y = ammod(x,Fc,Fs)
y = ammod(x,Fc,Fs,ini_phase)
y = ammod(x,Fc,Fs,ini_phase,carramp)
y = ammod(x,Fc,Fs) uses the message signal x to modulate a carrier signal with frequency Fc (Hz) using amplitude modulation. The carrier signal and x have sample frequency Fs (Hz). The modulated signal has zero initial phase and zero carrier amplitude, so the result is suppressed-carrier modulation.
Note: The x, Fc, and Fs input arguments must satisfy Fs > 2(Fc + BW), where BW is the bandwidth of the modulating signal x.
y = ammod(x,Fc,Fs,ini_phase) specifies the initial phase in the modulated signal y in radians.
y = ammod(x,Fc,Fs,ini_phase,carramp) performs transmitted-carrier modulation instead of suppressed-carrier modulation. The carrier amplitude is carramp.
The example below compares double-sideband and single-sideband amplitude modulation.
% Sample the signal 100 times per second, for 2 seconds. Fs = 100; t = [0:2*Fs+1]'/Fs; Fc = 10; % Carrier frequency x = sin(2*pi*t); % Sinusoidal signal % Modulate x using single- and double-sideband AM. ydouble = ammod(x,Fc,Fs); ysingle = ssbmod(x,Fc,Fs); % Compute spectra of both modulated signals. zdouble = fft(ydouble); zdouble = abs(zdouble(1:length(zdouble)/2+1)); frqdouble = [0:length(zdouble)-1]*Fs/length(zdouble)/2; zsingle = fft(ysingle); zsingle = abs(zsingle(1:length(zsingle)/2+1)); frqsingle = [0:length(zsingle)-1]*Fs/length(zsingle)/2; % Plot spectra of both modulated signals. figure; subplot(2,1,1); plot(frqdouble,zdouble); title('Spectrum of double-sideband signal'); subplot(2,1,2); plot(frqsingle,zsingle); title('Spectrum of single-sideband signal');