---
+ Post New Thread
Results 1 to 9 of 9
  1. #1
    Newbie level 6
    Points: 1,295, Level: 8

    Join Date
    Jan 2006
    Posts
    11
    Helped
    0 / 0
    Points
    1,295
    Level
    8

    convolution

    hi all ,
    i'm new to dsp . i want to know the exact purpose for convolution . Why cant we just multiply the two signals ?
    any one ready to help me ?

    •   Alt22nd January 2006, 15:07

      advertising

        
       

  2. #2
    Member level 1
    Points: 2,053, Level: 10

    Join Date
    May 2004
    Posts
    39
    Helped
    10 / 10
    Points
    2,053
    Level
    10

    Re: convolution

    when give delta function signal to input of some system ,
    you will see on output of system some response.



  3. #3
    Full Member level 4
    Points: 2,906, Level: 12

    Join Date
    Aug 2005
    Location
    Salvador-BA-Brazil
    Posts
    226
    Helped
    28 / 28
    Points
    2,906
    Level
    12

    convolution

    When a signal go through a linear system, its frequency components are affected by the linear system, the frequencies results is a weight composition of the system frequency response. What happens is a multiplication in frequency not in time. You will learn that multiplication in frequency domaing is equivalent of convolution in time domain. Multipling signals in time domain is associated with displacement in frequency, for instance modulation process, wich for its turn is equivalent of convolution in frequency.

    Go ahead in your studying and you will son realise the diferrences.



    •   Alt22nd January 2006, 22:57

      advertising

        
       

  4. #4
    Full Member level 2
    Points: 2,806, Level: 12

    Join Date
    Nov 2005
    Posts
    137
    Helped
    31 / 31
    Points
    2,806
    Level
    12

    convolution

    In mathematics and in particular, functional analysis, convolution is a mathematical operator which takes two functions f and g and produces a third function that in a sense represents the amount of overlap between f and a reversed and translated version of g. A convolution is a kind of very general moving average, as one can see by taking one of the functions to be an indicator function of an interval.

    to get more understanding on Convolution go through these links...
    1) http://en.wikipedia.org/wiki/Convolution
    2) http://www.sfu.ca/~truax/conv.html
    3) http://www.jhu.edu/~signals/convolve/index.html
    4) http://www.ece.gatech.edu/research/c.../convolve.html

    cheers...



    •   Alt23rd January 2006, 04:31

      advertising

        
       

  5. #5
    Newbie level 6
    Points: 1,315, Level: 8

    Join Date
    Nov 2005
    Posts
    11
    Helped
    0 / 0
    Points
    1,315
    Level
    8

    Re: convolution

    Convolution is a simple mathematical operation which is fundamental to many common image processing operators. Convolution provides a way of multiplying together two arrays of numbers, generally of different sizes, but of the same dimensionality, to produce a third array of numbers of the same dimensionality.
    This can be used in image processing to implement operators whose output pixel values are simple linear combinations of certain input pixel values.



  6. #6
    Newbie level 1
    Points: 1,260, Level: 8

    Join Date
    Dec 2005
    Posts
    1
    Helped
    0 / 0
    Points
    1,260
    Level
    8

    Re: convolution

    ....
    "Why cant we just multiply the two signals "
    ...
    we want to find response of a filter(system ,..) to one input
    assume x[n] pass through a filter h[n].

    generally speaking , x[n] is a sample of a phenoma that depends on time(..) , (and so we dont have all of samples at the same time.)

    we consider the actual consequence of signal samples by inversing signal samples : x[-n]
    by this work , the first generated samples passes through filter sooner than last generetad samples.



  7. #7
    Newbie level 1
    Points: 1,377, Level: 8

    Join Date
    Jan 2006
    Posts
    0
    Helped
    4 / 4
    Points
    1,377
    Level
    8

    convolution

    It is basically a multiplication analogy in time domain



  8. #8
    Newbie level 2
    Points: 1,420, Level: 8

    Join Date
    Feb 2005
    Posts
    2
    Helped
    0 / 0
    Points
    1,420
    Level
    8

    Re: convolution

    In LTI systems the output is the convolution between the input signal and system impulse responce.
    In DSP LTI systems like filters could be designed in time-domain by designing impulse responce and signal processing will take action by convoluting this impulse signal with the input signal.



  9. #9
    Full Member level 1
    Points: 7,209, Level: 20
    purnapragna's Avatar
    Join Date
    Oct 2005
    Posts
    107
    Helped
    85 / 85
    Points
    7,209
    Level
    20

    Re: convolution

    any signal can be represented as scaled summation version of scaled impulses. If you consider an LTI system the out put can be viewed as summation of the corresponding scaled impulse responses. This is nothing but convolution. This is obviously different from multiplication which will not give the output of the system for the corresponding input.

    thnsx
    purna!



+ Post New Thread
Please login