<< Chapter < Page Chapter >> Page >

The James Brown canon represents a vast catalogue of recordings—the mother lode of beats—a righteously funky legacy ofgrooves for us to soak in, sample, and quote.

—John Ballon in “MustHear Review,” http://www.musthear.com/reviews/funkypeople.html

As foreshadowed in [link] , transmission systems cannot be fully digital because themedium through which the signal propagates is analog. Hence, whether the signal begins as analog (such as voiceor music) or whether it begins as digital (such as mpeg, jpeg or wav files), it will be converted to a highfrequency analog signal when it is transmitted. In a digital receiver, the received signal must betransformed into a discrete-time signal in order to allow subsequent digital processing.

This chapter begins by considering the sampling process in both the time domainand in the frequency domain. Then "Exploring Sampling in MATLAB" discusses how M atlab can be used to simulate the sampling process. This is not completely obvious becauseanalog signals cannot be represented exactly in the computer. Two simple tricks are suggested. The first expressesthe analog signal in functional form and takes samples at the desired times. The second oversamples the analog signal so that it is represented at a high datarate; the “sampling” can then be done on the oversampled signal.

Sampling and quantization are important because they translate the signal from analog to digital. It is equally important to be ableto translate from digital back into analog, and the celebrated Nyquist sampling theorem shows that this is possible for any bandlimited signal, assuming the sampling rate is fast enough.When the goal of this translation is to rebuild a copy of the transmitted signal, this is called reconstruction . When the goal is to determine the value of the signalat some particular point, it is called interpolation . Techniques (and M atlab code) for both reconstruction and interpolation appear in "Interpolation and Reconstruction" .

[link] shows the received signal passing through a BPF (which removes out-of-band interferenceand isolates the desired frequency range) followed by a fixed demodulation to the intermediate frequency (IF) wheresampling takes place. The automatic gain control (AGC) accounts for changes in the strength of thereceived signal. When the received signal is powerful, the gain a is small; when the signal strength is low, the gain a is high. The goal is to guarantee that the analog to digital converterdoes not saturate (the signal does not routinely surpass the highest level that can be represented), and that it doesnot lose dynamic range (the digitized signal does not always remain in a small number of the possible levels).The key in the AGC is that the gain must automatically adjust to account for the signal strength, which may vary slowlyover time.

The front end of the receiver. After filtering and demodulation, the signal is sampled. An automatic gain control (AGC) is needed to utilize the full dynamic range of the quantizer.
The front end of the receiver. After filtering and demodulation, the signal is sampled. An automatic gaincontrol (AGC) is needed to utilize the full dynamic range of the quantizer.

The AGC provides the simplest example of a system element that must adapt to changes in its environment (recall the “fifthelement” of Chapter  [link] ). How can such elements be designed? Software Receiver Design suggests a general method based on gradient-directed optimization. First, a “goal” and an associated “objective function” arechosen. Since it is desired to maintain the output of the AGC at a roughly constantpower, the associated objective function is defined to be the average deviation of the power from that constant; the goal is to minimizethe objective function. The gain parameter is then adjusted according to a“steepest descent” method that moves the estimate “downhill” towards the optimal value that minimizes theobjective. In this case the adaptive gain parameter is increased(when the average power is too small) or decreased (when the average power is too large), thus maintaininga steady power. While it would undoubtedly be possible to design asuccessful AGC without recourse to such a general optimization method, the framework developed in Sections "Iteration and Optimization" through "Automatic Gain Control" will also be useful in designing other adaptive elementssuch as the phase tracking loops of Chapter  [link] , the clock recovery algorithms of Chapter  [link] , and the equalization schemes of Chapter  [link] .

Questions & Answers

how did Mc connel defined economics
Isaac Reply
what is a economy planning?
Jacob Reply
what is demand
Sunday Reply
demand means desire for a commodity backed by willingness & ability to pay for that commodity
what is supply
supply means suppliers supplying more commodities when price's high or less when price's low to satisfy human want
the coefficient of price elasticity of supply is the measure of percentage change in the quantity supplied of a good due to a given percentage change in its price.
Please what is Economics of Scales?
what is cardinal and ordinal utility?
Cardinal utility is the satisfaction derived by the consumers from the consumption of goods and services while ordinal is ranked in terms of preference.
Please explain what is meant by Economic Integration?
Please I need help!!!!
economics scales I don't know but I know laws of returns to scale
can someone help explain to me what is fairly inelastic dd
Economics Economics - The study of how people use their limited resources to try to satisfy unlimited wants
Economic integration has been one of the main economic developments affecting international trade in the last years. Countries have wanted to engage in economic cooperation to use their respective resources more effectively and to provide large markets for member-countries of the resulting integrate
Inelastic Demand When consumers are relatively unresponsive to price changes. A PED coefficient of less than one means that a particular change in the price of a good will be met by a proportionally smaller change in the quantity demanded.
what is development planning?
Emmanuel Reply
What is economics?
Shubham Reply
economics is study of scarcity and how humans make decisions.
reason for development planning in West Africa
what is development planning?
What is homo Economicus?
nongo Reply
when a person is part 50% rational and the other part of him is 50% focused on money as an incentive
what makes the economy to be stable
what measures are necessary to the economy which is not doing fine
must find out the problems originating from and take remedy for it.
Economics as a social science Discuss
list and explain three implication of balance of payment disequilibrium
Jayson Reply
In economics pollution, what's spillover?
Chinedum Reply
what is net national income
Ibrahim Reply
relation between business economics and traditional economics
Netra Reply
more explanation on GDP
Isaac Reply
it is a country total out put of goods and services divided by the total population of the country.I think it can also be derived from the country labour force,,because it mostly depend on the labour force and the level of technology .
labour force and technological progress leads to greater production increases the GDP
what is elasticity of demand
degree of responsiveness of demand to changes in price and other factors that influence demand.
It is the degree of responsiveness of demand and supply to a little change in price of a goods and services
What is economics?
Bubu Reply
by this time
It is a social science that analyses production,distribution and consumption of goods and services
A social science that study human behavior in relationship with decision making
a social science that studies human behavior as a relationship between ends and scarce means which has alternative uses
it is a science that study human begin as a relation to ends and scarce should which have alternative uses
the science in which we study about the investement of our wealth.
what is competitive demand
a competitive demand is also known as substitute demand .the moment the price of the commodity increase consumers will purchase the other other commodity which it's price is low and the vice versa. an example is milo and bournvita
what is different between equilibrium and demand?
equilibrium is a situation where market is stable there is no entry nor exit. demand is the willingness to pay Which is backed by law.
list and explain three implication of balance of payment disequilibrium?
Economics is a social science that study's human behaviour as a relationship between ends and scares means which have alternative uses
What are the typical patterns of GDP for a high-income economy like the United States in the long run and the short run?
mwangala Reply
What are the limitation and significant of macroeconomic
Usman Reply
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?