# What is Received power value when distance value is 0 in Friis equation [closed]

The Friis equation is as follow.

$$P_r = P_tA_rA_t(\lambda/(4\pi d))^\alpha$$

where $$d$$ is distance between terminals, $$P_r$$ is received power, $$P_t$$ is transmission power, $$A_r, A_t$$ are the rx, tx antenna gains, respectively, and $$\lambda$$ is wavelength.

If $$d$$ is 0, the $$P_r$$ must be $$P_t$$. But in this equation, the $$P_r$$ is infinity.

How can I find $$P_r$$ in this situation? What formula is needed?

This formula is only valid for distances $$d$$ where the antennas are in the far field of each other, which implies that $$d >> \lambda$$.
When the distance is $$d=0$$, then there is no attenuation and basically you have a wired system with $$P_r=P_t$$; no formula is necessary.