Pulse Modulation Techniques (PAM, PWM, PPM, PCM) /Pulse Amplitude, Pulse Width, Pulse Position, Code

Here we will discuss in details, Pulse modulation and pulse modulation techniques like Pulse Amplitude Modulation (PAM), Pulse Width Modulation (PWM), Pulse Position Modulation (PPM) and Pulse Code Modulation (PCM). Here Basics and waveform of each Pulse Modulation Technique has been discussed in detail.

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Pulse Modulation Techniques (PAM, PWM, PPM and PCM)
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Pulse Modulation Techniques -
Basic difference between Continuous Wave Modulation and Pulse Modulation.
In Continuous Wave Modulation (Amplitude Modulation, Frequency Modulation, Phase Modulation) the carrier wave used is continuous in nature, while in case of pulse modulation, the carrier wave is in the form of pulses.
So now let's discuss different types of Pulse Modulation Techniques in detail-
Pulse modulation can be categorized broadly into two types-
Analog and Digital
The analog modulation can again be of two types-
#Pulse Amplitude Modulation (PAM)
#Pulse Time Modulation (PTM)
The Pulse Time Modulation (PTM) can further be classified into two types of modulation-
#Pulse Width Modulation (PWM)/Pulse Duration Modulation (PDM)
#Pulse Position Modulation (PPM)
Pulse Code Modulation (PCM) is a digital pulse modulation technique.
You can see the classification of pulse modulation
To see the classification of all types of modulations including pulse modulation and continuous wave modulation
Here we will discuss all types of pulse modulation techniques i.e. Pulse Amplitude Modulation (PAM), Pulse Width Modulation (PWM)/Pulse Duration Modulation (PDM), Pulse Position Modulation (PPM) and also Pulse Code Modulation (PCM).
So let's start with Pulse Amplitude Modulation (PAM)-
Here we will see the definition of pulse amplitude modulation and waveform of pulse amplitude modulation.

Pulse Amplitude Modulation (PAM)
Definition:-
The modulation technique in which the instantaneous amplitude of the pulsed carrier is varied according to the modulating signal (message signal) is called as pulse amplitude modulation.

Waveform of pulse amplitude modulation
Here in this image, you can see, three waveforms. The first waveform is of modulating signal (message signal), the second one is of the pulsed career wave and the third waveform is of the pulse amplitude modulated wave (PAM).
The message signal can have multiple frequencies and variable amplitude. Here we have used a sinusoidal message signal. The carrier wave that we have used here, is a train of pulses having high frequency. Since we know that in Pulse modulation, the carrier wave is in the form of pulses.

As we have discussed that in Pulse amplitude modulation, the instantaneous amplitude of the pulsed carrier is varied according to the modulating signal (message signal). Now look at the image shown above very carefully, observe that, as the amplitude of the modulating signal (message signal or baseband signal) increases, the amplitude of the pulsed carrier wave increases and becomes maximum when the amplitude of the modulating signal reaches at its maximum. Now the amplitude of the carrier wave starts decreasing with decrease in amplitude of the modulating signal. So it is clear from the image that the amplitude of the pulsed carrier wave varies according to the instantaneous value of the message signal.
Important Observations-
#As it is Pulse Amplitude Modulation (PAM), therefore only the amplitude of the pulsed carrier changes. There is no change in the width or position of the pulsed carrier wave. So the width and position of the carrier wave pulse is constant here. Therefore we can say that, all the information of the modulating signal is contained in the amplitude variations of the pulses. No information is present in the width or position of the pulses.

Pulse Time Modulation (PTM)
In pulse time modulation, the width or position of the pulsed carrier wave is varied (variations on the time axis) as per the changes in the amplitude of the modulating signal.
As we have discussed already that Pulse time modulation is of two types-
Pulse Width Modulation (PWM)/Pulse Duration Modulation (PDM) and
Pulse Position Modulation (PPM)
So first let's start with pulse width modulation.

Pulse Width Modulation (PWM)/Pulse Duration Modulation (PDM)
Definition:-
In Pulse width modulation, width (duration) of the pulses of the carrier wave is varied according to the modulating signal (message signal).
Now we will understand the waveform of pulse width modulation.
Look at the image given below to see the waveform of pulse width
modulated signal.

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