Pulse Amplitude Modulation (PAM): 5 Important Explanations

Subject of Discussion: Pulse Amplitude Modulation (PAM)

  • What is pulse amplitude modulation?
  • Flat top and natural PAM
  • What is PWM and PPM
  • Advantages and disadvantages of PAM
  • Comparison of PAM vs PWM vs PPM

What is Pulse Amplitude Modulation?

Definition of Pulse Amplitude Modulation:

“The modulation technique which is utilized to state the transfiguration of the analog signal to a pulse-type signals in that the amplitude of the pulse signifies the analog info”.

The modulator performs the primary steps while the conversion of analog signal to a Pulse Code Modulated Signal. In a number of application the Pulse Amplitude Modulation signal is used directly and complex conversion such as PCM is not at all required.

Types of Pulse Analog Modulation

The Pulse Analog Modulation can be classified into three categories. They are –

  1. Pulse Amplitude Modulation (PAM)
  2. Pulse width Modulation (PWM)
  3. Pulse Position Modulation

The relation between the pulse and constant amplitude of the message signal is proportional. As explained here, PAM is to a certain extent analogous to natural sampling technique, in which the message signal is multiplied by a periodic square pulses. In regular sampling process, however, the modulated square pulse is acceptable to vary with the message signal, however in pulse-amplitude modulation it is retained as flat signal.


Types of Pulse Amplitude Modulation

Pam can be categorized into two categories. They are – Flattop Pulse Amplitude Modulation and Natural Pulse amplitude modulation.

Flat Top Pulse Amplitude modulation:

The pulses’ amplitudes are dependent on the amplitude of the message signal.

Flat Top Pulse Amplitude modulation
Flat Top Pulse Amplitude modulation

Natural PAM:

Natural Pulse Amplitude modulation
Natural Pulse Amplitude modulation

Write down some of the Applications of PAM?

Applications of PAM

There are several applications of Pulse Amplitude modulation such as

  • PAM is used in Ethernet Communication.
  • PAM is used in many micro-controllers to generate some control signals.
  • In Photo-biology system, PAM is also used.

What are the advantages of PAM?

Advantages of Pulse Amplitude modulation

  • Pam is a better straightforward, less complex process for the modulations as well as demodulations.
  • The design of transmitters and receivers of PAM is quite a straightforward job and less complex than other design. 
  • Pulse Amplitude Modulation be able to produce other pulse modulation signals and transport the message signal at that time.

What are the disadvantages of PAM?

Disadvantages of Pulse Amplitude modulation

  • For PAM, bandwidth should be larger for transmission.
  • PAM has a great noise problem.
  • The PAM signal will changes, so that the power requisite for transmission may increase.

What is Pulse Width Modulation?

Definition of Pulse Width Modulation (PWM):

  •  “This is an analog modulating technique in which the duration, width, and time of the pulse carrier will be changed in proportion to the amplitude of the message signals.”
  • The pulses’ widths change in this technique. Though pulse’s magnitude remains the same.
  • In PWM, amplitude limiters are utilized as to create the amplitude of the signal as constant.

This PWM is also recognized as a Pulse Duration Modulation (PDM) and the Pulse Time Modulation (PTM) technique.

Pulse Width Modulation
An example of PWM in an idealized inductor driven by a voltage source modulated as a series of pulses, resulting in a sine-like current in the inductor.
Image source – ZureksPWM, 3-levelCC BY-SA 3.0
delta PWM
Principle of the delta PWM. Output signal (blue), limits (green).

Image Credit: Delta_PWM.png: Cyril BUTTAY derivative work: Krishnavedala (talk), Delta PWMCC BY-SA 3.0
Sigma Delta PWM

Image Credit :Sigma_delta.png: Cyril BUTTAY derivative work: Krishnavedala (talk), Sigma-delta PWMCC BY-SA 3.0

What is Pulse Position Modulation?

Definition of Pulse Position Modulation (PPM):

In the pulse-amplitude modulation or pulse-width modulation or pulse-length modulation technique, the pulse amplitude is the variable parameter, so it changes. The pulse’s period is one of the important parameter. The modulating signal is changes with the time of incidence of the leading or trailing edges, or both edges of the pulse.

Comparative analysis of PAM, PWM and PPM:

            PAM            PWM             PPM
In PAM amplitude keeps varying.In case of pulse amplitude modulation, the BW is dependent on the width of the following pulse.In PPM, the BW of the pulse is dependent on the rising-time of the pulse.
In PAM, the bandwidth depends on the width of the following pulse.In Pulse Width Modulation, Bandwidth is depended on the rising time of the pulseIn PPM, Bandwidth is depended on the rise time of the pulse
In Pulse amplitude Modulation (PAM) , System or circuit design is complex.In Pulse width modulation (PWM), System or circuit design is less complex.In Pulse position modulation (PPM), System or circuit design is less complex.
  High noise interference  Low noise interference  Low noise interference

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Read more about Amplitude Modulation and Demodulation.

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