RF Josephson Arbitrary Waveform Synthesizer With Integrated Superconducting Diplexers

We present the design and characterization of a broadband RF Josephson arbitrary waveform synthesizer (RF-JAWS) with a series array of 4500 Josephson junctions (JJs) and integrated low-pass/high-pass five-pole superconducting diplexers. The integrated diplexers enable broadband filtering of the feedthrough signal components in the drive-current pulses with decade-wide instantaneous bandwidth. The diplexers have at least 30 GHz passband with less than 0.8 dB insertion loss. The JJ array is driven with a delta-sigma pulse sequence that encodes 10 kHz and 1.005 GHz tones, and generates an open-circuit voltage of 22 mV rms (−26.18 dBm available power assuming a 50
$\mathrm{\Omega }$
Thevenin equivalent source) at 1.005 GHz—a 25% increase compared to the state of the art. The drive current pulses undergo a three-step equalization to compensate for the linear distortion of the room-temperature electronics, the on-chip diplexers, and the remaining on- and off-chip components. The measured parasitic feedthrough voltages at 1.005 GHz are around −33 dBc, and their effect on the quantum locking ranges (QLRs) is quantified by measurements. The results demonstrated in this article show a significant step toward a broadband, integrated, quantum-based microwave voltage source with useful power above −30 dBm.