Frequency acquisition system

A frequency acquisition system for a tunable oscillator comprising:

• a frequency-locked loop circuit including a frequency detector responsive to the frequency of an output signal of a tunable oscillator and the frequency of a first reference signal, to provide a digital output signal representative of a difference in frequency between said output signal and the first reference signal;
• a drift compensation loop circuit including a phase detector responsive to the phase of the output signal of the tunable oscillator and the phase of a second reference signal to provide a second output signal representative of a difference in phase between said output signal and the second reference signal;
• a loop filter, responsive to said second output signal representative of the difference in phase, for providing a fine control signal to a fine control of the tunable oscillator to drive the frequency of the output signal of the tunable oscillator toward the frequency of said second reference signal;
• and
• an accumulator circuit for digitally storing the present state of either the fine control signal or the digital output and for providing a coarse control signal to a coarse control of the tunable oscillator to update the tunable oscillator to drive the frequency of the output signal of the tunable oscillator towards the frequency of the second reference signal.