JPH07162045A - DC driven superconducting quantum interference device - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize a dc SQUID that is not affected by fluctuations in the bias current and that is simple in connection with the drive circuit. [Structure] The bias line 8 for supplying the bias current to the dc SQUID is inserted between the two Josephson junctions 1 and taken out from the center of the damping resistor 3, so that the bias line 8 can be formed without forming a loop. Make wiring. [Effect] Wiring of the bias line is possible without forming a loop, and fluctuations in the bias current do not affect as magnetic flux noise. Further, since all the pads can be arranged on the Josephson junction side, the connection with the drive circuit is simple and the mounting is easy.

Description

Detailed Description of the Invention

[0001]

This invention relates to a high-sensitivity electromagnetic sensor,
The present invention relates to a dc SQUID applied to an ammeter, a displacement meter, a high frequency signal amplifier, or the like.

[0002]

2. Description of the Related Art FIGS. 5 and 7 are plan views showing the structure of a conventional dc SQUID, and FIGS. 6 and 8 are equivalent circuit diagrams thereof. 1 is a Josephson junction, 2 is a shunt resistor, 3 is a damping resistor, 4 is a washer coil, 5 is an input coil, 6 is a feedback modulation coil, 7 is a bias line, 8 is a voltage detection line, 9 is a pad, and 10 is a bias. Current supply circuit, 11 is feedback modulation current supply circuit, 12 is feedback circuit, 1
3 is a voltage amplification circuit, 14 is a drive circuit, and 15 is a connection line. 6 and 8 both have a structure in which a bias line 7 for supplying a bias current is inserted from the center of the washer coil 4 and taken out from between two Josephson junctions 1. The bias current is supplied from the bias current supply circuit 10 to the dc SQUID through the bias line 7.
The voltage signal of dc SQUID is amplified by the voltage amplifier circuit 13 and transmitted to the feedback circuit 12. A feedback modulation current corresponding to the magnitude of the voltage signal is sent from the feedback modulation current supply circuit 11 to the feedback modulation coil 6 to generate dc as feedback modulation magnetic flux.
Returned to SQUID. In FIG. 5, all the pads 9 for connecting to the drive circuit 14 including the bias current supply circuit 10, the feedback modulation current circuit 11 and the voltage amplification circuit 13 are arranged on the Josephson junction 1 side. With this configuration, a loop composed of the bias line 7 is formed around the washer coil 4, and the magnetic flux generated from the bias line 7 intersects with the washer coil 4 when the bias current flows. In FIG. 7, two pads connected to the bias line 7 are separately arranged on the washer coil 4 side and the Josephson junction 1 side, and the bias line 7 does not form a loop.

[0003]

[Problems to be Solved by the Invention] Conventional dc SQUI
In D, as shown in FIG. 5, when the structure in which all the pads are arranged on the Josephson junction side in consideration of the connection with the driving circuit, the bias current loop directly affects the fluctuation of the bias current as a magnetic flux noise. was there. Further, as shown in FIG. 7, when the structure of the loop of the bias line is not formed, the position of the pad for the bias current has to be divided into two hands, which causes a problem that the connection with the drive circuit becomes complicated. It was

[0004]

In order to solve the above problems, a bias line is inserted between the two Josephson junctions and taken out from the center of the damping resistor.

[0005]

With the dc SQUID constructed as described above, the bias line can be wired without forming a loop. In addition, all pads can be placed on the Josephson junction side.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention dc S
It is the figure which showed the structure of QUID. 2 shows an equivalent circuit diagram thereof.

1 is a Josephson junction, 2 is a shunt resistor, 3 is a damping resistor, 4 is a washer coil, 5 is an input coil, 6 is a feedback modulation coil, 7 is a bias line, 8 is a voltage detection line, and 9 is a pad. Reference numeral 10 is a bias current supply circuit, 11 is a feedback modulation current supply circuit, 12 is a feedback circuit, 13 is a voltage amplification circuit, 14 is a drive circuit, and 15 is a connection line. A bias line 7 for supplying a bias current is inserted between the two Josephson junctions 1 and taken out from the center of the damping resistor 3.

The bias line 7 also serves as a voltage detection line 8 for extracting the SQUID voltage signal. Drive circuit 1
All the pads connected to 4 are arranged on the Josephson junction side. The bias current is supplied from the bias current supply circuit 10 to the dc SQUID through the bias line 7. The voltage signal of the dc SQUID is the voltage amplification circuit 13
Is amplified by and is transmitted to the feedback circuit 12. A feedback modulation current corresponding to the magnitude of the voltage signal is sent from the feedback modulation current supply circuit 11 to the feedback modulation coil 6 and fed back to the dc SQUID as feedback modulation magnetic flux. Since this configuration does not form a loop composed of the bias line 7 around the washer coil 4, the fluctuation of the bias current does not affect the magnetic flux noise.

FIG. 3 shows a second embodiment of the present invention dc S
It is the figure which showed the structure of QUID. Further, FIG. 4 shows an equivalent circuit diagram thereof. The bias line 7 is inserted between the two Josephson junctions 1 and taken out from the center of the damping resistor 3. One of the two voltage detection lines 8 is taken out from the same position as the bias current line 7, and the other is taken out from one end of the damping resistor 3. All pads connected to the drive circuit 14 are arranged on the Josephson junction side.

[0010]

As described above, according to the present invention, d
In the S SQUID, the wiring of the bias line can be performed without forming a loop, and the fluctuation of the bias current does not affect the magnetic flux noise. Further, since all the pads can be arranged on the Josephson junction side, the connection with the drive circuit is simple and the mounting is easy.

[Brief description of drawings]

FIG. 1 is a plan view of a dc SQUID showing a first embodiment of the present invention and a connection diagram with a drive circuit.

FIG. 2 is an equivalent circuit diagram of a dc SQUID showing the first embodiment of the present invention. However, the input coil and the feedback modulation coil are omitted.

FIG. 3 is a plan view of a dc SQUID showing a second embodiment of the present invention and a connection diagram with a drive circuit.

FIG. 4 is an equivalent circuit diagram of a dc SQUID showing a second embodiment of the present invention. However, the input coil and the feedback modulation coil are omitted.

FIG. 5 is a plan view of a dc SQUID showing a first conventional example and a connection diagram with a drive circuit.

FIG. 6 is an equivalent circuit diagram of a dc SQUID showing a first conventional example. However, the input coil and the feedback modulation coil are omitted.

FIG. 7 is a plan view of a dc SQUID showing a second conventional example and a connection diagram with a drive circuit.

FIG. 8 is an equivalent circuit diagram of a dc SQUID showing a second conventional example. However, the input coil and the feedback modulation coil are omitted.

[Explanation of symbols]

 1 Josephson junction 2 ・ Shunt resistance 3 Damping resistance 4 Washer coil 5 Input coil 6 Feedback modulation coil 7 Bias line 8 Voltage detection line 9 Pad 10 Bias current supply circuit 11 Feedback modulation current supply circuit 12 Feedback circuit 13 Voltage amplification circuit 14 Drive Circuit 15 connection line

Claims (1)

[Claims] 1. A washer coil having two ends connected to each other.
A superconducting ring is formed by Josephson junctions, and a shunt resistor connected in parallel to the Josephson element,
A bias in a direct current driven superconducting quantum interference device (dc SQUID) made of a thin film, which includes a damping resistor connected to both ends of the washer coil, an input coil magnetically coupled to the washer coil, and a feedback modulation coil. A bias line, which is a wire for supplying a current, is inserted between the two Josephson junctions,
A dc SQUID having a structure of taking out from a central portion of the damping resistor.