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Many decades ago I was shown a high quality digital spectrum analyser, as I was completing
some qualifications.
Since then I've become quite familiar with the fft , I realise that the fft is just a part of the signal
processing; prior to that filters and mixers are used to select a portion of...
As some of you maybe familiar with octave, or matlab, here is a
script that replicates what I've done so far with maxima cas .
This uses the Octave syntax, to convert to matlab equivalent, replace
endfor with end, endfunction with end, then most everything else
should be compatible.
[
#...
This is what I've done so far for simultaneous
amplitude and frequency modulation .
It involves the sum of frequency shifted sinusoids,
x dependent amplitude modulation and zero extension.
Perhaps your approach has a place within this
scheme.
Where the function, floor, is similar to...
I used two separate p
lots and noted that all peaks were the same amplitude.
What I'm attempting to do is combine frequency modulation and amplitude
modulation with a generalised signal like this:
A(x)*sin(2*pi*t*x)
then have that replicated, in some way , in the frequency domain.
Partial...
Zero extension, in the time domain appears to overcome a lot of the problems relating to
the amplitude of the frequency shifted signal , at the expense of some extra lobes.
With this approach I just put values within the first quarter of the input array, the other three quarters remained
at...
If I apply the fft to
sin(t*2*%pi*f)
where f, the frequency, is an integer, and n equals
the number of samples, then the peaks in the frequency
domain appear at f+1 and n+1-f and the absolute amplitude is
always 0.5.
If f isn't an integer, then the peaks are 'smeared out' and
the only...
I used maxima computer algebra system to examine this.
I have , and have used the Matlab clone, Octave, however
maxima is quite useful and nowadays has ffts available that
aren't necessarily radix 2 or radix 4 .
Already I need to correct a few details and reload the graph with
the proper labels for the axes.
abs(a + i*b) = sqrt(a*a + b*b)
frequency range is 0 to approximately 400 Hz
Thank you for your answer.
If I use a particular length fft, not necessarily radix 2, will this correct the situation ?
So that everyone comprehends what I did, here are some details:
ω0 = 50
f1(t,x) = sin(ω0*2*pi*t*x)
N=1024 number of points
x = 1 to 18 , step 1
frequency range is then 0...
To determine the response of the fft to a sinusoidal of increasing
frequency yet same amplitude of 1.
I used a pure sine wave sin(2*pi*t*a) , where the multiplier 'a'
determines the period , and hence frequency of the wave.
Now examining the fft, the peak does indeed shift as expected,
the...
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