Abstract: The disclosed complex SQUID circuit achieves a high signal gain and high sensitivity for detecting a weak magnetic field. It is characterized by concentric loops of superconducting material, each loop incorporating preferably a pair of Josephson Junctions, the Josephson Junctions all aligned in a diameter generally transverse to the diameter defined by the connectors interconnecting the loops.

Abstract: The SQUID device consists of a loop of superconducting film material applied to the face of a substrate, the loop having a first width. A Josephson Junction is formed in the loop of the superconducting film material by pads of superconducting film material overlying one another and separated by a layer of insulating material. The pads have a second width larger than the first width. To increase the gain and improve the signal-to-noise ratio, the SQUID device may include a plurality of SQUID loops connected to one another in parallel. These loops may be overlie one another, or be adjacent to one another, or both, and may be either conventional SQUID loops or the improved SQUID loops with wide pads.