Antenna gain and aperture

Question

Consider two different antennas with equal gain. Let's say one of them is a vivaldi antenna

and the other is a horn antenna

I want to learn how much of the incident power these antenna will be able to receive. As I have specified, their gain (in terms of dBi) are equal. But it makes no sense to me that an antenna like the vivaldi antenna would be able to receive the same amount of power as a horn antenna since it is so very thin.

However, Friis Transmission Formula does only cares about the antenna gains. Am I missing something, would the cross sectional area make no difference?

Answer 1

The receiving and transmitting patterns of a antenna are the same. That's a fundamental property of antennas from physics.

So yes, your two antennas with the same gain, pointed at the same transmitting antenna will received the same strength of signal.

You mention that the first antenna is very thin, so you wonder how it can handle the same power. It can't, but that is independent of the fraction of power from the transmitting antenna it will receive. Generally receiving power is very low, so this doesn't usually matter. However, the total power the first antenna can handle before it melts or whatever is lower, but it will still receive the same power until then.

This is the same as a 1/4 W 10 kΩ resistor used in a 5 V opamp circuit acts the same as a 2 W power resistor of 10 kΩ. You only see the difference when you try to put more power into the resistors. Up until 1/4 W, you can't electrically tell the difference between the two. At 2 W, the first resistor will melt, vanish into a cloud of greasy black smoke, or whatever, while the second resistor keeps on going.