JPH0555647A - Superconducting mixer element - Google Patents

Abstract

PURPOSE:To efficiently produce an intermediate frequency output by providing a tunable impedance matching circuit in an intermediate frequency output fetch unit in a superconducting mixer element having a Josephson junction. CONSTITUTION:A tunable impedance matching circuit 3 formed on a board 1 for impedance-matching a detector 2 with an intermediate frequency amplifier to be connected to a superconducting mixer element, is provided. The circuit 3 has a pair of meander type superconducting thin film inductors 4, 5. The inductor 5 of an output side is formed on a thin film heater 6 formed on the board 1 through an insulating layer. The impedance matching of the detector 2 to an intermediate frequency amplifier is conducted by the L-coupling of the inductors 4, 5. In this case, the temperature of the heater 6 is controlled to effectively fetch an intermediate frequency output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting mixer element having a Josephson junction.

[0002]

2. Description of the Related Art Research on superconducting mixer elements utilizing the Josephson effect, which is a phenomenon peculiar to superconductors, has been made for a long time. In particular, research on Josephson devices is centered on so-called SIS tunnel junction devices having a laminated structure of superconductor / insulator / superconductor, and research on superconducting mixer devices is also centered on SIS quasi-particle mixers. (Japanese Patent Publication No. 60-3797 and Japanese Unexamined Patent Publication No. Sho 6)
No. 1-733691).

However, with the recent development of telecommunication technology, in the field of information communication utilizing communication hygiene,
With the increasing demand for higher frequency bands, the importance of receivers in the millimeter wave and sub-millimeter wave bands, that is, Josephson mixers, has been reviewed.

Conventionally, a metallic superconductor such as Nb or Y
BaCuO type, BiSrCaCuO type, TlSrCaC
At the laboratory level, Josephson mixers made of oxide superconductors represented by uO system are
Its characteristics have been obtained with point contact type and crack junction type elements.

[0005]

However, surface oxidation (deterioration) at the contact portion, which is a drawback of the point contact type element, deterioration of characteristics in the heat cycle and change with time,
Due to various problems such as lack of reproducibility, it is difficult to put them into practical use.

With regard to the weak link type element (weakly coupled element), which has relatively few of these problems, the element impedance is low, so that the intermediate frequency output after mixing is efficiently taken out and led to the intermediate frequency amplifier in the subsequent stage. It has the drawback of being difficult.

An object of the present invention is to provide a superconducting mixer element which can efficiently take out an intermediate frequency output.

[0008]

A superconducting mixer element according to the present invention is characterized in that a tunable impedance matching circuit is provided in an intermediate frequency output extraction portion of the superconducting mixer element composed of a Josephson junction.

The tunable impedance matching circuit is composed of, for example, a pair of meander type superconducting thin film inductors, and at least one of the pair of superconducting thin film inductors is formed on the thin film heater via an insulating film.

[0010]

In the superconducting mixer element having the Josephson junction, since the tunable impedance matching circuit is provided in the intermediate frequency output extraction section, the intermediate frequency output can be extracted efficiently.

[0011]

Embodiments of the present invention will be described below.

FIG. 1 shows a superconducting mixer element.

The superconducting mixer element has an impedance of a detecting element 2 made of a superconductor formed on a substrate 1 and an intermediate frequency amplifier (not shown) formed on the substrate 1 and connected to the detecting element 2 and the superconducting mixer element. It comprises a tunable impedance matching circuit 3 for matching.

The tunable impedance matching circuit 3 comprises a pair of meander type superconducting thin film inductors 4 and 5. The inductor 5 on the output side is formed on the thin film heater 6 formed on the substrate 1 via an insulating layer.

The detecting element 2 is produced as follows.

First, Y ₂ O ₃ , BaCO ₃ and CuO powder were prepared, weighed at a ratio of Y: Ba: Cu = 1: 2: 3, and then pressed at a pressure of about 1 ton / cm ² to form raw material pellets. To form. The pellets are heated to 2000 ° C. or higher by an argon arc or the like to be melted for several seconds, and then the molten pellets are rapidly cooled at about 10 ³ ° C./sec to obtain an oxide superconductor material.

Next, this material is sliced to a thickness of 1 mm or less, preferably 0.3 mm or less, and the sliced material is heated in an oxidizing atmosphere such as oxygen or air to a temperature below the melting point of the sliced material, for example, 1000 ° C. Annealing is performed for 3 hours to uniformly incorporate oxygen into the slice to form a single-phase oxide superconducting slice represented by YBa ₂ Cu ₃ O _7-r .

Next, the oxide superconducting slice is bonded to the substrate 1. The thermal expansion coefficient of the slice of YBa ₂ Cu ₃ O _7-r obtained by the above method is around 160 × 10 ^-7 / ° C. As the substrate 1, a ZnO—Al ₂ O ₃ —SiO ₂ system having a thermal expansion coefficient substantially equal to that of the slice is used. That is, the ZnO-Al ₂ O ₃ -SiO ₂
The coefficient of thermal expansion of the system crystallized glass is 140 to 160 × 10.
^-7 / ° C, which is very close to that of slices.

