Multi-level phase detector in a baseband phase locked loop

An apparatus, comprising:

• means for generating an oscillating signal, including a digitally-controlled oscillator that is controlled by a feedback signal;
• means for generating a plurality of frequency-divided signals, wherein each frequency-divided signal is phase shifted with respect to the other frequency-divided signals and is a frequency-divided version of the oscillating signal;
• means for generating a plurality of phase error signals representative of phase errors in a plurality of frequency-divided signals, including a phase detector;
• and
• means for generating the feedback signal, including
• a multi-level code generation circuit configured to generate a gain control signal responsive to the plurality of phase error signals and to a signal indicative of gain of the phase detector, and
• a digital filter configured to low-pass filter the gain control signal to obtain the feedback signal.

A method for controlling phase error in a phase-locked loop, comprising:

• generating a plurality of frequency-divided signals, wherein each frequency-divided signal is phase shifted with respect to the other frequency-divided signals and is a frequency-divided version of an oscillating signal received from a digitally-controlled oscillator;
• providing a plurality of phase error signals representative of phase errors in the plurality of frequency-divided signals;
• configuring a gain control signal responsive to the plurality of phase error signals and to a signal indicative of gain of a phase detector that generates the plurality of phase error signals;
• and
• controlling frequency of the oscillating signal by providing a filtered version of the gain control signal to the digitally-controlled oscillator.