5.3. 1 Amplitude modulation and demodulation The product of signal x(t)and the carrier is equivalent in frequency domain to a process of shifting the spectrum of x(t to the position of carrier frequency fo (Fig. 5. 14(b)), that is, the AM process is a process of frequency-shifting Sinusoidal signal as the modulating signal Let the modulating signal x t=As sino t, and the carrier signal y(t=Ac sin ot The modulated Signal is then xm=x()·y()=AsmO,t· A sim o t(625.3.1 Amplitude modulation and demodulation The product of signal x(t) and the carrier is equivalent in frequency domain to a process of shifting the spectrum of x(t) to the position of carrier frequency f0 (Fig. 5.14(b)), that is, the AM process is a process of frequency-shifting. ◼Sinusoidal signal as the modulating signal Let the modulating signal x(t)=As sinωs t , and the carrier signal y(t)= Ac sin ωc t. The modulated signal is then x x(t) y(t) A t A t m s s c c =  = sin  sin (5.26)