Extended range phaselocked loop

A phaselocked loop circuit having a comparator adapted to generate a control signal proportional to a phase difference between signals at a pair of inputs thereof to which are respectively coupled an independent input signal and a local input signal dependently related to an output signal of a controllable oscillator, and filter means coupling the control signal to the oscillator for acquisition at a predetermined rate, the circuit comprising:

• means for generating a threshold signal in predetermined phase relation with the independent signal;
• delay means operatively connected to the oscillator for generating a plurality of sequential signals in successively delayed phase relation with the oscillator output signal;
• detector means responsive to coincidence of the threshold signal and the delayed signals for generating a phase error signal indicative of a predetermined phase difference between the independent and local input signals;
• and
• commutator means controllably responsive to the phase error signal for selecting individual ones of the delayed signals at a predetermined phase delay thereof and applying the delayed signals to the local signal input for generating an enhanced control signal proportional to an apparent increased phase difference between the independent and local input signals, thereby increasing the rate of acquisition to pre-empt concurrent cycle slipping of the controllable oscillator.