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Microwave Engineering Viva Questions and Answers

1. Give the range of frequency Band of Microwave?

Microwaves are signals in the form of electromagnetic waves with wavelengths ranging from 1m to 1mm. The frequency range of microwaves is from 3 GHz to 300 GHz. The different frequency range bands are given below.
2. Why the Micro wave got the name as microwaves?
The meaning of microwaves is the small waves used for communication. Microwaves can travel in straight line. So in satellite communication, microwaves are most commonly used.
3. Discuss in detail about Electromagnetic Frequency Spectrum?
The different ranges of frequency in spectrum are given below:
4. List the major advantages of Microwaves?
The major advantages of microwaves are:
a. Microwave Supports larger bandwidth, so microwaves are widely used for point-to-point communications.
b. By using microwaves, it is possible to attain antenna gain more.
c. Since the bandwidth is more, high data transmission rates are possible.
d. As the frequency increases, the size of antenna gets reduced
e. Low power consumption.
f. Effect of fading is less.
g. Gives effective reflection area in the radar systems.
h. Used in Satellite and terrestrial communications
i. Effective spectrum usage.
5.  List the major applications of Microwaves?
Microwaves can be used in wide variety of applications like Military, Food industry, radio astronomy, medical applications, radar, semiconductor processing techniques,  spectroscopy etc.
6. Give the frequency band of Infrared Rays (IR)?
The range of IR of the visible spectrum at is from 700 nanometers (nm) to 1 millimeter (mm). This leads to a frequency range of approximately 430 THz down to 300 GHz.
7. Discuss the band of visible Light?
The frequency band of light is from about 4 × 1014 to 8 × 1014 cycles per second, or hertz (Hz) and wavelengths ranges from 740 nanometers (nm) or 2.9 × 10−5 inches, to 380 nm (1.5 × 10−5 inches).
8. Mention the band of  X Rays?
The frequency band of X rays ranges from10 picometres to 10 nanometres, and the frequencies ranges from 30 petahertz to 30 exahertz (3×1016 Hz to 3×1019 Hz).
9. What is the band of gamma Rays?
The frequency range of gamma rays are from 1020 - 1024 and the wavelength is in the range < 10 - 12 m
10. Define Phase velocity and Group velocity?
The velocity having a wave packet that travels is referred as group velocity. Whereas, the velocity having the phase of a wave that travels is referred as phase velocity.
11. The standard frequency used in Microwave Oven for heating is?
The most modern microwave ovens use a frequency of 2450 MHz (2.45 GHz) for heating.
12. Give the speed of Electromagnetic waves in free space?
In free space, the electromagnetic waves has a speed same as that of light, c = 3 x 108 m/s.
13. Explain about the propagation of EM waves?
When an electric charge (q) vibrates, the electromagnetic waves are generated. This generated wave has both an electric and a magnetic component. Light waves are the example of EM waves.
14. What is Faraday's law?
Faraday's law is defined as a current that would be induced in a conductor which is exposed to a varying magnetic field
15. Define Gauss law?
Gauss's law is defined as the net flux of an electric field that is closed in an enclosed surface is directly proportional to the enclosed electric charge.
16. Define Ampere's law?
Ampere’s law states that “the magnetic field caused by an electric current would be proportional to the size of electric current having a constant of proportionality corresponding to the permeability of free space”.
17. Define TEM wave?
Transverse electromagnetic (TEM) waves are those waves with a mode of propagation of waves, while the electric and magnetic field lines are transverse (normal wave) to the direction of propagation.
18. What you understand by Transverse Electric (TE) wave?
TE wave is an electromagnetic wave propagating in a medium, including free space, or any other medium in such a manner that the electric field vector is directed entirely transverse (perpendicular), to the general forward direction of propagation.
19. What is mean by Transverse magnetic (TM) waves?
TM waves, also known as E waves are characterised by the fact that the magnetic vector (H vector) is always perpendicular to the direction of propagation.
20. What you understand about EM wave?
Electromagnetic waves (EM) waves are the type of waves which are created by a result of vibrations between an electric field and a magnetic field. That is we can say that the EM waves are composed of oscillating magnetic and electric fields.
21. Discuss about the need of Transmission line?
The main use of transmission line is to reduce power loss, dissipated as heat because of the resistance of the conductors. For long distance power transmissions, high voltage transmission lines are mostly used. 
22. Discuss about the types of transmission lines?
The different types of transmission lines are:
a. Wave Guide
b. Fiber Optic
c. Balanced two wire
d. Co-axial cable
e. Microstrip
23. What is single stub matching?
In order to match any complex load to a transmission line, stub matching is used. Stub matching is group of shorted or opened segments of the line, which are connected in parallel or in series with the line at an appropriate distances from the load.
24. List the main advantages of microwave integrated circuits (MIC)?
The main advantages of MIC are:
a. Many (thousands) of devices can easily be fabricated in a single MMIC at the same time.
b. Overall cost of MMIC is less.
c. Mismatches in the MMIC between components are less.
d. Since the distances between the components are less, the signal delay is less in a MMIC.
e. The wire bond reliability issues are less.
25. Discuss about reflection coefficient?
Reflection coefficient can be defined as a parameter that describes how much of a wave is reflected by an impedance discontinuity in the transmission medium. In other words, reflection coefficient gives the amount of reflected waves in a transmission medium due to the impedance mismatching. 
26. Discuss about the different types of losses in transmission lines?
The losses occurred in transmission lines are mainly classified into three types. They are:
a. Copper Losses
b. Dielectric Losses
c. Radiation (Induction) Losses

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