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ammod

Amplitude modulation

Description

example

y = ammod(x,Fc,Fs) returns an amplitude modulated (AM) signal y, given the input message signal x, where the carrier signal has frequency Fc. The carrier signal and x have a sampling frequency Fs. The modulated signal has zero initial phase and zero carrier amplitude, so the result is suppressed-carrier modulation.

Note

The value of Fs must satisfy Fs ≥ 2Fc.

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 where carramp is the carrier amplitude of the modulated signal.

Examples

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Set the sample rate to 100 Hz. Create a time vector 100 seconds long.

fs = 100;
t = (0:1/fs:100)';

Set the carrier frequency to 10 Hz. Generate a sinusoidal signal.

fc = 10;
x = sin(2*pi*t);

Modulate x using single- and double-sideband AM.

ydouble = ammod(x,fc,fs);
ysingle = ssbmod(x,fc,fs);

Create a spectrum analyzer object to plot the spectra of the two signals. Plot the spectrum of the double-sideband signal.

sa = dsp.SpectrumAnalyzer('SampleRate',fs, ...
    'PlotAsTwoSidedSpectrum',false, ...
    'YLimits',[-60 40]);
step(sa,ydouble)

Plot the single-sideband spectrum.

step(sa,ysingle)

Input Arguments

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Input message signal, specified as a scalar, vector, matrix, or a 3-D array. Each element of x must be real.

Data Types: single | double

Carrier signal frequency in hertz (Hz), specified as a positive real scalar.

Data Types: single | double

Sampling frequency of carrier signal and input message signal in hertz (Hz), specified as a positive real scalar. To avoid aliasing, the value of Fs must satisfy Fs > 2(Fc + BW), where BW is the bandwidth of x.

Data Types: single | double

Initial phase of the modulated signal in radians, specified as a real scalar.

Data Types: single | double

Carrier amplitude of the modulated signal, specified as a real scalar.

Data Types: single | double

Output Arguments

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Amplitude modulated signal, returned as a scalar, vector, matrix, or 3-D array.

Introduced before R2006a