Amplitude Response Curves of Frequency-Locked Rotations

This letter studies frequency-locked rotations in a phaselocked loop (PLL) circuit as FM demodulator. A rotation represents a desynchronized steady state in the PLL circuit and is regarded as another type of self-excited oscillations with natural rotation frequencies. The rotation frequency can be locked at driving frequencies of modulation signals. This letter shows response curves for harmonic amplitude of frequencylocked rotations. They have several different features from response curves of van der Pol oscillator. key words: phase-locked loop, frequency entrainment, rotation, response curve