US 6,388,440 B1 · Magnetic field bias adjusting device for SQUID modulation drive circuit achieving easy adjustment

Abstract

A modulation current at a predetermined frequency f is applied from an AC source to a flux locked loop for maintaining magnetic flux supplied to a SQUID at a constant value. An output voltage is picked out from the SQUID in this state to which a predetermined bias current is being applied from a current and field bias application circuit, and the picked out voltage passed through a filter and a rectifier is monitored by a voltage monitor. The filter picks out a frequency component of 80 kHz which is twice as high as the frequency component f, 40 kHz, applied from the AC source, and maximizes it. In this way, a method and a device for easily adjusting magnetic field bias in a modulation drive circuit for a SQUID can be provided.

Claims12

Dependent claims

A method of adjusting magnetic field bias in a modulation drive circuit for a SQUID, comprising the steps of:

applying an AC bias modulation signal at a predetermined first frequency to a flux located loop maintaining magnetic flux supplied to said SQUID at a constant value;
applying an alternating current of a rectangular wave having a predetermined second frequency to a coil adjacent to said SQUID to adjust the magnetic field bias;
picking out an output voltage from said SQUID to which said AC bias modulation signal at the predetermined first frequency and said alternating current of the rectangular wave having the predetermined second frequency are applied;
and
picking out said output voltage such that a frequency component of the voltage which is twice as high as said first frequency is a maximum frequency.

2 more elements

Dependencies are inferred from the claim text.

Magnetic field bias adjusting device for SQUID modulation drive circuit achieving easy adjustment

Life of this patent

Magnetic field bias adjusting device for SQUID modulation drive circuit achieving easy adjustment

Life of this patent

Abstract

Claims12