JP2003309454A - Variable attenuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable attenuator capable of reducing pass band phase fluctuations of a high frequency signal transmitted from an input terminal to an output terminal at passing amplitude switching. <P>SOLUTION: The variable attenuator comprises: a series circuit section 8a including a switching transistor 3a and a series resistor 5a in parallel connection; a first parallel circuit section 9a including a switching transistor 3b and a parallel resistor 6a in series connection; and a second parallel circuit section 9b including a switching transistor 3c and a parallel resistor 6b in series connection, and varies the amplitude of a high frequency signal received from an input terminal 1 and outputs the result to an output terminal 2. Phase correction reactance elements 7a, 7b are provided to at least one of the first and second parallel circuit sections 9a, 9b to correct a passing phase difference of the high frequency signal from the input terminal 1 to the output terminal 2. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable attenuator capable of reducing the pass phase difference by providing a pass phase correcting reactance element when the pass amplitude is changed.

[0002]

2. Description of the Related Art FIG. 12 is a block diagram of a conventional variable attenuator described in, for example, the proceedings of the 1999 IEICE General Conference. As shown in FIG. 12, this variable attenuator is composed only of resistors and switching transistors.

In FIG. 12, 1 is a high frequency signal input terminal, 2 is a high frequency signal output terminal, 3a, 3b and 3c are switching transistors, 4a and 4b are switching transistors 3a, 3b and 3c for switching the passing amplitude. Control terminal for controlling ON / OFF of the switch, 5a is a series resistance, 6a and 6b are parallel resistances, 8 is a series circuit section including a switching transistor 3a and a series resistance 5a, 9a is a switching transistor 3b and a parallel resistance 6a. First parallel circuit section, 9
b is a second parallel circuit section including a switching transistor 3c and a parallel resistor 6b, 15 is a power supply terminal, 16a, 16
b and 16c are switching transistors 3a, 3b and 3c
And a gate resistor 17 connected to the control terminal 4a, respectively.
An inverter that inverts a control signal applied from the device, 18 is a series circuit unit 8, parallel circuit units 9a and 9b, and a gate resistor 16
This is a single-bit variable attenuator composed of a, 16b, 16c and an inverter 17.

Next, the operation will be described. The conventional variable attenuator shown in FIG. 12 outputs the amplitude of the high frequency signal input from the input terminal 1 by switching the amplitude value to 32 states by a 5-bit variable attenuator composed of five single-bit variable attenuators. It is output from the terminal 2. Here, in order to facilitate comparison with the variable attenuator according to the present invention, the single-bit variable attenuator 18 will be described. The conventional variable attenuator has a combination of the single-bit variable attenuator 18,
By describing only the single-bit variable attenuator 18, comparison with the variable attenuator according to the present invention is possible.

In the single-bit variable attenuator 18, the control signals applied from the control terminals 4a and 4b are directly input to the switch transistors 3b and 3c, and the inverted signal is passed through the inverter 17 to the switch. Input to the transistor 3a, 3a, 3b and 3c
Is turned on / off to change the amplitude of the high frequency signal input from the input terminal 1.
In the reference state, that is, when the switching transistor 3a is on and 3b and 3c are off, the high frequency signal input from the input terminal 1 has a very small on-resistance exhibited by the switching transistor 3a. If the off-capacitance presented is very small, it passes through the single-bit variable attenuator 18 with little attenuation.

On the other hand, when the switching transistor 3a is in the off state and the switching transistors 3b and 3c are in the on state, the high frequency signal input from the input terminal 1 has a very small off capacitance exhibited by the switching transformer 3a. ,
Assuming that the on-resistances exhibited by 3b and 3c are very small, π consisting of a series resistor 5a and parallel resistors 6a and 6c
Can be regarded as a type attenuator, and the high frequency signal input from the input terminal 1 is a series resistor 5a forming a π type attenuator,
It is attenuated by the attenuation amount set by the parallel resistors 6a and 6c.

