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..., .. & .. . 2011-12: 06-06-2012 3 : 20-06-2012
, , , 11.00-14.00
1 (-): , . 2.1.12, -
2 (-): , ,. 1.1.23,
: - . .
3.1() Fourier (DTFT) X()
x[n] =
2(1 jnj/3); jnj 3;0; .
() X(), - Fourier (DFT) Y [k]
y[n] =1X
k=1x[n 10k]:
3.2 z , - .() x1[n] = n(n 1)(n 2)2n3u[n k] k = 0; 1; 2; 3.() x2[n] =
13
nu[n+ 4]
14
nu[n+ 2]
.
() x3[n] = 1n!anu[n].
3.3 ... -
y[n] 3y[n 2] + 2y[n 3] = x[n] + 4x[n 1] + 3x[n 2] .() H(z)
z = 1.() ; ;
1
() .
3.4 t 2 (1; 1), xt[n] - Z Xt(z) = f(t; z1) jzj > 1,
f(t; z) = (1 2tz + z2)1/2
jtj < 1; jzj < 1. t 2 (1; 1), xt[n] (n+ 1)xt[n+ 1] (2n+ 1)txt[n] + nxt[n 1] = 0
n 0. f(t; z) xt[n] n 0 z. .
3.5 x[n] 0 n N 1 N . f [n] = x[2n] g[n] = x[2n+ 1] x[n], .
X[k] =N1Xn=0
x[n]wnkN
k = 0; : : : ; N 1, Fourier (DFT) N x[n], wN = ej2/N F [k], G[k] DFT N/2 f [n], g[n] , :() f [n] g[n] 0 n N/2 1.() F [k +N/2] = F [k] G[k +N/2] = G[k] k.
() X[k] = 12(F [k] + wkNG[k]) k = 0; : : : ; N 1:
N = 2L, X[k] k = 0; : : : ; N 1;
2