Using method of slowly changing amplitudes for analysing oscillations in phase-locked loops

The phase-locked loop has been found to be a very useful element in many types of communication systems. It is used in two fundamentally different ways [Gardner (1981), Encinas (1993)]: (1) For demodulation, where it is used to follow phase or frequency modulation of the input signal. (2) For tracking a carrier or synchronizing signal which may vary in frequency with time. The authors discuss stability loss criteria, loop oscillations and stationary loop oscillations.