Absolute Power Measurement
| Method | Accuracy | Frequency-resolved? |
|---|---|---|
| Power meter + sensor | ±0.03 dB (traceable) | No (total power only) |
| Spectrum analyzer | ±0.5–1.5 dB | Yes (frequency-selective) |
| VNA S21 (relative) | Relative only | Yes (with calibration) |
EIRP Calculation
EIRP = P_tx + G_antenna − losses [all in dBm or dBi] Example: smartphone LTE TX PA output: +24 dBm Cable + switch loss: −0.8 dB Antenna gain (PIFA): −1 dBi (inefficient on small handset) EIRP = 24 − 0.8 − 1 = +22.2 dBm (166 mW EIRP) 3GPP LTE UE spec: EIRP ≤ +23 dBm → OK ✓
Free-Space Path Loss
FSPL (dB) = 20·log₁₀(4πdf/c) Simplified: FSPL ≈ 20·log₁₀(f_MHz) + 20·log₁₀(d_km) + 40 At 2.4 GHz, 100m: FSPL = 67.6 + (−20) + 40 = 87.6 dB At 2.4 GHz, 1km: FSPL = 67.6 + 0 + 40 = 107.6 dB
RF View dBm Calculator: Convert between dBm, watts, and EIRP in RF View's Utilities tab. Compute link budgets using NF Cascade Calculator for receiver sensitivity. Free on Android.