We have developed a matching scheme for the operation of a rf superconducting quantum interference device (SQUID) with a lumped-element tank circuit at pumping frequencies up to 1 GHz. This conventional LC
resonant circuit is inductively coupled to a matching coil, which is connected to the 50 Ω transmission line. We characterized the flux noise of high-temperature rf SQUIDs at resonant frequencies between 221 and 950 MHz. At about 900 MHz, we obtained the white flux noise of about 14.6 μϕ0/
with a SQUID inductance LS = 150 pH
and 20 μϕ0/
with LS = 260 pH.
Several of such tank circuits can be driven in parallel or in series with only one cable. © 1998 American Institute of Physics.