JPH1098306A - Variable attenuator for microwave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable attenuator for microwaves which makes a reflection quantity zero, even when varying an attenuation quantity. SOLUTION: This attenuator is provided with a λ/4 line 4 having an electrical length of λ/4 at a using frequency, plural serial resistors 3a and 3c connected serially to the input side of the λ/4 line 4, plural serial resistors 3b and 3d connected serially to the output side of the λ/4 line 4, plural parallel resistors 5a and 5b connected serially between an input terminal 1 and the serial resistor 3c on the input side, a metallic line 6 and connecting terminals 7 and 8 for short-circuiting and inserting these resistors 3a to 3d, 5a and 5b. Then the reflecting quantity of the attenuator is made zero by cancelling the reflecting quantities of the serial resistors 3b and 3d by loading these parallel resistors 5a and 5b, and the reflecting quantity is made zero even varying the attenuating quantity by connecting a serial resistor and a parallel resistor by switching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave variable attenuator used for a communication device such as a microwave circuit.

[0002]

2. Description of the Related Art FIG. 7 is a circuit diagram showing a conventional microwave variable attenuator disclosed in FIG. 7 of JP-A-6-104676. In FIG. 7, 1 is an input terminal and 2 is an output terminal. , 3a, 3b, 3c, and 3d are series resistors connected in series between the input terminal 1 and the output terminal 2;
This is a λ / 4 line with an impedance Z ₀ inserted between a and 3b and an electrical length of λ / 4 at the used center frequency.
Further, a predetermined resistance is selectively selected according to the attenuation amount.
Short circuit. Here, the resistors 3c and 3d are short-circuited.

Next, the operation will be described. In FIG. 7, the input signal is attenuated by the resistor 3a, passes through the λ / 4 line 4, is attenuated by the resistor 3b, and is output after obtaining a predetermined amount of attenuation. The λ / 4 line 4 is inserted to reduce the reflection of the resistors 3a and 3b. Also, the resistance values of the resistors 3a and 3b are
And R11, when representing a reflection S11 in the input side in R11, Z ₀

S11 = R11 ² / (R11 ² + 2R11 · Z ₀ + 2Z ₀ ² ) (1)

[0005] Assuming that the amount of attenuation is K1, K1, R11 and Z
The relational expression for ₀ is

K1 ・ R11 ² + 2K1 ・ R11 ・ Z ₀ + 2Z ₀ ²・ (K1-1) = 0 (2)

[0007] Also, the metal wire 6 is removed and the resistors 3c and 3d are inserted, and the amount of attenuation when the resistors 3a and 3b are short-circuited is K2, and the resistance of the resistors 3c and 3d is R12.
By converting R11 in the above equations (1) and (2) into R12,
Relationship of the reflection characteristic and K2, R12, Z ₀ at this time is obtained.

Further, when the metal wire 6 is removed and all the resistors are inserted, the amount of attenuation is K1 · K2. Therefore, by short-circuiting and opening the resistor, it is possible to obtain a variable attenuator capable of varying the attenuation in three stages up to the attenuation amounts K1, K2, and K1 · K2.

[0009]

In the conventional variable attenuator for microwaves configured as described above, the resistors 3a, 3a
The reflection can be reduced by canceling the reflection at b, 3c, and 3d with the λ / 4 line 4, but the reflection amount does not become zero. Further, there is a problem that the reflection amount increases as the attenuation amount increases. This is clear from equation (1).

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a microwave variable attenuator capable of keeping the amount of reflection at zero even if the amount of attenuation is increased. Aim.

[0011]

SUMMARY OF THE INVENTION In view of the above-mentioned object, the first invention of the present invention provides that the electric length is 1/1/100 at the operating frequency.
A four-wavelength λ / 4 line, an input-side series resistor group consisting of a plurality of series resistors connected in series between the input side and the input terminal of the λ / 4 line, An output-side series resistor group including a plurality of series resistors sequentially connected in series between an output side and an output terminal; and a plurality of at least parallel resistors connected in parallel to the input side of the λ / 4 line. Parallel circuit means including a plurality of parallel circuits, and connection switching means for short-circuiting and opening predetermined ones of each series resistor of the series resistor group on the input side and the output side and each parallel circuit of the parallel circuit means. The connection is switched by the connection switching means so that the amount of attenuation is changed and the amount of reflection becomes zero.

