Josephson voltage standard using a biharmonic drive

A novel approach to a Josephson voltage standard is presented. It uses as the drive signal the combination of a 10-GHz signal and its second harmonic. The effect of this biharmonic drive is to enhance the constant-voltage step amplitudes with respect to those obtained with a single-frequency drive. The optimum operating conditions are discussed, and the first experimental results obtained with Josephson devices containing both single junctions and small arrays are reported.