How is antenna gain measured?
Antenna gain is measured mainly by gain transfer (substitution), comparing the AUT’s received power with that of a reference antenna of known gain such as a standard gain horn, and by the three-antenna method, which uses three pairwise Friis measurements to determine all three gains without a prior reference. Both are described in IEEE Std 149.[1][2]
How does gain transfer work?
With identical setup and range, GAUT(dBi) = Gref(dBi) + PAUT(dBm) − Pref(dBm), correcting for any mismatch differences. Accuracy depends on the reference antenna’s calibration, typically a few tenths of a dB for standard gain horns.[1]
How does the three-antenna method work?
For each pair (i, j) measured at distance R: Gi + Gj = 20·log10(4πR/λ) + 10·log10(Pr/Pt) in dB. Three equations give the three unknown gains. Far-field distance, polarization alignment and mismatch correction must be maintained.[1][2]
How is gain related to directivity measurement?
Directivity comes from integrating a full 3D pattern; dividing measured gain by directivity gives radiation efficiency. Partial gains for two orthogonal polarizations must be summed for total gain.[1][3]
Frequently asked questions
What is a standard gain horn?
A pyramidal horn with gain calculated or calibrated accurately, used as a reference.
Does mismatch affect gain measurement?
Yes; correct for it to obtain gain, or include it to report realized gain.
Can gain be measured in a near-field range?
Yes, by comparison or with calibrated probe and insertion measurements.
See also
References
Online sources accessed October 21, 2026; printed works cited by edition. See all sources.
- “IEEE Recommended Practice for Antenna Measurements (IEEE Std 149-2021)”. IEEE Antennas and Propagation Society. 2022.
- “Antenna Theory: Analysis and Design, 4th ed.”. C. A. Balanis, Wiley. 2016.
- “IEEE Standard for Definitions of Terms for Antennas (IEEE Std 145-2013)”. IEEE Antennas and Propagation Society. 2014.