JPH06152205A - Attenuator - Google Patents

Abstract

PURPOSE:To set the attenuation at a minimum transmission loss to a value close to 0dB substantially and to simplify the structure. CONSTITUTION:A 1st circulator 12 and a 2nd circulator 14 are provided and the 1st terminal of a 1st circulator 12 is connected to an input terminal 11, a 2nd terminal is connected to a switch 13, and a 3rd terminal is connected to the attenuation circuit 16 of plural bit steps. Furthermore, the 1st terminal of a 2nd circulator 14 is connected to the switch 13, a 2nd terminal is connected to an output terminal 15 and a 3rd terminal is connected to the attenuation circuit 16 of the plural bit steps. That is, the attenuation at a minimum transmission loss is set closer to 0dB.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an attenuator used for communication equipment in high frequency bands such as microwaves and millimeter waves.

[0002]

2. Description of the Related Art Here, an example of a conventional damping device will be described with reference to FIG.

Reference numeral 31 is an input terminal, and an input signal input from the input terminal 31 is added to an attenuator circuit 32 having a plurality of bit steps. The multiple-bit-step attenuating circuit 32 attenuates the input signal in multiple-bit, for example, 4-bit steps (stages), and outputs the attenuated signal to the output terminal 33.

Attenuation circuit 32 having a plurality of bit steps
Is composed of four 1-bit attenuators 321 to 324 as shown.

For example, the 1-bit attenuator 321 is ideally 0 dB or 1 dB for the signal passing therethrough.
Is configured to provide damping of either. Also, 1
The bit attenuator 322 provides 0 dB or 2 dB attenuation,
The 1-bit attenuator 323 provides 0 dB or 4 dB, and the 1-bit attenuator 324 provides 0 dB or 8 dB.
It is configured to provide dB attenuation.

In principle, each of the 1-bit attenuators 321 to 324 is constructed as shown in FIG.

That is, the input terminal 32A is provided on the input side of the signal located on the left side of the figure, and the output terminal 32B is provided on the output side located on the right side of the figure. And the input terminal 32A
Is connected to the switch 32C, and the switch 32D is connected to the output terminal 32B.

The switches 32C and 32D are configured to operate in conjunction with each other.

When the switches 32C and 32D are connected to the terminals c1 and d1 on the upper side of the drawing, the input signal input from the input terminal 32A passes through the line 32E and the output terminal 32B.
Is output to. At this time, the input signal is output with an attenuation amount of 0 dB.

When the switches 32C and 32D are connected to the terminals c2 and d2 on the lower side of the figure, the input terminal 32A is used.
The input signal input from is output to the output terminal 32B through the resistance circuit 32F. At this time, the input signal is attenuated by the resistance circuit 32F and output.

The resistance circuit 32F is configured so that the signal passing therethrough has an attenuation amount of, for example, 1 dB or 2 dB, 4 dB, or 8 dB, depending on the type of the 1-bit attenuator.

That is, the resistance r which constitutes the resistance circuit 32F
1, r2, r3 form a T-shaped attenuator, and resistors r1, r
The values of 2 and r3 are the attenuation of the 1-bit attenuator, 0 dB, 2
It is determined according to dB, 4 dB, and 8 dB.

Therefore, if the switches 32C and 32D are switched in conjunction with each other, 0 dB attenuation occurs when the input signal input from the input terminal 32A passes through the line 32E, and preset when passing through the resistance circuit 32F. The attenuation amount is output, for example, 0 dB, 2 dB, 4 dB, and 8 dB.

By the way, in the 1-bit attenuator, when the input signal passes through the line 32E side, the insertion loss of the line 32E is almost zero, so the attenuation amount passing therethrough should be 0 dB.

However, actually, attenuation of about 0.3 dB occurs.

Therefore, as shown in FIG. 3, four 1-bit attenuators are connected in series to form a 4-bit step attenuator circuit 3.
When 2 is formed, 1.2 dB (= 0.3 × 4d) is required even when it is desired to reduce the attenuation of the signal passing therethrough to a minimum of 0 dB.
Attenuation of about B) occurs. That is, a transmission loss of 24% occurs.

