Battery-Powered Wireless Flux-Locked Loop Circuit for Operating High-Tc SQUID

A battery-operated wireless flux-locked-loop (FLL) circuit for operating a high-Tc superconducting quantum interference device (SQUID) was developed and tested. This wireless battery-type FLL circuit consists of an FLL unit and a PC interface. A local area network with the TCP-IP protocol for wireless mode was used for communication between the PC interface and a controlling PC. The battery unit can power the FLL circuits for four hours. The FLL circuit had two bias modes: ac and dc. When the wireless-battery-type FLL circuit was implemented in a SQUID, the system noise generated by a wireless network became intrinsic high-Tc SQUID noise. Also, a 1/f noise was reduced in the case of the ac-bias-current mode. Consequently, the wireless-battery-type FLL circuit can operate a high-Tc SQUID with high sensitivity.