Abstract
To make the experimental setup of the Josephson arbitrary waveform synthesizer less complex by reducing the number of RF cables between room and cryogenic temperature, we developed on-chip RF power dividers. By integration of these components, we can eventually increase the number of Josephson junctions operated by one single pulse-pattern generator channel, and thus reduce the costs of the setup. At Physikalisch-Technische Bundesanstalt, we designed, fabricated, and investigated the performance of two different RF power dividers types: the serial–parallel and the Wilkinson power divider. Spectrally pure sinusoidal waveforms were successfully synthesized with both types of power dividers. With the Wilkinson power divider, we obtained 17.55 mV (rms) at a clock frequency of 15 GHz combined with a test array of 1000 Josephson junctions. As for the serial–parallel power divider combined with a test array of 2000 Josephson junctions, we synthesized rms output voltages of 19.0 mV.
Highlights
T HE Josephson arbitrary waveform synthesizer (JAWS) is based on a series array of nonhysteretic SNS Josephson junctions (JJs) (S: superconducting, N: normal metal) driven by a high-speed digital sequence of short current pulses from a commercial pulse-pattern generator (PPG), in which the corresponding waveform is encoded by ΣΔ analog-to-digital conversion
Our results show that without the pulse input all JJs on the arrays were properly biased at 4 K
The array size was here limited to 1000 JJs (Wilkinson power divider: 2 × 500 JJs) and 2000 JJs, respectively, to better compare the performance of the power dividers
Summary
T HE Josephson arbitrary waveform synthesizer (JAWS) is based on a series array of nonhysteretic SNS Josephson junctions (JJs) (S: superconducting, N: normal metal) driven by a high-speed digital sequence of short current pulses from a commercial pulse-pattern generator (PPG), in which the corresponding waveform is encoded by ΣΔ analog-to-digital conversion. These pulse-driven series arrays operated at 4 K enable spectrally pure ac voltages to be synthesized in a wide frequency range from dc up to MHz [1]–[3].
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