According to a second aspect of the present invention, in the variable microwave device according to claim 1, the parallel circuit means is connected between the input terminal and an input-side series resistor group. In the attenuator.

According to a third aspect of the present invention, the microwave circuit according to claim 1, wherein the parallel circuit means is connected between the input side series resistor group and a λ / 4 line. Variable attenuator.

According to a fourth aspect of the present invention, each parallel circuit of the parallel circuit means comprises a parallel resistor, and the connection switching means comprises a metal wire for selectively short-circuiting the series resistor; The microwave variable attenuator according to any one of claims 1 to 3, comprising a connection terminal provided on the series resistance side of the resistor and a metal wire for selectively short-circuiting and opening the connection terminal.

According to a fifth aspect of the present invention, each parallel circuit of the parallel circuit means comprises a parallel resistor and a λ / 4 line connected in series with the parallel resistor on a side opposite to the series resistor of the parallel resistor, The connection switching means selects a metal wire for selectively short-circuiting the series resistance, a connection terminal provided between a side opposite to the parallel resistance of the λ / 4 line of each of the parallel circuits and ground, and a connection between the connection terminals. The microwave variable attenuator according to any one of claims 1 to 3, wherein the variable attenuator is formed of a metal wire that is short-circuited and opened.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below according to each embodiment. Embodiment 1 FIG. A microwave variable attenuator according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 (a)
1 is an equivalent circuit diagram of the attenuator according to the embodiment, and FIG. 2B is an external view of the attenuator. The same or corresponding parts as those in FIG. 7 are denoted by the same reference numerals, and description thereof is omitted.

According to this embodiment, the parallel resistors 5a and 5b are loaded in parallel between the input terminal 1 and the resistor 3c. The connection terminals 7, 8 which are short-circuited by a metal wire 6 in series with the parallel resistors 5a and 5b, respectively,
Is provided. Here, the series resistors 3c and 3d are short-circuited by the metal wire 6, and the connection terminal 8 of the parallel resistor 5b is open.

The parallel resistors 5a and 5b each constitute a parallel circuit, and all of them constitute parallel circuit means. The metal wires 6 and the connection terminals 7 and 8 constitute connection switching means.

Next, the operation will be described. The operation of the thus configured microwave variable attenuator is the same as that of the above-described conventional attenuator.
According to the above, the resistance 5 is connected in parallel between the input terminal 1 and the resistance 3c.
By loading "a", the deviation of the reflection of the resistors 3a and 3b is corrected while attenuating somewhat even in this portion. Now, the series resistance 3a, the resistance values of 3b and R11, and the resistance of the parallel resistors 5a and R21, represent the impedance of the lambda / 4 lines 4 as Z _0, the reflection S11 in the input side in R11, R21, Z ₀ When

[0020] ^{_{S11 = (Z 0 2 · R11}} + R21 · R11 2 -Z 0 3) / (2Z 0 · R11 · R21 + 2Z 0 2 · R21 + Z 0 2 · R11 + R11 2 · R21 + Z 0 3 ) ・ ・ ・ (3)

From the condition that the reflection amount becomes zero, R21
If the represented by R11 and Z _0,

R21 = (Z ₀ ³ -Z ₀ ² · R11) / R11 ² (4)

[0023] next, when the attenuation and K1, K1, R1, Z ₀
Is

R11 = (1-K1) · Z ₀ (5)

## EQU1 ## Here, the relationship between the attenuation K1 and R11 and R21 when Z ₀ = 50Ω is as shown in FIGS.

Next, the metal wire 6 is removed and the series resistance 3
c, 3d and a parallel resistor 5b, and a series resistor 3a,
3b is short-circuited, the amount of attenuation when the connection terminal 7 of the parallel resistor 5a is opened is K2, the resistance of the resistors 3c and 3d is R12, and the resistance of the resistor 5b is R22. (3) R11 and R2 in the formulas (4) and (5)
By converting each 1 to R12, R22, relationship of the reflection characteristic and K2, R12, Z ₀ at this time is obtained. The relationship between the attenuation K2 and R12, R22 is also as shown in FIGS.

