0.5 Sampling with automatic gain control  (Page 19/19)

 Page 19 / 19

This figure was generated using the following code:

n=50000;                           % number of steps in simulation r=randn(n,1);                      % generate raw random inputsenv=0.75+abs(sin(2*pi*[1:n]'/n));  % the fading profiler=r.*env;                          % apply profile to raw input r[k] ds=0.5;                            % desired power of output = d^2a=zeros(1,n); a(1)=1;              % initialize AGC parameter s=zeros(1,n);                      % initialize outputsmu=0.01;                           % algorithm stepsize for k=1:n-1  s(k)=a(k)*r(k);                  % normalize by a(k) to get s[k]   a(k+1)=a(k)-mu*(s(k)^2-ds);      % adaptive update of a(k)end agcvsfading.m compensating for fading with an AGC (download file) 

The “fading profile” defined by the vector env is slow compared with the rate at which the adaptive gain moves, which allows the gain to track the changes. Also, the

power of the input never dies away completely. The problemsthat follow ask you to investigate what happens in more extreme situations.

Mimic the code in agcvsfading.m to investigate what happens when the input signal diesaway. (Try removing the abs command from the fading profile variable.) Can you explain what you see?

Mimic the code in agcvsfading.m to investigate what happens when the power of the input signalvaries rapidly. What happens if the sign of the gain estimate is incorrect?

Would the answers to the previous two problems change if usingalgorithm [link] instead of [link] ?

Summary

Sampling transforms a continuous-time analog signal into a discrete-time digital signal. In the time domain, thiscan be viewed as a multiplication by a train of pulses. In the frequency domain this corresponds to a replication ofthe spectrum. As long as the sampling rate is fast enough that the replicated spectra do not overlap, the samplingprocess is reversible; that is, the original analog signal can be reconstructed from the samples.

An AGC can be used to make sure that the power of the analog signal remains in the region where the sampling deviceoperates effectively. The same AGC, when adaptive, can also provide a protection against signal fades. The AGC can be designedusing a steepest descent (optimization) algorithm that updates the adaptive parameter by moving in thedirection of the negative of the derivative. This steepest descent approach to the solutionof optimization problems will be used throughout Software Receiver Design .

For further reading

Details about resampling procedures are available in the published works of

• Smith, J. O. “Bandlimited interpolation—interpretation and algorithm,” 1993,

which is available at his website at http://ccrma-www.stanford.edu/ $\stackrel{˜}{}$ jos/resample/.

A general introduction to adaptive algorithms centered around the steepest descent approach can be found in

• B. Widrow and S. D. Stearns, Adaptive Signal Processing, Prentice-Hall, 1985.

One of our favorite discussions of adaptive methods is

• C. R. Johnson Jr., Lectures on Adaptive Parameter Estimation, Prentice-Hall, 1988.

This whole book can be found in .pdf form on the website accompanying this book.

Questions & Answers

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
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
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
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
Daniel
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Software receiver design. OpenStax CNX. Aug 13, 2013 Download for free at http://cnx.org/content/col11510/1.3
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