JP2593131B2 - SQUID device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a medical diagnostic apparatus for measuring a magnetic field generated from a human or a living body, a physical property measuring apparatus for measuring a magnetic permeability of a material, and an interface for magnetic signal transmission. Communication device, SQUID constructing Josephson computer, SQUID (Superconducting) usable as buffer amplifier and clock generator of Josephson electronic circuit such as oscillation circuit
The present invention relates to a Quantum Interference Device.

[0002]

2. Description of the Related Art Conventionally, relaxation oscillators (relaxation oscillators: Relaxa
tion Oscillator (hereinafter referred to as “RO”) or relaxation oscillation (Relaxation Oscillation) type SQUID
Devices (hereinafter referred to as “ROS”) are known. As an example of the configuration of the RO, as shown in FIG. 3, one Josephson junction, a shunt inductor Ls, and a shunt resistor Rs
And a circuit installed in an ultra-low temperature environment is known. Further, as an example of the configuration of the ROS, as shown in FIG. 4, a SQUID loop installed in an ultra-low temperature environment and a shunt resistor R connected in parallel to this SQUID loop
It is known to have a shunt circuit having s and a shunt inductor Ls. In this case, the outputs of RO and ROS have been directly extracted.

[0003]

However, in the above-described conventional RO or ROS, the output can be taken out only as a voltage change V oscillating at the frequency f. RO or RO
This is because the output impedance of S is usually 1 Ω or less, so that it is difficult to extract it as a current. RO
Alternatively, there is a case where another Josephson circuit is desired to be connected to the subsequent stage of the ROS. However, since the Josephson circuit is usually a current drive circuit, there is a problem that the connection cannot be made as it is. The present invention has been made in order to solve the above problems, and has as its object to provide a SQUID device such as an RO or ROS capable of extracting an output with a current.

[0004]

Means for Solving the Problems To solve the above problems, a SQUID device according to the first invention of the present application is a relaxation oscillation circuit having one Josephson junction, a shunt inductor, and a shunt resistor. A SQUID device comprising a SQUID loop having a Josephson junction and a non-latch type SQUID gate having a load resistance, wherein the shunt inductor and the SQUID are provided.
A non-latch type SQUID by magnetically coupling
It is configured to obtain an oscillation output current from the D gate . Further, the SQUID device according to the second invention of the present application includes a first SQUID loop having two Josephson junctions, a relaxation oscillation type SQUID having a shunt inductor and a shunt resistor, and a second SQUID having two Josephson junctions. a SQUID device and a non-latching SQUID gate with two of the SQUID loop and load resistance, the magnetically coupled with the shunt inductor and the SQUID loop, the non-latching SQUID gate
Is configured to obtain an oscillation output current from

[0005]

According to the present invention having the above structure, RO or R
By magnetically coupling the OS to the non-latch type SQUID gate, it is possible to extract the oscillation output of the RO or ROS by current.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an equivalent circuit diagram showing a configuration of a SQUID device according to one embodiment of the present invention.

As shown in the figure, this SQUID device
Installed in ultra-low temperature environment (Relaxation Oscil
relation) type SQUID (ROS) and a non-latch type SQUID magnetically coupled to the shunt inductor of this ROS
It consists of an ID gate. In some cases, the following circuit is connected after the SQUID device.

As shown on the left side of FIG. 1, the ROS includes a SQUID loop having two Josephson junctions installed in an ultra-low temperature environment, a shunt resistor Rs and a shunt inductor Ls connected in parallel to the SQUID loop.
And a shunt circuit having the following. As shown in the right side of FIG. 1, the non-latch type SQUID gate has an SJT having two Josephson junctions installed in an ultra-low temperature environment.
It comprises a QUID loop and a load resistor RL connected to the output side of the SQUID loop. in this case,
The ROS shunt inductor on the left and the SQUI on the right
The D loop is magnetically coupled. Here, the value of the load resistance RL is set so as to be in the non-latch mode. Here, RGN is the non-latching SQUA on the right side of FIG.
3 shows the normal conduction resistance of the ID gate.

FIG. 2 is an input / output characteristic diagram of the SQUID device shown in FIG. FIG. 2A shows the ROS shown on the left side of FIG.
2 (B) shows an output signal IL (oscillation current flowing on the shunt side) of FIG.
The output signal Iout of the D gate is shown.