Further, when all the series resistors 3a to 3d are inserted and the connection terminals 7 and 8 are short-circuited by the metal wire 6, the amount of attenuation is
K1 and K2. Therefore, the value of the resistor is determined so that the equation (4) is established, and the resistor and the connection terminal are short-circuited and opened, so that the reflection is zero and the variable attenuation can be varied in three stages of attenuation K1, K2, and K1 · K2. You can get a bowl.

Embodiment 2 FIG. 4 is a circuit diagram of the microwave variable attenuator according to the second embodiment. The attenuator of this embodiment is provided with the parallel resistors 5a and 5b constituting the parallel circuit means of the first embodiment between the series resistor 3a and the λ / 4 line 4, and is referred to as parallel resistors 9a and 9b. In FIG. 4, the series resistors 3c and 3d are short-circuited, and the connection terminal 8 of the parallel resistor 9b is opened.

The operation is the same as in the first embodiment. Now, assume that the resistance value of the parallel resistor 9a is R31, and the reflection characteristic in this case is:

S11 = (R31 · R11 ² -Z ₀ ² · R11-Z ₀ ³ -Z ₀ · R11 ² ) / (2Z ₀ · R11 · R31 + 2Z ₀ ² · R31 + Z ₀ ² · R11 + R11 ²・ R31 + Z ₀ ³ + Z ₀・ R11 ² ) (6)

From the condition that the reflection amount becomes zero, R31
A Expressed in R11 and Z ₀

[0032] ^{_{R31 = (Z 0 3 + Z}} 0 2 · R11 + Z 0 · R11 2) / R11 2 (7)

Assuming that the amount of attenuation is K1, K1, R11, Z
The relational expression for ₀ is

K1 · R11 ² + K1 · Z ₀ · R11 + (K1-1) · Z ₀ ² = 0 (8)

## EQU1 ## Next, the metal wire 6 is removed and the series resistors 3c and 3d and the parallel resistor 9b are inserted, the series resistors 3a and 3b are short-circuited, and the amount of attenuation when the connection terminal 7 of the parallel resistor 9a is opened is K2. The resistance value of the series resistors 3c and 3d is R12, and the parallel resistor 9b is R32. R6 in equations (6), (7) and (8)
By converting each 1, R31 to R12, R32, relationship of the reflection characteristic and K2, R12, Z ₀ at this time is obtained.
The relationship between the attenuation K2 and R12, R22 is also as shown in FIGS.

Further, when all the series resistors 3a to 3d are inserted and the connection terminals 7 and 8 are short-circuited by the metal wire 6, the amount of attenuation is
K1 and K2. Therefore, the value of the resistor is determined so that the equation (7) is satisfied, and the resistor and the connection terminal are short-circuited and opened, so that the reflection is zero and the variable attenuation is variable in three stages of attenuation K1, K2, and K1 · K2. You can get a bowl.

Embodiment 3 FIG. 5A shows the third embodiment.
FIG. 2 is an equivalent circuit diagram of the microwave variable attenuator of FIG. 1, and (b) is an external view of the attenuator. The attenuator according to this embodiment has a λ / 4 between the parallel resistances 5a and 5b of the first embodiment and the ground.
The lines 12a and 12b are provided, the connection terminal 10 is provided between the λ / 4 line 12a and the ground, and the connection terminal 11 is provided between the λ / 4 line 12b and the ground. In FIG. 5, the series resistance 3
c, 3d and the connection terminal 11 are short-circuited by the metal wire 6.

The parallel resistor 5a and the λ / 4 line 12a,
The parallel resistor 5b and the λ / 4 line 12b each constitute a parallel circuit, and all of them constitute parallel circuit means, and the metal wire 6 and the connection terminals 10 and 11 constitute connection switching means.

Next, the operation will be described. Where λ / 4
The lines 12a and 12b are provided because, in the case of a microwave, the other end is short-circuited when one end of the λ / 4 line is open and the other end is short-circuited when one end of the λ / 4 line is short at the center frequency. Is used to open the connection terminal 11, that is, when the connection terminal 11 is short-circuited by the metal wire 6, B
The point becomes short-circuited, the impedance from the point A to the λ / 4 line 12b side becomes open in the microwave with respect to the center frequency, and the resistor 5b is connected to the main line to which the series resistors 3a to 3d are connected. It will be unloaded.

