In-situ phase noise compensation for phononic frequency combs

A method of improving the stability of a phononic frequency comb enhanced clock, comprising:

• generating a drive signal;
• splitting the drive signal into a first portion and a second portion;
• generating a phononic frequency comb in response to the first portion of the drive signal;
• dividing phase modulation (PM) noise of an mth tooth of the phononic frequency comb by amplitude modulation (AM) noise of the drive signal to compute a filter function, wherein the mth tooth has highest AM/PM noise conversion;
• and
• applying the filter function to a real-time demodulated AM noise;
• and
• correcting phase of an nth tooth of the phononic frequency comb in response to the filter function, wherein the nth tooth of the phononic frequency comb is least sensitive to frequency changes of the drive signal.

A system for a phononic frequency comb enhanced clock, comprising:

• a first oscillator for generating a drive signal;
• a nonlinear resonator for generating a phononic frequency comb in response to the drive signal;
• a second oscillator for selecting and correcting an nth tooth of the phononic frequency comb;
• a transfer function circuit, comprising:
• a first circuit for measuring the phase noise of an mth tooth of the phononic frequency comb and the amplitude noise of the drive signal to reduce phase noise caused by AM-PM cross-correlated noise on said nth tooth;
• and
• a second circuit for periodically updating a filter function using an uncorrected relative noiser tooth.

A phononic frequency comb enhanced oscillator comprising:

• a first oscillator for generating a drive signal;
• a signal splitter for splitting the drive signal into a first signal and a second signal;
• a nonlinear resonator responsive to the first signal for producing a phononic frequency comb;
• a phase locked loop (PLL) and a second oscillator, the phase locked loop being configured to lock the second oscillator to a first tooth of the phononic frequency comb, wherein the first tooth is the least sensitive to frequency changes of the first signal compared to other teeth of the phononic frequency comb;
• an AM-PM noise correction circuit including at least an amplitude detector and a phase shifter, the amplitude detector being configured to use a periodic measurement of an AM noise of the second signal and a PM noise of a second tooth of the phononic frequency comb for calculating and storing filter coefficients for an AM to PM transfer function, and to apply the transfer function to a current AM noise of the second signal to generate a PM noise correction signal that causes the phase shifter to produce an output signal of the AM-PM noise correction circuit that is equal to an output of the second oscillator with a phase corrected by the PM noise correction signal.

A phononic frequency comb enhanced oscillator comprising:

• a first oscillator for generating a drive signal;
• a signal splitter for splitting the drive signal into a first signal and a second signal;
• a nonlinear resonator responsive to the first signal for producing a phononic frequency comb;
• an AM-PM noise correction circuit including at least an amplitude detector and a phase shifter, the amplitude detector being configured to use a periodic measurement of an AM noise of the second signal and a PM noise of a second tooth of the phononic frequency comb for calculating and storing filter coefficients for an AM to PM transfer function, and to apply the transfer function to a current AM noise of the second signal to generate a PM noise correction signal that causes the phase shifter to produce a corrected phononic frequency comb equal to said phononic frequency comb having a phase corrected by the PM noise correction signal;
• a phase locked loop (PLL) and a second oscillator, the phase locked loop being configured to lock the second oscillator to a first tooth of said corrected phononic frequency comb, wherein the first tooth is the least sensitive to frequency changes of the first signal compared to other teeth of the corrected phononic frequency comb.