z = amdemod(y,Fc,Fs)
z = amdemod(y,Fc,Fs,ini_phase)
z = amdemod(y,Fc,Fs,ini_phase,carramp)
z = amdemod(y,Fc,Fs,ini_phase,carramp,num,den)
z = amdemod(y,Fc,Fs) demodulates
the amplitude modulated signal
y from a carrier
signal with frequency
Fc (Hz). The carrier signal
y have sample frequency
The modulated signal
y has zero initial phase and
zero carrier amplitude, so it represents suppressed carrier modulation.
The demodulation process uses the lowpass filter specified by
z = amdemod(y,Fc,Fs,ini_phase) specifies
the initial phase of the modulated signal in radians.
z = amdemod(y,Fc,Fs,ini_phase,carramp) demodulates
a signal that was created via transmitted carrier modulation instead
of suppressed carrier modulation.
carramp is the
carrier amplitude of the modulated signal.
z = amdemod(y,Fc,Fs,ini_phase,carramp,num,den) specifies
the numerator and denominator of the lowpass filter used in the demodulation.
Set the sample rate and carrier frequency.
fc = 10e3; fs = 80e3;
Generate a sinusoidal signal having a 0.01 s duration.
t = [0:1/fs:0.01]'; s = sin(2*pi*300*t)+2*sin(2*pi*600*t);
Create a lowpass filter.
[num,den] = butter(10,fc*2/fs);
Amplitude modulate the signal,
y = ammod(s,fc,fs);
Demodulate the received signal.
s1 = amdemod(y,fc,fs,0,0,num,den);
Plot the original and demodulated signals.
plot(t,s,'c',t,s1,'b--') legend('Original Signal','Demodulated Signal') xlabel('Time (s)') ylabel('Amplitude')
The demodulated signal is nearly identical to the original signal.