US Patent 11002844 Radar system with internal ramp linearity measurement capability

A phase-locked loop (PLL) for a radar system includes an oscillator configured to have an output frequency and a multi-modulus divider (MMD) configured to implement successive frequency modulation ramps of the oscillator output frequency, each frequency modulation ramp beginning at a first frequency and ending at a second frequency. The PLL is operated by downmixing an output of the MMD to a frequency above zero Hertz, measuring the downmixed output of the MMD to generate a plurality of MMD output measurements for each frequency modulation ramp, and calculating the frequency of the MMD based on the plurality of MMD output measurements for each frequency modulation ramp.