| EC-302 Microwave Engineering (B.Tech 6th & 7th Semester, 2063) Time : 3 Hours Maximum Marks : 60 NOTE:- This paper consist of Three Sections. Section A is compulsory. Do any Four questions from Section B and any two questions from Section C Section-A Marks : 20 1 (a) What is back heating in tubes at microwave frequencies ? (b) List various methods of beam focusing in TWT's. (c) What is velocity modulation ? (d) What is current modulation ? (e) Why is tunnel diode loosely coupled to its cavity ? (f) What is the main idea behind obtaining -ve Resistance in a Gunn diode ? (g) List the biggest disadvantages of IMPATT diode. (h) What happens to the performance of PIN diode above 100 MHz ? (i) Why circular waveguides are preffered over rectangular waveguides in some applications ? (j) Why van TEM waves not be propagated in waveguides ? Section-B Marks:5 Each 2. Discuss probelms of transmit time effect in tubes at microwave frequencies. 3. Why stopping is needed in case of travelling wave magnitron ? 4. Discuss the applicaion of PIN diode as a modulator. 5. What is S-matrix ? Discuss properties of S-matrix. 6. A rectangular waveguide is 4.1 by 1.8 cm. Calculate the cut-off frequency of the dominant mode. Also determine a mode closest to the dominant mode. Section-C Marks : 10 Each 7. Discuss the operation of Travelling wave magnetron for pi-mode in detail and also discuss its applications. 8. What are the directional coupler ? Discuss the principle of operation and application of a two pole directional coupler. 9. Discuss Miscowave Bipolar Transistor and FETs ? Also discuss the high frequency limitations of Bipolar Transistors. |
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