JPH0746070A - Microwave circuit - Google Patents

Abstract

PURPOSE:To prevent the output of excessive power by outputting RF through a superconducting filter. CONSTITUTION:Input RF signals are amplified in an RF circuit 1 and outputted through a serially connected RF circuit 2. The superconducting filter 3 is interpolated between the circuits 1 and 2 and when the power level of RF signals outputted from the circuit 2 is lower than a prescribed level, the filter 3 maintains a superconductive state and outputs the RF signals with minute insertion loss. On the other hand, when the power level becomes higher than the prescribed level, the superconductive state is lost, the filter 3 is turned to a normal conductive state and functions as a resistor and the microwave circuit capable of preventing the RF output of the excessive power is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave circuit having an excessive output preventing function.

[0002]

2. Description of the Related Art Conventionally, a microwave circuit has an input R
Since the F (Radio-Frequency) has a small gain, a configuration is used in which RF circuits for amplification are connected in multiple stages. That is, as shown in FIG. 3, the RF circuit 11,
RF input from the input side by configuring 12 connected in series
The electric power of 1 is sequentially amplified by the RF circuits 11 and 12 and output to the output side.

[0003]

However, in the above-mentioned conventional microwave circuit, the RF output power is set to the RF circuit 1
Since the structure is such that 1 and 12 superimpose and amplify, when the RF input power P1 ′ is large, the RF output power P2 ′ is output as an excessive power that has reached the saturation output level, and is shown in the subsequent stage. There was a risk of destroying the device.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a microwave circuit capable of preventing the output of excessive electric power.

[0005]

In order to achieve the above object, the present invention provides an input RF (Radio-Frequency).
In a microwave circuit provided with an RF circuit for amplifying and outputting the signal (energy), a superconducting filter which becomes a normal conduction state when the output power from the RF circuit becomes a predetermined level or more is provided on the output side of the RF circuit, RF is output through this superconducting filter.

Further, the superconducting filter has a structure in which when the output power from the RF circuit exceeds a predetermined level, the superconducting filter is brought into a normal conduction state in which the output power is reduced to a constant level other than zero level.

Further, the superconducting filter is based on the RF.
When the output power from the circuit becomes equal to or higher than a predetermined level, the output power is reduced to the zero level, and the normal conduction state is set.

[0008]

According to the above microwave circuit, when the output power from the RF circuit exceeds a predetermined level, the superconducting filter is in the normal conducting state and has a resistance.
Excessive output power from the circuit is reduced and output by this superconducting filter. Particularly, according to the microwave circuit of the second aspect, the superconducting filter can reduce the excessive power output from the RF circuit to a desired level. Further, according to the microwave circuit of the third aspect, the superconducting filter can eliminate excessive power output from the RF circuit.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a microwave circuit according to an embodiment of the present invention, and FIG. 2 is a line diagram showing its input / output levels.

The microwave circuit of this embodiment has a structure in which a superconducting filter 3 is interposed between RF circuits 1 and 2 connected in series. Reference numeral 4 is an input terminal,
Reference numeral 5 is an output terminal.

The RF circuit 1 inputs an input RF (hereinafter referred to as "input RF-IN") which is a microwave from the input terminal 4, and outputs this input RF-IN at a predetermined amplification factor corresponding to a predetermined gradient. It has the function of amplifying and outputting. Specifically, as shown in FIG. 2, when the input power level of the input RF-IN is P1, the power of the input RF-IN is amplified with an amplification factor corresponding to the gradient of (P2-P1) / a. It has become.

On the other hand, the RF circuit 2 amplifies the power of the RF output from the superconducting filter 3 and is an amplified microwave RF (hereinafter referred to as "output RF-OUT").
Is output to the output terminal 5. Specifically, as shown in FIG. 2, when the power level of the output RF from the superconducting filter 3 is P3, the gradient (P4−P3) / c−
The output RF-OUT is output at the amplification factor corresponding to b.

The superconducting filter 3 is a filter which becomes a normal conduction state when the input power exceeds a predetermined level, and its input side is connected to the output side of the RF circuit 1 and its output side is the input side of the RF circuit 2. Connected to the RF circuit 1,
It is arranged between two.

That is, the superconducting filter 3 is in a superconducting state when the input power level of the input RF is below a certain level and has a high Q (selection index) and a low loss BPF (bandpass filter). To work as. Specifically, as shown in FIG. 2, the RF output from the RF circuit 1
When the power level P2 of P is smaller than the reference power level PL, the superconducting state is maintained and the input RF is output with a small insertion loss L1. Therefore, in FIG. 2, the output power P2 of the RF input to the superconducting filter 3
Will be output as P2-L1 = P3.

Further, the superconducting filter 3 has an input RF
When the input power level of is above a certain level, the superconducting state is broken and the normal conducting state is reached, and the Q thereof is lowered, which has the function of increasing the power loss of the input RF. Specifically, as shown in FIG. 2, R output from the RF circuit 1
When the power level of F becomes higher than the reference power level PL, the state is changed to the normal conduction state, and the power level is lowered by the insertion loss L2 which is significantly larger than the insertion loss L1. That is, when the RF of the reference power level PL is input to the superconducting filter 3, the state shown by the alternate long and short dash line in FIG. 2 is obtained, and the RF-OUT of the saturated output level P8 becomes R.
It may be output from the F circuit 2. However, since the superconducting filter 3 is in the normal conducting state and has a remarkably large insertion loss L2, the RF power output from the superconducting filter 3 is attenuated as PL-L1-L2 = P6. .

