A receive antenna, with gain and noise temperature T S = 120 K, feeds a coaxial cable. The cable…

A receive antenna, with gain  and noise temperature TS = 120 K, feeds a coaxial cable. The cable line has length dC = 10 km and a specific attenuation  at the frequency of 1 MHz. The coaxial cable is followed by an amplifier with gain (gA)dB = 20 dB and noise figure (FA)dB = 5 dB. Let the system be matched. Determine:

a) The amplifier output power if the received power at the antenna input is

and the transmitted signal is narrowband with bandwidth B = 5 MHz centered at f0 = 100 MHz.

b) The noise power at the system output.

c) How does the noise power change if the cascade cable-amplifier is substituted by two coaxial cables each of length 5 km (and with the same characteristics of the 10 km cable) and each followed by a repeater with gain (gA)dB = 10 dB and noise figure (FA)dB = 6 dB?


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