  We report a photonic-based radio frequency (RF) arbitrary waveform generator
(AWG) using a soliton crystal micro-comb source with a free spectral range
(FSR) of 48.9 GHz. The comb source provides over 80 wavelengths, or channels,
that we use to successfully achieve arbitrary waveform shapes including square
waveforms with a tunable duty ratio ranging from 10% to 90%, sawtooth waveforms
with a tunable slope ratio of 0.2 to 1, and a symmetric concave quadratic chirp
waveform with an instantaneous frequency of sub GHz. We achieve good agreement
between theory and experiment, validating the effectiveness of this approach
towards realizing high-performance, broad bandwidth, nearly user-defined RF
waveform generation.
