AC coupling technique for Josephson waveform synthesis

Abstract

We demonstrate a new bias technique that uses low-pass and high-pass filters to separate the current paths of the sampling and signal frequencies in a Josephson waveform synthesizer.This technique enables the output voltage of the array to be directly grounded by removing the low-frequency common mode signal that previously prevented direct measurement of the array voltage with low-impedance instruments.We directly measure the harmonic spectra of 1 kFIz and 50 kEFz synthesized sine waves.We also use a thermal transfer standard to compare the rms voltages of synthesized sine waves at frequencies from 1 MIZ to 50 IrHz.Finally, we describe a new circuit that should enable a significant increase in output voltage by allowing several distributed arrays to be biased in parallel at high frequency, while combining their low frequency output voltages in series.