 is a diagram for explaining the overall configuration of a variable attenuator related to the comparison.
As shown in FIG. 2, the proportional variable attenuator 9 includes a Lange coupler 10, a variable voltage source 13, and an attenuation adjustment unit 91. Here, the Lange coupler 10 and the variable voltage source 13 are the same as those provided in the variable attenuator 1 according to the first embodiment.
As shown in FIG. 2, the attenuation adjustment unit 91 according to proportionality includes a first FET 120, a third FET 122, a resistance element R1, and a resistance element R3. The aspects (material, size, etc.) of these FETs and resistance elements are the same as those in the first embodiment.

In the attenuation adjustment unit 91 related to the proportionality, the first FET 120 is inserted between the second output port Pout2 of the Lange coupler 10 and the ground terminal GND, and the drain terminal D and the source of the first FET 120 are connected to the second output port Pout2 and the ground terminal GND. Terminals S are connected to each other. The third FET 122 is inserted between the third output port Pout3 and the ground terminal GND of the Lange coupler 10, and the drain terminal D and the source terminal S of the third FET 122 are connected to the third output port Pout3 and the ground terminal GND, respectively.
The variable attenuator 9 having such a configuration also operates in the same manner as the variable attenuator 1 (FIG. 1) according to the first embodiment.

As shown in FIGS. 1 and 2, the variable attenuator 1 according to the first embodiment has each of the second output port Pout2 and the third output port Pout3 compared to the variable attenuator 9 according to the proportionality. 2 differs in that two FETs are connected in series. Next, the effect of two FETs connected in series in the variable attenuator 1 according to this embodiment will be described in detail.

FIG. 3A and FIG. 3B are first diagrams illustrating the operational effects of the variable attenuator according to the first embodiment.
FIG. 3A shows an equivalent circuit of the first FET 120 that constitutes the attenuation adjustment unit 91 of the variable attenuator 9 (FIG. 2) that is in proportion. FIG. 3B shows an equivalent circuit of the first FET 120 and the second FET 121 that are included in the variable attenuator 1 (FIG. 1) according to the present embodiment and that are connected in series.

The circuit diagram shown in FIG. 3A is a general equivalent circuit of an FET.
According to the configuration (FIG. 2) of the attenuation adjustment unit 91 of the variable attenuator 9 according to the comparison, as shown in FIG. 3A, a parasitic capacitance Cds is provided between the drain terminal D and the source terminal S of the first FET 120. (Hereinafter also referred to as “drain-source capacitance Cds”). This drain-source capacitance Cds is mainly caused by a pn junction formed inside the FET.
When the drain terminal D and the source terminal S of the first FET 120 are connected between the second output port Pout2 and the ground terminal GND of the Lange coupler 10, between the second output port Pout2 and the ground terminal GND, A drain-source capacitance Cds is always connected. Then, even if the first FET 120 is in an OFF state, a high frequency signal flows to the ground terminal GND via the drain-source capacitance Cds. That is, even when it is desired to transmit without causing a passage loss, a high-frequency signal passage loss is caused by the drain-source capacitance Cds that is always present.
Here, “passage loss” is a value (unit: dB) indicating a ratio of the level of the high-frequency signal RFout output from the first output port Pout1 to the level (intensity) of the high-frequency signal RFin input to the input port Pin. is there. When the input level of the high-frequency signal RFin is equal to the output level of the high-frequency signal RFout (that is, when no loss occurs), the passing loss is 0 dB. When the output level of the high-frequency signal RFout is lower than the input level of the high-frequency signal RFin (that is, when a predetermined amount of loss occurs), the passage loss is indicated by a negative value.

Generally, when the gate width W of the FET is reduced, the area in which the parasitic capacitance (drain-source capacitance Cds) based on the pn junction is formed is reduced accordingly, so that the drain-source capacitance Cds is reduced. Therefore, in order to suppress the passage loss, it is necessary to reduce the gate width W of the first FET 120. However, if the gate width W of the FET is made too small, the high-frequency characteristic distortion characteristics of the FET may deteriorate and the high-frequency signal may be distorted. Therefore, there is a limit to reducing the gate width W for the purpose of reducing the drain-source capacitance Cds. Therefore, the variable attenuator 9 according to the proportionality cannot sufficiently reduce the drain-source capacitance Cds, and has a large passage loss of the high-frequency signal.

