Monday, March 14, 2011

Modulation technique in wireless communication


 Modulation has been defined as the process of combining an input signal and a carrier signal with a specified frequency,to produce a modulated signal whose bandwidth is centered on carrier signal frequency.Modulation is the process of transforming a message signal to make it easier to work with. Modulation is the process of changing one or more properties of high frequency signal or carrier with respect to modulating signal. It usually involves varying one waveform in relation to another waveform. In telecommunications, modulation is used to convey a message, or a musician may modulate the tone from a musical instrument by varying its volume, timing and pitch. In radio communications for instance, electrical signals are best received when the transmitter and receiver are tuned to resonance. Therefore keeping the frequency content of the message signal as close as possible to the resonant frequency of the two is ideal. Often a high-frequency sinusoid waveform is used as carrier signal to convey a lower frequency signal. The three key parameters of a sine wave are its amplitude ("volume"), its phase ("timing") and its frequency ("pitch"), all of which can be modified in accordance with a low frequency information signal to obtain the modulated signal.
Modulation is the process of facilitating the transfer of information over a medium.Sound transmission in air has limited range for the amount of power your lungs can generate.To extend the range your voice can reach,we need to transmit it through a medium other than air,such as a phone line or radio.The process of converting information so that it can be successfully sent though a medium is called modulation.

There are two types of modulation
All of these techniques vary a parameter of a sinosoid to represent the information which we wish to send.A sinusoid has three different parameter then can be varied.These are its amplitude,frequency and phase. Modulation is the process of mapping such that it takes your voice converts it into some aspect of a sine wave and then transmit the sine wave,leaving the actual voice behind.The sine wave on the other side is remapped back to a near copy of your sound.

The medium is the thing through which the sine wave travels.So wire is a medium and so are air,water and space.The sine wave is called the carrier.The information to be sent,which can be voice or data is called the information signal.Once the carrier is mapped with the information to be sent,it is to longer a sine wave and we call it the signal.the signal has the unfortunate luck of getting corrupted by noise as it travels.

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