UNIT-V
PROPAGATION
PART – A
1.Define Sky wave.
Waves that arrive at the receiver after reflection in the ionosphere is called sky wave.
2.Define Tropospheric wave.
Waves that arrive at the receiver after reflection from the troposphere region is called Tropospheric wave.(ie 10 Km from Earth surface).
3.Define Ground wave.
Waves propagated over other paths near the earth surface is called ground wave propagation.
4.What are the type of Ground wave.
Ground wave classified into two types.
i. Space wave
ii. Surface wave.
5. What is meant by Space Wave?
It is made up of direct wave and ground reflected wave. Also includes the portion of energy received as a result of diffraction around the earth surface and the reflection from the upper atmosphere.
6. What is meant by Surface Wave?
* Wave that is guided along the earth’ s surface like an EM wave is guided by a transmission is called surface wave. Attenuation of this wave is directly affected by the constant of earth along which it travels.
7. What is meant by fading?
Variation of signal strength occur on line of sight paths as a result of the atmospheric conditions and it is called .It can not be predicted properly.
8. What are the type of fading?
Two types. i. Inverse bending.
ii. Multi path fading.
9. What is inverse and multi path fading?
Inverse bending may transform line of sight path into an obstructed one. Multi path fading is caused by interference between the direct and ground reflected waves as well as interference between two are more paths in the atmosphere.
10.What is meant by diversity reception?
To minimize the fading and to avoid the multi path interference the technique used are diversity reception. It is obtained by two ways.
i. Space diversity reception.
ii. Frequency diversity reception.
iii. Polarization diversity.
11. Define Space diversity Reception.
This method exploits the fact that signals received at different locations do not fade together. It requires antenna spaced at least 100 l apart are referred and the antenna which high signal strength at the moment dominates.
12 .Define frequency diversity Reception.
This method takes advantage of the fact that signals of slightly different frequencies do not fade synchronously. This fact is utilized to minimize fading in radio telegraph circuits.
13. Define polarization diversity reception.
* It is used in normally in microwave links, and it is found that signal transmitted over the same path in two polarizations have independent fading patterns. In broad band dish antenna system, Polarization diversity combined with frequency diversity reception achieve excellent results.
14.What is meant by Faraday’ s rotation?
Due to the earth’ s magnetic fields, the ionosphere medium becomes anisotropic and the incident plane wave entering the ionosphere will split into ordinary and extra ordinary waves/modes.
When these modes re-emerge from the ionosphere they recombine into a single plane wave again.
Finally the plane of polarization will usually have changed, this phenomenon is known as Faraday’ s rotation.
15. What are the factors that affect the propagation of radio waves?
i. Curvature of earth.
ii. Earth’ s magnetic field.
iii. Frequency of the signal.
iv. Plane earth reflection.
.16. Define gyro frequency.
Frequency whose period is equal to the period of an electron in its orbit under the influence of the earths magnetic flux density B.
17. Define critical frequency.
For any layer , the highest frequency that will be reflected back for vertical incidence is fcr =9Ömax
18. Define Magneto-Ions Splitting.
The phenomenon of splitting the wave into two different components (ordinary and extra-ordinary) by the earths magnetic field is called Magneto-Ions Splitting.
19. Define LUHF.
The lowest useful HF for a given distance and transmitter power is defined as the lowest frequency that will give satisfactory reception for that distance and power.
It depends on
i. The effective radiated power
ii. Absorption character of ionosphere for the paths between transmitter and receiver.
iii. The required field strength which in turn depends upon the radio noise at the receiving location and type of service involved .
20. Define Refractive index.
It is defined as n = c = Velocity of light in vaccum
---- ------------------------------------
Vp Phase velocity in medium
N=Öer
21. Define maximum Usable Frequency.
The maximum Frequency that can be reflected back for a given distance of transmission is called the maximum usable frequency (MUF) for that distance.
MUF = fcr_secFi
22. Define skip distance.
* The distance with in which a signal of given frequency fails to be reflected back is the skip distance for that frequency.The higher the frequency the greater the skip distance.
23.Define Optimum frequency?
Optimum frequency for transmitting between any two points is therefore selected as some frequency lying between about 50 and 85 percent of the predicted maximum usable frequency between those points.
