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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

what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
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Cied
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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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