The operating point IGB (bias current of the SQUID gate) of the non-latch type SQUID gate on the right side of FIG. 1 is the maximum critical current Ic0 when the magnetic flux entering the gate is zero, and the critical current when the magnetic flux is Φ0. Icf.

The oscillation current IL of the ROS on the left side of FIG. 1, that is, the value I at which the input signal to the SQUID gate on the right side of FIG.
When G is exceeded, the magnetic flux .PHI.0 enters the SQUID loop of the gate during that time, so that the critical current of the gate becomes lower than the current at the operating point, and the gate switches to the voltage state (between TG in FIG. 2B). .

The oscillation current IL of the ROS on the left side of FIG. 1, that is, the value I at which the input signal to the SQUID gate on the right side of FIG.
When the value falls below G, the magnetic flux Φ from inside the SQUID loop of the gate
0 is released, the critical current returns, and the gate returns to the superconducting state again (FIG. 2).

The current IL is given by IRB-I0 (IR
B: the bias current of the ROS, and I0: the offset current corresponding to the maximum critical current of the ROS (FIG. 2A).
It is necessary to design the loop inductance of the SQUID gate so that G (the current level at which the magnetic flux Φ0 can enter the SQUID loop) is between IRB-I0 and IRB-Imin. In this case, in order to make the output cycle equal to the input cycle, the gate must be designed so that no magnetic flux enters the gate by more than Φ0 / 2.

As described above, the relationship between the input signal and the output signal of the SQUID device of this embodiment is as shown in FIG.
The output current is a square wave. Further, the duty (TG / T) of the output wave is somewhat shorter than the duty (TR / T) of the input wave. Thus, although the period T of the input signal does not change, the duty of the output wave changes according to the setting of IG.

The output current Iout is about the gate bias current, and the output voltage Vout is about the gap voltage (2.8 mV). The input signal is analog, but the output signal is a digital signal. Output current I
out is the drive current of the subsequent circuit. Non-latch type SQ
The UID gate functions as a so-called buffer amplifier.

In the above description, the reason why the non-latch type SQUID gate is used is that, in the case of the latch type SQUID gate, once the gate is switched, the bias current must be reduced to zero, and the gate corresponding to the oscillating current of RO or ROS. This is because the latch type SQUID gate is not suitable for reproducing the oscillation cycle of RO or ROS faithfully.

The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the claims of the present invention, and any device having the same function and effect can be realized by the present invention. It is included in the technical scope of the invention.

[0018] For example, in the above embodiment, the input stage side of the non-latching SQUID gate has been described an example of providing the R O S, not limited thereto, may be provided RO.

[0019]

As described above, according to the present invention having the above structure, RO or ROS can be set to the non-latch type SQUID.
By magnetic coupling with the D gate, RO or R
The oscillation output of the OS can be obtained by current.

[Brief description of the drawings]

FIG. 1 is an equivalent circuit diagram showing a configuration of a SQUID device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an operation of the SQUID device shown in FIG.

FIG. 3 is an equivalent circuit diagram showing a configuration of a conventional relaxation oscillator.

FIG. 4 is an equivalent circuit diagram showing a configuration of a conventional relaxation oscillation type SQUID.

[Explanation of symbols]

 Ls shunt inductance Rs shunt resistance

Claims (2)

(57) [Claims] 1. A relaxation oscillation circuit having one Josephson junction, a shunt inductor, and a shunt resistor, comprising: a SQUID loop having two Josephson junctions; and a non-latch type SQUID gate having a load resistance. An apparatus, wherein the shunt inductor and the SQUID loop are magnetically coupled from the non-latched SQUID gate.
S is characterized in that it is configured to obtain an oscillation output current.
QUID device. 2. A first SQUID loop having two Josephson junctions, a relaxation oscillation type SQUID having a shunt inductor and a shunt resistor, and a second SQUID loop having two Josephson junctions and a load resistance. non latch-type SQUID gate having, a SQUID device having a the said shunt inductor and said SQUID loop magnetically coupled, from the non-latching SQUID gate
S is characterized in that it is configured to obtain an oscillation output current.
QUID device.