376 results about "Digital controlled oscillator" patented technology

A digital phase locked loop with fast locking capability includes a digitally controlled oscillator for producing an output signal phase locked to an input reference clock, a phase detector for measuring the phase difference between said input reference clock and a feedback clock, and a loop filter for producing a control signal for the digitally controlled oscillator The loop filter includes a proportional circuit for developing a first signal proportional to said phase difference, an integrator for developing a second integrated signal from said first signal, an adder for adding said first and second signals to develop said control signal, and a weighting circuit, preferably a linear multiplier, for selectively adding extra weight to the first signal at an input to the integrator to shorten the locking time of the phase locked loop in a fast locking mode and to rapidly achieve a stable frequency in holdover mode.

A clock recovery circuit for recovering clock signals from one of a plurality of input reference signals, includes an acquisition phase locked loop (PLL) for each input. The acquisition PLL having phase comparator for comparing the phase of an input signal to a feedback signal, and first and second digital controlled oscillators (DCOs) receiving an input from the phase comparator. The first DCO of the acquisition PLL is in a feedback loop to supply an input to the phase comparator and the second DCO of the acquisition PLL has a control input to introduce a phase offset therein relative to said the DCO of the acquisition PLL and provides an output for the acquisition PLL. An output PLL has a phase comparator selectively connectable to the output of each of the acquisition PLLs. The output PLL has a first DCO providing an output for the circuit and a second DCO in a feedback loop providing a feedback signal to the phase comparator of the output PLL. The second DCO of the output PLL has a control input to introduce a phase offset therein relative to the first DCO of the output PLL. A control unit for sets the phase of the second DCO of the acquisition circuit and the second DCO of the output PLL to a common value during changeover from one input to another to avoid an instantaneous phase error upon switching reference signals.