This set of RF & Microwave Circuit Design Multiple Choice Questions & Answers (MCQs) focuses on “Noise Figure”.

1. __________ is defined as the ratio of input signal to noise ratio to the output signal to noise ratio.

a) Noise figure

b) Noise temperature

c) SNRo

d) None of the mentioned

2. The equivalent noise temperature of a network given the noise figure of the network or system is:

a) T_{0}(F-1)

b) T_{0}(F+1)

c) T_{0}(F)

d) T_{0}/F

3. ___________ is defined as the ratio of desired signal power to undesired noise power.

a) Signal to noise ratio

b) Noise to signal ratio

c) Noise figure

d) Noise temperature

4. Noise figure can be defined for any microwave network irrespective of any other constraints.

a) True

b) False

5. Noise equivalent temperature of a transmission line that adds noise to the noise of a device is:

a) T (L-1)

b) T (L+1)

c) T (L)

d) T/L

6. Noise equivalent temperature of a 2 stage cascade network is given by:

a) Te_{1} + Te_{2}/ G_{1}

b) Te_{1} + Te_{1}

c) Te_{1} / Te_{1}

d) None of the mentioned

7. Expression for noise of a two port network considering the noise due to transmission line and other lossy components is:

a) GkTB + GN_{added}

b) GkTB

c) GN_{added}

d) None of the mentioned

8. If the noise figures of the first stage of a two stage cascade network is 8 dB and the noise figure of the second stage is 7 dB and the gain of the first stage is 10, then the noise figure of the cascade is:

a) 8. 6 dB

b) 7.6 dB

c) 5.6 dB

d) 8.9 dB

9. When a network is matched to its external circuitry, the gain of the two port network is given by:

a) │S_{21}│^{2}

b) │S_{22}│^{2}

c) │S_{12}│^{2}

d) │S_{11}│^{2}

10. Noise equivalent temperature of Wilkinson coupler having a gain of 1/2L is given as:

a) T (2L-1)

b) T (2L+1)

c) T (2L*1)

d) T / (2L-1)

11. For a Wilkinson power divider of insertion loss L and the coupler is matched to the external circuitry, and then the gain of the coupler in terms of insertion loss is:

a) 2L

b) 1/2L

c) L

d) 1/L

12. Expression for over all noise figure of a mismatched amplifier is:

a) 1+ (F-1)/ (1 -│Г│^{2})

b) 1

c) 1+ (F-1)

d) (F-1)/ (1 -│Г│^{2})