What is the relationship between directivity, gain, and efficiency in antenna performance?

What is the relationship between directivity, gain, and efficiency in antenna performance?

• A. Gain equals efficiency times directivity
• B. Directivity equals gain
• C. Efficiency does not affect gain
• D. Gain equals directivity plus efficiency

Answer: (A)

The relationship being tested is how the antenna’s ability to concentrate energy in a direction and its efficiency in converting input power to radiated power combine to determine the actual gain. Directivity measures how focused the radiation pattern is, relative to an isotropic source, and ignores losses. Efficiency tells what fraction of the input power is radiated rather than wasted. The realized gain in any direction is the product of these two quantities: G = η × D. So when efficiency is 1 (a perfect, lossless antenna), gain equals directivity. If efficiency is less than 1, gain is reduced accordingly. The other statements don’t fit because directivity alone ignores losses, efficiency alone doesn’t describe directional performance, and adding them is not how power transfer works.

The relationship being tested is how the antenna’s ability to concentrate energy in a direction and its efficiency in converting input power to radiated power combine to determine the actual gain. Directivity measures how focused the radiation pattern is, relative to an isotropic source, and ignores losses. Efficiency tells what fraction of the input power is radiated rather than wasted. The realized gain in any direction is the product of these two quantities: G = η × D. So when efficiency is 1 (a perfect, lossless antenna), gain equals directivity. If efficiency is less than 1, gain is reduced accordingly. The other statements don’t fit because directivity alone ignores losses, efficiency alone doesn’t describe directional performance, and adding them is not how power transfer works.