Conversely, when the connection terminal 10 is opened, the point B is opened, and the λ / 4 line 12
The impedance anticipated on the a side is short-circuited by the microwave with respect to the center frequency, and the main line is loaded with the resistor 5a. That is, contrary to the above embodiment, the connection terminal 10 or 11 is connected to the metal wire 6.
In this case, the parallel resistance is not in the unloaded state when it is short-circuited, and in the open state, the parallel resistance is loaded.

Thus, for example, when loading the resistors 3c, 3d and 5b to increase the amount of attenuation, the resistors 3c, 3d and 5b
The metal wire 6 shorting d is cut, and the metal wire 6 connected to the connection terminal 11 is cut. Therefore, the attenuation can be increased or decreased only by one type of operation, that is, by cutting the metal wire. As in the first embodiment, the resistors 5a and 5b
When the λ / 4 lines 12a and 12b are not provided between the ground and the ground, when the resistors 3c, 3d and 5b are loaded in order to increase the attenuation, the metal wire short-circuiting the resistors 3c and 3d is cut off. Since the connection terminal 8 is connected by adding the metal wire 6, two kinds of operations are required.

Here, when the resistors 3c and 3d and the connection terminal 11 are short-circuited as shown in FIG.
c, 3d are inserted, the connection terminal 11 is opened, and the resistors 3a,
When 3b and the connection terminal 10 are short-circuited, the attenuation becomes K2. When all the resistors are inserted and both connection terminals are short-circuited, the attenuation becomes K1 · K2. The reflection characteristics in this case are also the same as in the first embodiment.

Embodiment 4 FIG. FIG. 6 is a circuit diagram of the microwave variable attenuator according to the third embodiment. The attenuator of this embodiment is provided with λ / 4 lines 12a and 12b between the parallel resistors 9a and 9b of the second embodiment and the ground, and
A connection terminal 10 is provided between the λ / 4 line 12 and the ground.
A connection terminal 11 is provided between b and the ground. here,
The connection terminal 10 is opened and the connection terminal 11 is short-circuited.

The operation is the same as in the third embodiment. The reflection characteristics in this case are the same as in the second embodiment.

Here, when the resistors 3c and 3d and the connection terminal 11 are short-circuited as shown in FIG.
c, 3d are inserted, the connection terminal 11 is opened, and the resistor 3a,
When 3b and the connection terminal 10 are short-circuited, the attenuation becomes K2, and when all the resistors are not short-circuited and the connection terminal is not opened,
The attenuation is K1 · K2.

[0046]

As described above, according to the first aspect of the present invention, the electric length is between the λ / 4 line having the quarter wavelength at the operating frequency and the input side and the input terminal of the λ / 4 line. An input side series resistor group consisting of a plurality of series resistors connected in series and an output side consisting of a plurality of series resistors connected in series between an output side and an output terminal of the λ / 4 line. A series resistor group, parallel circuit means including a plurality of parallel circuits including at least a parallel resistor connected in parallel to the input side of the λ / 4 line, and each series of the input side and output side series resistor groups A connection switching means for short-circuiting and opening a predetermined one of the resistor and each of the parallel circuits of the parallel circuit means, so that the parallel resistor of the parallel circuit cancels the reflection amount of the series resistance to reduce the reflection amount of the attenuator. Can be zero,
Even if the amount of attenuation is changed, it is possible to obtain effects such as providing a microwave variable attenuator capable of canceling out the entire amount of reflection and making the reflection zero.

According to the second aspect of the present invention, the parallel circuit means is connected between the input terminal and the input side series resistor group, and is capable of reducing the reflection to zero even if the attenuation is changed. Such as providing a variable attenuator for use.

According to the third aspect of the present invention, the parallel circuit means is connected between the input side series resistance group and the λ / 4 line.
Even if the amount of attenuation is changed, effects such as providing a variable attenuator for microwaves that can make the reflection zero can be obtained.