In contrast, the configuration of the attenuation adjustment unit 11 of the variable attenuator 1 according to the present embodiment (FIG. 1) will be described below. In this case, in the equivalent circuit of FIG. 3B, the drain terminal D of the first FET 120 is connected to the second output port Pout2 of the Lange coupler 10 (see FIG. 1). Further, the gate terminals G of the first FET 120 and the second FET 121 are connected to the variable voltage source 13 through the resistance element R1 and the resistance element R2, respectively (see FIG. 1). As described above, in the attenuation amount adjusting unit 11 according to the present embodiment, the two drain-source capacitances Cds are connected in series between the second output port Pout2 and the ground terminal GND. Then, since the net parasitic capacitance generated between the second output port Pout2 and the ground terminal GND is ½ × Cds, according to the attenuation amount adjustment unit 11 having such a configuration, the relative attenuation is obtained. Compared with the quantity adjustment unit 91, it is possible to suppress the passage loss of the high-frequency signal.

FIG. 4A and FIG. 4B are second diagrams for explaining the effects of the variable attenuator according to the embodiment.
The graph shown in FIG. 4A shows the characteristics of the passage loss of the variable attenuator 9 according to the comparison. Moreover, the graph shown to FIG. 4B has shown the characteristic of the passage loss of the variable attenuator 1 which concerns on 1st Embodiment. 4A and 4B, the characteristics of the passage loss when the off voltage (−1V) is applied to the gate terminals G of the first FET 120 to the fourth FET 123 are indicated by solid lines, and the gate terminals G of the first FET 120 to the fourth FET 123 are turned on. The characteristics of the passage loss when a voltage (+1 V) is applied are indicated by broken lines.

As shown in FIG. 4A, the variable attenuator 9 according to the proportionality is about −3.5 dB in a high-frequency signal having a frequency of 90 GHz even though the off-voltage is applied to the gate terminals G of the first FET 120 and the third FET 122. (See the solid line in FIG. 4A). As described above, this passage loss is caused by the drain-source capacitance Cds of the first FET 120 (third FET 122).
On the other hand, as shown in FIG. 4B, in the variable attenuator 1 according to the present embodiment, when the off voltage is applied to the gate terminals G of the first FET 120 to the fourth FET 123, the passage loss in the high-frequency signal of 90 GHz is − It is suppressed to about 1.5 dB. This is because the drain-source capacitance Cds parasitic to the first FET 120 and the second FET 121 (the third FET 122 and the fourth FET 123) is connected in series, so that the second output port Pout2 (the third output port Pout3) and the ground terminal GND are connected. This is because the parasitic capacitance generated between them is reduced to ½.

On the other hand, the passing loss when the on-voltage (+ 1V) is applied to the gate terminals G of the first FET 120 to the fourth FET 123 is about -11.0 dB in the high-frequency signal with the frequency of 90 GHz, which is equivalent to the variable attenuator 9 related to the comparison. It is a characteristic. That is, it can be seen that the variable attenuator 1 according to the present embodiment can control the amount of attenuation by the applied gate voltage in the same manner as the variable attenuator 9 according to the comparative example.

