prof. girish kumar - nptelnptel.ac.in/courses/108101092/week-12-reflector-antennas.pdf · reflector...
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![Page 1: Prof. Girish Kumar - NPTELnptel.ac.in/courses/108101092/Week-12-Reflector-Antennas.pdf · Reflector Antennas Prof. Girish Kumar Electrical Engineering Department, IIT Bombay gkumar@ee.iitb.ac.in](https://reader031.vdocuments.us/reader031/viewer/2022020204/5aeb3f947f8b9a585f8d61af/html5/thumbnails/1.jpg)
Reflector Antennas
Prof. Girish KumarElectrical Engineering Department, IIT Bombay
(022) 2576 7436
![Page 2: Prof. Girish Kumar - NPTELnptel.ac.in/courses/108101092/Week-12-Reflector-Antennas.pdf · Reflector Antennas Prof. Girish Kumar Electrical Engineering Department, IIT Bombay gkumar@ee.iitb.ac.in](https://reader031.vdocuments.us/reader031/viewer/2022020204/5aeb3f947f8b9a585f8d61af/html5/thumbnails/2.jpg)
Flat Reflector Antennas
CornerPlane
![Page 3: Prof. Girish Kumar - NPTELnptel.ac.in/courses/108101092/Week-12-Reflector-Antennas.pdf · Reflector Antennas Prof. Girish Kumar Electrical Engineering Department, IIT Bombay gkumar@ee.iitb.ac.in](https://reader031.vdocuments.us/reader031/viewer/2022020204/5aeb3f947f8b9a585f8d61af/html5/thumbnails/3.jpg)
Curved Reflector Antennas
Prime Focus Reflector Cassegrain Reflector
![Page 4: Prof. Girish Kumar - NPTELnptel.ac.in/courses/108101092/Week-12-Reflector-Antennas.pdf · Reflector Antennas Prof. Girish Kumar Electrical Engineering Department, IIT Bombay gkumar@ee.iitb.ac.in](https://reader031.vdocuments.us/reader031/viewer/2022020204/5aeb3f947f8b9a585f8d61af/html5/thumbnails/4.jpg)
Vertical Dipole Antenna over Infinite Perfect Ground Plane (Reflector)
![Page 5: Prof. Girish Kumar - NPTELnptel.ac.in/courses/108101092/Week-12-Reflector-Antennas.pdf · Reflector Antennas Prof. Girish Kumar Electrical Engineering Department, IIT Bombay gkumar@ee.iitb.ac.in](https://reader031.vdocuments.us/reader031/viewer/2022020204/5aeb3f947f8b9a585f8d61af/html5/thumbnails/5.jpg)
Directivity and Radiation Resistance of Vertical Dipole Antenna over Infinite Reflector
Directivity and radiation resistance of a vertical
infinitesimal dipole as a function of its height
above an infinite perfect electric conductor
![Page 6: Prof. Girish Kumar - NPTELnptel.ac.in/courses/108101092/Week-12-Reflector-Antennas.pdf · Reflector Antennas Prof. Girish Kumar Electrical Engineering Department, IIT Bombay gkumar@ee.iitb.ac.in](https://reader031.vdocuments.us/reader031/viewer/2022020204/5aeb3f947f8b9a585f8d61af/html5/thumbnails/6.jpg)
Radiation Pattern of Vertical Dipole Antenna over Infinite Ground Plane (Reflector)
Elevation patterns of a vertical infinitesimal dipole for
different heights above an infinite perfect electric conductor
![Page 7: Prof. Girish Kumar - NPTELnptel.ac.in/courses/108101092/Week-12-Reflector-Antennas.pdf · Reflector Antennas Prof. Girish Kumar Electrical Engineering Department, IIT Bombay gkumar@ee.iitb.ac.in](https://reader031.vdocuments.us/reader031/viewer/2022020204/5aeb3f947f8b9a585f8d61af/html5/thumbnails/7.jpg)
Horizontal Dipole Antenna over Infinite Ground Plane (Reflector)
![Page 8: Prof. Girish Kumar - NPTELnptel.ac.in/courses/108101092/Week-12-Reflector-Antennas.pdf · Reflector Antennas Prof. Girish Kumar Electrical Engineering Department, IIT Bombay gkumar@ee.iitb.ac.in](https://reader031.vdocuments.us/reader031/viewer/2022020204/5aeb3f947f8b9a585f8d61af/html5/thumbnails/8.jpg)