[0007]

In the conventional variable attenuator described above, when the switching amplitude is switched by the switching transistor, the off-state capacitance component and parasitic component of the transistor (parasitic components caused by technical restrictions in manufacturing the transistor). There is a problem that the passing phase fluctuates due to the path difference in the length of the transmission line in the case of an element) or an IC. The present invention has been made to solve the above problems, and an object of the present invention is to realize a variable attenuator capable of reducing the fluctuation of the passing phase when switching the passing amplitude.

[0008]

According to a first aspect of the present invention, there is provided a series circuit section having a first switching transistor and a first resistor connected in parallel, a second switching transistor connected in series and a second switching transistor. A first parallel circuit section having a second resistance, a second parallel circuit section having a third switching transistor and a third resistance connected in series, and a high frequency wave inputted from an input terminal In a variable attenuator that changes the amplitude of a signal and outputs it to an output terminal, at least one of the first parallel circuit section and the second parallel circuit section is provided with a high-frequency signal to be transmitted from the input terminal to the output terminal. A phase-correcting reactance element for correcting the passing phase difference is provided.

A second aspect of the present invention is to connect between the second resistor and the ground or between the third resistor and the ground, or to connect the second switch transistor and the second resistor. And a phase-correcting reactance element connected between the third switching transistor and the third resistor.

A third aspect of the invention comprises a phase-correcting reactance element connected to at least one end of the first switching transistor and the first resistor.

A fourth aspect of the invention comprises a DC operating point determining resistor which is connected in parallel with the phase correcting reactance element and which avoids an indefinite state of the DC operating point.

According to a fifth aspect of the invention, a first series circuit portion having a first switching transistor and a first resistor connected in parallel, a second switching transistor and a second resistor connected in parallel are provided. And a parallel circuit section having a third switching transistor and a third resistor connected in series, and changing the amplitude of the high frequency signal input from the input terminal. In the variable attenuator for outputting to an output terminal, the parallel circuit section is provided with a phase correcting reactance element for correcting a passing phase difference of a high frequency signal transmitted from the input terminal to the output terminal.

According to a sixth aspect of the present invention, there is provided a phase-correcting reactance element connected between the third resistor and the ground or between the third switching transistor and the third resistor. Be prepared.

In a seventh aspect of the invention, the phase-correction reactance element is connected to at least one end of the first switching transistor, the second switching transistor, the first resistor and the second resistor. The phase-correcting reactance element is provided.

An eighth aspect of the invention comprises a DC operating point determining resistor which is connected in parallel with the phase correcting reactance element and which avoids an indefinite state of the DC operating point.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. 1 is a configuration diagram (circuit diagram) of a variable attenuator according to a first embodiment of the present invention. In FIG. 1, 1 is a high frequency signal input terminal, 2 is a high frequency signal output terminal, 3a, 3b and 3c are switching transistors, 4a and 4b are on / off states of the switching transistors 3a, 3b and 3c for switching the passing amplitude. Control terminal for controlling OFF, 5a is series resistance, 6a and 6b are parallel resistance,
Reference numerals 7a and 7b are phase-correcting reactance elements, 8a is a series circuit section including a switching transistor 3a and a series resistor 5a, and 9a is a first circuit including a switching transistor 3b, a parallel resistor 6a, and a phase-correcting reactance element 7a.
The parallel circuit section 9b is a second parallel circuit section including the switching transistor 3c, the parallel resistor 6b, and the phase correction reactance element 7b.

Next, the operation and effect will be described. The variable attenuator of the present embodiment uses the switching transistor 3 according to the control signal applied from the control terminals 4a and 4b.
By turning on / off a, 3b, and 3c, the amplitude of the high-frequency signal input from the input terminal 1 is changed, and is extracted from the output terminal 2.

FIG. 2 is an equivalent circuit diagram of the reference state of the variable attenuator in which the switching transistor 3a is on and the switching transistors 3b and 3c are off. FIG. 3 is an equivalent circuit diagram of the attenuation state of the variable attenuator in which the switching transistor 3a is off and the switching transistors 3b and 3c are on.