In order to eliminate such transmission loss, conventionally, an attenuation device as shown in FIG. 5 has been used.

In FIG. 5, reference numeral 51 denotes an input terminal, which is an input terminal 51.
A switch 52 is connected to. The line 53 is connected to the upper terminal 521 of the switch 52, and the lower terminal 522
A 4-bit step attenuation circuit 54 similar to that of FIG.

The line 53 and the attenuation circuit 54 are connected to the switch 55 on the output side and to the output terminal 56.

The switches 52, 55 are interlocked, and when the switches 52, 55 are connected to the upper side 521, 551, the input signal is transmitted on the line 53, and the switch 5
If 2, 55 are connected to the lower side 522, 552, transmit attenuation circuit 54.

Here, the amount of attenuation when the input signal is transmitted through the transmission line 53 will be considered.

In this case, the amount of attenuation of the input signal is the sum of the loss of the switches 52 and 55 and the loss of the transmission line 53.

When the input signal is transmitted through the attenuator circuit 54 having a plurality of bit steps, each 1-bit attenuator 54 is used.
It is the sum of the attenuation amounts set for each of 1, 542, 543, 544.

In the configuration of FIG. 5, the input signal is bypassed to the line 53 side when the transmission loss is minimized.

Therefore, even if the number of stages of the 1-bit attenuator constituting the attenuator circuit 54 of multiple bit steps is increased,
As shown in FIG. 3, the minimum attenuation does not increase due to the increase in the number of bits. Therefore, the minimum attenuation is constant,
And can be minimized.

However, in the configuration of FIG. 5, the switches 52,
Two 55 are added.

Therefore, the structure of the drive circuit for switching the switches 52 and 55 becomes complicated, and the drive circuit becomes a cause of trouble, and the product price increases.

[0028]

As described above, in the attenuator of FIG. 3, for example, even if it is desired to set the minimum transmission loss to 0 dB, one 1-bit attenuator attenuates about 0.3 dB. Therefore, if the attenuator circuit having a plurality of bit steps is composed of a plurality of 1-bit attenuators, the transmission loss increases accordingly.

Further, in the attenuator of FIG. 5, the minimum attenuation amount can be suppressed to be small regardless of the number of bits of the attenuator circuit having a plurality of bit steps. However, a switch that switches between the attenuator circuit having a plurality of bit steps and the line is required, which complicates the configuration of the drive circuit that controls this switch and also increases the product price.

It is an object of the present invention to solve the above-mentioned drawbacks and to provide an attenuating device which can make the attenuation at the time of the minimum transmission loss substantially close to 0 dB and has a simple structure and a low cost. And

[0031]

SUMMARY OF THE INVENTION A damping device of the present invention comprises a first circulator having first to third terminals, the first terminal being connected to an input terminal, and the first circulator. A switch connected to the second terminal of the first circulator; and a multi-bit step attenuator circuit having one end connected to the third terminal of the first circulator; A second circulator having a third terminal, a first terminal connected to the switch, and a third terminal connected to the other end of the multi-bit step attenuator circuit; An output terminal connected to the second terminal of the second circulator.

[0032]

According to the above construction, when the minimum transmission loss is desired, the input signal is the first circulator and
It is output through the switch and the second circulator. In this way, the input signal is output without passing through the attenuator circuit having a plurality of bit steps. Therefore, at the minimum transmission loss, the transmission loss amount between the input and the output is always constant and small.

When the input signal is attenuated, the input signal is output through the first circulator, the attenuator circuit having a plurality of bit steps, the second circulator, etc. by the switching operation of the switch. To be done.

Further, since the switching operation of the switch is only opening and closing of the switch, the structure of the switch is simple and the drive circuit for driving the switch can be simplified.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIG.

The input signal is input from the input terminal 11.
The input signal input from the input terminal 11 is applied to the terminal 12a of the first circulator 12.