FIG. 5 is a third diagram for explaining the operational effects of the variable attenuator according to the first embodiment.
The graph shown in FIG. 5 shows the relationship between the gate voltage Vgs and the passage loss at a frequency of 90 GHz of the variable attenuator 9 (broken line) according to the proportionality and the variable attenuator 1 (solid line) according to the present embodiment. Yes.
As shown in FIG. 5, when the gate voltage Vgs applied to the gate terminals G of the first FET 120 and the third FET 122 of the variable attenuator 9 which is proportional to each other is changed from −1.5 V to +1.5 V, the variable attenuator The passing loss of the high-frequency signal transmitted from the nine input ports Pin to the first output port Pout1 varies from −3.5 dB to −11.0 dB.
On the other hand, when the gate voltage Vgs applied to each gate terminal G of the first FET 120 to the fourth FET 123 of the variable attenuator 1 according to this embodiment is changed from −1.5 V to +1.5 V, the variable attenuator 1 The passing loss of the high-frequency signal transmitted from the input port Pin to the first output port Pout1 varies from −1.0 dB to −11.0 dB.
As described above, the variable attenuator 1 according to the present embodiment reduces the parasitic capacitance generated between the second output port Pout2 (third output port Pout3) and the ground terminal GND, so that the variable attenuation according to the proportionality is achieved. The range of attenuation that can be controlled is larger than that of the device 9.

FIG. 6 is a fourth diagram illustrating the operational effect of the variable attenuator according to the first embodiment.
The graph shown in FIG. 6 shows the characteristic of the third-order intermodulation distortion (IM3) with respect to the gate voltage Vgs of the variable attenuator 9 (broken line) and the variable attenuator 1 (solid line) according to the present embodiment. Yes. As shown in FIG. 6, the variable attenuator 1 according to the present embodiment has a distortion characteristic improved by about 8 dB compared to the variable attenuator 9 according to the proportionality when the gate voltage Vgs is −1V. When the gate voltage Vgs is +1 V, the distortion characteristics of the variable attenuator 1 are improved by about 15 dB compared to the variable attenuator 9 according to the proportionality.
In this way, by connecting FETs used for attenuation control in multiple stages in series, the voltage applied between the source and drain of each FET is reduced, so that the distortion characteristics can be improved.

As described above, according to the variable attenuator 1 according to the first embodiment, the loss and distortion of the high-frequency signal to be transmitted are obtained by connecting the FET for controlling the attenuation amount in series through the source terminal and the drain terminal. The characteristics can be improved.

In the variable attenuator 1 according to the present embodiment, two FETs (first FET 120 to fourth FET 123) are connected in series in each of the second output port Pout2 and the third output port Pout3 of the Lange coupler 10. However, other embodiments are not limited to this aspect. For example, the number of FETs connected in series to each of the second output port Pout2 and the third output port Pout3 of the Lange coupler 10 may be three or more. By doing so, the loss and distortion characteristics of the high-frequency signal to be transmitted can be further improved.

Further, the same number (two) of the attenuation adjustment units 11 according to the present embodiment is provided between the second output port Pout2 and the ground terminal GND of the Lange coupler 10 and between the third output port Pout3 and the ground terminal GND. FETs are connected in series. Thereby, it becomes easy to uniformly change the impedance of the FET connected to the second output port Pout2 and the impedance of the FET connected to the third output port Pout3.
However, the variable attenuator 1 according to another embodiment is not limited to this aspect. That is, even if the number of FETs connected in series to the second output port Pout2 is different from the number of FETs connected in series to the third output port Pout3, the second output port Pout2 or the third output port Pout3 Similar effects can be obtained if the overall impedance of the FETs connected to is uniform.

Further, the attenuation adjustment unit 11 according to the present embodiment has been described as having a single control terminal C connected to all the gate terminals G of the first FET 120 to the fourth FET 123. Thereby, the variable voltage source 13 can apply the same gate voltage Vgs to the gate terminals G of all FETs only by applying a desired DC voltage only to the single control terminal C. Therefore, it is possible to easily change the impedance of the FET connected to the second output port Pout2 and the impedance of the FET connected to the third output port Pout3 uniformly.
However, the variable attenuator 1 according to another embodiment is not limited to this aspect. That is, the gate voltage Vgs is individually applied to the gate terminals G of two or more FETs connected in series to the second output port Pout2 and two or more FETs connected in series to the third output port Pout3. May be applied. In such an embodiment, even if different gate voltages Vgs are applied, if the overall impedance of each FET connected to the second output port Pout2 or the third output port Pout3 is uniform, the same applies. The effect of this can be obtained.