In FIG. 2, 10a is the on resistance of the switch transistor 3a in the on state, and 11b and 11c are the switch transistors 3b and 3c in the off state, respectively.
Is the off capacity of. Here, assuming that the on-resistance 10a is ideally small enough to be ignored and the off-capacitances 11b and 11c are small enough to be ignored, the amplitude of the high-frequency signal input from the input terminal 1 is hardly attenuated from the output terminal 2. Is output.

On the other hand, also in FIG.
1a is so small that it can be ignored, and the on resistances 10b, 10
Assuming that c is ideally small enough to be ignored, and the phase-correcting reactance elements 7a and 7b are not provided, the circuit shown in FIG. 3 has a series resistor 5a and parallel resistors 6a and 6b.
Can be regarded as a type attenuator, and the high frequency signal input from the input terminal 1 is a series resistor 5a forming a π type attenuator,
It is attenuated by the attenuation amount set by the parallel resistors 6a and 6b, and is output from the output terminal 2.

When the desired frequency is high, the off capacitance 1
The passing phase fluctuations due to 1a, 11b, and 11c cannot be ignored, and a passing phase difference occurs in the reference state shown in FIG. 2 and the damping state shown in FIG. At this time, by connecting the phase-correction reactance elements 7a and 7b to the parallel circuit units 9a and 9b, it is possible to adjust the phase in the attenuated state with almost no change in the phase in the reference state.

FIG. 4 shows the reactance element 7 for phase correction.
It is the equivalent circuit diagram which connected the phase correction inductors 12a and 12b as a and 7b. FIG. 5 shows a phase correction capacitor 13 as the phase correction reactance elements 7a and 7b.
It is the equivalent circuit diagram which connected a and 13b. When the phase in the reference state is advanced as compared to the attenuated state, the phase correction inductors 12a and 12b are used as the phase correction reactance elements 7a and 7b, as shown in FIG. As shown, the phase correction capacitors 13a, 1
By connecting 3b, the passing phase difference can be corrected.

As described above, according to the present embodiment, the switching transistors 3a, 3b and 3c are turned on / off by the control signal applied from the control terminals 4a and 4b, so that the input from the input terminal 1 is performed. Since the amplitude of the high frequency signal can be varied and the passing phase difference of the high frequency signal transmitted from the input terminal 1 to the output terminal 2 can be corrected, when the passing amplitude of the high frequency signal input from the input terminal 1 is switched. It is possible to reduce the passing phase fluctuation that occurs.

Although the phase-correcting reactance elements 7a and 7b are connected to both the first parallel circuit section 9a and the second parallel circuit section 9b here, they are connected by connecting to at least one of them. It is possible to correct the phase difference.
Further, here, the phase correction reactance elements 7a and 7b are used.
Are connected between the parallel resistors 6a and 6b and the ground, but are connected to the switching transistors 3b and 3c and the parallel resistor 6
You may connect between a and 6b. Furthermore, here, the passing phase variation due to the off capacitors 11a, 11b, and 11c is described, but the parasitic component of the switching transistor, the IC
It is also possible to correct the passing phase difference caused by the transmission line in the case of conversion.

Embodiment 2. 6 is a configuration diagram (circuit diagram) of a variable attenuator according to a second embodiment of the present invention. In FIG. 6, the series circuit portion 8a is a switching transistor 3
a, the series resistance 5a, and the phase correction reactance element 7a,
7b and. The first parallel circuit section 9a includes a switching transistor 3b and a parallel resistor 6a, and the second parallel circuit section 9b includes a switching transistor 3c and a parallel resistor 6b.

The operation is basically the same as that of the first embodiment, except that the phase-correcting reactance elements 7a and 7b are connected in series to the series resistor 5a forming the series circuit section 8a. Here, in the case where the phase in the reference state is advanced as compared with the attenuated state, the phase correction capacitor is connected as the phase correction reactance element, and the phase correction inductor is connected in the case where the phase is delayed, the embodiment is realized. The same effect as 1 can be obtained. Although the phase-correcting reactance elements 7a and 7b are connected to both ends of the series resistor 5a here, they may be connected to at least one of them.

