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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

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
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
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
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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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