MICROWAVE Engineering VIVA Questions :-
1. What is Microwave Engineering?
Ans. Microwave engineering is the study and design of microwave circuits , components , and systems. Fundamental principles are applied to analysis , design and measurement techniin this field.The short wavelengths involved distinguish this discipline from electronic engineering . This is because there are different interactions with circuits, transmissions and propagation characteristics at microwave frequencies.
2. Define s-matrix and its properties?
Ans. In a microwave junction there is an interaction of three or more components.There will be an output port, in addition there may be reflection from the junction of other ports. Totally there may be many combination, these are represented easily using a matrix called S matrix.
Properties of s- matrix
1. it possess symmetric properties sij=sji
2. it possess unitary property
3. Write the applications of microwave engineering?
Ans. Following are the applications of microwave engineering-
1. Antenna gain is proportional to the electrical size of the antenna. At higher frequencies, more antenna gain is therefore possible for a given physical antenna size, which has important consequences for implementing miniaturized microwave systems.
2. More bandwidth can be realized at higher frequencies. Bandwidth is critically important because available frequency bands in the electromagnetic spectrum are being rapidly depleted.
3. Microwave signals travel by line of sight are not bent by the ionosphere as are lower frequency
signals and thus satellite and terrestrial communication links with very high capacities are possible.
4. Why is s-matrix used in MW analysis?
Ans. Matrix is used in MW analysis to overcome the problem which occurs when H,Y & Z parameter are used in high frequencies.
5. What are the advantages of ABCD matrix?
Ans. The advantages of ABCD matrix are as follows-
1. They are used in power transmission lines
2. They are helpful in case of cascade networks.
6. What are junctions ? Give some example
Ans. A microwave circuit consists of several microwave devices connected in some way to achieve the desired transmission of MW signal. The interconnection of two or more microwave may be regarded as MW junction.
E.g.: TEE, HYBRID RING
7. What are non-reciprocal devices ?Give two examples?
Ans. The devices which are having the properties that the forward characteristics are not equal to the reverse characteristics are called non-reciprocal devices.
8. What are the applications of reflex klystron?
Ans. The main applications of a reflex klystron are as follows-
1. Signal source in MW generator
2. Local oscillators in receivers
3. It is used in FM oscillator in low power MW links.
4. In parametric amplifier as pump source.
9. What is the purpose of slow wave structures used in TWT amplifiers?
Ans. Slow wave structures are special circuits that are used in microwave tubes to reduce wave velocity in a certain direction so that the electron beam and the signal wave can interact. In TWT, since the beam can be accelerated only to velocities that are about a fraction of the velocity of light, slow wave structures are used.
10. Give two examples for two port junctions?
Ans. Following are the two examples of two port junctions-
1. The junction of two rectangular guides of unequal height
2. A symmetrical junction consisting of two similar rectangular guides joined by an Intermediate guide of greater width.
11. Which frequency is used in Microwave Oven?
12. What is the speed of Electromagnetic waves in free space?
13. How EM wave Propagates?
14. What is Ampere’s law?
15. what is Faraday’s law?
16. What is Gauss law?
17. What is mean by TEM wave?
18. What is mean by TE wave?
19. What is mean by TM wave?
20. What is mean by HE wave?
21. What is the role of Transmission line?
22. How many types of transmission lines are there?
23. What is the bandwidth of two wire transmission line?
24. Define Reflection coefficient?
25. Define VSWR?
26. What are the various losses occurred in transmission lines?
27. What is Stub and what are the various types?
28. What is single stub matching?
29. What is Double stub matching?
30. What is Wave guide?
31. Microwave travels in which form?
32. What are the various transmission lines for microwaves?
33. Multi conductor lines supports which mode of waves?
34. Single conductor lines supports which mode of waves?
35. Open Boundary structure supports which waves?
36. Which transmission line are unbalanced transmission lines?
37. What is mean by Dominant mode?
38. What is the dominant mode in Co axial line?
39. What are the lower order and higher order modes in co axial cables?
40. At which frequencies strip lines are widely used?
41. What is the dominant mode for strip line?
42. What are the losses in micro strip lines and how those can be compensated?
43. Which mode does not exist in micro strip lines?
44. Which transmission line has higher Quality factor?
45. What are the various types of micro strip lines?
46. Parallel strip lines supports which mode?
47. Why micro strip antenna are more popular?
48. What are the general modes in wave guides?
49. Define Phase velocity and Group velocity?
50. What is the dominant mode in Circular wave guide?
51. What are the main advantages of microwave integrated circuits?
52. What is planar transmission line?