demod - Demodulation for communications simulation

amdsb-sc

or

am

Amplitude demodulation, double sideband, suppressed carrier. Multiplies y by a sinusoid of frequency fc and applies a fifth-order Butterworth lowpass filter using filtfilt.

x = y.*cos(2*pi*fc*t);

[b,a] = butter(5,fc*2/fs);

x = filtfilt(b,a,x);

amdsb-tc

Amplitude demodulation, double sideband, transmitted carrier. Multiplies y by a sinusoid of frequency fc, and applies a fifth-order Butterworth lowpass filter using filtfilt.

x = y.*cos(2*pi*fc*t);

[b,a] = butter(5,fc*2/fs);

x = filtfilt(b,a,x);

If you specify opt, demod subtracts scalar opt from x. The default value for opt is 0.

amssb

Amplitude demodulation, single sideband. Multiplies y by a sinusoid of frequency fc and applies a fifth-order Butterworth lowpass filter using filtfilt.

x = y.*cos(2*pi*fc*t);

[b,a] = butter(5,fc*2/fs);

x = filtfilt(b,a,x);

fm

Frequency demodulation. Demodulates the FM waveform by modulating the Hilbert transform of y by a complex exponential of frequency -fc Hz and obtains the instantaneous frequency of the result.

pm

Phase demodulation. Demodulates the PM waveform by modulating the Hilbert transform of y by a complex exponential of frequency -fc Hz and obtains the instantaneous phase of the result.

ppm

Pulse-position demodulation. Finds the pulse positions of a pulse-position modulated signal y. For correct demodulation, the pulses cannot overlap. x is length length(t)*fc/fs.

pwm

Pulse-width demodulation. Finds the pulse widths of a pulse-width modulated signal y. demod returns in x a vector whose elements specify the width of each pulse in fractions of a period. The pulses in y should start at the beginning of each carrier period, that is, they should be left justified.

qam

Quadrature amplitude demodulation.

[x1,x2] = demod(y,fc,fs,'qam') multiplies y by a cosine and a sine of frequency fc and applies a fifth-order Butterworth lowpass filter using filtfilt.

x1 = y.*cos(2*pi*fc*t);

x2 = y.*sin(2*pi*fc*t);

[b,a] = butter(5,fc*2/fs);

x1 = filtfilt(b,a,x1);

x2 = filtfilt(b,a,x2);