Patent ID: 10496040

Abstract:
A digital synthesizer includes a ramp generator that generates a signal of frequency control words, FCW, that describes a desired frequency modulated continuous wave; a digitally controlled oscillator, DCO, that receives the FCW signal and outputs a DCO signal; and a feedback loop that includes a dual time-to-digital converter, TDC, circuit to measure a delay between a representation of the DCO signal and a reference signal. The TDC circuit comprises a medium-resolution TDC circuit coupled to a fine-resolution TDC circuit; and a phase comparator coupled to the ramp generator that compares a phase of the FCW signal output from the ramp generator and a signal fed back from the DCO via the feedback loop and output a N-bit oscillator control signal. The medium-resolution TDC circuit comprises a plurality of individual delay cells, where each of the plurality of individual delay cells is coupled to a respective individual fine-resolution TDC circuit.