Abstract：The Josephson arbitrary waveform synthesizer (JAWS) is being developed as ac Josephson Voltage Standard (acJVS). It can provide low frequency ac waveforms with a calculable rms voltage, as well as stable arbitrary dc voltages. The superconducting chips are the core part of the JAWS system. We present the development results of JAWS chips in National Institute of Metrology (NIM, China). In the chip design, a Josephson junction array consisted by 4000 2-stack Nb/NbxSi1–x/Nb junctions, so there are totally 8000 junctions in serially connection. The junctions are with sharp critical currents. Tapered coplanar waveguide was applicated in the chip. An oversampled delta-sigma pulse modulation system is used to generate a 14.4 Gbps bitstream to drive this JJ array. This array is capable to provide a 150 mV rms 1 kHz ac voltage output. The highest harmonic is the second, which is suppressed by at least 105 dBc.
2025, Vol. 46 
