Which term describes how focused the antenna radiation pattern is?

• A. Directivity
• B. Gain
• C. Efficiency
• D. Bandwidth

Answer: (D)

Directivity describes how concentrated the energy from an antenna is in a particular direction. It compares the radiation intensity in the direction of strongest focus to the average intensity radiated in all directions. A sharper, narrower main lobe means higher directivity because more power is directed into a smaller solid angle.

Gain is related but not the same: it accounts for how effectively the antenna converts input power into radiation in that direction, so losses reduce gain even if directivity is high. Efficiency is about how much of the input power actually becomes radiated power, regardless of direction. Bandwidth is about the range of frequencies over which the antenna performs well, not how tightly the radiation is focused.

So the term that captures how focused the radiation pattern is called directivity.