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Homework Help: A digitised signal

  1. Oct 14, 2008 #1
    1. The problem statement, all variables and given/known data
    Determine the digitised signal x[n] and use MATLAB to produce an annotated plot of x[n]
    x(t) = sin(2*pi*F_1*t) + sin(2*pi*F_2*t)
    F_1 = 0.5 khz
    F_2 = 5 khz
    F_s = 44.1khz

    2. Relevant equations
    t = n/F_s

    3. The attempt at a solution

    i got x[n] = cos([pi*n/44.1] - pi/2) + cos([10*pi / 44.1] - pi/2)
    i need to double check that.

    also i used the following matlab code to plot it:

    Code (Text):

    Fs = 44100; % sampling rate = 44.1 kHz

    Ts = 1/Fs;  % sampling period

    F1 = 500;   % signal1 frequency 0.5 kHz

    F2 = 5000;  % signal2 frequency 5 kHz

    t_d = 0:Ts:10; % sampling points 0, Ts, 2Ts, ... 1

    n_d = round(t_d/Ts); % integer index, used for plotting

    x_d1 = sin(2*pi*F1*t_d); % discrete-signal x_d1

    x_d2 = sin(2*pi*F2*t_d); % discrete-signal x_d2

    stem(n_d, x_d1); % plot x_d versus sample index

    stem(t_d, x_d1); % plot x_d versus time

    stem(n_d, x_d2); % plot x_d versus sample index

    stem(t_d, x_d2); % plot x_d versus time

    i need to check that what i am doing is correct before i move on to the other sections of the question.

  2. jcsd
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