Ultra-low-noise regenerative frequency divider for high-spectral-purity RF signal generation

We implement an ultra-low-noise frequency divider chain from 8 GHz to 5 MHz that utilizes custom-built regenerative frequency divide-by-2 circuits. The single-sideband (SSB) residual phase-noise of this regenerative divider at 5 MHz output is -163 dBc/Hz at 10 Hz offset frequency. This level is achieved with custom-built mixers that use 2N2222A bipolar junction transistors in a conventional double-balanced diode ring. We report absolute phase-noise of radio-frequency (RF) signals at 10 MHz and 5 MHz obtained by dividing an 8 GHz signal generated from ultra-stable optical comb-based frequency division. The absolute SSB phase-noise for a 10 MHz and 5 MHz signal at 1 Hz offset is -143 dBc/Hz and -150 dBc/Hz, and at 100 kHz offset is -174 dBc/Hz and -177 dBc/Hz, respectively