What is Directivity (D) defined as?

What is Directivity (D) defined as?

• A. Directivity
• B. HPBW
• C. BWFN
• D. Radiation Pattern

Answer: (A)

Directivity tells you how focused the radiated power is in a particular direction compared with the average power across all directions. It is defined as the ratio of the radiation intensity in a given direction to the average radiation intensity over all directions. Since the average intensity is the total radiated power divided by 4π, you can write D = U(θ, φ) / (P_rad / 4π) = 4π U(θ, φ) / P_rad. An isotropic radiator has D = 1, and more directional antennas have D > 1. The radiation pattern is the graphical representation of U(θ, φ) versus direction; measures like HPBW or BWFN describe the beam’s angular extent but are not the definition of directivity itself.

Directivity tells you how focused the radiated power is in a particular direction compared with the average power across all directions. It is defined as the ratio of the radiation intensity in a given direction to the average radiation intensity over all directions. Since the average intensity is the total radiated power divided by 4π, you can write D = U(θ, φ) / (P_rad / 4π) = 4π U(θ, φ) / P_rad. An isotropic radiator has D = 1, and more directional antennas have D > 1. The radiation pattern is the graphical representation of U(θ, φ) versus direction; measures like HPBW or BWFN describe the beam’s angular extent but are not the definition of directivity itself.