24. What is wave impedance?
h= h0/Ö 1-(fc/f)
i.e., h= 377/Ö 1-(fc/f)
25. Define wave velocity and Group velocity?
Wave velocity vp = c / Ö(fc / f)2
Group velocity, vp vg = c2 vg=c2 /vp
PART –B
1. Explain in details about ionosphere? (8)
2. Explain space wave propagation and sky wave propagation? (16)
3. Explain the ground wave propagation? (8)
4. Discuss the effects of earth’s magnetic field on ionosphere radio wave
Propagation? (10)
5. Describe the troposphere and explain how ducts can be used for
Microwave propagation? (8)
6. Explain in details, the diversity reception methods? (8)
7. Explain the advantages of Tropospheric wave propagation and sky
wave propagation ? (8)
8. Deduce an expression for the critical frequency of an ionized region in
terms of its maximum ionization density ? (10)
9. Derive an expression for the refractive index of the ionosphere in
terms of the electron number density and frequency ? (10)
KEYWORDS:2009 ANNA UNIVERSITY CHENNAI B.E ELECTRONICS & COMMUNICATION ENGINEERING EC1352 (UNIT V) QUESTION PAPER,ANNA UNIVERSITY QUESTION PAPER,ANNA UNIVERSITY,ANNA UNIVERSITY CHENNAI,ANNA UNIVERSITY COIMBATORE,ANNA UNIVERSITY TRICHY,ANNA UNIVERSITY TIRUNELVELI,ANNA UNIVERSITY MADURAI,ANNA UNIVERSITY SYLLABUS,ANNA-UNIVERSITY RESULTS,ANNA UNIVERSITY DISTANCE EDUCATION,ANNA UNIVERSITY MBA-CENTRE FOR DISTANCE EDUCATION,ANNA UNIVERSITY SCHEDULE OF EXAMINATIONS,ANNA UNIVERSITY ADMISSION,ANNA UNIVERSITY COURSES,ANNA UNIVERSITY ACADEMIC,ANNA UNIVERSITY DEPARTMENTS,ANNA UNIVERSITY RESEARCH,ANNA UNIVERSITY MAIL,ANNA UNIVERSITY QUESTION PAPERS,ANNA UNIVERSITY COUNSELLING DATES,ANNA UNIVERSITY RE-EVALUATION RESULTS
PROPAGATION
PART – A
1.Define Sky wave.
Waves that arrive at the receiver after reflection in the ionosphere is called sky wave.
2.Define Tropospheric wave.
Waves that arrive at the receiver after reflection from the troposphere region is called Tropospheric wave.(ie 10 Km from Earth surface).
3.Define Ground wave.
Waves propagated over other paths near the earth surface is called ground wave propagation.
4.What are the type of Ground wave.
Ground wave classified into two types.
i. Space wave
ii. Surface wave.
5. What is meant by Space Wave?
It is made up of direct wave and ground reflected wave. Also includes the portion of energy received as a result of diffraction around the earth surface and the reflection from the upper atmosphere.
6. What is meant by Surface Wave?
* Wave that is guided along the earth’ s surface like an EM wave is guided by a transmission is called surface wave. Attenuation of this wave is directly affected by the constant of earth along which it travels.
7. What is meant by fading?
Variation of signal strength occur on line of sight paths as a result of the atmospheric conditions and it is called .It can not be predicted properly.
8. What are the type of fading?
Two types. i. Inverse bending.
ii. Multi path fading.
9. What is inverse and multi path fading?
Inverse bending may transform line of sight path into an obstructed one. Multi path fading is caused by interference between the direct and ground reflected waves as well as interference between two are more paths in the atmosphere.
10.What is meant by diversity reception?
To minimize the fading and to avoid the multi path interference the technique used are diversity reception. It is obtained by two ways.
i. Space diversity reception.
ii. Frequency diversity reception.
iii. Polarization diversity.
11. Define Space diversity Reception.
This method exploits the fact that signals received at different locations do not fade together. It requires antenna spaced at least 100 l apart are referred and the antenna which high signal strength at the moment dominates.
12 .Define frequency diversity Reception.
This method takes advantage of the fact that signals of slightly different frequencies do not fade synchronously. This fact is utilized to minimize fading in radio telegraph circuits.
13. Define polarization diversity reception.
* It is used in normally in microwave links, and it is found that signal transmitted over the same path in two polarizations have independent fading patterns. In broad band dish antenna system, Polarization diversity combined with frequency diversity reception achieve excellent results.
