A 2–20-GHz Ultralow Phase Noise Signal Source Using a Microwave Oscillator Locked to a Mode-Locked Laser

In this article, we develop the theory of a special type optoelectronic phase-locked loop (PLL). The output signal PLL is in electrical domain and its reference oscillator, typically mode-locked laser, operates optical domain. uses balanced microwave phase detector (BOMPD). order to model PLL, nonlinear characteristic function gain BOMPD are derived analytically. Using results analysis, an using such developed. Based on theoretical broadband frequency synthesizer with programmable range from 2 20 GHz designed implemented. Phase noise measurements show that achieves integrated rms-jitter (1 kHz-100 MHz) less than 4 fs 5 typical value minimum 3 fs. This first reported wideband achieving sub-10-fs GHz. A comparison best-in-class laboratory-grade synthesizers shows lower any electronic for offset frequencies larger kHz.