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Interpolation: by an integer factor l

Interpolation means increasing the sampling rate, or filling in in-between samples. Equivalent to sampling abandlimited analog signal L times faster. For the ideal interpolator,

X 1 ω X 0 L ω ω L 0 L ω
We wish to accomplish this digitally. Consider [link] and [link] .
y m X 0 m L m 0 ± L ± 2 L 0
The DTFT of y m is
Y ω m ω y m ω m n x 0 n ω L n n x n ω L n X 0 ω L
Since X 0 ω is periodic with a period of 2 , X 0 L ω Y ω is periodic with a period of 2 L (see [link] ).
By inserting zero samples between the samples of x 0 n , we obtain a signal with a scaled frequency response that simply replicates X 0 ω L times over a 2 interval!

Obviously, the desired x 1 m can be obtained simply by lowpass filtering y m to remove the replicas.

x 1 m y m h L m
Given H L m 1 ω L 0 L ω In practice, a finite-length lowpass filter is designed using any of the methods studied so far ( [link] ).

Interpolator block diagram

Decimation: sampling rate reduction (by an integer factor m)

Let y m x 0 L m ( [link] )

That is, keep only every L th sample ( [link] )
In frequency (DTFT):
Y ω m y m ω m m x 0 M m ω m n M m n x 0 n k δ n M k ω n M ω ω M n x 0 n k δ n M k ω n DTFT x 0 n DTFT δ n M k
Now DTFT δ n M k 2 k 0 M 1 X k δ ω 2 k M for ω as shown in homework #1, where X k is the DFT of one period of the periodic sequence. In this case, X k 1 for k 0 1 M 1 and DTFT δ n M k 2 k 0 M 1 δ ω 2 k M .
DTFT x 0 n DTFT δ n M k X 0 ω 2 k 0 M 1 δ ω 2 k M 1 2 μ X 0 μ 2 k 0 M 1 δ ω μ 2 k M k 0 M 1 X 0 ω 2 k M
so Y ω k 0 M 1 X 0 ω M 2 k M i.e. , we get digital aliasing .( [link] )
Usually, we prefer not to have aliasing, so the downsampler is preceded by a lowpass filter to remove all frequencycomponents above ω M ( [link] ).

Rate-changing by a rational fraction l/m

This is easily accomplished by interpolating by a factor of L , then decimating by a factor of M ( [link] ).

The two lowpass filters can be combined into one LP filterwith the lower cutoff, H ω 1 ω L M 0 L M ω Obviously, the computational complexity and simplicity of implementation will depend on L M : 2 3 will be easier to implement than 1061 1060 !

Questions & Answers

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.
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
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
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
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
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
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Source:  OpenStax, Digital signal processing: a user's guide. OpenStax CNX. Aug 29, 2006 Download for free at http://cnx.org/content/col10372/1.2
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