Question
What is the difference in radiated power between a lossless antenna with gain and an isotropic radiator driven by the same power?
Answer Options
- A) The power radiated from the directional antenna is increased by the gain of the antenna
- B) The power radiated from the directional antenna is stronger by its front-to-back ratio
- C) They are the same
- D) The power radiated from the isotropic radiator is 2.15 dB greater than that from the directional antenna
Correct Answer: C
Explanation
The gain of an antenna is a measure of its directivity, meaning how well it concentrates its total radiated power in a specific direction. Since both the antenna with gain and the hypothetical isotropic radiator are defined as lossless, they both radiate 100% of the power fed to them.
Since no power is lost to heat in either scenario, the total power radiated by both antennas is mathematically the same. The difference is merely in the distribution of that power: the hypothetical isotropic radiator distributes it equally in all directions, while the directional antenna concentrates it in the direction of its main lobe, resulting in its gain (a higher power density in that specific direction).
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