FIG. 7 is another configuration diagram (circuit diagram) of the variable attenuator of the second embodiment. As shown in FIG. 7, the phase correction reactance element 7 is connected to the switching transistor 3a.
The same effect can be obtained by connecting a and 7b. In this case, when the phase in the reference state is advanced compared to the attenuated state, the phase correction capacitor is connected as the phase correction reactance element, and when it is delayed, the phase correction inductor is connected. Also at this time, the phase-correcting reactance elements 7a and 7b are connected to both ends of the switching transistor 3a, but it is sufficient that they are connected to at least one of them.

In FIG. 6, the phase-correcting reactance element 7 is provided on at least one of both ends of the series resistor 5a.
7A and 7b are connected, and in FIG. 7, the case where the phase correction reactance elements 7a and 7b are connected to at least one of both ends of the switching transistor 3a has been described, but both ends of the series resistor 5a and the switching transistor 3a are described. The same effect can be obtained even if the phase-correction reactance element is connected to all or some one of both ends of the.

Embodiment 3. FIG. 8 is a configuration diagram (circuit diagram) of a variable attenuator according to a third embodiment of the present invention. In FIG. 8, 8a is a first series circuit section and 8b is a second series circuit section. The first series circuit part 8a is composed of a switching transistor 3a and a series resistor 5a, and the second series circuit part 8b is composed of a switching transistor 3d and a series resistor 5b. The first parallel circuit section 9a includes a switching transistor 3b, a parallel resistor 6a, and a phase correction reactance element 7a.

The operation and effect are basically the same as those of the first embodiment, except that the T-type variable attenuator has two series circuit parts 8a and 8b and one parallel circuit part 9a.
Although the phase correction reactance element 7a is connected between the parallel resistor 6a and the ground here, it may be connected between the switching transistor 3b and the parallel resistor 6a.

Fourth Embodiment 9 is a configuration diagram (circuit diagram) of a variable attenuator according to a fourth embodiment of the present invention. In FIG. 9, the first series circuit portion 8a includes a switching transistor 3a, a series resistor 5a, and phase correction reactance elements 7a and 7b, and the second series circuit portion 8b includes a switching transistor 3d and a series resistor. 5b and phase correcting reactance elements 7c and 7d. The first parallel circuit section 9a is composed of a switching transistor 3b and a parallel resistor 6a.

The operation and effect are basically the same as those of the third embodiment, and the phase correcting reactance elements 7a, 7b, 7 are used.
The difference is that c and 7d are connected in series to the series resistors 5a and 5b that form the series circuit units 8a and 8b, respectively.
Although the phase correction reactance elements 7a and 7b are connected to both ends of the series resistor 5a and the phase correction reactance elements 7c and 7d are connected to both ends of the series resistor 5b, at least these four phase correction reactances are connected. One of the elements 7a, 7b, 7c, 7d may be connected.

FIG. 10 is another configuration diagram (circuit diagram) of the variable attenuator of the fourth embodiment. As shown in FIG. 10, the same effect can be obtained by connecting the phase correction reactance element to the switching transistors 3a and 3d. Also at this time, the phase correction reactance elements 7a and 7b are provided at both ends of the switching transistor 3a, and the phase correction reactance element 7 is provided at both ends of the switching transistor 3d.
c and 7d are connected, but at least one of these four phase correction reactance elements 7a, 7b, 7c and 7d
It only has to be connected.

In FIG. 9, phase correction reactance elements 7a and 7b are provided at both ends of the series resistor 5a, and phase correction reactance elements 7c and 7d are provided at both ends of the series resistor 5b.
In FIG. 10, the case where the phase correction reactance elements 7a and 7b are connected to both ends of the switching transistor 3a and the phase correction reactance elements 7c and 7d are connected to both ends of the switching transistor 3d has been described. Similar effects can be obtained even if the phase correction reactance elements 7a, 7b, 7c, and 7d are connected to both ends of the series resistors 5a and 5b and the switching transistors 3a and 3d as described above.

