Ultra-Low Phase Noise and Frequency Agile X-Band Frequency Synthesizer Based on a Phase Locked Optoelectronic Oscillator

Low noise microwave source is essential for many subjects, including radar, communication, test instrumentation, and sensing. Photonic-based optoelectronic oscillator (OEO) can address some challenges faced by electronic oscillators, including phase noise performance, and wideband frequency tunability. However, a scaling challenge for the OEO is the frequency control, including long-term stability, frequency resolution, frequency accuracy and frequency settling time. In this paper, an ultra-low phase noise and frequency agile X-band frequency synthesizer based a phase locked OEO and a direct digital synthesizer is proposed and experimentally demonstrated. Single-sideband (SSB) phase noise of -139 dBc/Hz at 10 kHz offset and frequency switching time of 176 ns are achieved.