What is Modulation? Modulation can be simply defined as a way of facilitating the transfer of information over a certain medium. For example, sound generated from our lungs, transmitted through the air can only travel for a limited distance depending on the amount of power we consume. In order to extend the distance, a proper medium is required such as phone line or radio wireless. This conversion process of voice to travel in such a medium is known as modulation.
Modulation can be divided into two sub categories based on the modulation process. Continuous Wave Modulation 2. Pulse Code Modulation PCM is used mainly to encode both digital and analog information in the binary format.
Radio and television broadcast stations typically use the above mentioned AM or FM. Most radio companies who use two way radios use FM. Optical signals on fiber are modulated using an electromagnetic current applied to alter the intensity of a laser beam. What is the difference between Encoding and Modulation? Dingshengwei Electronics Co.
Information Theory , IT January , 50— Carlson, B. Deshpande, G. Divsalar, D. Com March , — Forney, D. IEEE , 61 March — Freeman, R. Gagliardi, R. Gregg, W. Gronemeyer, S. Mazur, B. McLane, P. Proakis, J. Rodin, M. Scharf, L. Demodulation is the process of extracting an information signal from the carrier signal. Demodulation process should be exactly compatible with the modulation method otherwise, the destination end will not be able to extract the original information signal from the carrier signal.
Therefore, the initial handshake should take place in a proper mechanism to negotiate the modulation and demodulation methods in advance, for a dynamic environment. For an example, in mobile communications, modulation methods could change on the fly. Therefore, handshaking takes place before shifting from one method to another or uses special algorithms at the destination end to extract the information by identifying the original modulation method. Equipment that does both modulation and demodulation is called a modem.
Modulation and demodulation processes mainly aim to achieve the transfer of information with the minimum distortion or corruption, minimum loss to the carrier signal, and efficient use of the spectrum. Even though there are a number of methods or schemes for modulation and demodulation process, they have their own advantages and disadvantages as well. Modulation is the process of impinging useful information on the carrier signal, while demodulation is the recovery of original information from the carrier signal.
Usually, modulation occurs at the transmitter while demodulation occurs at the receiver. The difference between the modulation and demodulation is that modulation is to transfer the message signal by adding it with the carrier signal while demodulation is the process of filtering out the actual message signal from the carrier signal. Both modulation and demodulation processes are equally important to transfer an information signal using a carrier signal. Therefore, the modulation method we use at the transmitter must be exactly compatible with the demodulation method at the receiver end to achieve a proper transfer of information from one location to another.
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