RF instrumentation based on superconducting quantum interference

The application of the superconducting quantum interference device (SQUID) to RF measurements is reviewed. The SQUID can be adapted as a broadband standard of RF current, power and attenuation and may be used as the sensor for an extremely good regulator of RF current. Bandwidths of dc to 100 MHz and dc to 1 GHz have been demonstrated with a power sensitivity of ∼-100 dBm (100-MHz bandwidth, 0.1-dB resolution). In the measurement of attenuation 0.002 dB uncertainty can be achieved with similar bandwidths.