pls explain modulation and demodulation???/
Modulation is the process of varying one or more properties of a high frequency carrier signal, with respect to the message signal. Different types of modulation are: amplitude modulation (AM), frequency modulation (FM) and phase modulation (PM).
The need for modulation can be summarized as follows:
(1) The antenna needed for transmitting signals should have size at least λ/4, where, λ is the wavelength. The information signal, also known as baseband signal is of low frequency (and therefore the wavelength is high). If we need to transmit such a signal directly, the size of the antenna will be very large and impossible to build. Hence direct transmission is not practical.
(2) The radiated power by an antenna is inversely proportional to the square of the wavelength. So, if we use high frequency signals, the power radiated will be increased.
(3) If we transmit the baseband signals directly, the signals from different transmitters will get mixed up and the information will be lost.
Because of these reasons, we use the technology of modulation, for transmitting message signals effectively for long distances.
Demodulation is the process of retrieval of information from a carrier wave at the receiver. It is the reverse process of modulation (ie; modulation is used for sending the signal whereas demodulation is used for receiving the signal.
MODULATION:-In electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted. This is done in a similar fashion to a musician modulating a tone (a periodic waveform) from a musical instrument by varying its volume, timing and pitch. The three key parameters of a periodic waveform are its amplitude ("volume"), its phase ("timing") and its frequency ("pitch").
DEMODULATION:-Demodulation is the act of extracting the original information-bearing signal from a modulated carrier wave. A demodulator is anelectronic circuit (or computer program in a software-defined radio) that is used to recover the information content from the modulatedcarrier wave.