Antenna Gain

Formula

Description

Antenna gain relates the effective aperture area of an antenna to the wavelength of the signal. A larger effective area captures more of the incoming wavefront, producing higher gain. The gain is referenced to an isotropic radiator (dBi), which is a theoretical point source radiating equally in all directions. This formula shows that for a fixed physical size, gain increases with frequency (shorter wavelength). This is why dish antennas and horn antennas become increasingly effective at higher frequencies. The effective area is typically smaller than the physical area due to aperture efficiency (typically 50-70% for parabolic dishes).

Variables

• G — Antenna gain (dBi)
• Ae — Effective aperture area (m²)
• λ — Wavelength (m)

Practical Notes

Typical antenna gains: dipole 2.15 dBi, patch antenna 6-9 dBi, Yagi 6-15 dBi, parabolic dish 20-40+ dBi. Higher gain antennas have narrower beamwidths: a 20 dBi dish has a beamwidth of about 10-15 degrees. For omnidirectional coverage, use low-gain antennas; for point-to-point links, use high-gain directional antennas.