dpsk .wav file in matlab

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jess17

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ok, i need to modulate this .wav file in matlab. I tried the command

%to read .wav
[y,fs,n]=wavread('wavefile');
t = (1:n) / fs;
sound; %plays the sound and plots it.
figure(1)
plot

%carrier signal.
% frequency
fc = fs/3;
c = cos(2 * pi * fc * t);
figure(2)
plot(t,c);

to modulate,
M=4;
sig =dpskmod(x,M)

i get an error saying "Error using ==> dpskmod at 41
Elements of input X must be integers in the range [0, M-1]."

what should the value of M be?
 

where is x?
 

jess17 said:
to modulate,
M=4;
sig =dpskmod(x,M)

i get an error saying "Error using ==> dpskmod at 41
Elements of input X must be integers in the range [0, M-1]."

what should the value of M be?
Click to expand...

First of all you did not specify x. It should be quantized value of the signal y. You must first quantize y with n bits resolution and then form symbols with values 0,1,2 or 3 using consecutive 2 bits of quantized signal (for M=4) . Store the resulting symbols in x and then execute
Code: 
sig =dpskmod(x,M)
 

i tried with

M = 4; % Use DQPSK in this example, so M is 4.
Fs = 100;
t = [0:2*Fs+1]'/Fs;
Fc = 10; % Carrier frequency
x = sin(2*pi*t); % Sinusoidal signal

but keep getting the same error. Is quantising like converting it to digital form?
 

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