Radiated Immunity Required Power (V/m → W)
Estimate the amplifier power needed for radiated-immunity testing from target field, distance and antenna gain, including 80 % AM.
Worked example
Input: Target field strength 10 V/m, Antenna-to-EUT distance 3 m, Antenna gain 8 dBi
Result: Required power (unmodulated) 4.75468 W, Required power (unmodulated) 36.7712 dBm, Required power with 80 % AM 15.4052 W, Required power with 80 % AM 41.8767 dBm
Result: Required power (unmodulated) 4.75468 W, Required power (unmodulated) 36.7712 dBm, Required power with 80 % AM 15.4052 W, Required power with 80 % AM 41.8767 dBm
Formula
E = √(30·P·G) / d → P = (E·d)² / (30·G)
80 % AM: peak envelope ×1.8 → power ×3.24 (+5.1 dB)
How it works
In the far-field approximation E = √(30·P·G)/d, so the required power is P = (E·d)²/(30·G). The peak envelope of an 80 % AM signal is 1.8× the unmodulated amplitude, so the amplifier must deliver 3.24× the power (about +5.1 dB).
Practical tipThis is an idealised estimate. Actual power is settled in the chamber field-uniformity calibration and also includes cable and coupler losses and antenna mismatch. Select the amplifier with at least 3 dB of headroom, based on P1dB.
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Results and summaries are for reference. For certification and test reports use the latest official standard text and calibrated instrument data. Last updated: 2026-10-10