JP2009278327A - Step attenuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a step attenuator for regularly changing an amount of attenuation of the step attenuator even by using an integrated circuit element. <P>SOLUTION: The step attenuator 1A is provided with a plurality of fixed attenuators 3 and first switching elements 4A as many as the fixed attenuators 3. The fixed attenuators 3 includes print resistors 3a and 3b. In the respective fixed attenuators 3, print resistors 3a and 3b having the same resistor values, the same shape and size are placed in the same way, so that the fixed attenuators 3 have congruence and the same attenuation amount. Also, the first switching elements 4A are placed at the post stage of the respective fixed attenuators 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a step attenuator, and more particularly to a step attenuator that can be suitably used when incorporated in an integrated circuit.

  In the conventional step attenuator 101, as shown in FIG. 4, three (a plurality of) fixed attenuators 103A, 103B, and 103C and whether to pass these fixed attenuators 103A, 103B, and 103C are selected. Three (plural) switching elements 104A, 104B, and 104C are combined. The attenuation amounts of the plurality of fixed attenuators 103A, 103B, and 103C are different from each other, for example, AdB (A is an arbitrary positive integer such as 2), 2AdB, and 4AdB. Therefore, the number of resistors and other attenuating elements used in the fixed attenuators 103A, 103B, and 103C can be reduced. Such a configuration is often seen as a discrete component.

Japanese Patent Laid-Open No. 7-249954

  However, when the conventional step attenuator 101 is integrated, the signal passing loss in the printed resistor and other attenuating elements used for the plurality of fixed attenuators 103A, 103B, and 103C and the FET used for the plurality of switching elements 104A, 104B, and 104C. Therefore, there is a problem that an error occurs in each of them, and the attenuation amount of the step attenuator 101 changes irregularly.

  For example, in the case of the conventional step attenuator 101 shown in FIG. 4, the three fixed attenuators 103A, 103B, 103C are (A + α) dB, (2A + β) dB, (4A + γ) dB in order from the left. Pass losses αdB, βdB, and γdB respectively, and the three switching elements 104A, 104B, and 104C have a pass loss xdB such as (0 + x) dB, (0 + y) dB, and (0 + z) dB in order from the left. ydB and zdB occur respectively. Since there is no regularity in the passage loss of these fixed attenuators 103A, 103B, 103C and the switching elements 104A, 104B, 104C, the attenuation amount of the step attenuator 101 obtained by combining them is also regular in the passage loss portion. There is no.

  For example, when the desired attenuation amount of the step attenuator 101 is set to AdB, a signal input from the input terminal 102 passes through the first fixed attenuator 103A, the second switching element 104B, and the third switching element 104C. Therefore, the actual attenuation amount of the step attenuator 101 is (A + α + y + z) dB, and when the desired attenuation amount of the step attenuator 101 is set to 6 AdB, the signal input from the input terminal 102 is the first switching element 104A, Since the second fixed attenuator 103B and the third fixed attenuator 103C are passed, the actual attenuation amount of the step attenuator 101 is (6A + β + γ + x) dB. Here, the value of the desired attenuation is 6 AdB, which is 6 times that of AdB. However, since the passage loss of each part is irregular, (β + γ + x) dB does not become 6 times the value of (α + y + z) dB. . This causes the attenuation amount of the step attenuator 101 to change irregularly. When the conventional step attenuator 101 is integrated, the change rate of the attenuation amount of the step attenuator 101 is usually 10% or more, and thus is not a negligible value.

  Therefore, the present invention has been made in view of these points, and it is an object of the present invention to provide a step attenuator that can regularly change the attenuation of the step attenuator even if an integrated circuit element is used. It is aimed.

  In order to achieve the above-described object, a step attenuator of the present invention has, as a first aspect, a plurality of fixed attenuators in which one or two or more printed resistors are arranged, and a plurality of fixed attenuators. And a plurality of first switching elements for selecting which fixed attenuator to pass, and the plurality of fixed attenuators have the same resistance and the same shape and the same size in each fixed attenuator Since the printed resistors having the same value are arranged in the same manner, the fixed attenuators have the same relationship and the same attenuation.

  According to the step attenuator of the first aspect of the present invention, the amount of attenuation in each fixed attenuator becomes equal, so that the passage loss can be equalized. Thereby, it is possible to prevent the attenuation amount of the step attenuator from changing irregularly in accordance with the number of passages of the fixed attenuator, and to reliably change the attenuation amount regularly.

