Phase startable clock device having improved stability

Abstract

A phase stable clock circuit includes a phase gate having track-and-hold (T/H) circuits with each T/H circuit receiving a phase shifted continuous sinusoidal signal of predetermined phase and a control input signal to hold, at a selected time during the signal epoch of the respective sinusoidal signals, phase values of the sinusoidal signals. The respective phase values are coupled to an infinite track-and-hold circuit to generate replicas of the phase values. The phase values and the replica phase values are coupled to respective multiplexers that selectively couple the phase values to multipliers during a first time period and replica phase values during a second time period. The output of each multiplexer is coupled to a multiplier that receives one of the phase shifted continuous sinusoidal signals. The output of the multipliers are summed in a summing circuit to generate an output signal with a predetermined stable startup phase relative to the transition. The use of the infinite track-and-hold improves the long-term stability of the output signal from the summing circuit.