Further, the variable attenuator 1 according to the present embodiment includes the Lange coupler 10 and the components of the attenuation adjustment unit 11 (first FET 120 to fourth FET 123, resistance element R1 to resistance element R4, etc.) on the same semiconductor substrate. It is good also as an aspect formed integrally. By doing so, the variable attenuator 1 can be reduced in size, which contributes to a reduction in manufacturing cost.
However, in other embodiments, the present invention is not limited to this mode. For example, the constituent elements of the Lange coupler 10 and the attenuation amount adjustment unit 11 may be individually mounted.

Further, the configuration of the Lange coupler 10 according to the present embodiment is not limited to the above-described aspect. For example, the Lange coupler 10 may be a distributed constant branch line coupler. If the frequency of the high frequency signal is relatively low, a lumped constant branch line coupler using a spiral inductor may be used.

FIG. 7 is a diagram illustrating a functional configuration of an attenuation adjustment circuit according to another embodiment.
The attenuation adjustment circuit 11A distributes a high-frequency signal input from the input port and outputs a high-frequency signal distributed from each of the first output port, the second output port, and the third output port. And at least two FETs 12 connected in series via a source terminal S and a drain terminal D between the first output terminal and the ground terminal GND and between the third output port of the coupler and the ground terminal GND. .

Further, in the attenuation adjustment method according to another embodiment, the high frequency signal RFin is input to the input port Pin of the coupler 10 having the input port Pin, the first output port Pout1, the second output port Pout2, and the third output port Pout3. , At least 2 connected in series via the source terminal S and the drain terminal D between the second output port Pout2 and the ground terminal GND and between the third output port Pout3 and the ground terminal GND, respectively. A voltage is applied to the gate terminals of one or more FETs 12 to adjust the attenuation amount of the high-frequency signal RFout output to the first output port Pout1.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof, as long as they are included in the scope and gist of the invention.

This application claims priority based on Japanese Patent Application No. 2014-101112 filed in Japan on May 15, 2014, the contents of which are incorporated herein by reference.

The present invention can be applied to, for example, gain control of a high frequency signal. According to the present invention, loss and distortion characteristics of a high-frequency signal to be transmitted can be improved.

1 Variable attenuator 10 Lange coupler (coupler)
100 first coupled line 101 second coupled line 11 attenuation adjustment unit 11A attenuation adjustment circuit 12 FET
120 1st FET
121 2nd FET
122 3rd FET
123 4th FET
13 Variable voltage source

Claims

A coupler that distributes a high-frequency signal input from the input port and outputs a high-frequency signal distributed from each of the first output port, the second output port, and the third output port;
An attenuation having at least two FETs connected in series via a source terminal and a drain terminal between the second output port and the ground terminal and between the third output port and the ground terminal, respectively. An amount adjustment unit;
A variable attenuator comprising:
The attenuation adjustment unit
The variable attenuator according to claim 1, wherein the number of the FETs connected in series between the second output port and the ground terminal and in series between the third output port and the ground terminal is the same. .
The attenuation adjustment unit
The variable attenuator according to claim 2, further comprising a control terminal connected to all of the gate terminals of the FET.
The coupler and the attenuation adjustment unit are:
The variable attenuator according to any one of claims 1 to 3, wherein the variable attenuator is integrally formed on the same substrate.
Between the second output port and the ground terminal of the coupler that distributes the high frequency signal input from the input port and outputs the high frequency signal distributed from each of the first output port, the second output port, and the third output port; And an attenuation adjustment circuit having at least two FETs connected in series via a source terminal and a drain terminal, respectively, between the third output port of the coupler and the ground terminal.
A high frequency signal is input to the input port of the coupler having an input port, a first output port, a second output port, and a third output port;
Gates of at least two FETs connected in series via a source terminal and a drain terminal between the second output port and the ground terminal and between the third output port and the ground terminal, respectively. Attenuation adjustment method to apply voltage to terminals.