What is Pulse Amplitude Modulation

What is Pulse Amplitude Modulation

Pulse Amplitude Modulation is the basic form of pulse modulation in which the signal is sampled at regular intervals such that each amplitude and sample are proportional. Let’s study the basics of modulation.

What is modulation?

Modulation is defined as the process of changing the characteristics of a carrier signal. Frequency, amplitude, and width are the characteristics of the signals.  

Modulation types

Following are the types of modulation:

      1. Continuous-wave modulation

  • Amplitude modulation
  • Angle modulation
    • Frequency modulation
    • Phase modulation

       2. Pulse modulation

  • Analog modulation
    • PAM (Pulse Amplitude Modulation)
      • Single polarity PAM
      • Double Polarity PAM
    • PWM (Pulse Width Modulation)
    • PPM (Pulse Position Modulation)
  • Digital modulation
    • Pulse code modulation
      • Delta modulation

Continuous-wave Modulation

In continuous wave modulation, the carrier signal is modulated depending on the three parameters namely: frequency, amplitude and phase. Therefore, continuous-wave modulation is classified as:

  1. Amplitude modulation
  2. Frequency modulation
  3. Phase modulation

Pulse Modulation

In pulse modulation, the information is carried by the signals in pulses. Pulse modulation is divided into analog pulse modulation and digital pulse modulation. 

Analog pulse modulation is further classified as PPM, PWM and PAM.

Pulse Amplitude Modulation

Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled such that they are proportional to the instantaneous amplitude of the message signal. Pulse amplitude modulation (PAM) is obtained from the pure sine wave. Following are the types of sampling techniques for transmitting the signal using PAM. 

  • Flat top PAM: At the time of pulse occurrence, the amplitude of each pulse is proportional to the amplitude of the modulating signal such that the peaks of the amplitude remain flat.
  • Natural PAM: At the time of pulse occurrence, the amplitude of each pulse is proportional to the amplitude of the modulating signal such that the amplitude of the pulse follows the half cycle for the rest of the process.

Types of PAM

Following are the types of PAM:

  1. Single Polarity PAM
  2. Double Polarity PAM

Applications of PAM

Following are the application of PAM:

  1. Photobiology uses of PAM
  2. PAM is used for LED lighting in an electronic driver 
  3. PAM is used in micro-controllers for generating controlled signals

Advantages and disadvantages of PAM

Advantages:

  1. For modulation and demodulation, the PAM process is simple
  2. The circuits used in the construction of the transmitter and receiver are simple and easy

Disadvantages:

  1. The noise generation is too high
  2. For the transmission of PAM, the bandwidth should be large

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