MU Electronics and Telecom Engineering (Semester 8)
May 2012
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1 (a) Explain the properties of S-parameter.
5 M
1 (b) Explain Stability circles and its importance in amplifier design.
5 M
1 (c) Explain how noise parameters at microwave frequencies can be determined.
5 M
1 (d) Explain 1dB compression point.
5 M

2 (a) Find S parameters of 3 dB attenuator shown in Figure -
10 M
2 (b) Derive the Transducer Power gain as
10 M

3 (a) Define the figure of merit in unilateral microwave amplifiers. If unilateral gain of microwave amplifier is

show that

where GT is the transducer gain and GTU is the transducer gain in unilateral case.
10 M
3 (b) A BJT has the following S-parameters as a function of three frequencies. Determine in which of these cases, device is unconditionally stable and which has the greatest stability.
 Frequency (MHz) S11 S12 S21 S22 500 0.7∠-570 0.04∠470 10.5∠1360 0.79∠-330 750 0.56∠-780 0.05∠330 8.6∠1220 0.66∠-420 1000 0.46∠-970 0.06∠220 7.1∠1120 0.57∠-480
10 M

4 Design a transistor oscillator at 4 GHz using FET in a common gate configuration. An inductor of value 5nH is placed in series with the gate to increase stability. Choose a Terminating network to match a 50Ω load and an appropriate tuning network. The S-parameters of the transistor in a common gate configuration are:
S11=2.18∠-35°
S12=1.26∠18°
S21=2.75∠96°
S22=0.52∠155°
20 M

5 (a) For a two port oscillator at steady state oscillations prove that if, Ï„L Ï„in=1 then Ï„TÏ„OUT=1
10 M
5 (b) Discuss microwave amplifiers versus microwave oscillators.
10 M

6 GaAs FET has the following scattering and noise parameters at 4 GHz measured with 50Ω systems:
S11=0.6∠-60°
S12=0.05∠26°
S21=1.9∠81°
S22=0.5∠-60°
and Fmin=1.6dB, RN=20Ω and Γopt = 0.62°100°
Assuming the FET to be unilateral, design an amplifier using open circuited shunt stubs and transmission line lengths for a maximum possible gain and a noise figure no more than 2.0dB. Estimate the error introduced in GT due to this assumption.
20 M

Write shorts notes any two of the following:-
7 (a) Balanced FET mixer.
10 M
7 (b) Power Distributed Amplifiers.
10 M
7 (c) Microwave Resonators.
10 M

More question papers from Advanced Microwave Engg