AM, FM Heterodyne and Homodyne - help needed

Hi,

I am new to transceiver design. I had a simple question about modulation techniques. Are heterodyne and homodyne different types of AM or FM. Could someone explain exactly what is AM and FM.

In heterodyne system the signal is mixed with a carrier frequency so there is a shift in the frequency, so that should make it FM. Is that correct?

What exactly is AM?

I really need is information fast.

Thanks a lot!

No. As far as receivers go, a hetrodyne system downconverts the received frequency to some low frequency, such as 10.7 MHz, etc. A homodyne system downconverts the received signal to be centered right at 0 Hz. In either case, the signal is then converted into some useful form of data...often with an analog to digital converter and some further digital processing.

FM or AM are forms of modulation, and they are caused at the other side of the link...at the transmitter. An AM signal has a single carrier that stays on one frequency, but its amplitude goes up and down. AN FM signal has a single carrier that stays at a constant amplitude, but its frequency goes up and down around a center point.