Embodiment 5. 11 is a configuration diagram (circuit diagram) of a variable attenuator according to a fifth embodiment of the present invention. Figure 1
In FIG. 1, 14a, 14b, 14c and 14d are DC operating point determining resistors. The series circuit section 8a includes a switching transistor 3a and a series resistor 5a. The first parallel circuit section 9a includes a switching transistor 3b, a parallel resistor 6a, and DC operating point determining resistors 14a and 14b. The second parallel circuit section 9b includes a switching transistor 3c and a parallel resistor 6b. And DC operating point determination resistor 14
c and 14d.

In the first to fourth embodiments, the connecting portions of the switching transistors 3b and 3c and the parallel resistors 6a and 6b which form the parallel circuit portion are the switching transistor 3
When 3b and 3c exhibit off-capacitance in the off state, and when the phase-correction reactance elements 7a and 7b are capacitances, the DC operating point is not fixed and the DC becomes unstable, which may cause a problem in actual use. There is a nature.

On the other hand, the DC operating point determining resistor 14
a and 14c are connected in parallel to the switching transistors 3b and 3c, and the DC operating point determining resistors 14b and 14d are connected in parallel to the phase correcting reactance elements 7a and 7b, respectively. The on-resistances of the switching transistors 3b and 3c and the impedance of the phase-correcting reactance element are set sufficiently higher than the impedance at the desired frequency, so that the operation at the desired frequency is hardly affected and the DC operating point becomes unstable. You can avoid the situation.

Although FIG. 11 shows the case where the present invention is applied to the first embodiment, the same effect can be obtained when applied to the second to fourth embodiments. However, in the second and fourth embodiments, since the phase-correction reactance element is connected to the series circuit portion, the DC operating point determining resistor is the switching transistor 3a (in the case of FIG. 6 of the second embodiment) or It may be connected to the switch transistors 3a and 3d (in the case of FIG. 9 of the fourth embodiment). Further, in the first and third embodiments, when the phase correction reactance element is an inductor, the DC operating point determining resistors are similarly used for the switch transistors 3b and 3c (in the case of FIG. 1 of the first embodiment) or the switch. Transistor 3b (in the case of FIG. 8 of the third embodiment)
Connect to.

[0039]

Since the present invention is constructed as described above, it has the following effects.

In the first and second inventions, the series circuit section having the first switching transistor and the first resistor connected in parallel, the second switching transistor and the second resistor connected in series are provided. And a second parallel circuit unit having a third switching transistor and a third resistor connected in series, and the amplitude of the high-frequency signal input from the input terminal. In a variable attenuator for varying the output of the first parallel circuit and the second attenuator.
Since at least one of the parallel circuit section and the parallel circuit section is provided with a phase correction reactance element that corrects the passing phase difference of the high frequency signal transmitted from the input terminal to the output terminal, the passing phase difference of the high frequency signal can be corrected It is possible to reduce the fluctuation of the passing phase that occurs when the passing amplitude is switched.

In the third aspect of the invention, the phase-correcting reactance element is connected to at least one end of the first switching transistor and the first resistor, so that the passing phase difference of the high-frequency signal can be corrected. It is possible to reduce the fluctuation of the passing phase that occurs when the passing amplitude is switched.

In the fourth and eighth inventions, the DC operating point is unstable because the DC operating point determining resistor for avoiding the uncertain state of the DC operating point is connected in parallel with the phase correcting reactance element. You can avoid the situation.

In the fifth and sixth inventions, the first series circuit portion having the first switching transistor and the first resistor connected in parallel, the second switching transistor connected in parallel and the first series circuit portion are connected. An amplitude of a high-frequency signal input from the input terminal, the second serial circuit section having two resistors, and the parallel circuit section having the third switch transistor and the third resistor connected in series. In the variable attenuator that varies the output to the output terminal, by providing the parallel circuit unit with the phase correction reactance element that corrects the passing phase difference of the high frequency signal transmitted from the input terminal to the output terminal,
Since the passing phase difference of high frequency signals can be corrected,
It is possible to reduce the fluctuation of the passing phase that occurs when the passing amplitude is switched.

