The invention is entitled RF frequency synthesis based on offset optical frequency combs in ring resonators. The invention discloses an optical frequency comb generator device. In one implementation,the optical frequency comb generator device comprises a bus waveguide, at least a first optical ring resonator optically coupled to the bus waveguide, and at least a first grating located on the firstoptical ring resonator opposite from the bus waveguide. The first optical ring resonator and the first grating are configured to generate counter-propagating optical frequency combs that are offset from each other at a controllable bandwidth.