  The step attenuator according to the second aspect of the present invention is the step attenuator according to the first aspect, wherein the plurality of fixed attenuators are connected in series with the input terminal as the front stage, and the plurality of first switching elements Are the same number of ON / OFF switches as the plurality of fixed attenuators, and are arranged between the rear side of each fixed attenuator and the common line connected to the output terminal, and the plurality of first attenuators. The first switching element between the last row of fixed attenuators through which the signal input to the input terminal of the switching elements passes and the front row of fixed attenuators through which no signal passes is in the ON state, and the others The first switching element is in an OFF state.

  According to the step attenuator of the second aspect of the present invention, the number passing through the first switching element is always one regardless of the number of passages of the fixed attenuator between the input terminal and the output terminal. Therefore, the passage loss can be made constant. Thereby, it is possible to prevent the attenuation amount of the step attenuator from changing irregularly according to the number of passages of the first switching element.

  The step attenuator according to the third aspect of the present invention is the step attenuator according to the second aspect, wherein the front row fixed attenuator and the common line are selected between the input terminal and the front row fixed attenuator. Thus, a second switching element that performs switching is arranged.

  According to the step attenuator of the third aspect of the present invention, the number of passages of the fixed attenuator between the input terminal and the output terminal can be set to 0, and the number of passages of the fixed attenuator is 0. In this case, a plurality of fixed attenuators can be completely disconnected from the output terminal. In addition, when passing through one or more fixed attenuators, the number of passages of the first switching element and the second switching element is always one, so that the passage loss can be made constant. it can. Thereby, it is possible to prevent the attenuation amount of the step attenuator from changing irregularly according to the number of passages of the first switching element and the second switching element.

  A step attenuator according to a fourth aspect of the present invention is the step attenuator according to the first aspect, wherein the plurality of fixed attenuators are connected in series with the input terminal as the front stage, and the plurality of first switching elements Is the same number of selection switches as a plurality of fixed attenuators, and is arranged on the front side of each fixed attenuator, and selects each fixed attenuator and a common line connected to the output terminal. Between the last row of fixed attenuators through which a signal input to the input terminal of the plurality of first switching elements passes and the front row of fixed attenuators through which no signal passes are formed. The first switching element is in a state of selecting a common line, and the other first switching elements are in a state of selecting a fixed attenuator.

  According to the step attenuator of the fourth aspect of the present invention, no matter how many fixed attenuators pass from the input terminal to the output terminal, the number passing through the first switching element is always fixed attenuation. Since the number is equal to the number of passages of the +1, the passage loss can be set to a constant ratio. Thereby, it is possible to prevent the attenuation amount of the step attenuator from changing irregularly according to the number of passages of the first switching element.

  A step attenuator according to a fifth aspect of the present invention is the step attenuator according to the fourth aspect, wherein the step attenuator performs the ON / OFF switching between the rear stage side of the fixed attenuator in the last row and the common line. The switching element is arranged.

  According to the step attenuator of the fifth aspect of the present invention, the fixed attenuator through which no signal passes and the output terminal can be completely separated. Further, since the arrangement is such that the third switching element that is in the ON state only passes through all the fixed attenuators, the passage loss can be made regular. Thereby, even if a 3rd switching element is arrange | positioned, it can prevent that the attenuation amount of a step attenuator changes irregularly.

  A step attenuator according to a sixth aspect of the present invention is the step attenuator according to any one of the first to fifth aspects, wherein any of the first switching element, the second switching element, and the third switching element is Is also a MOSFET.

  According to the step attenuator of the sixth aspect of the present invention, these switching elements can be easily created and integrated, and the gate current can be brought close to zero.

  A step attenuator according to a seventh aspect of the present invention is the step attenuator according to the sixth aspect, formed by a fixed attenuator, a first switching element, a second switching element, a third switching element, and a printed line. The common line, the input terminal and the output terminal are integrated in the same integrated circuit.

  According to the step attenuator of the seventh aspect of the present invention, the amount of attenuation does not change irregularly even if an integrated circuit element is used. Therefore, it is possible to arrange them together with an integrated TV tuner of a small portable device. it can.

