공학수학 | Fourier 스펙트럼 1 |

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작성자 cemtool 작성일14-06-16 16:35 조회8,981회 댓글0건

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다음과 같이 진폭이 A이고 주기가 T인 함수를 생각해보자.

$f(t)=\left \{ \begin{matrix} A, & (0<t<\frac{T}{2})\\-A,&(-\frac{T}{2}<t<0)\end{bmatrix} \right.$

이 함수에 대한 전력 스펙트럼(power spectrum)을 구하여라.

function;
virtual <> f,F,xunit
 
/*
 clptdscf(f,F,xunit) Plot a discrete spectrum [f F] Input to function is        f       - frequencies
        F       - spectral values
        xunit   - units of frequency (Hz or rad/sec) Input title of graph from keyboard*/
 
nl=length(f);                // Number of f points
fmin=min(f);                 //  and range
fmax=max(f);
Fmax=max(F);
 
for(I=1;I<=nl;I++){    fplots=[f(I) f(I)];
    Fplot=[0 F(I)];
    plot(fplots,Fplot)         // Plot one line at a time
    holdon
}title("Frequency Spectrum")xtitle(["Frequency in ", xunit])ytitle("Amplitude")

ex8_6.cem

/*
 Example 8.6 CEMTool Fourier spectrum
*/
 
// Plot positive frequency spectrum of square wave
// The components are 2/(n pi); n odd.
// Plot 10 components of the discrete spectrum [f F]// by calling function clptdscf
 
xunit="Hertz";          // Units of frequency
f=[0:10:1];             // Frequency scale
Fn=zeros(1,11);             // Row vector of 11 elements
// Frequency spectrum
for(n=1;n<=5;n++){              // Compute 5 positive components
    Fn(2*n-1)=2/((2*n-1)*pi);
}Fn=[0 Fn];                      // Add the zero value
 
clptdscf(f,Fn,xunit);    // Call for plot