Reasons for modulation

[Highlander-SP]

reasons for modulation

Can anyone explain detailed the reasons for modulation?

Is there eny ebook / site with relevant informations?

tks

 

[master_slave]

reasons of modulation

You can refer to this site within the edaboard.com to answer your question in general sense:



As for ebooks, there are plenty of ebooks about communication here in edaboard.com.

 

[truebs]

reason for modulation

Please refer to any book on analog and digital modulation, B.P. Lathi is good.
same title by Couch is good.

Please check out basic tutorial at : http://www.williamson-labs.com/480_mod.htm

cya

 

[jallem]

reasons for modulating

Usually the main reason given in books for modulation is the size of the
antenna. The higher the frequency the lower the size.
But in reality for any particular frequency a very small antenna can be
used for transmitting. That is the concept of "small antenna" or
infinitesimal small antenna. What happens is, for this small antennas
the input impedance is too small and the matching is difficult and the
efficiency of the antenna is small. The characteristic impedance of
a transmission lines can be anything from a few ohm to a few hundreds.
For regular transmission lines(coaxial, flat TV cable, etc) the matching
is easier when the antenna impedance is close to the impedance of the
cable. Besides,the efficiency increases. And this occurs when the size
of the antenna is a mutiple of the wavelength as in λ/2, λ/8 and so fore.

So, then the connection between the frequency and the size of the
antenna, the higher the frequency the lower the antenna size.

 

[magnetra]

reason of modulation

You can go through the book Modern Digital and Analog Communication Systems by B.P Lathi. The author has give the reasons for modulation.

Magnetra

 

[Lupin]

purpose reason for modulation

"Modulation" people,

Can anyone explain to me what is a modulation scheme?

The concept of modulation is clear to me.. but I really don't know what's the meaning of a schme... according to what?

I really need this support.. thanks in advance.

Lupin

 

[asim_baig2002]

the reasons why modulation has to take place

hi.
hope u know the meaning of modulation
anyways,hope this might help u.
to deliver a message signal from an information source in recognizable form to a user destination,with the source and the user being physically seperated from each other.To do this , the transmitter modifes the message signal into a suitable for transmission over the channel.This modification is acheived by means of a process known as modulation,which involves varing some parameter of a carrier wave in accordance with the message signal.the receiver recreates the orignal message signal from a degraded version of the transmitted signal after propogation through the channel.This recreation can be acheived by means a process called demodulation.
however due to unavoidable presence of noise and distortion in the received signal,we find that the receiver cannot recreate the orignal message signal exactly.the resulting degradation in overall system performance is influenced by the type of modulation scheme used.Specifically we find thatsome modulation schemes are less sensitive to the effects of noise and distortion than others.we can classify modulation process or schemes as 1:continuous wave modulation{C.W}
IN C.W:there are angle modulation and amplitude modulation....etc
2ulse modulation.
in this case there are pulse analog and digital modulation respectively ...they can b further subclassifed..
hope this might help u out


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[Prakash]

reasons for modulation in communicaation systems

Modulation schemes is nohing but different techniques of transmitting data.....
In analog modulation there are two types amplitude modulation and frequency modulation..(it can further divided into angle or phae mod.. techniques).

similarly for digital modulation there are types..

Using all these modulation types we can send any type of data... Each and every modulation is having its own merits and demerits. According to our situation we have to adapt any one type.

 

[amir1981]

reason why modulation takes place

1-low frequency data has a long wave len which is proportional with the antena len
2-the posibility of transfering multiple message on the same chanel

 

[azaz104]

reason modulation

In fact, there are many misconceptions about modulation:


1- using high frequency doesn't improve the signal in means of the the quantity of noise incurred on the signal because white noise ( the type of noise dominant in our systems) exists by the same anount in all the frequency spectrum.

2- imagine yourself in a class, and the teacher asks a question, now if everyone of the bright students talk at the same time, no one will understand a thing, something called interference....but if everyone of them is given a time slot to talk into, so that everyone will understand. the same thing happens when you use sinusoids, you must use different sinusoids in order to accomodate different user, but how can this be, if our voice signals (all human beings) have approximately the same bandwidth? ....
This can be accomplished by transating this signal into a higher frequency ( and not giving this spectrum to anyone else as long as this user is using it)

3- translation of this information signal into higher frequencies enables us to put this information into many forms, and because we are using sinusoids as the means of doing that then it means that we are restricted to what this signal offers us ( which is limited to amplitude, phase and frequency) so that we can convey this information via manipulation of one or more of these three.

4- another misconception is the idea that low frequency signals get attenuated more than high frequency signals, which is of course WRONG, because it's the reverse thing actually, but as was mentioned before, it's the antenna hight that makes us use the high frequency spectrum, since we need an antenna that's relatively in the order of the wavelength to obtain a good gain....

i hope i didn't bore you

 

[elf61]

two reasons for modulation

GOodnight
See also the book on communication systems by Carlson.

 

[Lupin]

reasons for modulation

Hi elf61,

where can I find this book? Is also the spurious modulation mentioned?

Thanks in advance.

Lupin