1(a)
Define signal to noise ration and noise figure with help of a noisy network. Explain test set up to measure signal to noise ratio.

5 M

1(b)
Prove that scattering matrix is symmetrical and reciprocal.

5 M

1(c)
Explain unilateral figure of merit.

5 M

1(d)
Explain the terms conversion loss and Isolation with reference to mixer.

5 M

2(a)
Consider two power BJT amplifiers used in circuit configuration shown below having following specification:

Assume that operating frequency is 1 Ghz and input power is 5.5 dBm. Specify correct BJT amplifiers that must be used at each stage to obtain 29.5 dBm output power. Assume each two way divider/combiner has 0.5 dB insertion loss.

Amplifier | Go(dB) | Gi(dB) | PidB(dBm) |

1 | 8 | 7 | 27 |

2 | 10 | 9 | 22 |

Assume that operating frequency is 1 Ghz and input power is 5.5 dBm. Specify correct BJT amplifiers that must be used at each stage to obtain 29.5 dBm output power. Assume each two way divider/combiner has 0.5 dB insertion loss.

10 M

2(b)
Discuss amplifier linearisation methods.

10 M

3(a)
For an ideal transformer with turns ratio n=n

_{1}/n_{2}prove that the scattering matrix is \[ S= \begin{bmatrix}\frac {n^2-1}{n^2+1} & \frac {2n}{n^2 +1} \\ \frac {2n}{n^2+1} & \frac {1-n^2}{n^2+1} \end{bmatrix} \]
10 M

3(b)
Define and explain noise correlation matrix for general noisy two port network. What is congruence transformation?

10 M

4
Design a transistor oscillator at 6GHz using an FET in CS configuration driving a 50Ω load on drain side. The S-parameters at 50 Ω are \[ S= \begin{bmatrix} 0.9 \angle 150 &0.2 \angle -15 \\ 2.6 \angle 50 & 0.5 \angle 105 \end{bmatrix} \] Calculate and plot output stability circle for \[|\Gamma_{IN}| >> 1. \ Choose \ \Gamma_T \ so \ that \ |\Gamma_{IN}|>>1 \] Design load and terminating networks.

20 M

5 (a)
Discuss various mixer topologies. Compare performance of various topologies.

10 M

5 (b)
Discuss generalised single ended mixer design approach. Give design consideration.

10 M

6 (a)
For a two port network the ABCD matrix is given as: \[ \begin{bmatrix} A &B \\C &D \end{bmatrix}= \begin{bmatrix}0.5 &j1.6 \\j1.6 &0.5 \end{bmatrix} \] Find scattering matrix if Zo=50 Ω. Find condition of reciprocity.

10 M

6 (b)
Discuss generator tuning networks for microwave oscillators.

10 M

7 (a)
A GaAs FET is biased for minimum noise figure and has following S parameters and noise parameter at 4 Ghz (Zo=50 Ω). \[ S= \begin{bmatrix}0.6 \angle -60 &0.05 \angle 26 \\ 1.9 \angle 81 & 0.5 \angle -60 \end{bmatrix} \\ F\min =1.6 dB \ \Gamma_{opt}=0.62 \angle 100 \ R_N=20 \Omega \] Design an amplifier with 2dB noise figure and maximum gain compatible with this noise figure. Assume device is unilateral

15 M

7 (b)
Consider the amplifier circuit shown below. The input and output matching network are to be designed using open circuited stubs for Γ

_{S}=0.5 ∠120 and Γ_{L}=0.4∠90. User Smith Chart.

5 M

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