Phase-locked loop frequency tracking device including a direct digital synthesizer

A method of producing a loop output which tracks the frequency of an input carrier signal comprising the steps of:

• applying the input carrier signal to a phase detector;
• applying an output of the phase detector to a narrow band VCO;
• applying an output of the VCO to a direct digital synthesizer;
• and
• using an output of the direct digital synthesizer as the loop output and as the second input to the phase detector.

A method of generating an output signal which tracks the frequency of an input signal comprising the steps of:

• comparing the phase of an input signal with the phase of a return signal;
• generating a magnitude signal representative of the comparison;
• applying the magnitude signal to an input of a VCO to generate an oscillating signal having a frequency indicative of the comparison;
• generating the input signal tracking output signal by using the oscillating signal as a frequency clock signal input to a signal generator;
• and
• employing the input signal tracking output signal as the return signal.