Directivity and Radiation Resistance of Horizontal Dipole Antenna over Infinite Reflector
Directivity
Radiation Resistance
Radiation resistance and directivity of a horizontal
infinitesimal electric dipole as a function of its height
above an infinite perfect electric conductor
![Page 9: Prof. Girish Kumar - NPTELnptel.ac.in/courses/108101092/Week-12-Reflector-Antennas.pdf · Reflector Antennas Prof. Girish Kumar Electrical Engineering Department, IIT Bombay gkumar@ee.iitb.ac.in](https://reader031.vdocuments.us/reader031/viewer/2022020204/5aeb3f947f8b9a585f8d61af/html5/thumbnails/9.jpg)
Radiation Pattern of Horizontal Dipole Antenna over Infinite Ground Plane (Reflector)
Elevation patterns of a horizontal infinitesimal dipole for
different heights above an infinite perfect electric conductor
![Page 10: Prof. Girish Kumar - NPTELnptel.ac.in/courses/108101092/Week-12-Reflector-Antennas.pdf · Reflector Antennas Prof. Girish Kumar Electrical Engineering Department, IIT Bombay gkumar@ee.iitb.ac.in](https://reader031.vdocuments.us/reader031/viewer/2022020204/5aeb3f947f8b9a585f8d61af/html5/thumbnails/10.jpg)
Corner Reflector Antenna
Top View of Corner
Reflector Antenna
Wave incident at 900 Corner
Reflector reflects back in the
same direction
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Corner Reflector Antenna
Prospective View Wire Grid Arrangement
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Images for Corner Reflector Antennas
3 Images for 900 Corner
Reflector Antenna 5 Images for 600 Corner
Reflector Antenna
![Page 13: Prof. Girish Kumar - NPTELnptel.ac.in/courses/108101092/Week-12-Reflector-Antennas.pdf · Reflector Antennas Prof. Girish Kumar Electrical Engineering Department, IIT Bombay gkumar@ee.iitb.ac.in](https://reader031.vdocuments.us/reader031/viewer/2022020204/5aeb3f947f8b9a585f8d61af/html5/thumbnails/13.jpg)
Images for Corner Reflector Antennas
7 Images for 450 Corner
Reflector Antenna11 Images for 300 Corner
Reflector Antenna
No. of Images = 360/α - 1
![Page 14: Prof. Girish Kumar - NPTELnptel.ac.in/courses/108101092/Week-12-Reflector-Antennas.pdf · Reflector Antennas Prof. Girish Kumar Electrical Engineering Department, IIT Bombay gkumar@ee.iitb.ac.in](https://reader031.vdocuments.us/reader031/viewer/2022020204/5aeb3f947f8b9a585f8d61af/html5/thumbnails/14.jpg)
90° Corner Reflector Antenna
1 1 2 2 3 3 4 4, , , , , , , , , ,E r E r E r E r E r
Total field will be sum of contributions
from the feed and its images.
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Array Factor for 90° Corner Reflector Antenna
Array factor of the 90° Corner Reflector Antenna:
In the Azimuthal Plane, ( = /2)
0
, 2 cos sin cos cos sin sinE
AF ks ksE
0
/ 2, 2 cos cos cos sinE
AF ks ksE
![Page 16: Prof. Girish Kumar - NPTELnptel.ac.in/courses/108101092/Week-12-Reflector-Antennas.pdf · Reflector Antennas Prof. Girish Kumar Electrical Engineering Department, IIT Bombay gkumar@ee.iitb.ac.in](https://reader031.vdocuments.us/reader031/viewer/2022020204/5aeb3f947f8b9a585f8d61af/html5/thumbnails/16.jpg)
Radiation Pattern of 900 Corner Reflector Antenna
For s > 0.7λ, main
beam splits.