In the seventh invention, the phase-correcting reactance element is connected to at least one end of the first switching transistor, the second switching transistor, the first resistor and the second resistor, so that the high frequency Since it is possible to correct the passing phase difference between the signals, it is possible to reduce the passing phase fluctuation that occurs when the passing amplitude is switched.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a variable attenuator according to a first embodiment.

FIG. 2 is an equivalent circuit diagram of a reference state of the variable attenuator according to the first embodiment.

FIG. 3 is an equivalent circuit diagram of a damping state of the variable attenuator according to the first embodiment.

FIG. 4 is a phase correction reactance element 7a, 7b in the first embodiment as a phase correction inductor 12a,
The equivalent circuit diagram which connected 12b.

FIG. 5 is a phase correction reactance element 7a, 7b in the first embodiment as a phase correction capacitor 13a,
The equivalent circuit diagram which connected 13b.

FIG. 6 is a configuration diagram of a variable attenuator according to a second embodiment.

FIG. 7 is another configuration diagram of the variable attenuator according to the second embodiment.

FIG. 8 is a configuration diagram of a variable attenuator according to a third embodiment.

FIG. 9 is a configuration diagram of a variable attenuator according to a fourth embodiment.

FIG. 10 is another configuration diagram of the variable attenuator of the fourth embodiment.

FIG. 11 is a configuration diagram of a variable attenuator according to a fifth embodiment.

FIG. 12 is a configuration diagram of a conventional variable attenuator.

[Explanation of symbols]

1 input terminal, 2 output terminal, 3a, 3b, 3c switch transistor, 4a, 4b control terminal, 5a series resistance, 6a, 6b parallel resistance, 7a, 7b phase correction reactance element, 8a series circuit section, 9a 1st Parallel circuit part, 9b second parallel circuit part.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Suematsu             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Kenichi Maeda             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Takayuki Ikushima             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. F term (reference) 5J098 AA03 AA11 AA14 AA16 AB32                       AB34 AC04 AC05 AC10 AC20                       AD14 DA08 EA01 GA09

Claims (8)

[Claims] 1. A series circuit unit having a first switching transistor and a first resistor connected in parallel, and a first parallel circuit having a second switching transistor and a second resistor connected in series. A circuit part and a second parallel circuit part having a third switching transistor and a third resistor connected in series, the amplitude of a high-frequency signal input from the input terminal is varied, and output to the output terminal. In the variable attenuator, a phase-correcting reactance that corrects a passing phase difference of a high-frequency signal transmitted from the input terminal to the output terminal in at least one of the first parallel circuit section and the second parallel circuit section. A variable attenuator comprising an element. 2. The phase-correcting reactance element is connected between the second resistor and the ground or between the third resistor and the ground, or the second switching transistor and the second switching transistor. Between the two resistors or the third
The variable attenuator according to claim 1, wherein the variable attenuator is connected between the switching transistor and the third resistor. 3. The variable attenuator according to claim 1, wherein the phase-correction reactance element is connected to at least one end of the first switching transistor and the first resistor. 4. The DC operating point determining resistor for avoiding an indefinite state of the DC operating point, which is connected in parallel with the phase-correcting reactance element, and is provided with any one of claims 1 to 3. Variable attenuator described in. 5. A first series circuit section having a first switching transistor and a first resistor connected in parallel, and a second series transistor having a second switching transistor and a second resistor connected in parallel. 2 series circuit part and 3rd connected in series
A variable attenuator configured to change the amplitude of a high frequency signal input from an input terminal and output the output to an output terminal. A variable attenuator comprising a phase-correcting reactance element that corrects a passing phase difference of a high-frequency signal transmitted from a terminal to the output terminal. 6. The phase-correcting reactance element is connected between the third resistor and ground or between the third switching transistor and the third resistor. The variable attenuator according to claim 5, which is characterized in that: 7. The phase-correcting reactance element is connected to at least one end of the first switching transistor, the second switching transistor, the first resistor and the second resistor. The variable attenuator according to claim 5. 8. A DC operating point determining resistor that is connected in parallel with the phase correcting reactance element and that avoids an indefinite state of the DC operating point. Variable attenuator described in.