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As the frequency of the sine wave continues to increase beyond that point, without a corresponding change in the sampling frequency, it is impossible todetermine from the samples so obtained whether the frequency is increasing or decreasing.

An ambiguity in the spectrum analysis

As a result, the spectrum analysis process was unable to determine if the peak in the frequency spectrum was below or above the folding frequency. Thus,the bottom trace in Figure 3 shows two peaks which are mirror images of one another with the folding frequency being half way between the two peaks.

(As a practical matter, when doing spectrum analysis, there is no point in computing the values above the folding frequency. I did that here just toillustrate that there is a folding frequency, which is equal to one-half the sampling frequency.)

Let's see some code

The class used to produce the data displayed in Figure 3 is named Dsp002 . A complete listing of this class definition is shown in Listing 38 near the end of the module.

I will break this class down into fragments and briefly discuss it to show how you can define significant classes and easily connect them to the generalizedplotting program named Graph01 .

As before, having compiled the class named Dsp002 , you would exercise it by entering the following at a command prompt:

java Graph01 Dsp002

Different from the previous example class

This class differs from the class named Graph01Demo in one very significant way. In that class, all the values returned by the methods named f1 through f5 were computed on the fly as the methods were called.

In this new class named Dsp002 , all the data is generated and stored in array objects when an object of the class named Dsp002 is instantiated. When the methods named f1 through f5 are called later, they simply retrieve the data from the array objects and return that data to the plotting program.

Basic operation of the program

As mentioned earlier, this program applies a narrow-band convolution filter to white noise, and then computes the amplitude spectrum of the filtered noiseusing a Discrete Fourier Transform (DFT) algorithm. The spectrum of the white noise is also computed. All of the processing occurs when an object of the classis instantiated, and the processed results are saved in arrays.

The input noise, the filter, the filtered output, and the two spectra are deposited in five arrays for later retrieval and display. The data in the fivearrays are returned by the methods named f1 , f2 , f3 , f4 , and f5 respectively.

The values that are returned by the methods are scaled for appropriate display in the plotting areas provided by the program named Graph01 .

Beginning of the class named Dsp002

The code in Listing 9 establishes the data lengths for the white noise, the convolution filter, the filtered output, and the spectrum.

Listing 9. Beginning of the class named Dsp002.
class Dsp002 implements GraphIntfc01{ int operatorLen = 33;int dataLen = 256+operatorLen; int outputLen = dataLen - operatorLen;int spectrumPts = outputLen;

Questions & Answers

are nano particles real
Missy Reply
yeah
Joseph
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
Lale Reply
no can't
Lohitha
where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
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Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
has a lot of application modern world
Kamaluddeen
yes
narayan
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
Bhagvanji
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
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
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Alexandre
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
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Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
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Mahi
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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
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Berger describes sociologists as concerned with
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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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