Aperture Antenna Gain & Far-Field Distance
For an aperture antenna — a parabolic dish, horn, or array face — the gain grows with the physical area in wavelengths, scaled by the aperture efficiency. This tool gives the gain in dBi and the far-field (Fraunhofer) distance beyond which the radiation pattern is fully formed, which sets the minimum range for gain measurements.
Equations & Parameters ▸
\(G = \eta_a\dfrac{4\pi A}{\lambda^2} \qquad A_e = \eta_a A \qquad R_{\text{ff}} = \dfrac{2 D^2}{\lambda}\)
| A | Physical aperture area (m²). |
| ηa | Aperture efficiency (0–1). Typical dishes 0.5–0.7; horns 0.5–0.8. |
| f | Operating frequency (GHz). |
| D | Largest aperture dimension (m), for the far-field distance. If blank, a circular aperture of area A is assumed. |
| Ae | Effective aperture — the area an ideal antenna would need for the same gain. |
References: C. A. Balanis, Antenna Theory: Analysis and Design, 4th ed., Wiley, 2016. · J. D. Kraus & R. J. Marhefka, Antennas for All Applications, 3rd ed., McGraw-Hill, 2002.
Inputs
m²
Physical area0–1
GHz
Frequencym
For far-fieldResults
Gain
Gain—
Effective aperture—
Max (η=1)—
Range
Far-field distance—
Wavelength—
Diagram