A source with equivalent noise temperature T_s = 1000? K is followed by a cascade of three amplifiers having the specifications shown in Table A. 1. Assume a band width of 50 kHz.

(a) Find the noise figure of the cascade.

(b) Suppose amplifiers 1 and 2 are interchanged. Find the noise figure of the cascade.

(c)?Find the noise temperature of the systems of parts (a) and (b).

(d)?Assuming the configuration of part (a), find the required input signal power to give an output signal-to-noise ratio of?40?dB. Perform the same calculation for the system of part (b).

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Table A.1 Amplifier no. Te Gain 300 K 10 dB 30 dB 6 dB 30 dB 11 dB 3