14.What is meant by Faraday’ s rotation?
Due to the earth’ s magnetic fields, the ionosphere medium becomes anisotropic and the incident plane wave entering the ionosphere will split into ordinary and extra ordinary waves/modes.
When these modes re-emerge from the ionosphere they recombine into a single plane wave again.
Finally the plane of polarization will usually have changed, this phenomenon is known as Faraday’ s rotation.
15. What are the factors that affect the propagation of radio waves?
i. Curvature of earth.
ii. Earth’ s magnetic field.
iii. Frequency of the signal.
iv. Plane earth reflection.
.16. Define gyro frequency.
Frequency whose period is equal to the period of an electron in its orbit under the influence of the earths magnetic flux density B.
17. Define critical frequency.
For any layer , the highest frequency that will be reflected back for vertical incidence is fcr =9Ömax
18. Define Magneto-Ions Splitting.
The phenomenon of splitting the wave into two different components (ordinary and extra-ordinary) by the earths magnetic field is called Magneto-Ions Splitting.
19. Define LUHF.
The lowest useful HF for a given distance and transmitter power is defined as the lowest frequency that will give satisfactory reception for that distance and power.
It depends on
i. The effective radiated power
ii. Absorption character of ionosphere for the paths between transmitter and receiver.
iii. The required field strength which in turn depends upon the radio noise at the receiving location and type of service involved .
20. Define Refractive index.
It is defined as n = c = Velocity of light in vaccum
---- ------------------------------------
Vp Phase velocity in medium
N=Öer
21. Define maximum Usable Frequency.
The maximum Frequency that can be reflected back for a given distance of transmission is called the maximum usable frequency (MUF) for that distance.
MUF = fcr_secFi
22. Define skip distance.
* The distance with in which a signal of given frequency fails to be reflected back is the skip distance for that frequency.The higher the frequency the greater the skip distance.
23.Define Optimum frequency?
Optimum frequency for transmitting between any two points is therefore selected as some frequency lying between about 50 and 85 percent of the predicted maximum usable frequency between those points.
24. What is wave impedance?
h= h0/Ö 1-(fc/f)
i.e., h= 377/Ö 1-(fc/f)
25. Define wave velocity and Group velocity?
Wave velocity vp = c / Ö(fc / f)2
Group velocity, vp vg = c2 vg=c2 /vp
PART –B
1. Explain in details about ionosphere? (8)
2. Explain space wave propagation and sky wave propagation? (16)
3. Explain the ground wave propagation? (8)
4. Discuss the effects of earth’s magnetic field on ionosphere radio wave
Propagation? (10)
5. Describe the troposphere and explain how ducts can be used for
Microwave propagation? (8)
6. Explain in details, the diversity reception methods? (8)
7. Explain the advantages of Tropospheric wave propagation and sky
wave propagation ? (8)
8. Deduce an expression for the critical frequency of an ionized region in
terms of its maximum ionization density ? (10)
9. Derive an expression for the refractive index of the ionosphere in
terms of the electron number density and frequency ? (10)
KEYWORDS:2009 ANNA UNIVERSITY CHENNAI B.E ELECTRONICS & COMMUNICATION ENGINEERING EC1352 (UNIT V) QUESTION PAPER,ANNA UNIVERSITY QUESTION PAPER,ANNA UNIVERSITY,ANNA UNIVERSITY CHENNAI,ANNA UNIVERSITY COIMBATORE,ANNA UNIVERSITY TRICHY,ANNA UNIVERSITY TIRUNELVELI,ANNA UNIVERSITY MADURAI,ANNA UNIVERSITY SYLLABUS,ANNA-UNIVERSITY RESULTS,ANNA UNIVERSITY DISTANCE EDUCATION,ANNA UNIVERSITY MBA-CENTRE FOR DISTANCE EDUCATION,ANNA UNIVERSITY SCHEDULE OF EXAMINATIONS,ANNA UNIVERSITY ADMISSION,ANNA UNIVERSITY COURSES,ANNA UNIVERSITY ACADEMIC,ANNA UNIVERSITY DEPARTMENTS,ANNA UNIVERSITY RESEARCH,ANNA UNIVERSITY MAIL,ANNA UNIVERSITY QUESTION PAPERS,ANNA UNIVERSITY COUNSELLING DATES,ANNA UNIVERSITY RE-EVALUATION RESULTS