Harald Friis
1893 – 1976
Bell Labs radio engineer; the transmission and noise-figure formulas are his.
A Danish-born Bell Labs engineer, Friis brought order to radio-link design in the 1940s. His transmission formula relates transmitted and received power through antenna gains, wavelength, and distance; his noise-figure definition, referenced to 290 K, standardized how receiver sensitivity is stated.
Working from the horn antennas at Holmdel, he built the accounting that scales from a Wi-Fi link to a deep-space downlink. The link-budget and noise tools here are, in effect, Friis calculators.
Portrait: a stylized blueprint-line rendering, not a photograph.
Contributions in the toolbox
- 1944
Noise-figure convention fixes T₀ = 290 K.
→ Thermal Noise Floor - 1944
Noise figure defined; 290 K reference set.
→ Noise Figure ⇄ Noise Temperature - 1944
Cascade formula — first-stage dominance proven.
→ Cascade Noise Figure - 1946
The Friis transmission formula — FSPL formalized.
→ Free-Space Path Loss - 1946
Transmission formula — the budget's physics.
→ RF Link Budget - 1946
Isotropic-referenced link budgets — EIRP's home turf.
→ ERP ⇄ EIRP