Modulation ?

1. May 9, 2009

ecestar

what is the meaning of modulation and what is types
can any one explain that to me

and give me any book.

2. May 9, 2009

JoAuSc

You need to give us a lot more information before we can tell what you're asking for. Where did you hear about "modulation"? Is it in reference to "amplitude modulation" or "frequency modulation", both of which describe ways information is encoded in radio waves?

3. May 9, 2009

ecestar

at first i want to now what is the fm modulation and the am modulation and what is the difference between both and how can i choose the type of the modulation

and what is the value of the carier that must be used

4. May 10, 2009

JoAuSc

Let's say the signal we want to transmit is $$s(t)$$. AM modulation is the following:

$$s(t) A \sin(\omega t)$$

Here $$\sin(\omega t)$$ is the carrier signal, $$\omega$$ is its angular frequency, $$A$$ is a constant, and $$t$$ is time.

FM modulation is the following:

$$A \sin(B s(t) t)$$

$$B$$ is a constant, and the other variables are the same as they were above.

I don't know the specifics of how these are used in radio.

5. May 11, 2009

ecestar

how can i choose the type of modulation i mean depended on what?