An agile radio-frequency source using internal linear sweeps of a direct digital synthesizer

Abstract: Agile rf sources are a common requirement for control systems in quantum science and technology platforms. The direct digital synthesizer (DDS) often fills this role by allowing programmable control of the rf signals. Due to limitations of the DDS architecture, implementing an agile rf source requires rapid and precisely-timed programming of discrete updates that restrict the source's agility. Here, we describe a microcontroller-based interface that exploits the DDS's internal linear sweep accumulator to perform both sequential linear sweeps, and standard discrete updates, at the ~10$\mu$s scale. This allows updates to the swept parameter as fast as every 8 ns with greatly reduced communication and memory overhead. We demonstrate the utility of this system by using it as the reference to an optical phase-locked-loop to implement rapid, adjustable laser frequency sweeps in a Rydberg Electromagnetically Induced Transparency spectroscopy measurement.