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Question and comments

Questions or comments concerning this laboratory should be directedto Prof. Charles A. Bouman, School of Electrical and Computer Engineering, Purdue University, West Lafayette IN 47907;(765) 494-0340; bouman@ecn.purdue.edu


The purpose of this lab is to illustrate the properties of continuous and discrete-time signals using digital computersand the Matlab software environment. A continuous-time signal takes on a value at every pointin time, whereas a discrete-time signal is only defined at integer values of the “time” variable.However, while discrete-time signals can be easily stored and processed on a computer,it is impossible to store the values of a continuous-time signal for all points along a segment of the real line.In later labs, we will see that digital computers are actuallyrestricted to the storage of quantized discrete-time signals. Such signals are appropriately known as digital signals.

How then do we process continuous-time signals? In this lab, we will show that continuous-time signalsmay be processed by first approximating them by discrete-time signals using a process knownas sampling. We will see that proper selectionof the spacing between samples is crucial for an efficient and accurate approximationof a continuous-time signal. Excessively close spacing will lead to too much data,whereas excessively distant spacing will lead to a poor approximation of the continuous-time signal.Sampling will be an important topic in future labs, but for now we will use sampling to approximatelycompute some simple attributes of both real and synthetic signals.

Be sure to read the guidelines for the written reports.

Matlab review

Practically all lab tasks in the ECE438 lab will be performed using Matlab. Matlab (MATrix LABoratory) is a technical computing environmentfor numerical analysis, matrix computation, signal processing, and graphics.In this section, we will review some of its basic functions. For a short tutorial and some Matlab examples click here .

Starting matlab and getting help

You can start Matlab (version 7.0) on your workstation by typing the command


in a command window. After starting up, you will get a Matlab window.To get help on any specific command, such as “plot”, you can type the following

help plot

in the “Command Window” portion of the Matlab window. You can do a keyword search for commands related to a topic by using thefollowing.

lookfor topic

You can get an interactive help window using the function


or by following the Help menu near the top of the window.

Matrices and operations

Every element in Matlab is a matrix. So, for example, the Matlab command

a = [ 1 2 3 ]

creates a matrix named “ a ” with dimensions of 1 × 3 . The variable “ a ” is stored in what is called the Matlab workspace. The operation

b = a .'

stores the transpose of “ a ” into the vector “ b ”. In this case, “ b ” is a 3 × 1 vector.

Since each element in Matlab is a matrix, the operation

c = a * b

computes the matrix product of “ a ” and “ b ” to generate a scalarvalue for “ c ” of 14 = 1 * 1 + 2 * 2 + 3 * 3 .

Questions & Answers

so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
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
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what is biological synthesis of nanoparticles
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
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
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the Beer law works very well for dilute solutions but fails for very high concentrations. why?
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Smarajit Reply
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