JPH01174101A - Microwave circuit - Google Patents

Abstract

PURPOSE:To vary the line constant in a non-contact state by constituting part of a microstrip line by a superconducting material, applying a magnetic field thereto to bring the part of the superconducting material into the normal conducting state, bringing the other part into the superconducting state and moving the region of the superconducting state in response to the strength of the magnetic field. CONSTITUTION:When a current flows to a coil 14, since a magnetic field H in the range of hatched lines as A-B in figure exceeds a critical magnetic field Hc of the superconducting material, the range A-B represents the normal conducting state. Thus, a loss depending on the superconducting material is caused in the range AB. As the current flowing to the coil 14 is increased, the magnetic field is increased, the area broken with the superconducting state is widened and the transmission loss is increased. Conversely, when the current flowing to the coil 14 is decreased, since the magnetic field is weakened, the area with broken superconducting state is made narrow and the transmission loss is decreased. Thus, the transmission loss is made variable in response to the current.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to microwave circuits.

[Conventional technology]

A conventional microwave circuit of this type has a configuration as shown in FIG. 4, for example.

4(a), (b), and (o) are a side view, a front view, and a sectional view of a conventional microwave circuit, respectively.

In Figure 4, (1) is a strip conductor made of metal etc., (2) is a WllE body made of ceramic etc., (3) is a strip conductor made of metal etc.
) is the ground conductor.

Figure 5 shows λ using a conventional microstrip line.
/4 Oven resonant circuit, Figure 6 is a directional coupler circuit in which two conventional microstrip lines are closely connected.
In the figure, (5) shows 742 strip lines.

Next, the operation will be explained. In FIG. 4, a strip conductor (1) and a ground conductor (3) form a parallel plate line with a dielectric (2) in between. FIG. 4(c) is a cross-sectional view taken along the C-σ line in FIG. 4(b), and the electric field between the strip conductor (1) and the ground conductor (3) is shown by the broken line. As shown in FIG. 4(b), such a parallel plate line can send a wide band of magnetic waves ranging from direct current to microwave bands in the vertical direction. This is generally called a microstrip line.

The loss of a microstrip line is mainly determined by the loss of the dielectric and the loss of the conductor, so if you change the conductivity of the conductor,
Its passing loss can be varied. If a conductor with high conductivity is used, the passing loss will be small, and if a conductor with low conductivity is used, the passing loss will be large.

Also, a long microstrip line as shown in Figure 5 is
When viewed from the left end, the resonator appears to have a low impedance (short circuit) with respect to electromagnetic waves with wavelength λ=4·L.

In addition, as shown in Figure t@6, strip lines (1) and (
5) are separated by a distance id, a directional coupler with a coupling state corresponding to the length of d is obtained.

[Problem that the invention seeks to solve]

Conventional microwave circuits are configured as described above, so for example, to change the transmission loss, it is necessary to change the type of conductor, and to change the resonant wavelength λ, the line length must be changed. If you want to change the coupling state of the coupler, you have to change the distance d between the lines, so there is a problem that a variable element cannot be obtained.

This invention was made to solve the above-mentioned problems, and aims to provide a microwave circuit that can easily change the loss of the microstrip line, the line length, and the distance between the double line lines. .

[Means for solving problems]

In the microwave circuit according to the present invention, a microstrip line is made of a superconductor, a fl1cm field is applied thereto, a part of the region to which the magnetic field is applied is transferred to a normal conduction state, and a desired state is achieved according to the strength of the magnetic field. However, it is possible to make the loss dimension of the line variable by making the region normal conductive and the remaining region superconducting.

[Effect]

The microwave circuit of this invention applies an appropriate magnetic field to a microstrip line by utilizing the phenomenon that a superconductor becomes a normal conductor or semiconductor when subjected to a predetermined magnetic field strength He and a magnetic field H greater than that. By switching the line between a superconductor region and a normal conductor or semiconductor region at an arbitrary position, the line loss dimension etc. can be made variable.

Although the superconducting state can be broken by applying heat instead of a magnetic field, we used a magnetic field because it is easier to change and can change at a higher speed.

Hereinafter, one embodiment of the present invention will be described in detail using the drawings.

t@1 Figures (a), (b), and (e) are a side view, a front view, and c-c of a microwave circuit that is an embodiment of the present invention.
It is a cross-sectional view when cut along the ' line.

In Figure 1, α0 is a strip line made of a superconductor, @ is a dielectric, and the side is a ground plate made of a superconductor, a
4 is a ring-shaped coil for generating a magnetic field. When no current is flowing through the annular coil Q4, the strip line αO is in a superconducting state over its entire length, and the conductivity is ■, so the passing loss is almost zero.