  According to the step attenuator of the present invention, the passage loss of the fixed attenuator and the first switching element, the second switching element, and the third switching element is regularly set. Even if each part is formed, it is possible to prevent the attenuation amount of the step attenuator from changing irregularly according to each part.

  Hereinafter, the step attenuator of the present invention will be described with reference to the first and second embodiments with reference to the drawings.

  First, the step attenuator 1A of the first embodiment will be described with reference to FIG. 1 and FIG. FIG. 1 shows a step attenuator 1A of the first embodiment, and FIG. 2 shows a fixed attenuator 3 of the first embodiment.

  As shown in FIG. 1, the step attenuator 1A of the first embodiment includes an input terminal 2, a plurality of fixed attenuators 3, a plurality of first switching elements 4A, a common line 5, and an output terminal 6. . Further, the step attenuator 1A of the first embodiment is selectively provided with the second switching element 7 although it is not essential. The fixed attenuator 3, the first switching element 4A, the second switching element 7, the common line 5, the input terminal 2 and the output terminal 6 are integrated in the same integrated circuit, and the steps of the first embodiment The attenuator 1A is formed as an IC package.

  The plurality of fixed attenuators 3 are connected in series with the input terminal 2 as the front stage. As shown in FIG. 2, the fixed attenuator 3 is formed by using two printed resistors 3a and 3b. These two printed resistors 3a and 3b have the same shape, the same size, the same single resistance value, and the same combined resistance value in the respective fixed attenuators 3, and the arrangement thereof is also the same. . That is, the mutual fixed attenuators 3 are in a congruent relationship and have the same attenuation amount AdB. Assuming that the passing loss of one fixed attenuator 3 is α dB, the actual attenuation amount (A + α) dB of the fixed attenuator 3 is obtained (A and α are arbitrary numbers). The number of the printed resistors 3a and 3b in each fixed attenuator 3 may be one or two or more depending on the design change.

  The plurality of first switching elements 4 </ b> A are arranged so as to select which fixed attenuator 3 among the plurality of fixed attenuators 3 is allowed to pass. In the first embodiment, the number of the first switching elements 4A is set to be equal to the number of the fixed attenuators 3 and is connected to the rear stage side of each fixed attenuator 3 and the output terminal 6. One each is arranged between the common line 5. The passing loss of the first switching element 4A is x dB (x is an arbitrary number). The first switching element 4A is an ON / OFF switch and is preferably a MOSFET.

  The switching control of the first switching element 4A is determined by which fixed attenuator 3 among the plurality of fixed attenuators 3 is passed. Various patterns can be considered for this control, and all possible patterns can be adopted. In the first embodiment, the last row of fixed attenuators 3 through which a signal input to the input terminal 2 of the plurality of first switching elements 4A passes, and the front row of fixed attenuators 3 through which no signal passes, The first switching element 4A is turned on and the other first switching elements 4A are turned off.

  A specific example of switching control will be described. As shown in FIG. 1, when the signal input from the input terminal 2 is passed through the first fixed attenuator 31 and the second fixed attenuator 32 counted from the input terminal 2 side, The last row fixed attenuator 3 through which the input signal passes becomes the second fixed attenuator 32, and “the front row fixed attenuator 3 through which the signal does not pass” becomes the third fixed attenuator 33. In addition, the “first switching element 4A between” is the second first switching element 4A2 between the second fixed attenuator 32 and the third fixed attenuator 33. Therefore, as shown in FIG. 1, the second first switching element 4A2 counted from the input terminal 2 side is turned on, and the other first switching elements 4A are turned off. As a result, the signal input from the input terminal 2 passes through the first fixed attenuator 31, the second fixed attenuator 32, and the second first switching element 4 </ b> A <b> 2 in order, and is connected to the output terminal 6. Propagates to the common line 5.

  As the common line 5 connected to the output terminal 6, a conductive pattern printed on a substrate surface (not shown) or a via formed on a multilayer substrate (not shown) is used. That is, it may be a printed line in a broad sense.

  The second switching element 7 is disposed between the input terminal 2 and the first fixed attenuator 31 (the front row fixed attenuator 3). As the second switching element 7, a selection switch for selecting and switching either the first fixed attenuator 31 or the common line 5 is used. Specifically, it is preferably a MOSFET. The passing loss of the second switching element 7 is ydB (y is an arbitrary number).

  Next, the operation of the step attenuator 1A of the first embodiment will be described.

