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Baldwin explains the meaning of sampling, and identifies some of the problems that arise when sampling and processing analog signals. He explains the concept of the Nyquist folding frequency and illustrates the folding phenomena by plotting time series data as well as spectral data.

Revised: Fri Oct 16 23:11:24 CDT 2015

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This is one in a series of modules designed to teach you about Digital Signal Processing (DSP) using Java. The purpose of the miniseries is topresent the concepts of DSP in a way that can be understood by personshaving no prior DSP experience. However, some experience in Java programming would be useful. Whenever it is necessary for me to write a program toillustrate a point, I will write it in Java.

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I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the Figureswhile you are reading about them.


  • Figure 1 . Samples from five different sinusoids.
  • Figure 2 . Rectangular representations of samples from five sinusoids.
  • Figure 3 . Trapezoidal representations of samples from five sinusoids.
  • Figure 4 . Most common representations of samples from five sinusoids.
  • Figure 5 . Five sampled sinusoids
  • Figure 6 . Result of re-sampling the five sinusoids.
  • Figure 7 . Spectral analyses of five sinusoids with no sampling problems.
  • Figure 8 . Spectral analyses of five sinusoids with sampling problem.
  • Figure 9 . Spectral analyses of five sinusoids with no sampling problems.
  • Figure 10 . Spectral analyses of five sinusoids with sampling problem


I will explain the meaning of sampling, and will explain some of the problems that arise when sampling and processing analog signals. Those problems generallyrelate to the relationship between the sampling frequency and the high-frequency components contained in the analog signal.

I will explain the concept of the Nyquist folding frequency , which is half the sampling frequency (more commonly called the sampling rate) .

I will illustrate the frequency folding phenomena by plotting sampled time series data as well as spectral data.


Sinusoids, time series, composition, and decomposition

I introduced you to sinusoids and sampled time series in an earlier module . I taught you about sine and cosine functions, and the Java methods used to calculate their values. I also introduced the concepts of period and frequency for sinusoids.

Questions & Answers

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s. Reply
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are you nano engineer ?
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.
what is the actual application of fullerenes nowadays?
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.
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Mostly, they use nano carbon for electronics and for materials to be strengthened.
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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.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
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Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
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I'm interested in nanotube
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Sravani Reply
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