Apparatus for tracking the fundamental frequency of a signal with harmonic components stronger than the fundamental

A frequency-locked loop circuit comprising:

• a digitally controlled oscillator con figured to generate a first frequency;
• an auto-tuning low-pass filter that receives an input signal and outputs a reference frequency,
• a dropout detector configured to receive the reference frequency, and generate a dropout value;
• and
• a digital frequency iteration engine comprising:
• a first circuit configured to receive the first frequency and the reference frequency, and generate a number of first frequency cycles in one reference frequency cycle;
• and
• a second circuit configured to receive the number of first frequency cycles, and generate a second frequency based on a predetermined frequency multiplication factor, the dropout value, the determined number of first frequency cycles, the first frequency, and the reference frequency, wherein the predetermined frequency multiplication factor provides a target relationship between the first frequency and the reference frequency, and wherein a divider is configured to receive the first frequency from the digitally controlled oscillator, generate a third frequency, and transmit the third frequency to the dropout detector.

A frequency-locked loop circuit comprising:

• an auto-tuning low-pass filter that receives an input signal and outputs a reference frequency,
• a digitally controlled oscillator configured to generate a first frequency;
• and
• a digital frequency iteration engine comprising:
• a first circuit configured to receive the first frequency and the reference frequency, and generate a number of first frequency cycles in one reference frequency cycle;
• and
• a second circuit con figured to receive the number of first frequency cycles, and generate a second frequency based on a predetermined frequency multiplication factor, the determined number of first frequency cycles, the first frequency, and the reference frequency, wherein the predetermined frequency multiplication factor provides a target relationship between the first frequency and the reference frequency, and
• a counter con figured to receive the reference frequency and the first frequency, the counter coupled to the digital frequency iteration engine.

A frequency synthesizer comprising:

• a frequency-locked loop circuit comprising:
• a digitally controlled oscillator configured to generate a first frequency;
• an auto-tuning low-pass filter that receives an input signal and outputs a reference frequency,
• a dropout detector configured to receive the reference frequency and a first frequency, and generate a dropout value;
• and
• a digital frequency iteration engine comprising:
• a first circuit comprising a Gray-code counter, a Gray-to-binary converter, a first plurality of flip-flops, the first circuit configured to receive the first frequency and a reference frequency, and generate a number of first frequency cycles in one reference frequency cycle;
• and
• a second circuit comprising a multiplexor, a second plurality of flip-flops, and an estimation module, the second circuit configured to receive the number of first frequency cycles, and generate a second frequency based on a predetermined frequency multiplication factor, the dropout value, the determined number of first frequency cycles, the first frequency, and the reference frequency, wherein the predetermined frequency multiplication factor provides a target relationship between the first frequency and the reference frequency.