Low crest factor multitone waveform synthesis with the AC Josephson voltage standard

Minimizing the crest factor of a multitone waveform helps to increase the signal to noise ratio in the measurement and decrease the nonlinear distortions. This paper uses the ac Josephson voltage standard to synthesize multitone waveforms and the L∞ algorithm to optimize the harmonic phases and thus to minimize the crest factor. In the optimization, both random and Schroeder harmonic phases are adopted as initial phases for the algorithm. With the crest factor minimized, the operating margin is increased significantly and the maximum output tone amplitude is doubled from 400 μVrms to 800 μVrms for the multitone waveform composed of 200 continuous harmonics.