 |
Search Sci.Electronics.Basics |
|
|
|
|
|
|
 |
|
|
Sci.Electronics.Basics -> Fourier Transform
There are 4 messages in this thread.
You are currently looking at messages 1 to 4.
|
|
|
Fourier Transform is difficult for me. How can i practic this?
|
|
|
|
Author: Bob MastaDate: 09:04 29-04-07
|
|
On 29 Apr 2007 01:19:41 -0700, polian22@gmail.com wrote:
>Fourier Transform is difficult for me. How can i practic this?
>
I have some "Gut-Level Fourier Transforms" tutorials at:
www.daqarta.com/author.htm
There is also an extensive tutorial section in the Help
system of my Daqarta software. That section is available
on-line at
www.daqarta.com/sw_0h0i.htm
But you are welcome to download the program itself
at
www.daqarta.com/dqdown.htm
Daqarta includes a signal generator and FFT spectrum
analyzer, plus a waveform (scope) display, so you can
experiment with the effects of different waveforms,
window functions, quantization levels, noise, dither, etc
for some "hands on" leaning. Daqarta is nominally
$29 shareware, but that's only if you need to analyze
external signals via the sound card inputs. The output
functions and all the display modes keep on working
after the trial period expires. You are welcome to
use it this way for free, for as long as you like. You
will not only have a powerful signal generator, but
a handy learning tool.
Best regards,
Bob Masta
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!
|
|
|
|
Author: John LarkinDate: 13:27 29-04-07
|
|
On 29 Apr 2007 01:19:41 -0700, polian22@gmail.com wrote:
>Fourier Transform is difficult for me. How can i practic this?
Given a periodic waveform, draw or plot it on a sheet of paper... not
a computer screen. Step back and look at it. If it seems to be, on
avearge, above or below zero, guess the average value. That is the DC
term, the first (actually, the 0th) Fourier component.
You can usually spot a basic repetitive period visually. Now, on a
separate piece of paper, draw a sine wave of that "fundamental"
period. Hold the sine wave paper under the waveform paper and slide it
horizontally. You are trying to visualise how much your input waveform
resembles the perfect sine. The best horizontal alignment is the phase
of the fundamental (1st) Fourier component, and the relative height of
the match is its amplitude.
You can do the higher harmonics this way. Draw a 2F sinewave and see
if there'd anything in your original waveform that visually matches up
with 2F.
The Fourier math is just a way of accurately quantizing the
"resemblence" of your waveform to a set of possible perfect sines. The
math is similar to your visual process is actually doing: multiply the
input waveform by a sine wave, point by point, and see if the summed
products are nonzero, and then how big the sum is.
When you slide the pieces of paper, you are finding the phase where
the match is best. The mathematical discrete Fourier operation
separates the "match" into sine and cosine components, 0 and 90
degrees, whose sum will be that same best-match phase angle. It's
really the same thing; it's just that the mathematical method is too
dumb to do the visual slide-for-best-match, so it has to do the math
twice, at 0 and 90 degrees.
So: Fourier analysis is a formal way of saying how much a waveform
looks like DC, then how much is looks like a low frequency sine, then
how much it looks like a 2x sine, etc. The formal mathematical
expression of the step-by-step procedure is called a "transform" and
is compact but not totally obvious, so take it one step at a time.
John
|
|
|
|
Author: Bob MastaDate: 09:01 01-05-07
|
|
On Sun, 29 Apr 2007 13:04:10 GMT, NoSpam@daqarta.com (Bob Masta)
wrote:
>On 29 Apr 2007 01:19:41 -0700, polian22@gmail.com wrote:
>
>>Fourier Transform is difficult for me. How can i practic this?
>>
>
>I have some "Gut-Level Fourier Transforms" tutorials at:
> www.daqarta.com/author.htm
>
>There is also an extensive tutorial section in the Help
>system of my Daqarta software. That section is available
>on-line at
> www.daqarta.com/sw_0h0i.htm
>
>But you are welcome to download the program itself
>at
> www.daqarta.com/dqdown.htm
>
>Daqarta includes a signal generator and FFT spectrum
>analyzer, plus a waveform (scope) display, so you can
>experiment with the effects of different waveforms,
>window functions, quantization levels, noise, dither, etc
>for some "hands on" leaning. Daqarta is nominally
>$29 shareware, but that's only if you need to analyze
>external signals via the sound card inputs. The output
>functions and all the display modes keep on working
>after the trial period expires. You are welcome to
>use it this way for free, for as long as you like. You
>will not only have a powerful signal generator, but
>a handy learning tool.
Follow-up: I just uploaded Daqarta v3.03.2, which
fixes a bug in v3.03(a) that caused incompatibility with certain
recent sound cards/chipsets that declare input and output
as separate devices (instead of the more-traditional
separate lines on the same device). Also, the earlier
v3.03 had a defective build that disabled the free trial
system. Sorry for any inconvenience.
Best regards,
Bob Masta
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!
|
|
|
|
1 |
|
|
|
|
Contact | Electronic Portal
|
|
|
