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A sample fft spectral analysis

The output produced by running Dsp030 using the input parameters shown in Figure 17 is shown in Figure 18 .

Figure 18. FFT of five sinusoids.
missing image

Nothing special here

There is nothing special about this particular spectral analysis. I presented it here to illustrate the use of the FFT algorithm for spectral analysis. Youshould be able to produce the same results using the same program and the same parameters.

A matching dft spectral analysis

Figure 19 shows the parameters required for the program named Dsp028 to perform a DFT spectral analysis producing the same results as those producedby the FFT analysis shown in Figure 18 . Note that the data length has been set to 256 and the computational frequency range extends from zero to the samplingfrequency in Figure 19 .

Figure 19. Parameters for A matching DFT spectral analysis.
Data length: 256 Sample for zero time: 0Lower frequency bound: 0.0 Upper frequency bound: 1.0Number spectra: 5 Frequencies0.1 0.20.3 0.50.0050 Amplitudes90.0 90.090.0 90.090.0

The matching DFT output

The DFT output produced by running Dsp028 with the parameters shown in Figure 19 is shown in Figure 20 .

Figure 20. DFT of five sinusoids.
missing image

Hopefully you noticed that Figure 20 looks almost exactly like Figure 18 . This is how it should be. The DFT algorithm and the FFT algorithm are simply twodifferent algorithms for computing the same results. However, the DFT algorithm is much more flexible than the FFT algorithm while the FFT algorithm is muchfaster than the DFT algorithm.

Repeat these two experiments

I recommend that you repeat these two experiments several times increasing the data length to a higher power of two each time you run the experiments.

On my machine, the DFT algorithm used by Dsp028 becomes noticeably slow by the time the data length reaches 2048 samples. However, theFFT algorithm used by Dsp030 is still reasonably responsive at a data length of 131,072 samples.

(Performing the DFT on five input samples each having a data length of 131,072 samples would require an intolerably long time on my machine.)

If what you need is speed for long data lengths, the FFT is your best approach. On the other hand, if you need more flexibility than the FFT providesand the data length is not too long, then the DFT may be your best approach.

The ForwardRealToComplexFFT01 class

The ForwardRealToComplexFFT01 class containing the method that implements the FFT algorithm is provided in Listing 23 near the end of this module.

The FFT algorithm is based on some very complicated signal processing concepts. I'm not going to explain how this algorithm works in this modulebecause I haven't given you the proper background for understanding it. I plan to explain additional signal processing concepts in future modules that willprepare you to understand how the FFT algorithm works.

Fortunately, you don't have to understand the mechanics of the FFT algorithm works to be able to use it.

Run the programs

I encourage you to copy, compile, and run the programs provided in this module. Experiment with them, making changes and observing the results of yourchanges.

Questions & Answers

find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
hmm well what is the answer
how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
is it a question of log
Commplementary angles
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what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
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Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
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Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
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Ramkumar Reply
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what is system testing?
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Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Digital signal processing - dsp. OpenStax CNX. Jan 06, 2016 Download for free at https://legacy.cnx.org/content/col11642/1.38
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