STUPIDSID
1 (a)
Find S-parameter of two port series-network with Z=100 ω and Zo=50ω.
5 M
1 (b)
Derive the expression of overall noise figure in three cascades stages of amplifiers.
5 M
1 (c)
Define stability. List the various criteria for stability.
5 M
1 (d)
What are the characteristics of power amplifiers?
5 M
2 (a)
A BJT with Ic=30mA and VCE=10V is operated at a frequency of 1.0 Ghz in a 50Ω system.
Its S-parameters are:
S11=0.73 ∠ 175° ;
S22=0.21 ∠ -80°
S12=0.0;
S21=4.45 ∠ 65°
Determine whether the transistor is unconditionally stable. If yes, calculate the optimum terminations.
Gs, max, GL, max and GTU, max.
Its S-parameters are:
S11=0.73 ∠ 175° ;
S22=0.21 ∠ -80°
S12=0.0;
S21=4.45 ∠ 65°
Determine whether the transistor is unconditionally stable. If yes, calculate the optimum terminations.
Gs, max, GL, max and GTU, max.
10 M
2 (b)
Explain using suitable diagrams two methods of designing broad band amplifier.
10 M
3 (a)
Determine stability of GaAs FET that has the following S-parameter at 2GHz in a 50Ω system both graphically and mathematically. \[ S= \begin{bmatrix}
0.89 \angle - 60^\circ & 0.02 \angle 62^\circ \\ 3.1 \angle 123 ^\circ
& 0.78 \angle -27 ^\circ
\end{bmatrix} \]
10 M
3 (b)
Derive the transducer power gain as: \[ G_T = \dfrac {P_L}{P_{avg}} = \dfrac {|s_{21}|^2 \left (1-|\Gamma s|^2 \right ) \left ( 1-|\Gamma L |^2 \right )}{|1-\Gamma s \Gamma in|^2 |1-ss_{22} \Gamma L |^2} \]
10 M
4
Design a transistor oscillator at 6GHz using an FET in CG configuration driving a 50ω load drain side. The S parameters at 50 Ω are \[S= \begin{bmatrix} 0.9 \angle 150^\circ &0.2 \angle - 156\circ \\2.6 \angle 50 ^\circ & 0.5 \angle 105^\circ \ \ \ \
\end{bmatrix} \] 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)
Compare microwave amplifier with microwave oscillators.
10 M
6 (a)
A GaAs FET is biased for minimum noise figure and has following S parameter and noise parameter at 4 Ghz (zo=50Ω) \[ S= \begin{bmatrix}
0.6 \angle -60 ^\circ & 0.05 \angle 26^\circ \ \ \\ 1.9 \angle 81 ^\circ \ \ \ \ & 0.5 \angle - 60^\circ
\end{bmatrix} \] Fmin=1.6 dB, Γopt=0.62 ∠ 100°, RN=20Ω.
Design an amplifier with 2 dB noise figure and maximum gain compatible with this noise figure. Assume device is unilateral.
Design an amplifier with 2 dB noise figure and maximum gain compatible with this noise figure. Assume device is unilateral.
15 M
6 (b)
Prove that scattering matrix is symmetrical and reciprocal.
5 M
7 (a)
Noise figure test equipment.
5 M
7 (b)
1 dB compression point.
5 M
7 (c)
Amplifier linearisation methods.
5 M
7 (d)
Single ended diode mixer.
5 M
More question papers from Advanced Microwave Engg