Modulation is the process of superimposing the information contents of a modulating signal on a carrier signal (which is of high frequency) by varying the characteristic of carrier signal according to the modulatingI like to share this
Introduction to Types of Modulation
We can divide modulation in two parts :-(1) Analog modulation.(2) Digital modulation.
Types of Modulation : Analog ModulationAnalog modulation can further divide in three parts :(i)Amplitude modulation :- In amplitude modulation the amplitude of high frequency carrier signal is varied in accordance with the instantaneous value of baseband modulating signal keeping frequency and phase of carrier signal constant. The frequency domain representation of the resultant modulated signal contains carrier signal plus two sidebands of modulating signal (information signal)
Amplitude modulation can be of three types :-(1) Full AM (In this modulated signal contains carrier signal & two side bands of modulating signal.)(2) DSB-SC (Double sideband suppressed carrier ) In this carrier signal is suppressed.(3) SSB-SC (Single sideband suppressed carrier) In this carrier signal plus one sideband is suppressed.(ii) Frequency modulation :- In frequency modulation, the frequency of high frequency carrier signal is varied in accordance with instantaneous value of modulating signal keeping amplitude constant.(iii)
Phase modulation :- In phase modulation, the phase of high frequency carrier signal is varied directly in accordance with instantaneous value of modulating signal keeping amplitude constant .Types of Modulation : Digital ModulationDigital modulation can be further divide into four parts :(i) Pulse code modulation :- In this technique the modulating signal is first passed through a sampler to which take samples of signal at discrete time intervals, then signal is passed through the quantizer its function is to convert signal into digital signal.
Then signal is passed through a encoder which assign n number of bits to each samples, and the signal is transmitted over the channel.(ii) Differential pulse code modulation :- The signal does not change rapidly from one sample to next, so instead of transmitting samples at each sampling instant , the difference between sample and its predicted value is transmitted in this technique. Thus due to this system efficiency is increased.(iii) Delta modulation :- Delta modulation is a one-bit pulse code modulation system in which staircase approximation of original signal is generated by oversampling the signal. The original signal can be obtained by passing the approximation signal through a low pass filter at the receiving end.(iv) Adaptive delta modulation :- The basic principal of ADM is to vary the step size in accordance with slope of input signal i.e. when slope of input is steep, step size must be increased and if input signal slope is small step size is reduced. This technique is more accurate then above method.