DTFT Properties Example- Determine the DTFT y(e/)of yr]=(m+1)pm],a<1 Let x[n]=a"u[n],a<1 We can therefore write n=nxn+xn From Table 3. 1, the dtFt of x[n] is given Y(e0) 1-ae y Copyright C 2001, S K Mitra
Copyright © 2001, S. K. Mitra 1 DTFT Properties • Example - Determine the DTFT of • Let • We can therefore write • From Table 3.1, the DTFT of x[n] is given by y[n] = (n +1) [n], 1 n x[n] = [n], 1 n y[n] = n x[n]+ x[n] − − = j j e X e 1 1 ( ) ( ) j Y e
DTFT Properties Using the differentiation property of the dtFT given in Table 3. 2. we observe that the dtftof nxin is given by dX(e/o). d de o J o1-0e Ja ae Jo Next using the linearity property of the dtFT given in Table 3. 2 we arrive at 0 ae Y(e/o) (1-ae)21-ae0(1-ae-0) Copyright C 2001, S K Mitra
Copyright © 2001, S. K. Mitra 2 DTFT Properties • Using the differentiation property of the DTFT given in Table 3.2, we observe that the DTFT of is given by • Next using the linearity property of the DTFT given in Table 3.2 we arrive at nx[n] 2 1 (1 ) ( ) 1 − − − − = − = j j j j e e d e d j d dX e j 2 2 (1 ) 1 1 1 (1 ) ( ) − − − − − = − + − = j j j j j e e e e Y e
DTFT Properties Example-Determine the dtfT V(e/o)of the sequence vIn] defined by dovIn]+div[n-1]=poo[n]+p 8[n-1 From Table 3. 1, the dtFt of Sn]is 1 Using the time-shifting property of the dtFT given in Table 3.2 we observe that the dtft of Sn-1]is e /o and the dtFT of v[n-1]is e v(el Copyright C 2001, S K Mitra
Copyright © 2001, S. K. Mitra 3 DTFT Properties • Example - Determine the DTFT of the sequence v[n] defined by • From Table 3.1, the DTFT of is 1 • Using the time-shifting property of the DTFT given in Table 3.2 we observe that the DTFT of is and the DTFT of is v[n −1] [ ] [ 1] [ ] [ 1] d0 v n + d1 v n − = p0 n + p1 n − [n] [n −1] − j e ( ) j V e ( ) − j j e V e
DTFT Properties Using the linearity property of Table 3. 2 we then obtain the frequency-domain representation of dovIn]+div[n-1]=poS[n]+p, 8[n-1 as J +dle e P0+p1 Solving the above equation we get V(e/o)=Po t p1e /o JQ 0 +1e Copyright C 2001, S K Mitra
Copyright © 2001, S. K. Mitra 4 DTFT Properties • Using the linearity property of Table 3.2 we then obtain the frequency-domain representation of as • Solving the above equation we get [ ] [ 1] [ ] [ 1] d0 v n + d1 v n − = p0 n + p1 n − − − + = + j j j j d V e d e V e p p e 0 1 0 1 ( ) ( ) − − + + = j j j d d e p p e V e 0 1 0 1 ( )
Energy Density Spectrun The total energy of a finite-energy sequence gIn is given by E g=△gln 1=-0 From Parseval's relation given in Table 3.2 we observe that T=∑ IG(eJo) do 2丌 丌 Copyright C 2001, S K Mitra
Copyright © 2001, S. K. Mitra 5 Energy Density Spectrum • The total energy of a finite-energy sequence g[n] is given by • From Parseval’s relation given in Table 3.2 we observe that 2 [ ] g n g n =− E = 2 2 1 [ ] ( ) 2 j g n g n G e d =− − E = =