The PbO-ZnO-Al ₂ O-SiO ₂ system was used for bonding the slice and the substrate 1.
Fb glass (not shown) having a composition of PbO of 20 to 70 atomic% is used. The thermal expansion coefficient of the frit glass having this composition is 120 × 10 ⁻⁷ / ° C., which is similar to that of the slice and the substrate 1, and the softening temperature thereof is about 300 ° C.

To bond the slices to the substrate 1, ZnO
Substrate consisting -Al ₂ O ₃ -SiO ₂ based crystallized glass 1
Of _{PbO-ZnO-Al 2 O-} SiO 2 system frit glass was applied to the surface, the oxide superconductor slice 4 while was placed and heated for about 30 minutes at 400 ° C. to 500 ° C. thereon, back to room temperature. The frit glass of this system exhibits a good adhesion state not only to the crystallized glass substrate 1 but also to the oxide superconducting slice, so that the slice is firmly adhered to the substrate 1.

As described above, since the substrate 1 and the slice and the frit glass for adhering both the substrate 1 and the slice have similar thermal expansion coefficients, almost no distortion occurs in the slice during the heat treatment in the adhering step and the subsequent cooling.

Next, with the slice adhered to the substrate 1, the slice surface is polished to a thickness of about 10 to 50 μm.
After that, a constricted portion 2a narrower than both end portions is formed in the central portion as shown in FIG. 1 by using a method such as ion beam sputtering, chemical etching, or laser patterning. The constricted portion 2a has, for example, a width of 0.03 to 0.
It is 3 mm and the length is about 0.05 to 0.5 mm. Thereby, the detection element 2 is obtained. In FIG. 1, 2b is a bias current terminal portion, and 2c is an intermediate frequency output terminal portion.

The tunable impedance matching circuit 3 is manufactured as follows. A first meandering type superconducting thin film inductor 4 is formed in the intermediate frequency output extraction portion of the detection element 2 on the substrate 1 so that both ends thereof are connected to the intermediate frequency output terminal portion 2c of the detection element 2.
Further, the thin film heater 6 made of a high resistance material such as nichrome is formed on the side of the substrate 3 where the intermediate amplifier is connected. After forming an insulating layer on the upper surface of the heater 6, a second meander type superconducting thin film inductor 5 facing the inductor 4 is formed. 6a is a heater current terminal portion.
An intermediate frequency amplifier (not shown) is connected to both ends of the inductor 5.

Impedance matching between the detecting element 2 and the intermediate frequency amplifier is performed by the L of the inductor 4 and the inductor 5.
It is done by combining. At that time, by controlling the temperature of the heater 6, the coupling degree between the inductors 4 and 5 is adjusted, and the intermediate frequency output is effectively taken out.

In the above embodiment, the glass substrate is used as the substrate 1, but an insulating single crystal substrate such as alumina or MgO may be used.

When an insulating single crystal substrate is used, the detection element 2, the inductor 4 and the heater 6 are formed on the substrate by sputtering, for example. The inductor 5 is formed by, for example, a sputtering method after forming an insulating layer on the heater 6.

FIG. 2 shows a detection circuit using the above superconducting mixer element.

The signal wave RF and the local oscillation wave LO are input to the superconducting mixer element 10. The output of the superconducting mixer element 10 is sent to the intermediate frequency amplifier 12 via the bandpass filter 11, and an intermediate frequency output is obtained from the intermediate frequency amplifier 12.

Table 1 shows the output of the intermediate frequency amplifier (IF amplifier) of the conventional superconducting mixer element (conventional example) without the tunable impedance matching circuit 3 and the superconducting mixer having the tunable impedance matching circuit 3. The output of the intermediate frequency amplifier of a plurality of examples which are elements and differ in heater current is shown. The frequency of the intermediate frequency output is 50 MHz.

[0030]

[Table 1]

As can be seen from Table 1, in the superconducting mixer element having the tunable impedance matching circuit 3, by adjusting the heater current, the mixing output was improved by 8 dB as compared with the conventional one.

[0032]

According to the present invention, the intermediate frequency output can be taken out efficiently.

[Brief description of drawings]

FIG. 1 is a perspective view of a superconducting mixer element showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a detection circuit using a superconducting mixer element.

[Explanation of symbols]

 1 substrate 2 detection element 3 tunable impedance matching circuit 4 inductor 5 inductor 6 heater

Claims (2)

[Claims] 1. A superconducting mixer element comprising a Josephson junction, wherein a tunable impedance matching circuit is provided in an intermediate frequency output extraction section. 2. The tunable impedance matching circuit comprises a pair of meander type superconducting thin film inductors, and at least one of the pair of superconducting thin film inductors is formed on a thin film heater via an insulating film. The superconducting mixer element according to claim 1, wherein