Superposition of Signals
When two signals share the same medium, they add together. This simple principle creates interference, beats, and ultimately makes all of wireless communication possible.
The Principle
The superposition principle states: when two signals occupy the same space at the same time, the resulting signal is their point-by-point sum.
Constructive Interference
When peaks align with peaks and troughs align with troughs, the waves reinforce each other. The result is a bigger signal — doubled amplitude at maximum.
Destructive Interference
When peaks align with troughs, the waves cancel each other. Two identical waves 180° apart produce total silence — zero signal.
Two Waves Meet
Beats
When two waves have slightly different frequencies, they create a pulsing pattern called beats. The amplitude rises and falls at the beat frequency.
Beat Frequency
Building a Square Wave
A square wave is actually infinite sine waves added together — only the odd harmonics (1, 3, 5, 7...) with decreasing amplitudes.
Build a Square Wave
Why Superposition Matters
Right now, thousands of radio signals are passing through your body. They all superpose. Your phone’s receiver uses filtering to extract just the one it needs. Without superposition, wireless would be impossible.
Noise as Superposition
Noise is unwanted signals superposed on your desired signal. Random thermal vibrations, interference from other devices — they all add up. The key metric is Signal-to-Noise Ratio (SNR).
Signal + Noise
Key Takeaways
- Signals add together — the superposition principle
- Constructive = in phase, Destructive = out of phase
- Close frequencies create beats
- Any waveform can be built from sine wave harmonics
- Noise is unwanted superposition — SNR is how we measure it
Three Down, One To Go
You’ve covered amplitude, frequency, phase, both domains, Fourier and superposition. One lesson left in Module 2 — and it is the unit that measures every one of them.