Consider a communications receiver with 50- input impedance, a bandwidth of 3 kHz, and a 4 dB noise figure. (a) Find the minimum detectable signal

Consider a communications receiver with 50-Ω input impedance, a bandwidth of 3 kHz, and a 4 dB noise figure.

(a) Find the minimum detectable signal (in volts), or noise floor, for an output signal-to-noise ratio of 10 dB.

(b) Now consider this receiver when it is connected to an antenna with a noise figure of 20 dB. Note that antenna noise factor (or ratio) is defined to be

F _ant = (noise _ant + thermal noise)/ thermal noise

Or noise _ant = (F _ant - 1) * thermal noise. Therefore, the output noise, when referred to input is

N ₀ = N _ant + N _i + N _added = N _ant + F _recvr * kTB

where F _recvr , is the receiver's noise factor. Now find the input signal, i.e., minimum detectable signal, required for a 10 dB output signal-to-noise ratio. Compare this to your answer in part (a).