# señal QAM

Páginas: 4 (969 palabras) Publicado: 21 de septiembre de 2014
﻿LAB0RATORIO 3
Modulación digital PSK, QAM,QPSK

1.- MARCO TEÓRICO
Uso de las funciones modulate() y demod() de Matlab para la modulación.
Uso de las funciones fftshift() y fft()deMatlab para el espectro de frecuencia.
Revisar el manual de usuario de Matlab para mas detalles de estas funciones.
A continuación mostraremos brevemente el funcionamiento de alguna de ellas.Modulate():Modulation for communications simulation
Syntax
y = modulate(x,fc,fs,'method')
y = modulate(x,fc,fs,'method',opt)
[y,t] = modulate(x,fc,fs)
MODULATE Signal modulation forcommunications simulations.Y = MODULATE(X,Fc,Fs,METHOD,OPT) modulates the message signal X with a carrier frequency Fc and sampling frequency Fs, using the modulationscheme in METHOD. OPT is an extrasometimes optional parameter whosepurpose depends on the modulation scheme you choose.Fs must satisfy Fs > 2*Fc + BW, where BW is the bandwidth of themodulated signal.
METHOD MODULATION SCHEME'am', Amplitude modulation, double side-band, suppressed carrier'amdsb-sc' OPT not used.
'amdsb-tc' Amplitude modulation, double side-band, transmitted carrier,OPT is a scalar which issubtracted from X prior to multiplication by the carrier cosine. It defaults tomin(min(X)) so the offset message signal is positive andhas a minimum value of zero.
'amssb' Amplitude modulation, singleside-band .OPT not used.
'fm' Frequency modulationOPT is a scalar which specifies the constant of frequency modulation kf. kf = (Fc/Fs)*2*pi/max(max(abs(X))) by default for a maximum frequencyexcursion of Fc Hertz.
'pm' Phase modulationOPT is a scalar which specifies the constant of phase modulation kp. kp = pi/max(max(abs(x))) by default for a maximum phase excursion of +/-piradians.
'pwm' Pulse width modulationIf you let OPT = 'centered', the pulses are centered on thecarrier period rather than being "left justified".
'ppm' Pulse position modulation. OPT is a...

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