Antenna gain expressed in dBi is measured relative to what reference?

Antenna gain expressed in dBi is measured relative to what reference?

• A. Isotropic radiator
• B. Dipole antenna
• C. Half-wave resonator
• D. Uniform radiation pattern

Answer: (A)

Antenna gain expressed in dBi is measured relative to an isotropic radiator. An isotropic radiator is a theoretical antenna that would emit power equally in all directions, with no preferred beam direction. When we say an antenna has a gain of X dBi, we’re comparing its radiation intensity in a given direction to what that same direction would receive from the isotropic reference, and we express that difference in decibels. The “i” in dBi stands for isotropic, providing a universal baseline. (For contrast, gains relative to a real dipole use dBd, and a half-wave dipole itself is about 2.15 dB above isotropic, so it would be 2.15 dBi higher than its dBd value.)

Antenna gain expressed in dBi is measured relative to an isotropic radiator. An isotropic radiator is a theoretical antenna that would emit power equally in all directions, with no preferred beam direction. When we say an antenna has a gain of X dBi, we’re comparing its radiation intensity in a given direction to what that same direction would receive from the isotropic reference, and we express that difference in decibels. The “i” in dBi stands for isotropic, providing a universal baseline. (For contrast, gains relative to a real dipole use dBd, and a half-wave dipole itself is about 2.15 dB above isotropic, so it would be 2.15 dBi higher than its dBd value.)