Assignment:
Consider the signal a(t) = V cos(2πƒat + Φa), with ƒa = 4kHz and V = 1mV.
Signal is shifted in frequency around the center frequency of 8 MHz and sent through a channel made by two sections: Section 1 is represented by a copper pair followed by an amplifier restoring the signal level. The cable impedance is 100 , the length is 5 km, and the specific attenuation at 2 MHz is 2 dB/km and it is at room temperature 290 K. The amplifier has noise figure F1 equal to 10 dB. Section 2 is represented by a link with the same cable, with length 10 km, followed by the amplifier-receiver with gain 12 dB and noise figure F2 = 6 dB.
a) Determine the effective noise temperature at the input of the first cable due only to Section 1.
b) Determine the effective noise temperature at the input of the first cable due to both Sections.
c) Determine the output SNR assuming the source temperature TS = 290 K.
d) Exchanging the value of only the noise figure of the two amplifiers, does the output SNR get better, worse, or remain unchanged? Why?