Abstract

The precision electronic oscillator is paramount for providing a frequency reference, timing, and synchronization in advanced technologies ranging from test and measurement, to communication networks, radar, and microwave atomic clocks. Recently, optical frequency division (OFD) of cavity-stabilized lasers has demonstrated microwave signals [1] with significantly improved noise as compared to oven-controlled crystals oscillators [2-3]. Although exquisitely stable, signals derived via OFD are typically at a fixed frequency. In our work we employ the microwave harmonic spectrum derived via OFD as a time base for digital synthesis, demonstrating agile signals in the X-band with instabilities of 1 part in 10¹⁵. Optoelectronic multiplication of the agile X-band signals via high-speed photodetection [4] of a phase modulated and filtered CW laser allows for high-fidelity extension of synthesis to the W-band covering a frequency range 98 – 102 GHz. As seen in Fig. 1, using these techniques we demonstrate tunable signals with greater than a factor of 50 dB (70 dB) improvement in close-to-carrier noise as compared to state-of-the-art electronic and photonic X-band (W-band) synthesizers.

© 2015 IEEE