In this Physics video lecture in Hindi for class 12 we explained modulation and demodulation in communication system. Amplitude modulation and frequency modulation are two types of analog signal modulation explained here. We explained the necessity of modulation and demodulation. We also differentiate between them.
Modulation is required in communication system for the following reasons:
1) Baseband signals have less energy due to their low frequency. We mix up high frequency carrier waves with the baseband signel and get modulated signal during modulation process. Due to its high frequency, and hence high energy, signal can propagate a long distance without being attenuated.
2) To distinguish the signals from different stations we use modulation technique.
3) If the baseband signal is propagated, due to its high wavelength the antenna needed to receive or emit signal would be of impractically large length.
