| Title: | Mathematics at DEC | 
| Moderator: | RUSURE::EDP | 
| Created: | Mon Feb 03 1986 | 
| Last Modified: | Fri Jun 06 1997 | 
| Last Successful Update: | Fri Jun 06 1997 | 
| Number of topics: | 2083 | 
| Total number of notes: | 14613 | 
    hi,
    I am looking for references on WAVELETS or any kind of time-frequency
    representations.
    Does anyone has heard about?
    marcel
     
| T.R | Title | User | Personal Name | Date | Lines | 
|---|---|---|---|---|---|
| 955.1 | such things exist | CTCADM::ROTH | Lick Bush in '88 | Fri Oct 21 1988 19:01 | 4 | 
|     It sounds like you want a joint time/frequency representation such
    as the Wigner distribution, but you'll have to be more specific.
    - Jim
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| 955.2 | more on wavelets | PRSUD1::CHALEAT | Tue Oct 25 1988 05:34 | 27 | |
|     
    thanks,you are right.
    I have seen time-frequency representation of signals showing much
    more features than the usual one obtained from Fourier transform.
    The underlying maths exceed my level ,and look  rather esoteric
    at least for me !
    At the last european signal processing conference it was a paper
    on "time scale representations obtained with wavelets".
    I can send you a copy if you are interested and if you provide
    me your mail address.
    Basically the transform for a signal s(t) is:
    
    	S(t,a) = //  s(b) f((t-b)/a) db
    
    from which is derived
    
    	S(t,a) = //  g^'(au) s^(u) exp(jtu) du 
    
    where g is the analyzing wavelet which is a bell shaped pulse
    
    I used following symbols:
    up arrow ^   for fourier transform
    apostroph '  for complex conjugation
    pair of back slashes // for the integral symbol.
                        
              marcel
    
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