Variable rate interpolation with numerically controlled oscillator

A method comprising:

• receiving a plurality of frequency control words in accordance with a variable clock signal;
• calculating, via a clock controller, a delay interval of the variable clock signal;
• accumulating the frequency control words in accordance with the delay interval to generate a phase word;
• converting the phase word to a waveform;
• calculating a timing drift from a ratio of an output sample rate to an input sample rate;
• and
• adjusting a length of the delay interval of the variable clock signal to reduce the calculated timing drift, wherein adjusting the length of the delay interval includes adjusting the length of the delay interval to a rate calculated from the calculated timing drift.

A numerically controlled oscillator comprising:

• a phase accumulator having a digital input module configured to receive a plurality of control words, a summation block configured to output a phase word representing an accumulation of the plurality of frequency control words, and a delay block configured to provide the accumulation of the plurality of frequency control words to the summation block;
• a clock configured to periodically output a variable clock signal in accordance with a delay interval, wherein the phase accumulator is configured to output the accumulation of frequency control words in response to receiving the clock signal;
• and
• a clock controller programmed to calculate a timing drift from a ratio of an output sample rate to an input sample rate and adjust a length of the delay interval to reduce the calculated timing drift, wherein the clock controller is programmed to adjust the length of the delay interval of the variable clock signal to a rate calculated from the calculated timing drift.