5. 3 Modulation and demodulation Modulation is a process of controlling or changing a parameter(amplitude, frequency, or phase)of a high-frequency oscillation by use of a measurand, usually a low-frequency signal >Controlled parameter is the amplitude of the high frequency oscillations: amplitude modulation or AM Frequency varied with the measurand frequency modulation, or FM >Controlled parameter is the phase of the oscillations: phase modulation, or PM5.3 Modulation and demodulation Modulation is a process of controlling or changing a parameter (amplitude, frequency, or phase) of a high-frequency oscillation by use of a measurand, usually a low-frequency signal. ➢Controlled parameter is the amplitude of the high frequency oscillations: amplitude modulation, or AM. ➢Frequency varied with the measurand: frequency modulation, or FM. ➢Controlled parameter is the phase of the oscillations: phase modulation, or PM