The document discusses investigating the influence of different feed types on the performance of a rectangular patch antenna designed for 9.8 GHz. It summarizes four common feed types: microstrip line, coaxial probe, aperture coupling, and proximity coupling. It then presents the design and simulation of a rectangular patch antenna using each feed type in the HFSS software. Performance metrics like return loss, bandwidth, and polarization are analyzed and compared for each feed type. The aperture coupling feed achieved the best results with highest bandwidth and lowest VSWR, while microstrip line feed had the worst polarization purity.

1. INVESTIGATE THE INFLUENCE OF DIFFERENT
TYPES OF FEEDS ON THE PERFORMANCE OF
RECTANGULAR PATCH ANTENNA
Pavan Kumar Akula [389187]
Masters Information and Communication Systems
3rd Semester
Technische Universität Chemnitz

2. Abstract
To simulate and analyze the performance of a Rectangular Patch Antenna for a
given desired frequency of 9.8 GHz by using standard and popular feeds like
Microstrip line, Coaxial probe, Aperture coupling and Proximity coupling feed by
examining various parameters like radiation pattern, Gain, Bandwidth, Impedance
and polarization. Also, to design a Microstrip patch in such a way that the pattern is
maximum and to introduce the concept of fringing effects which occurs while
simulating a Microstrip antenna using transmission-Line model. We begin with this
easier illustrative model in the initial stages, simulate and understand its
performance.
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3. Table of contents
1.What makes an antenna to be considered as a good antenna?
2.Introduction to Microstrip Antenna.
3.Popular feeding methods available.
4.Design Parameters and mathematical formulas.
5.Results and discussion.
6.Conclusion.
7.References.
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4. What makes an antenna to be considered as a
good antenna?
• Consider it as transmission line.
• Feed point location.
• Standing Waves formation.
• Voltage and Current distributions
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[5]

5. Introduction to Microstrip Antenna
Microstrip Antenna also known as Patch Antenna find its applications in
Satellite, Military based applications because of its properties.
Basic Configuration: A thin metallic microstrip patch on a thin and grounded
dielectric substrate.
Well-known shapes that Microstrip Antennas are available: Rectangular and
Circular.
Coordinate system used: Polar Coordinate System.
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6. Concept of Fringing Fields and Effective Length
• Fringing fields are responsible for radiation.
• Influences the resonant frequency of Antenna.
• Due to finite Length and Width dimensions, the field at the edges undergo
fringing.
• Electrical Length increases by a value of 2 L.
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7. Radiating and Nonradiating slots
Radiating slots (#1,#2): Electric fields are in-phase with same magnitude and add
up. These fields are normal to patch.
Nonradiating slots (#3,#4): Current densities are of same magnitude but are in
opposite direction.So they cancel out with each other.
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8. Concept of E - Plane and H - Plane
E - Plane:
It is the plane containing all the E-field vectors along the direction of maximum
radiation. It is obtained when:
ϴ = 90°, 0° ≤ φ ≤ 90° and 270° ≤ φ ≤ 360°
H- Plane:
It is the plane containing all the H-field vectors along the direction of maximum
radiation. It is obtained when:
φ = 0°, 0° ≤ ϴ ≤ 180°
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9. Popular Feed Methods
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Microstrip Feed
Coaxial Feed
Proximity Coupling Feed
Aperture Coupling Feed

10. Comparison of various feed techniques
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Type of Feed Bandwidth Return loss VSWR Polarization purity
Microstrip feed Good Less Good Poor
Coaxial feed Good More Better Poor
Proximity coupling
feed
Better More Best Poor
Aperture coupling
feed
Best Less Poor Excellent

11. Design Parameters and mathematical formula
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Resonant Frequency 9.8GHz
Substrate Used with
Dielectric Constant
Rogers RT / Duroid 5880
(εr = 2.2)
Height of Substrate 1.575mm (60 mils)
Impedance 50 ohms
Length 8.81 mm
Width 12.1 mm
εeff 2.56

12. Parameters to analyze
1. Reflection Coefficient.
2. VSWR.
3. Co-polarization and Cross Polarization.
Co-polarization: It is the desired quantity which is obtained in H-Plane (φ = 0°)
Cross polarization: It is the un-desired quantity obtained in the E-Plane. (ϴ = 90°)
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13. Software Tool Used: Ansoft HFSS 13.0
Note: In order to obtain better values for the output parameters, the Antenna
dimensions are adjusted.
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14. Microstrip feed
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15. Coaxial feed
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16. Proximity Coupling feed
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17. Aperture Coupling feed
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18. 18
S. No. Type of Feed Return-loss
(in dB)
VSWR
(in dB)
Band Width
(in MHz)
1. Microstrip Feed -13.070 3.98 450
2. Coax Feed -13.785 3.606 750
3. Proximity Coupling Feed -37.537 0.230 70
4. Aperture Coupling Feed -21.928 1.394 40

19. Conclusion
In this project, we were able to analyze the performance of patch antenna when it
is subjected to different feeds. Also, we have observed various other parameters
like return-loss (dB), Bandwidth (MHz), VSWR (dB) and co as well as cross
polarization (dB) of antenna.
It is possible to have two different types of feeds that can be applied to a single
patch antenna for better performance only if we include a power divider circuit
that divides the input power amongst the two feeds.
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20. References
1. Pozar, David M., "Microstrip Antennas," Proceedings of the IEEE, vol.80, no.1, pp.79 - 91, Jan 1992.
2. Lier, E.; Jakobsen, K., "Rectangular microstrip patch Antennas with infinite and finite ground plane dimensions," Antennas and
Propagation, IEEE Transactions on, vol.31, no.6, pp.978 - 984, Nov 1983.
3. Long, S.A.; Walton, M., "A dual-frequency stacked circular-disc antenna," Antennas and Propagation, IEEE Transactions on,
vol.27, no.2, pp.270-273, Mar 1979.
4. Balanis, Constantine A, "Antenna Theory: Analysis and Design," 2nd ed., 1992, John Wiley & Sons, Inc., pp. 727-752.
5. Basic Antenna Design, (2015, July 4th)
Retrieved from http://www.qsl.net/aa0ni/antennafaq.html
6. Ramesh Garg, Prakash Bhartia, Inder Bahl, "Microstrip antenna design handbook," 2nd ed., 2001, Artech House, pp. 253-296.
7. Rogers Corporation, (2015, Oct 24). Rogers RT/Duriod 5880 Datasheet. Retrieved from
https://www.rogerscorp.com/documents/606/acm/RT-duroid-5870-5880-Data-Sheet.pdf
8. Carver, Keith R.; Mink, J., "Microstrip antenna technology," in Antennas and Propagation, IEEE Transactions on , vol.29, no.1,
pp.2-24, Jan 1981.
9. Amit Kumar, Jaspreet Kaur, Rajinder Singh, “Performance Analysis of Different Feeding Techniques,” International Journal of
Emerging Technology and Advanced Engineering Journal, Volume 3, Issue 3, March 2013.
10. HFSS User Guide, Ansoft Corporation (2015, Oct. 24). Retrieved from
http://www.cnam.umd.edu/anlage/HFSSv10UserGuide.pdf
11. Peter Joseph Bevelacqua, (2015, Oct 24). VSWR (Voltage Standing Wave Ratio). Retrieved from http://www.antenna-
theory.com/definitions/vswr.php
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