Q. Explain Modulation and sampling?

Modulation is the process whereby the amplitude (or another characteristic) of a wave is varied as a function of the instantaneous value of another wave. The first wave, which is usually a single-frequency wave, is called the carrier wave; the second is called the modulating wave. Demodulation or detection is the processwhereby awave resulting frommodulation is so operated upon that a wave is obtained having substantially the characteristics of the original modulating wave. Modulation and demodulation are then reverse processes.

The information from a signal x(t) is impressed on a carrier waveform whose characteristics suit a particular application. If the carrier is a sinusoid, we will see that a phenomenon known as frequency translation occurs. If, on the other hand, the carrier is a pulse train, the modulating signal needs to be sampled as part of the modulation process. Frequency translation and sampling have extensive use in communication systems. Both of these lend to multiplexing, which permits a transmission system to handle two or more information-bearing signals simultaneously.