Next, the operation of the microwave circuit of this embodiment will be described. When the input power level of the input RF-IN input to the RF circuit 1 from the input terminal 4 is a normal level and is a small input power level P1 as shown in FIG. 2, the output power of the RF-IN is set. The level is amplified by the RF circuit 1 to the output power level P2 and output. Therefore, since the input power level P2 of RF output from the RF circuit 1 and input to the superconducting filter 3 is smaller than the reference power level PL, the superconducting filter 3 maintains the superconducting state. As a result, in the superconducting filter 3, the output power level P2 of the input RF is reduced by a slight insertion loss L1 and becomes the output power level P3.
It will be output to the circuit 2.

Thus, the RF input to the RF circuit 2
Since the input power level P3 of the RF signal is significantly smaller than the reference power level PL, the RF amplified and output by the RF circuit 2 is output.
The output power level P4 of -OUT is the reference power level PL
It becomes smaller than the above, and is output from the output terminal 5. That is, the RF-I input to the RF circuit 1
When the input power level of N is normal, the superconducting filter 3 maintains the superconducting state.
The insertion loss L1 due to is extremely small. Therefore, RF
A power level P3 close to the power level P2 of the RF output from the circuit 1 is output from the superconducting filter 3, and the RF of this power level P3 is amplified to a desired size by the RF circuit 2 and output terminal It will be output from 5.

On the other hand, when the input power level P5 of the RF-IN input from the input terminal 4 to the RF circuit 1 is considerably higher than the normal input power level P1, the RF circuit 1 outputs the signal as shown in FIG. The output power level of the output RF is amplified by the RF circuit 1 and reaches the reference power level PL. In this way, when the RF that has reached the reference power level PL is input to the superconducting filter 3, the superconducting filter 3 changes to the normal conducting state, giving a large insertion loss L2 to the power level of the input RF. Become. That is, the output power level P6 of the RF output from the superconducting filter 3 is lowered to the vicinity of the normal power level P3.

As a result, the input power level P6 of a power level close to the normal power level P3 is input to the RF circuit 2, and even if the RF input to the RF circuit 2 is amplified, the RF circuit 2 is input. The output power level 7 that is close to the normal output power level P4 output from is output. That is, the input RF− input to the RF circuit 1
When the input power level of IN is large, the power level of RF input to the superconducting filter 3 is the reference power level P.
Since it exceeds L, the power level of the input RF is greatly attenuated by the normal state of the superconducting filter 3. Then, from that state, the RF circuit 2 amplifies the RF signal at a constant amplification factor, so that the output power level P7 of the RF output from the RF circuit 2 remains at a power level smaller than the reference power level PL.

As described above, in the microwave circuit of this embodiment, the input RF-IN having the input power level at which the RF circuit 2 outputs an excessive output power level is changed to the RF circuit 1.
Is attenuated by the action of the superconducting filter 3, the output power level P7 of the RF-OUT output from the RF circuit 2 is always smaller than the reference power level PL. Therefore, by using the microwave circuit of the present embodiment, it is possible to reliably prevent the output of excessive power from the RF circuit 2.

In this embodiment, the insertion loss L2 of the superconducting filter 3 is arbitrarily set, but this can be determined depending on the type of composition constituting the superconducting filter 3. Therefore, the output power level from the superconducting filter 3 can be made zero by selecting the composition of the superconducting filter 3 and significantly increasing the insertion loss L2. As a result, it is possible to prevent the downstream device from being destroyed due to excessive output power.

Further, in this embodiment, one superconducting filter 3 is provided between the RF circuits 1 and 2, but the present invention is not limited to this, and an inexpensive superconducting filter is provided between the RF circuits 1 and 2. It is also possible to reduce the product cost of the microwave circuit by connecting a plurality of them in series.

Further, in this embodiment, the superconducting filter 3 is used.
Although it is provided between the RF circuits 1 and 2, it is not limited to this and can be provided on the output side of the RF circuit 2 at the final stage.

[0024]

As described above, according to the microwave circuit of the present invention, the excessive output power from the RF circuit can be lowered to a desired level by the superconducting filter, so that the output of the excessive power can be reliably ensured. Can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing a microwave circuit according to an embodiment of the present invention.

FIG. 2 is a line diagram showing input / output levels.

FIG. 3 is a block diagram showing a microwave circuit according to a conventional example.

[Explanation of symbols]

 1, 2 RF circuit 3 Superconducting filter 4 Input terminal 5 Output terminal RF-1N input RF RF-OUT output RF P1, ..., P8 Power level L1, L2 Insertion loss

Claims (3)

[Claims] 1. An input RF (Radio-Freque)
In a microwave circuit provided with an RF circuit for amplifying and outputting (energy), a superconducting filter is provided on the output side of the RF circuit, the superconducting filter being in a normal conduction state when the output power from the RF circuit exceeds a predetermined level. A microwave circuit which outputs RF through the superconducting filter. 2. The superconducting filter is in a normal conduction state in which when the output power from the RF circuit exceeds a predetermined level, the output power is reduced to a constant level other than zero level. Microwave circuit. 3. The microwave according to claim 1, wherein the superconducting filter is in a normal conduction state in which the output power is reduced to zero level when the output power from the RF circuit exceeds a predetermined level. circuit.