<< Chapter < Page Chapter >> Page >

The squaring nonlinearity is only one possibility in the pllpreprocess.m routine.

  1. Try replacing the r 2 ( t ) with | r ( t ) | . Does this result in a viable method of emphasizing the carrier?
  2. Try replacing the r 2 ( t ) with r 3 ( t ) . Does this result in a viable method of emphasizing the carrier?
  3. Can you think of other functions that will result in viable methods of emphasizing the carrier?
  4. Will a linear function work? Why or why not?

Determine the phase shift ψ of the BPF when

  1. fl=490, 496, 502 .
  2. Ts=0.0001, 0.000101 .
  3. M=19, 20, 21 . Explain why ψ should depend on fl , Ts , and M .

Squared difference loop

The problem of phase tracking is to determine the phase Φ of the carrier and to follow any changes in Φ using only the received signal. The frequency f c of the carrier is assumed known, though ultimately it too must be estimated.The received signal can be preprocessed (as in the previous section) to create a signal that strips away the data, in essence fabricating a sinusoid which has twice the frequency at twice the phase of the unmodulated carrier. This can be idealized to

r p ( t ) = cos ( 4 π f c t + 2 Φ ) ,

which suppresses An example that takes ψ into account is given in Exercise  [link] . the dependence on the known phase shift ψ of the BPF and sets the constant s a v g 2 2 to unity (compare with [link] ). The form of r p ( t ) implies that there is an essential ambiguity in the phase since Φ can be replaced by Φ + n π for any integer n without changing the value of [link] . What can be done to recover Φ (modulo π ) from  r p ( t ) ?

Is there some way to use an adaptive element? [link] suggested that there are three steps to the creation of a good adaptive element: setting a goal,finding a method, and then testing. As a first try, consider the goal of minimizingthe average of the squared difference between r p ( t ) and a sinusoid generated, using an estimate of the phase; that is, seek to minimize

J S D ( θ ) = avg { e 2 ( θ , k ) } = 1 4 avg { ( r p ( k T s ) - cos ( 4 π f 0 k T s + 2 θ ) ) 2 }

by choice of θ , where r p ( k T s ) is the value of r p ( t ) sampled at time k T s and where f 0 is presumed equal to f c . (The subscript SD stands for squared difference, and is used todistinguish this performance function from others that will appear in this and other chapters.)This goal makes sense because, if θ could be found so that θ = Φ + n π , then the value of the performance functionwould be zero. When θ Φ + n π , then r p ( k T s ) cos ( 4 π f 0 k T s + 2 θ ) , e ( θ , k ) 0 , and so J S D ( θ ) > 0 . Hence, [link] is minimized when θ has correctly identified the phase offset, modulo the inevitable π ambiguity.

While there are many methods of minimizing [link] , an adaptive element that descends the gradient of the performance function J S D ( θ ) leads to the algorithm Recall the discussion surrounding the AGC elements in Chapter [link] .

θ [ k + 1 ] = θ [ k ] - μ d J S D ( θ ) d θ θ = θ [ k ] ,

which is the same as [link] with the variable changed from x to θ .  Thus,

d J S D ( θ ) d θ = d avg { e 2 ( θ , k ) } d θ avg d e 2 ( θ , k ) d θ = 1 2 avg e ( θ , k ) d e ( θ , k ) d θ = avg { r p ( k T s ) - cos ( 4 π f 0 k T s + 2 θ ) sin ( 4 π f 0 k T s + 2 θ ) } .

Substituting this into [link] and evaluating at θ = θ [ k ] gives Recall the convention that θ [ k ] = θ ( k T s ) = θ ( t ) | t = k T s .

θ [ k + 1 ] = θ [ k ] - μ avg { ( r p ( k T s ) - cos ( 4 π f 0 k T s + 2 θ [ k ] ) ) sin ( 4 π f 0 k T s + 2 θ [ k ] ) } .

This is implemented in pllsd.m for a phase offset of phoff=-0.8 (i.e., Φ of [link] is - 0 . 8 , though this value is unknown to the algorithm). [link] plots the estimates theta for 50 different initial guesses theta(1) . Observe that many converge to the correct value at - 0.8. Others converge to - 0 . 8 + π (about 2 . 3 ) and to - 0 . 8 - π (about  - 4).

Questions & Answers

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 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
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
How can I make nanorobot?
Lily
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
how can I make nanorobot?
Lily
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
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.
Tarell
what is the actual application of fullerenes nowadays?
Damian
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.
Tarell
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Software receiver design. OpenStax CNX. Aug 13, 2013 Download for free at http://cnx.org/content/col11510/1.3
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Software receiver design' conversation and receive update notifications?

Ask