# ammod

Amplitude modulation

## Syntax

`y = ammod(x,Fc,Fs)y = ammod(x,Fc,Fs,ini_phase)y = ammod(x,Fc,Fs,ini_phase,carramp)`

## Description

`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`.

## Examples

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');```

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