Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

for a signal does freq spectrum change with time ?

Status
Not open for further replies.
C

ciitv

Junior Member level 2
Junior Member level 2
Joined
Dec 7, 2005
Messages
21
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,283
Activity points
1,463
hi,
i know that for a given signal, there exists a corresponding freq spectrum. but i'm am baffled by my thought. can somebody explain this:
imagine this time domain signal: 10*sin(wt)u(-t)+5sin(wt)u(t)..i.e.sinusoidal signal is at one amplitude for -inf to 0 and another amp for 0 to +inf and freq remains the same. i know that for a given time domain a corresponding time invariant freq domainl exists... does the freq domain change at time=0 ?
 

Hi,
If you look at your signal from minus inf. to inf. you see a frequency spectrum for it. it's the frequency response of your whole signal. the question is, can we see a sudden changing of local frequency in t=0 directly with my whole signal spectra and interpret it. your answer is no. but what is solution?. the main general approach for solving this problem is to look (ans process) our signal locally and with shifting in Time. => Time-Frequency Transforms.
one of solution is Short Time Fourier Transform (STFT). Ther are some other solutions like Wigner-Ville Trans., Wavelet Trans. (CWT & DWT).

Regards
 

    C

    ciitv

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top