High-resolution and agile frequency measurement

A method for generating a frequency estimate of an output signal, the method comprising:

• determining a clock cycle count associated with the output signal, the clock cycle count based on a reference clock signal,
• generating a cycle count based frequency estimation of the output signal using the clock cycle count, the cycle count based frequency estimation including an integer frequency component and a fractional frequency component;
• generating a fractional frequency estimation of the output signal based on the reference clock signal and a plurality of time-to-digital conversion phase samples of the output signal;
• and
• generating the frequency estimate of the output signal using the cycle count based frequency estimation within a range and a frequency error determined from the fractional frequency estimation, wherein the plurality of time-to-digital conversion phase samples and the cycle count based frequency estimation use a same number of reference clock cycles of the reference clock signal.

A digital frequency synthesizer, comprising:

• a reference signal generator configured to generate a reference clock signal;
• a time-to-digital-converter (TDC), the TDC configured to receive an output signal and the reference clock signal, and generate a plurality of time-to-digital conversion phase samples based on the output signal and the reference clock signal;
• a cycle counter (CC), the CC configured to receive the output signal and the reference clock signal, and generate a clock cycle count based on the output signal and the reference clock signal;
• and
• a frequency estimator, the frequency estimator configured to:
• generate a cycle count based frequency estimation of the output signal based on the reference clock signal and the clock cycle count;
• generate a fractional frequency estimation of the output signal based on the reference clock signal and a plurality of time-to-digital conversion phase samples of the output signal;
• and
• generate a frequency estimate of the output signal using the cycle count based frequency estimation within a range and a frequency error determined from the fractional frequency estimation, wherein the plurality of time-to-digital conversion phase samples and the cycle count based frequency estimation use a same number of reference clock cycles of the reference clock signal.