Development of 1.3GHz H<iopmath latex="$T_{\rm c}$">T<SUB>c</SUB></iopmath> rf SQUID

A new H<iopmath latex="$T_{\rm c}$">T_c</iopmath> rf SQUID working at around 1.3GHz has been developed to avoid electromagnetic interference such as growing mobile communication jamming. This new system works in a frequency range from 1.23 to 1.42GHz (centred at 1.3GHz), which is not occupied by commercial communication. The sensor used in the 1.3GHz rf SQUID is made of a H<iopmath latex="$T_{\rm c}$">T_c</iopmath> coplanar superconducting resonator and a large-area H<iopmath latex="$T_{\rm c}$">T_c</iopmath> superconducting film concentrator. We have achieved in the 1.3GHz H<iopmath latex="$T_{\rm c}$">T_c</iopmath> rf SQUID system a minimal flux noise of 2.5<iopmath latex="$\times $">×</iopmath>10<iopmath latex="$^{-5}\Phi_{0}$">⁻⁵Φ₀</iopmath>/<iopmath latex="$\sqrt {\rm Hz}$">(Hz)^1/2</iopmath> and a magnetic field sensitivity of 38fT/<iopmath latex="$\sqrt {\rm Hz}$">(Hz)^1/2</iopmath> in white noise range, respectively. The effective area of the concentrator fabricated on a 15<iopmath latex="$\times $">×</iopmath>15mm² substrate is 1.35mm². It is shown that the 1.3GHz rf SQUID system has a high field sensitivity. Design and implementation of 1.3GHz H<iopmath latex="$T_{\rm c}$">T_c</iopmath> rf SQUID offers a promising direction of rf SQUID development for higher working frequency ranges.