<< Chapter < Page
  Digital signal processing - dsp     Page 10 / 14
Chapter >> Page >

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

Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
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
hi
Loga
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Digital signal processing - dsp. OpenStax CNX. Jan 06, 2016 Download for free at https://legacy.cnx.org/content/col11642/1.38
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Digital signal processing - dsp' conversation and receive update notifications?

Ask