Decibel (dB) Mathematics
The Logarithmic Language of Power
The Power of Logarithms
A decibel is not an absolute value; it is a ratio. It represents how much stronger or weaker one signal is compared to another.
Logarithmic Scale Lab
dBm vs. Linear Power (mW)
On a linear scale, a signal at -30 dBm is 1000 times smaller than 0 dBm. It practically vanishes. The Decibel scale keeps it "visible" for engineering.
Adding a 10 dB amplifier at any level multiplies the power by 10. In logs, you just add 10. Simple addition vs billions in ratios.
Absolute Power: dBm
When we need to measure actual signal strength (like Wi-Fi RSSI or Optical TX Power), we use dBm. This is a ratio where the reference point () is pinned at exactly 1 Milliwatt.
- 0 dBm: 1 mW
- 20 dBm: 100 mW (Typical home router)
- 30 dBm: 1 Watt (Powerful outdoor radio)
Link Budgets
The beauty of decibels is in the Link Budget Calculation. Instead of multiplying efficiency percentages, we simply add gains and subtract losses.
Conclusion
Whether you are measuring light loss in a fiber splice (-0.05 dB) or the signal drop through an office wall (-15 dB), decibel mathematics is the universal standard for quantitative signal integrity.