Next, when a certain amount of current is passed through the coil α◆, as shown in Figure 1 (
b) Since the magnetic field H in the diagonally shaded range indicated by A-B in the middle exceeds the critical magnetic field Ho of the superconductor, the range A-B becomes a normal conduction state. Therefore, in the range A-B, a loss determined by the superconducting material occurs. Furthermore, if the current flowing through the coil 04 is increased, the magnetic field becomes stronger, the region where the superconducting state is broken becomes wider, and the passing loss increases. On the contrary, coil α◆
[If i is reduced, the magnetic field becomes weaker, the region where the superconducting state is broken becomes narrower, and the passing loss decreases.

In this way, a variable attenuator whose passing loss can be varied depending on the current can be realized.

In the embodiment shown in FIG. 1, the strip line αQ is made of only a superconductor, but if the conductivity of the superconductor in the normal rod state is too low and the loss becomes too large,
A conductor having an appropriate conductivity may be placed on the top surface of the superconductor or the surface on the dielectric side.

Furthermore, if we use a strip conductor made of a sufficiently thin film of a semiconducting superconductor that has sufficiently low conductivity in the normal conductive state, it becomes a microstrip line with extremely low loss in the superconducting state, and superconductivity can be achieved by a magnetic field, etc. When the state becomes a broken n-normal conduction state, a microstrip line that is almost an insulator can be realized. An application example of such a microstrip line will be explained with reference to FIGS. 2 and 3.

FIG. 2 shows an example of a microstrip having a length L made of the above-mentioned superconducting thin film. Coil α◆ is strip line Q
It is fixed to the top of O in the same way as (,) in Figure Wi1. When no current is passed through the coil Q4, the entire strip line aCt is in a superconducting state, so it acts as a long microstrip line resonator.When a certain current is passed through the coil Q4, the diagonal line between A and B in the figure appears. Since the magnetic field H in that part exceeds the critical magnetic field He, the ultra-wide conductive state is broken. Since this superconductor has extremely low conductivity and thin film thickness in the normal state, the range A-B can be regarded as an insulator, so the apparent length of the microstrip line is short L'. Become. In this way, the length of the microstrip line can be varied in accordance with the current flowing through the coil a4, and the resonant wavelength of the four-person resonator can be varied.

In addition, even in the case of a turntable as shown in Fig. 3, Fig. 1 (a
), depending on the current flowing through the coil αQ placed at the top of the turntable, a part of the superconducting state becomes a normal conductive state, that is, a quasi-insulating state, only within the area indicated by the diagonal lines in the same figure. The distance d between the couplers can be varied in accordance with the current flowing through the coil αQ, and the amount of coupling between the couplers can be varied.

Further, in the embodiment described below, the grounding plate (3) is made of a superconductor, but the same effect can be obtained even if the grounding plate (3) is made of a normal conductor. In this case, the coil Q4 or 0 can be placed on the lower surface of the ground plate 0 to obtain exactly the same effect. In this case, the coil α◆ or the Q sheet may be directly fixed to the ground plate (3) with adhesive or the like.

〔Effect of the invention〕

As described above, according to the present invention, a part of the microstrip line is made of a superconductor, and a magnetic field is applied to the superconductor.
One part of the superconductor is in a normal conductive state and the other part is in a superconducting state, and the superconducting region can be moved according to the strength of the magnetic field, making it possible to change the line constant without contact. A wave circuit is obtained.

[Brief explanation of the drawing]

Figure 1 (a) (b) (a) is a side view, front view and sectional view showing an embodiment of the present invention, Figure 2 is a front view showing another embodiment of the invention, and Figure 3 is a front view of this embodiment. 4(a), 4(b) and 4(e) are side views, front views and sectional views showing a conventional microwave circuit, and FIGS. 5 and 6 are front views showing still another embodiment of the invention. 1 is a front view showing a conventional microwave circuit. In the figure, αQ is a strip conductor, @ is a WsN body, (to) is a ground conductor, a4α· is a coil, and (to) is a strip conductor. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (7)

[Claims] (1) A microwave circuit characterized in that by applying a magnetic field to a superconducting microstrip line, a part of the line is made into a normal conduction state, and the remaining part is made into a superconducting state so that the constant of the line can be varied. . (2) By making the superconductor film extremely thin,
2. The microwave circuit according to claim 1, wherein most of the normally conductive portion can be regarded as an insulator. (3) The microwave circuit according to claim 1, characterized in that a conductor is provided in a layer above or below the superconductor. (4) The microwave circuit according to claim 1, wherein the ground conductor is a conductor so that a magnetic field is applied from the back surface of the substrate. (5) Among the constants of the line, mainly the amount of attenuation of the line can be varied.
Microwave circuit described in section. (6) The microwave circuit according to claim 2, wherein among the constants of the line, mainly the length of the line can be varied. (7) The microwave circuit according to claim 2, characterized in that the interval between the two superconducting microstrip lines is variable.