High linearity superconducting radio frequency magnetic field detector

摘要

A superconducting quantum interference devices (SQUID) comprises a superconducting inductive loop with at least two Josephson junction, whereby a magnetic flux coupled into the inductive loop produces a modulated response up through radio frequencies. Series and parallel arrays of SQUIDs can increase the dynamic range, output, and linearity, while maintaining bandwidth. Several approaches to achieving a linear triangle-wave transfer function are presented, including harmonic superposition of SQUID cells, differential serial arrays with magnetic frustration, and a novel bi-SQUID cell comprised of a nonlinear Josephson inductance shunting the linear coupling inductance. Total harmonic distortion of less than −120 dB can be achieved in optimum cases.

主权项

1. A broadband linear flux-to-voltage converter, comprising:
a superconducting quantum interference device (SQUID) comprising: at least two Josephson junctions, each being biased by a DC current bias above a respective critical current of each of the at least two Josephson junctions, connected to form an inductive loop, the inductive loop being adapted to couple to a magnetic flux external to the SQUID, the inductive loop being configured to produce a voltage across one of the at least two Josephson junctions, the voltage having a non-linear response to the magnetic flux; and at least one unbiased Josephson junction connected in parallel with the inductive loop, the at least one unbiased Josephson junction being configured to increase a linearity of the voltage in response to the magnetic flux as compared to the inductive loop absent the at least one unbiased Josephson junction; and an output port configured to convey a signal corresponding to the voltage.