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The results of the Fourier transform are stored in the array objects referred to by realSpect , imagSpect , and magnitude .

(The phase angle is also computed but is of no interest in this example.)

Apply the filter to the frequency data

Listing 11 applies the filter by setting sample values in a portion of the real and imaginary parts of the complex spectrum to zero.

Listing 11. Apply the filter to the frequency data.
for(int cnt = len/6;cnt<5*len/6;cnt++){ realSpect[cnt]= 0.0; imagSpect[cnt]= 0.0; }//end for loop

This code eliminates all energy between one-sixth and five-sixths of the sampling frequency. The modified data for the real and imaginary parts of thecomplex spectrum are shown in the second and third plots in Figure 4 .

Re-compute the magnitude

Listing 12 re-computes the magnitude values for the modified real and imaginary values of the complex spectrum.

Listing 12. Re-compute the magnitude.
//Recompute the magnitude based on the // modified real and imaginary spectra.for(int cnt = 0;cnt<len;cnt++){ magnitude[cnt]= (Math.sqrt(realSpect[cnt]*realSpect[cnt]+ imagSpect[cnt]*imagSpect[cnt])/len); }//end for loop

The modified data for the amplitude of the complex spectrum are shown in the fourth plot in Figure 4 .

Compute the inverse Fourier transform

Listing 13 uses the inverseTransform method to compute the inverse Fourier transform of the modified complex spectrum stored in realSpect and imagSpect.The results of the inverse transform are stored in timeOut.

Listing 13. Compute the inverse Fourier transform.
InverseComplexToRealFFT01.inverseTransform( realSpect,imagSpect, timeOut);}//end constructor

The results of the inverse transform are shown in the bottom plot in Figure 4 .

Listing 13 also signals the end of the constructor.

Display the results

Once the constructor returns, all of the data that is to be plotted has been stored in the various array objects. The remaining code in the program consistsof the definition of the six methods required by the interface named GraphIntfc01. These methods are required to make it possible to use the programnamed Graph03 to plot the results as shown in Figure 4 .

I have discussed these methods on numerous previous occasions, and won't repeat that discussion here.

One more example, Dsp038

Figure 5 illustrates one more example of performing frequency filtering by modifying the complex spectrum and then performing an inverse transform on themodified spectrum.

While discussing the program named Dsp037 , I told you that performing a different modification on the complex spectrum would result in a differentwaveform for the filtered impulse. The program named Dsp038 applies a different modification to the complex spectrum, but is otherwise the same as Dsp037.

(Because of the similarity of the two programs, I won't discuss the code in Dsp038. You can view that code in Listing 19 near the end of the module.)

Figure 5 shows the output produced by the program named Dsp038 .

Questions & Answers

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
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Adin
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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
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Damian Reply
absolutely yes
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characteristics of micro business
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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
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what is biological synthesis of nanoparticles
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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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