  In the step attenuator 1A of the first embodiment, as shown in FIG. 1, the attenuation amounts of the plurality of fixed attenuators 3 are all set to the same AdB. Further, as shown in FIG. 2, the printed resistors 3a and 3b used in the fixed attenuator 3 satisfy the same shape, the same size and the same resistance value in the mutual fixed attenuator 3, and are arranged in the same manner. It has become. Therefore, the joint relationship is satisfied in the mutual fixed attenuators 3. Therefore, the attenuation (AdB) and the passage loss (αdB) in each fixed attenuator 3 are equal. As a result, the attenuation amount of the step attenuator 1A obtained from the fixed attenuator 3 is a value obtained by adding the passage loss (αdB) to the attenuation amount (AdB) of the fixed attenuator 3 and then multiplying the number of passages of the fixed attenuator 3. Therefore, the attenuation amount of the step attenuator 1A obtained from the fixed attenuator 3 can be regularly changed.

  Such regularity can be seen not only in the fixed attenuator 3 but also in the first switching element 4A. In the step attenuator 1 </ b> A of the first embodiment, a plurality of first switching elements 4 </ b> A are respectively arranged between the rear stage side of each fixed attenuator 3 and the common line 5 connected to the output terminal 6. Yes. As described above, the first switching element 4A in the front stage of the fixed attenuator 3 in the foremost row that does not pass through the signal is set to the ON state, and the other first switching elements 4A are set to the OFF state. In FIG. 1, only the second first switching element 4A2 is set to the ON state. Therefore, regardless of the number of passes through the fixed attenuator 3, the number of passes through the first switching element 4A is always one, and the passage loss is constant. As a result, the attenuation amount of the step attenuator 1A generated by the first switching element 4A is the amount of passage loss (xdB) of the first switching element 4A. Therefore, even if the first switching element 4A is passed, the step is attenuated. The attenuation amount of the attenuator 1A can be changed regularly.

  Furthermore, in the first embodiment, the second switching element 7 is disposed between the input terminal 2 and the first fixed attenuator 31. Therefore, the number of passages of the fixed attenuator 3 can be set to 0, and the desired attenuation can be set to 0 dB. In this case, since all the first switching elements 4A are in the OFF state, the plurality of fixed attenuators 3 can be completely disconnected from the output terminal 6 when the number of passages of the fixed attenuators 3 is zero. On the other hand, if the number of passages of the fixed attenuator 3 is one or more, the number of passages of the first switching element 4A and the second switching element 7 is always one. Therefore, those passage losses can be made constant regardless of the number of passages of the fixed attenuator 3. As a result, the attenuation amount of the step attenuator 1A generated by the first switching element 4A is equal to the passage loss (xdB) of the first switching element 4A. The attenuation amount of the attenuator 1A can be changed regularly.

  In view of the above, the attenuation amount At1 in the step attenuator 1A of the first embodiment is At1 = N (A + α) + x + y (N: the number of passes through the fixed attenuator 3). Here, the passage loss in the step attenuator 1A is αN + x + y. That is, it turns out that the factor which changes irregularly from attenuation amount At1 of step attenuator 1A is excluded.

  In addition, since MOSFETs are selected as the first switching element 4A and the second switching element 7, not only can the gate current be brought close to 0, but also the creation and integration of these switching elements is facilitated. Can do. Here, considering that the fixed attenuator 3 is formed by the printed resistors 3a and 3b and the common line 5 is formed by the printed line, the step attenuator 1A can be easily downsized. .

  From the above, in the step attenuator 1A of the first embodiment, the fixed attenuator 3, the first switching element 4A, the second switching element 7, the common line 5, the input terminal 2, and the output terminal 6 are It is integrated in the same integrated circuit. Even if the step attenuator 1A of the first embodiment is integrated, the attenuation does not change irregularly due to the integrated circuit elements as described above. Therefore, the step attenuator 1A is integrated in a small portable device such as a cellular phone. They can be arranged together with the integrated TV tuner and the like.

  Next, the step attenuator 1B of the second embodiment will be described with reference to FIG. The difference from the first embodiment is the arrangement of the first switching element 4B and the type of the switching element.

