US Patent 11405043 Phase calibration with half-rate clock for injection-locking oscillators

A clock generation circuit has an injection-locked oscillator, a frequency doubler circuit, low pass filters and a calibration circuit. The injection-locked oscillator has an input coupled to a half-rate clock signal. The frequency doubler circuit has inputs coupled to outputs of the injection-locked oscillator. Each of the low pass filters has an input coupled to one of a plurality of outputs of the frequency doubler circuit. The calibration circuit includes comparison logic that receives outputs of the low pass filters. The calibration circuit has an output coupled to a control input of a source of a supply current in the injection-locked oscillator. In one example, the source of the supply current is a current digital to analog converter.