EC > GATE 2026 > Antennas
Consider the Friis’ transmission equation PR = (PTGTGRλ2)/(4πD)2, where PR and PT are the received and the transmitted powers, respectively.
GT and GR are the gain of transmitting and receiving antennas, respectively, D is the distance between the transmitting and receiving antennas, and λ is the wavelength in free space.
Given: GT = GR = 1.0, λ = 0.30 m and PT = +10 dBm.
Choose the distance (D), in km, from the following options at which the received power, PR = −90 dBm?
A
15/4π
B
15/2π
C
75/2π
D
3/4π

Correct :

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