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 G

show that

where G

_{T}is the transducer gain and G_{TU}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) | S_{11} | S_{12} | S_{21} | S_{22} |

500 | 0.7∠-57^{0} | 0.04∠47^{0} | 10.5∠136^{0} | 0.79∠-33^{0} |

750 | 0.56∠-78^{0} | 0.05∠33^{0} | 8.6∠122^{0} | 0.66∠-42^{0} |

1000 | 0.46∠-97^{0} | 0.06∠22^{0} | 7.1∠112^{0} | 0.57∠-48^{0} |

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:

S

S

S

S

S

_{11}=2.18∠-35°S

_{12}=1.26∠18°S

_{21}=2.75∠96°S

_{22}=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„_{T}Ï„_{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:

S

S

S

S

and F

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 G

S

_{11}=0.6∠-60°S

_{12}=0.05∠26°S

_{21}=1.9∠81°S

_{22}=0.5∠-60°and F

_{min}=1.6dB, R_{N}=20Ω and Γ_{opt}= 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 G

_{T}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