  The step attenuator 1B of the second embodiment includes an input terminal 2, a plurality of fixed attenuators 3, a plurality of first switching elements 4B, a common line 5, and an output terminal 6. Further, the step attenuator 1B of the second embodiment is selectively provided with the third switching element 8 although it is not essential. The fixed attenuator 3, the first switching element 4B, the third switching element 8, the common line 5, the input terminal 2, and the output terminal 6 are integrated in the same integrated circuit, and are the same as in the first embodiment. The step attenuator 1B of the second embodiment is formed as an IC package.

  Here, the configuration and arrangement of the input terminal 2, the plurality of fixed attenuators 3, the common line 5 and the output terminal 6 of the second embodiment are the same as those of the first embodiment.

  The first embodiment is that the plurality of first switching elements 4B select which one of the plurality of fixed attenuators 3 is allowed to pass, and the same number as the plurality of fixed attenuators 3. It is the same. However, the first switching element 4B is different from the first embodiment in that it is not a ON / OFF switch but a selection switch. Further, the plurality of first switching elements 4B are respectively arranged on the front side of each fixed attenuator 3, and each fixed attenuator 3 and the common line 5 are selected and switched to either one. It is also different in that it is formed.

  The switching control of the first switching element 4B is determined by which fixed attenuator 3 of the plurality of fixed attenuators 3 is passed, as in the first embodiment. Various patterns can be considered for this control, and all possible patterns can be adopted. In the second embodiment, the last row of fixed attenuators 3 through which a signal input to the input terminal 2 of the plurality of first switching elements 4B passes, and the front row of fixed attenuators 3 through which no signal passes, The first switching element 4B is controlled so that the common line 5 is selected, and the other first switching elements 4B are in the state where the fixed attenuator 3 is selected. So that it is controlled.

  A specific example of switching control will be described. As shown in FIG. 3, when the signal input from the input terminal 2 is passed through the first fixed attenuator 31 and the second fixed attenuator 32 counted from the input terminal 2 side, The last row fixed attenuator 3 through which the input signal passes becomes the second fixed attenuator 32, and “the front row fixed attenuator 3 through which the signal does not pass” becomes the third fixed attenuator 33. Further, the “first switching element 4B between” and the third switching element 4B3 between the second fixed attenuator 32 and the third fixed attenuator 33 is the first switching element 4B3 between the second fixed attenuator 32 and the third fixed attenuator 33. Therefore, as shown in FIG. 3, the control is performed so that the third first switching element 4B3 counting from the input terminal 2 side selects the common line 5, and the other first switching elements 4B. Controls so that the fixed attenuator 3 is selected. Thereby, the signal input from the input terminal 2 is the first first switching element 4B1, the first fixed attenuator 31, the first first switching element 4B2, and the second fixed attenuators 32 and 3. It passes through the first switching element 4B3 in order and propagates to the common line 5 connected to the output terminal 6.

  The third switching element 8 is an ON / OFF switch, and is disposed between the rear stage side of the last row of fixed attenuators 3 and the common line 5. The third switching element 8 is normally in an OFF state, and is controlled to be in an ON state only when a signal passes through the fixed attenuator 3 in the last row. The passage loss of the third switching element 8 is zdB (z is an arbitrary number).

  The first switching element 4B and the third switching element 8 are both MOSFETs as in the first embodiment.

  Next, the operation of the step attenuator 1B of the second embodiment will be described.

  In the step attenuator 1B of the second embodiment, as in the first embodiment, the fixed attenuator 3 is in the above-mentioned congruent relationship and has the same attenuation. For this reason, the amount of attenuation and the passage loss in each fixed attenuator 3 can be made equal, so that the amount of attenuation of the step attenuator 1B is prevented from changing irregularly according to the number of passages of the fixed attenuator 3. be able to.

  Such regularity can be seen not only in the fixed attenuator 3 but also in the first switching element 4B. The plurality of first switching elements 4 </ b> B are arranged one by one on the front side of each fixed attenuator 3. Therefore, regardless of the number of fixed attenuators 3 passing through, the number passing through the first switching element 4B is always the same as the number of fixed attenuators 3 passing through +1. As a result, the passage loss (xdB) of the first switching element 4B can be set to a constant ratio according to the number of passages. Thereby, it is possible to prevent the attenuation amount of the step attenuator 1B from changing irregularly according to the number of passages of the first switching element 4B.

