Question

3. (a) What is noise, noise voltage and noise power due to a resistor and why understanding and controlling of noise is critical in telecom signal transmission? Estimate the noise voltage and noise power generated by a 1 MO resistor at RT 40 °C if BW is 18 MHz. Is this noise significant? [Hint: en V 4kT (Bw)R, Pn kT (BW), k 1.38x102 [10] (b) Define channel capacity C and explain how it is affected by the S/N ratio. The bandwidth of an audio system is restricted to 20 kHz. Determine the system capacity if the S/N ratio is 10000, using Shannon Theorem. [Hints: C-(BW) logio (1+S/N)/logi02 [5] (c) Explain the concept of noise figure NF and noise ratio NR, and express them in dB form. If a receiver accept a 20 W signal with 0.1 W noise and add another 0.1 W noise from within itself, calculate the S/N ratio both at the input and out put of the receiver as ratio and dB form. Determine receiver's NF and NR. 10]

Answer 1

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