Transmission power for Parabolic Antenna

[Marco Giordani]

Hi everybody,

I am considering a scenario where a parabolic antenna is simulating a directional transmission. In the simulation, I vary the beam widths and I realized that, at a certain distance, in all the cases, the SINR (received power) is always the same. 

I mean, when the beam is narrow (i.e. 10°), the received power shouldn't be higher that the one received, at the same distance, for a wider beam (i.e. 90°) since, in the first case, the tx power is concentrated in a smaller area?

Is this right or am I missing something?

Thank you all for your time.