  If the third switching element 8 is arranged on the rear stage side of the fixed attenuator 3 in the last row, the fixed attenuator 3 through which no signal passes and the output terminal 6 can be completely separated. This is the same as the second switching element 7 in the first embodiment. Further, when the third switching element 8 is passed, the third switching element 8 is turned on only when the last row of fixed attenuators 3 is passed, that is, when all the fixed attenuators 3 are passed. The signal passes through the third switching element 8. As a result, the passage loss of the third switching element 8 can also be set regularly, so that the attenuation of the step attenuator 1B is prevented from changing irregularly even if the third switching element 8 is arranged. can do.

  In view of the above, the attenuation amount At2 in the step attenuator 1B of the second embodiment is At2 = N (x + A + α) + x or M (x + A + α) + z (N: the number of passages of the fixed attenuator 3 (however, M: number of fixed attenuators 3 arranged, A: set attenuation of fixed attenuator 3, α: pass loss of fixed attenuator 3, x: pass loss of first switching element 4B ). Here, the passage loss in the step attenuator 1B is N (x + α) + x or M (x + α) + z. That is, as in the first embodiment, it can be seen that the factor of irregularly changing from the attenuation amount At2 of the step attenuator 1B is eliminated.

  Note that the use of MOSFETs for the first switching element 4B and the third switching element 8 and the operation of integrating the step attenuator 1B are the same as in the first embodiment.

  That is, according to the step attenuators 1A and 1B of the present embodiment, the passage loss of the fixed attenuator 3, the first switching element 4A or 4B, the second switching element 7 and the third switching element 8 is regularly determined. Even if an integrated circuit element is used or each part is formed, the amount of attenuation of the step attenuators 1A and 1B can be prevented from changing irregularly according to each part. Produce.

  In addition, this invention is not limited to embodiment mentioned above etc., A various change is possible as needed.

The equivalent circuit diagram which shows the step attenuator of 1st Embodiment A circuit diagram showing a fixed attenuator of a first embodiment The equivalent circuit diagram which shows the step attenuator of 2nd Embodiment Equivalent circuit diagram showing an example of a conventional step attenuator

Explanation of symbols

1A, 1B Step attenuator 2 Input terminal 3 Fixed attenuator 4A, 4B First switching element 5 Common line 6 Output terminal 7 Second switching element 8 Third switching element

Claims (7)

A plurality of fixed attenuators formed by arranging one or more printed resistors;
A plurality of first switching elements for selecting which one of the plurality of fixed attenuators to pass; and
The plurality of fixed attenuators have the same relationship and the same amount of attenuation in the fixed attenuators by arranging the printed resistors having the same shape and the same size and the same resistance value in the respective fixed attenuators. A step attenuator. The plurality of fixed attenuators are connected in series with the input terminal as the front stage,
The plurality of first switching elements are the same number of ON / OFF switches as the plurality of fixed attenuators, and are respectively disposed between a rear side of the fixed attenuators and a common line connected to an output terminal. As well as
A first switching element between a last row of fixed attenuators through which a signal input to the input terminal of the plurality of first switching devices passes and a front row of fixed attenuators through which the signal does not pass; 2. The step attenuator according to claim 1, wherein the step attenuator is in an ON state and the other first switching elements are in an OFF state. Between the input terminal and the fixed attenuator in the front row, a second switching element that selects and switches the fixed attenuator in the front row and the common line is disposed. The step attenuator according to claim 2. The plurality of fixed attenuators are connected in series with the input terminal as the front stage,
The plurality of first switching elements are the same number of selection switches as the plurality of fixed attenuators, and are arranged on the front stage side of each of the fixed attenuators, and each of the fixed attenuators and output terminals. It is formed to select and switch the common line connected to the
A first switching element between a last row of fixed attenuators through which a signal input to the input terminal of the plurality of first switching devices passes and a front row of fixed attenuators through which the signal does not pass; 2. The step attenuator according to claim 1, wherein the common line is selected and the other first switching element is selecting the fixed attenuator. 3. 5. The step attenuation according to claim 4, wherein a third switching element that performs ON / OFF switching is disposed between a rear stage side of the fixed attenuator in the last row and the common line. vessel. The step attenuator according to any one of claims 1 to 5, wherein each of the first switching element, the second switching element, and the third switching element is a MOSFET. . The fixed attenuator, the first switching element, the second switching element and the third switching element, the common line formed by a printed line, the input terminal, and the output terminal are in the same integrated circuit. The step attenuator of claim 6, wherein the step attenuator is integrated.

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