According to the fourth aspect of the present invention, each parallel circuit of the parallel circuit means is constituted only by the parallel resistance, and the connection switching means is provided by a metal wire for selectively short-circuiting the series resistance and the parallel resistance of each parallel circuit. The connection terminals provided on the series resistor side and the metal wires that selectively short-circuit and open these connection terminals are constructed, so the structure is simple and the switching is easy, and even if the attenuation is changed, the reflection is not affected. There are obtained effects such as providing a microwave variable attenuator that can be set to zero.

According to the fifth aspect of the present invention, each parallel circuit of the parallel circuit means is constituted by a parallel resistor and a λ / 4 line connected in series with the parallel resistor on the side opposite to the series resistor of the parallel resistor. The switching means includes a metal wire for selectively short-circuiting a series resistor, a connection terminal provided between a side opposite to the parallel resistance of the λ / 4 line of each parallel circuit and ground, and a short-circuit between the connection terminals. Since it is constructed with open metal wires, the parallel circuit will cut the metal wire when loading a resistor, so microwaves that can change the amount of attenuation and reduce the reflection to zero just by cutting the metal wire Such as providing a variable attenuator for use.

[Brief description of the drawings]

FIG. 1A is an equivalent circuit diagram of a microwave variable attenuator according to the first embodiment of the present invention, and FIG. 1B is an external view of the attenuator.

FIG. 2 is a diagram showing a relationship between a resistor R1 and a predetermined attenuation K1 based on the invention of the first embodiment.

FIG. 3 is a diagram showing a relationship between a resistor R2 and a predetermined attenuation K1 based on the invention of the first embodiment.

FIG. 4 is an equivalent circuit diagram of the microwave variable attenuator of the second embodiment.

FIG. 5A is an equivalent circuit diagram of a microwave variable attenuator according to the third embodiment, and FIG. 5B is an external view of the attenuator.

FIG. 6 is an equivalent circuit diagram of a microwave variable attenuator according to a fourth embodiment of the present invention.

FIG. 7 is an equivalent circuit diagram of a conventional microwave variable attenuator.

[Explanation of symbols]

1 input terminal, 2 output terminal, 3a, 3b, 3c, 3d
Series resistance, 4, 12a, 12b λ / 4 line, 5a,
5b, 9a, 9b Parallel resistance, 6 metal wire, 7, 8, 1
0,11 Connection terminal.

Claims (5)

[Claims] 1. An λ / 4 line having an electrical length of １ ／ wavelength at a used frequency, and a plurality of series resistors connected in series between an input side and an input terminal of the λ / 4 line. An input-side series resistance group; an output-side series resistance group including a plurality of series resistors connected in series between an output side and an output terminal of the λ / 4 line; and an input side of the λ / 4 line A parallel circuit means including a plurality of parallel circuits including at least a parallel resistor connected in parallel to each other; and a predetermined series resistor for each series resistor of the input-side and output-side series resistor groups and each parallel circuit of the parallel circuit means. Shorting things,
A variable attenuator for microwaves, comprising: connection switching means for opening; and connection switching by the connection switching means such that the amount of attenuation is changed and the amount of reflection becomes zero. 2. The variable attenuator for microwave according to claim 1, wherein said parallel circuit means is connected between said input terminal and an input side series resistor group. 3. The variable attenuator for microwave according to claim 1, wherein said parallel circuit means is connected between said input side series resistance group and a λ / 4 line. 4. Each parallel circuit of said parallel circuit means comprises a parallel resistor, and said connection switching means is provided on a metal wire for selectively short-circuiting said series resistor, and on a series resistor side of said parallel resistor of each parallel circuit. The variable attenuator for microwave according to any one of claims 1 to 3, comprising a connection terminal provided and a metal wire for selectively short-circuiting and opening the connection terminal. 5. Each of the parallel circuits of the parallel circuit means comprises a parallel resistor and a λ / 4 line connected in series with the parallel resistor on the side opposite to the series resistor of the parallel resistor, and the connection switching means comprises A metal wire for selectively shorting the series resistance, a connection terminal provided between the side opposite to the parallel resistance of the λ / 4 line of each parallel circuit and the ground, and a metal for selectively shorting and opening the connection terminals 4. The variable attenuator for microwaves according to claim 1, wherein the variable attenuator is a line.