Solved Examples on PAM
Consider a sinusoidal modulating signal with amplitude 2V and frequency 1 kHz. Modulate this signal onto a carrier signal with amplitude 10V and frequency 10 kHz.
We know that equation for PAM signal :
s(t)=(A c +A m ⋅sin(2πf m t))⋅sin(2πf c t)
Substituting the given values:
s(t)=(10V+2V⋅sin(2π×1000×t))⋅sin(2π×10000×t)
The PAM signal, or carrier signal modulated by sinusoidal modulating signal, is represented by the above equation. The modulating signal’s amplitude affects the carrier signal’s amplitude. There are changes in the carrier’s amplitude at the modulating signal’s frequency because the carrier signal’s frequency is significantly greater than the modulating signal’s.
Consider a modulating signal with amplitude varying between -3V and +3V and a carrier signal with an amplitude of 5V. Modulate the carrier signal using PAM.
Equation for PAM signal is: s(t)=(Ac+Am(t))⋅c(t)
When the modulating signal is at +3V, the PAM signal will be at its maximum:
s(t)= 5V+3V=8V
When the modulating signal is at -3V, the PAM signal will be at its minimum:
s(t)= 5V – 3V= 2V
So, the PAM signal will vary between 2V and 8V, depending on the modulating signal.
Pulse Amplitude Modulation
Pulse Amplitude Modulation (PAM) is a key modulation technique used in digital communication for transmitting analog data and is one of the most widely used types of analog-to-digital conversion. Its process is simple where the amplitude of a sequence of pulses changes with the instantaneous amplitude of the analog message signal. The analog signal that is to be modulated is sampled by a sequence of pulses that are amplitude-modulated on the carrier to produce the amplitude-modulated pulses.
The analog signal is sampled at regular intervals to enable the amplitude of pulses due to be produced by the carrier to be varied. The sampled values are quantized to a specific number of quantization levels or discrete levels whereupon the process is repeated. Due to its simplicity of implementation and analysis, PAM is often employed in many applications including digital communication, audio transmission, and instrumentation among others. One of the biggest drawbacks of PCM is its sensitivity towards channel errors, as poor-quality channels will introduce noise and distortion, particularly over larger distances and lower data rates.
Table of Content
- What is PAM?
- PAM Block Diagram
- Types
- Mathematical expression
- Construction
- PAM Circuit
- Solved Examples on PAM
- Applications
- Advantages
- Disadvantages