For s = λ, null in
the broadside
direction.
![Page 17: Prof. Girish Kumar - NPTELnptel.ac.in/courses/108101092/Week-12-Reflector-Antennas.pdf · Reflector Antennas Prof. Girish Kumar Electrical Engineering Department, IIT Bombay gkumar@ee.iitb.ac.in](https://reader031.vdocuments.us/reader031/viewer/2022020204/5aeb3f947f8b9a585f8d61af/html5/thumbnails/17.jpg)
Array Factor of Corner Reflector Antenna for other α
= 60
, 4sin cos cos 32 2 2
oFor
X X YAF
= 45
, 2 cos( ) cos( ) 2cos cos2 2
oFor
X YAF X Y
= 30
3 3, 2 cos( ) 2cos cos cos( ) 2cos cos
2 2 2 2
oFor
Y XAF X X Y Y
sin cosX ks sin sinY ks where
![Page 18: Prof. Girish Kumar - NPTELnptel.ac.in/courses/108101092/Week-12-Reflector-Antennas.pdf · Reflector Antennas Prof. Girish Kumar Electrical Engineering Department, IIT Bombay gkumar@ee.iitb.ac.in](https://reader031.vdocuments.us/reader031/viewer/2022020204/5aeb3f947f8b9a585f8d61af/html5/thumbnails/18.jpg)
S-Limit for Corner Reflector Antennas
S < 0.7λ α = 900
There is Limit on S-value for
single lobe in the radiation pattern.
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Parabolic Reflector Antenna
For Parabola:
OP + PQ = constant = 2f
OP = r’ and PQ = r’cos’
So, r’ (1+ cos’) =2f
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Parabolic Reflector Antenna Equations
1 1
0 2 2
1
22tan tan1
16 16
fd
d
d ff
f d
f/d 0.4 0.5 0.6 0.7 0.8 1.0
θ0 64.0 53.1 45.2 39.3 34.7 28.1
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Gain and Aperture Efficiency of Parabolic Reflector Antenna
𝐒𝐩𝐢𝐥𝐥𝐨𝐯𝐞𝐫 𝐞𝐟𝐟𝐢𝐜𝐢𝐞𝐧𝐜𝐲 (∈𝒔): fraction of the total power that
is radiated by the feed, intercepted, and collimated by the
reflecting surface.
𝐓𝐚𝐩𝐞𝐫 𝐞𝐟𝐟𝐢𝐜𝐢𝐞𝐧𝐜𝐲 (∈𝒕) :uniformity of the amplitude
distribution of the feed pattern over the surface of the reflector.
𝐏𝐡𝐚𝐬𝐞 𝐞𝐟𝐟𝐢𝐜𝐢𝐞𝐧𝐜𝐲 (∈𝒑): phase uniformity of the field over
the aperture plane.
𝐏𝐨𝐥𝐚𝐫𝐢𝐬𝐚𝐭𝐢𝐨𝐧 𝐞𝐟𝐟𝐢𝐜𝐢𝐞𝐧𝐜𝐲 (∈𝒙) : polarization uniformity of
the field over the aperture plane
𝐁𝐥𝐨𝐜𝐤𝐚𝐠𝐞 𝐞𝐟𝐟𝐢𝐜𝐢𝐞𝐧𝐜𝐲 (∈𝒃)
𝑹𝒂𝒏𝒅𝒐𝒎 𝑬𝒓𝒓𝒐𝒓 𝑬𝒇𝒇𝒊𝒄𝒊𝒆𝒏𝒄𝒚 (∈𝒓)
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Effect of Feed Pattern on Efficiency
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Spillover and Taper Efficiencies of Parabolic Reflector Antenna
Reflector Aperture Angle, θ0
Spillover Efficiency
Taper Efficiency
Reflector Aperture Angle, θ0 (in degrees)
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Aperture Efficiency of Parabolic Reflector Antenna
Reflector Aperture Angle, θ0 (in degrees)
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Cassegrain Reflector Antenna
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Gain of Large Reflector Antennas