Noise temperature of a radio receiver

Question

Question 1: Describe without giving mathematical analyses, how Johnson noise in a resistor and short noise in a vacuum diode are produced?

Question 2: Define the term equivalent noise temperature of a radio receiver. Under what conditions could this be more helpful quantity than the noise figure?

Question 3: Deduce an expression for the mean square thermal noise voltage of a resistor at temperature T in a given bandwidth.

Question 4: Describe the equivalent noise bandwidth of the R-C filter.

Question 5: Define the signal-noise ratio and noise figure of a receiver. If the latter are more appropriate piece of information than the equivalent noise temperature, compute the total noise figure of n-cascaded networks.

Question 6: Categorize the noise in electrical communication and describe each one in short. In brief state the methods employed to decrease the noise in receivers.

Question 7: Compute the noise voltage at the input of a television R.F. amplifier, by using a device that consists of a 200 Ω equivalent noise resistance and a 300 Ω input resistance. The bandwidth of the amplifier is 6 MHz and the temperature is 17^oC. The value of Boltzmann’s constant can be taken as 1.38 .10^-28 J/K.

Question 8: Determine the value of minimum input signal needed for a 20 db signal to noise ratio in a receiver with a pas band of 10 KHz and an input circuit containing a resistance of 10 KΩ at room temperature.

Question 9: A diode operates in a temperature limited area with a noisy external load resistor R = 10 KΩ and a DC played current of 0.01 mA. Assess the total r.m.s noise voltage across the resistor for a bandwidth of 5 KHz.

Question 10: A receiver, connected to an antenna of resistance of 50 ohm, has an equivalent noise resistance of 30 ohm. Determine the receiver noise figure.