A SQUID gradiometer module with wire-wound pickup antenna and integrated voltage feedback circuit

► A dual-loop SQUID configuration was employed to suppress the external magnetic disturbances. ► An voltage feedback circuit was integrated on one SQUID chip for suppression of the preamplifier noise contribution. ► A compact gradiometer module was constructed to measure biomagnetic signals. ► The results were meaningful for the SQUID bootstrap circuit (SBC) in multi-channel systems.