Simple Fourier transform problem

Click For Summary
SUMMARY

The discussion centers on the Fourier transform of the sequence x[n] defined as x1[n]=[0.9ncos(0.6*pi*n)] * x[n-2]. Participants highlight the challenge of calculating the Fourier transform due to the non-summable nature of the term 0.9n, which lacks a valid Fourier transform. The relevant equations discussed include time shift, convolution, and frequency shift, which are crucial for understanding the transformations involved. Ultimately, the consensus is that the problem requires a deeper understanding of Fourier transforms and their properties, particularly in relation to non-summable sequences.

PREREQUISITES
  • Fourier Transform fundamentals
  • Convolution theorem in signal processing
  • Properties of time and frequency shifts
  • Understanding of summability in sequences
NEXT STEPS
  • Study the properties of non-summable sequences in Fourier analysis
  • Learn about the implications of the convolution theorem on Fourier transforms
  • Explore the concept of time and frequency shifting in signal processing
  • Investigate the conditions under which Fourier transforms exist for various sequences
USEFUL FOR

Students and professionals in electrical engineering, signal processing, and applied mathematics who are working with Fourier transforms and convolution in discrete-time signals.

asdf12312
Messages
198
Reaction score
1

Homework Statement


Given x[n] with transform X(ejw), find the Fourier transform in terms of X(ejw).

x1[n]=[0.9ncos(0.6*pi*n)] * x[n-2]

Homework Equations


time shift: x[n-k] -> e-jwkX(ejw)
convolution: x[n] * h[n] -> X(w)H(w)
freq. shift: x[n]ejwcn -> X(ew-wc)

The Attempt at a Solution


I think that this problem has no solution because 0.9n has no Fourier transform (not summable). 0.9nu[n] on the other hand does but not the same case here. am i doing this right?
 
Last edited:
Physics news on Phys.org
I am at a loss to understand the problem. It seems to me as if the problem is to calculate the Fourier transform of a constant - or a sequence of constants. Is that correct?
 
yeah, I guess i didn't word it correctly. what it reads exactly is 'given a sequence x[n] with Fourier transform Xejw, determine the Fourier transform of the sequences in terms of Xejw.
 
asdf12312 said:
'given a sequence x[n] with Fourier transform Xejw, determine the Fourier transform of the sequences in terms of Xejw.
Still does not make any sense to me...
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
3
Views
3K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
Replies
8
Views
5K
  • · Replies 6 ·
Replies
6
Views
5K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K