The amplitudes of stepwise-approximated sine waves generated by programmable Josephson voltage standards (PJVS) are not intrinsically accurate because the transitions between the quantized voltages depend on numerous conditions. We have developed a method that ensures that the total rms output voltages of arbitrary ac waveforms synthesized by the PJVS are accurate and referenced to the quantized Josephson voltages. This is accomplished by digitizing the entire output waveform, utilizing the quantized voltages to correct digitizer gain, noise, and nonlinearity, and then utilizing measurements of the bandwidth, risetime, and harmonic content to precisely tune the bias parameters. Our goal is to develop an AC standard source for voltage metrology that can directly synthesize voltages with the accuracy expected of a quantum-based standard without the use of a thermal voltage converter.
Citation: IEEE Transactions on Instrumentation and Measurement
Pub Type: Journals
Digital-analog conversion, Josephson arrays, Quantization, Signal synthesis, Standards, Superconducting integrated circuits, Voltage measurement