Consider a communications receiver with 50- input impedance, a bandwidth of 3 kHz, and a 4 dB
Question:
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).
Principles of Communications Systems, Modulation and Noise
ISBN: 978-8126556793
7th edition
Authors: Rodger E. Ziemer, William H. Tranter