An Ultra Low Phase Noise Frequency Synthesizer with Optical Output for 77 GHz Photonic Radar

This paper presents an ultra low phase noise frequency synthesizer with optical output for 77 GHz long range photonic radar. The system consist of an optoelectronic phase locked loop (OEPLL) using a mode locked laser (MLL) as reference clock, a frequency doubler for the upconversion to one half of the desired radar band, and an electrooptical (EO) modulator biased in the minimum point. The presented system achieves a channel spacing of 400 MHz in the frequency range from 74 GHz to 80 GHz. The phase noise after the optoelectronic (OE) conversion is better than -120 dBc/Hz at offset frequencies above 10 kHz.