MU Electronics and Telecom Engineering (Semester 8)
December 2014
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 is an unilateral figure of merit of an amplifier?
5 M
1 (b) What are the causes of low frequency noise and high frequency noise associated with the mixer?
5 M
1 (c) Derive the expression of overall noise figure in three cascaded stages of amplifiers.
5 M
1 (d) Prove that scattering matrix is symmetrical and reciprocal.
5 M

2 (a) Explain in the detail stability criteria for microwave amplifier.
10 M
2 (b) Explain two methods of broadband amplifier design.
10 M

3 Design an amplifier to have a gain 10 dB at 6 Ghz using a transistor with the following s-palameters (Z0=50Ω): [ S11=0.61angle-170^{circ}, S21=2.24angle 32^{circ}, S12=0 S22=0.72 angle -83^{circ} ] plot constant gain circle for Gs=1dB and GL=2 dB. Use matching sections with open-circuited shunt stubs.
20 M

4

A GaAs FET has the following S parameter and noise parameter at 1GHz (Z0=50Ω) S11=0.7$$\angle$$$$-155^{\circ}$$, S12=0, S21=5.0$$\angle$$180$$^{\circ}$$, S22=0.51$$\angle$$-20$$^{\circ}$$Fmin=3dB, $$\Gamma$$opt =0.45$$\angle$$180$$^{\circ}$$, $$R_N=4\Omega$$ .Design a Low noise amplifier for a noise figure of 3.5dB and power gain of 16dB.

20 M

5 (a)

A MOSFET is biased for Large signal class A operation with the following small-signal s-parameter at 5GHz.S11=0.55$$\angle$$-150$$^{\circ}$$, S12=0.04$$\angle$$20$$^{\circ}$$S21=3.5$$\angle$$170$$^{\circ}$$, S22=0.45$$\angle$$30$$^{\circ}$$The large signal S21=2.8$$\angle$$180$$^{\circ}$$.Design a Large signal class A amplifier with max. Transducer gain in 50Ω system.

10 M
5 (b) Derive the necessary condition for two port NR oscillator.
10 M

6 (a) Explain in detail signal ended diode mixer. Also explain mixer design aspects.
10 M
6 (b)

Design a transistor oscillator at 4GHz using GaAs FET in common gate configuration with 5nH inductor in series. Common gate configuration s-parameters are S11=2.18$$\angle$$ -35$$^{\circ}$$, S21=2.75$$\angle$$96$$^{\circ}$$,S12=1.26$$\angle$$18$$^{\circ}$$, S22=0.52$$\angle$$155$$^{\circ}$$.Select $$\Gamma_T$$ so that Gamma in >1

10 M

Write short note on:
7 (a) Noise figure test equipment
5 M
7 (b) Power amplifier linearity
5 M
7 (c) Comparison of microwave amplifier and oscillator.
5 M
7 (d) 1dB compression point.
5 M

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