MU Electronics and Telecom Engineering (Semester 8)
December 2013
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) What are the causes of low frequency noise and high frequency noise associated with the mixer?
5 M
1 (b) Find S-parameters of two port series network Z=50Ω and ZO=100Ω network.
5 M
1 (c) What are the characteristics of power amplifiers?
5 M
1 (d) Explain 1dB Compression point.
5 M

2 (a) A BJT with IC = 30 mA and VCE = 10V is operated at a frequency of 1 GHz in a 50Ω system. Its S-parameters are -
S11=0.73∠175°
S12=0
S21=4.45∠65°
S22=0.21∠-80°
Determine whether the transistor is unconditionally stable. If yes, calculate optimum terminations, GSmax, GLmax, GTUmax.
10 M
2 (b) Explain using suitable diagrams two methods of designing broad band amplifier.
10 M

3 (a) A BJT has the following s-parameters -
S11=0.65∠-95°
S12=0.035∠40°
S21=5∠115°
S22=0.8∠–35°
Is this transistor unconditionally stable? Draw input and output stability circles.
10 M
3 (b) Determine the stability of GaAs FET that has the following S-parameters at 2 GHz in a 50Ω systems both graphically and mathematically -
S11=0.89∠-60°
S12=0.02∠62°
S21=3.1∠123°
S22=0.7∠-27°
10 M

4 (a)

Derive the Transducer Power gain as
$$G_T = \dfrac {|S_{21}|^2 (1-|\tau_S|^2) (1-|\tau_L|^2)}{|1-\tau_S\tau_{in}|^2 |1 - S_{22}\tau_L|^2}$$

10 M
4 (b) If a one port microwave diode has Γin=1.5∠60° with respect to Z0=50Ω. Design an oscillator for desired frequency of 10GHz.
10 M

5 (a) Describe and classify in detail generator tuning networks.
10 M
5 (b) Explain in detail single ended diode mixer. What are mixer design considerations?
10 M

6 (a) Compare Microwave Amplifiers with Microwave Oscillators.
10 M
6 (b) What are the different techniques to obtain power amplifier linearity? Draw and explain feed forward technique.
10 M

7 (a) Balanced FET mixer.
5 M
7 (b) Noise figure test equipment.
5 M
7 (c) Power Distributed Amplifiers.
5 M
7 (d) Noise parameters at microwave frequencies.
5 M

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