The first circulator 12 has terminals 12b and 12c in the forward direction indicated by the arrow. A switch 13 is connected to the terminal 12b.

When the switch 13 is closed,
The input signal applied to the first circulator 12 is supplied from the switch 13 to the terminal 14a of the second circulator 14.
Added. The signal applied to the terminal 14a is output from the terminal 14b to the output terminal 15 according to the arrow.

As described above, when the switch 13 is closed, the input signal input from the input terminal 11 is output to the output terminal 15 without being attenuated.

At this time, since the input signal does not pass through the multi-bit step attenuator circuit, the attenuation can be substantially close to 0 dB at the minimum transmission loss.

Next, the case where the switch 13 is open will be described.

In this case, the input signal applied to the terminal 12a of the first circulator 12 is transmitted from the terminal 12b to the switch 13 and is totally reflected by the switch 13.

The signal totally reflected is the first circular image.
Then, the signal is returned to the terminal 12 and added to the attenuator circuit 16 having a plurality of bit steps from the terminal 12c.

The attenuator circuit 16 having a plurality of bit steps has four
Each of the 1-bit attenuating circuits 161 to 164 has a configuration similar to that of the multi-bit step attenuating circuit 32 described with reference to FIG.

Therefore, the input signal input to the attenuation circuit 16 is attenuated to a desired value and added to the terminal 14c of the second circulator 14. The signal applied to the terminal 14c is transmitted from the terminal 14a to the switch 13 and is totally reflected by the switch 13. The total reflected signal is the second
Is output to the output terminal 15 via the circulator 14.

According to the above construction, the operation of the switch 13 can be switched between open and closed, and the construction of the switch 13 can be simplified and the cost can be reduced.

The driving power source may be only that for the switch 13 except for the attenuator circuit 16 having a plurality of bit steps, and the driving circuit can be simplified and the device can have low power consumption.

Next, another embodiment of the present invention will be described with reference to FIG.
Will be described with reference to.

In the embodiment of FIG. 1, the switch 13 is the first
Is connected in series to the transmission line connecting the circulator 12 and the second circulator 14. However, in the embodiment of FIG. 2, the switch 20 is connected in parallel to the transmission line connecting the first circulator 12 and the second circulator 14, and the line between the transmission line and the ground is opened. , Or short-circuited.

In this way, only the arrangement of the switch 20 is different, and the other structure is the same as that of FIG. 1, so the same parts as those in FIG.

In the configuration of FIG. 2, when the switch 20 is open, the operation is the same as when the switch 13 is closed in FIG.

When the switch 20 is short-circuited, the switch 20 totally reflects the signal. Therefore, the operation is the same as when the switch 13 is opened in FIG.

As described above, according to the present invention, the minimum attenuation amount can be set to a value substantially close to 0 dB, and the switch drive circuit can be simply constructed, and the low-power attenuation device with low power consumption can be obtained. Can be provided.

Therefore, a remarkable effect can be obtained by adopting it in the output stabilizing circuit of the saturation type power amplifier.

[0055]

According to the present invention, when the attenuation of a plurality of bit steps is obtained, the minimum attenuation amount can be reduced to the same extent as when there is one 1-bit attenuator.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram showing another embodiment of the present invention.

FIG. 3 is a circuit configuration diagram showing a conventional example.

FIG. 4 is a circuit configuration diagram illustrating a conventional example.

FIG. 5 is a circuit configuration diagram showing a conventional example.

[Explanation of symbols]

 11 ... Input terminal 12 ... 1st circulator 13, 20 ... Switch 14 ... 2nd circulator 15 ... Output terminal 16 ... Attenuation circuit

Claims (1)

[Claims] 1. A first circulator having first to third terminals, the first terminal of which is connected to an input terminal, and a second circulator of the first circulator. A switch connected to the terminal, a multi-bit step attenuator circuit having one end connected to the third terminal of the first circulator, and first to third terminals. A second circulator connected to the switch and a third terminal to the other end of the multi-bit step attenuator circuit, and a second circulator of the second circulator. And an output terminal connected to the terminal of the attenuator.