This was final presentation of our B. Tech. Thesis Project (BTP). Hope it will help you.

1. Studies on Microstrip Patch
Antennas for Cognitive Radio
(Under the Guidance of Prof. M. V. Kartikeyan)
Bhanwar Singh
Prateek Batla
Pratik Kumar

2. Overview
• Motivation and Scope
• Problem Statement
• Literature Survey
• Work Done
– Simulation
– Hardware Realization
• Results and Discussions
• Future Work
• Publications

4. Cognitive Radio
• First proposed by Joseph Mitola III in 1998
• A radio that can change its transmitter
parameters based on interaction with the
environment in which it works.
• Currently under development

5. Need for CR
• Available wireless bandwidth is limited and
most of it is already allocated to different
wireless services.
• But some of the allocated spectrum remains
idle most of the time.
• Cognitive Radio makes use of spectrum when
it is idle.

6. Requisite for Antennas
• Monitoring of spectrum – To find out which
part of spectrum is idle. Requires UWB
antenna which can sense a broader
bandwidth.
• Reconfigurablity – Change parameters to
work in idle part of spectrum. Requires a
narrowband reconfigurable antenna.

7. Problem Statement
• To design, fabricate and test a UWB antenna
for CR with following specifications –
• BW = 3.1 to 10.6 GHz
• S11 < -10 dB
• Gain < 5 dB
• Pattern = Approximately Omni directional

9. Some implementation of CR

10. UWB Antennas- Methods to improve
BW
• Increase substrate height
• Decrease permittivity
• Introduce slots
• Proper impedance matching
• Unbalanced structure

12. Process of Design
Design Specification
Initial Design
Parametric Analysis
Optimization
Final Parameter Selection

13. Initial Design

14. Initial Design….

15. Substrate Selection
• Minimum Epsilon
– Radiation Max.
– Bandwidth Increase
– But losses increase
PTFE(Poly Tetra Fluro Ethylene) εr=2.5

16. Feeding – Why CPW, not MS ?
• Mode purity
• Truly planar structure, can easily be mounted.
• Less radiation and dielectric loss.
• Higher impedances can be realized, 30 -140 Ω.
• Same impedance can be realized using
different feed gap and feed width

17. Impedance Matching
• Input impedance should be close to 50 Ω.
• Tapering – Changing feed width and gap.
• Abrupt changes introduce parasitic reactive
elements which can be very high at higher
frequencies, hence avoided.

18. Parametric Analysis
• Investigate antenna by varying one parameter
and keep all others constant.
• Results to notice are |S11| and input line
impedance.
• Important parameters are dimensions of
ellipse, gap between ellipse and ground, feed
length and tapering parameters.

19. Dimensions of ellipse

20. Ground Line Length

21. Gaps

22. Feed Widths

23. Optimization

25. Hardware Realization
Circuit
Confirm Port Measurem-
CST AutoCAD Board
Dimensions Preparation ents
Plotter

26. Hardware Realization
• Export design to CAD.
• Print antenna using dry etching.

27. Antenna
Dimensions were confirmed using microscope

28. S11 Measurement
• R&S VNA
• CaliberationProcess

29. Radiation Pattern Measurement

30. Calculation of Gain
• Using Friis’s Transmission Equation
Where Pr = Received power
Pt = Transmitted power
G0t = gain of transmitting antenna
G0r = gain of receiving antenna

32. Results..
• An antenna can be looked as –
1. A one port device
2. An EM device

33. S11

34. S11
• The ripples in the experimental results are due
to instrumental errors.
• Contact losses between the port and the
antenna.

35. Analytical Line Impedance
Close to 50 Ohms
Tapering was done to make it close to 50 ohms.
Causes reflections.

36. Surface
Current
EM Radiation
Gain
Behavior Pattern
Electric
Field

37. Surface Current

38. Surface Current Density
f= 3.46 GHz f=5.59 GHz f=6.5GHz
f = 8.46 GHz f=11 GHz

39. 3D Radiation Pattern
f= 3.46 GHz f=5.59 GHz f=6.5GHz
f = 8.46 GHz f=11 GHz

40. Mode Coupling

41. 2D Radiation Pattern
E - Plane
H plane
f= 3.46 GHz f=5.5GHz

42. 2D Radiation Pattern
E - Plane H plane
f= 11 GHz

44. Electric Field
f= 3.46 GHz f=5.59 GHz f=6.5GHz
f = 8.46 GHz f=11 GHz

45. Gain
Frequency Simulated Gain Experimental Gain
3.46GHz 2.655dB 2.342dB
5.5GHz 4.076dB 3.985dB
11GHz 4.885dB 4.462dB
• Low frequencies -> Long Wavelength -> Standing
Waves -> Oscillating mode -> Less Gain
• High frequencies -> Travelling mode -> More Gain

46. Limitations
• Radiation pattern bandwidth of antenna is
very short.
• Contact losses are very high at high
frequencies as port is simply soldered to the
antenna feeding system.

47. Future Work

48. Other Antennas Studied

49. Publication Under Review
• National Conference on “RECENT TRENDS IN MICROWAVE
TECHNIQUES AND APPLICATIONS”, organized by “University
of Rajasthan, Jaipur”
• A Planar Elliptical Monopole Antenna for UWB Applications
( Ref. No. MW1258)
• Antenna System for Cognitive Radio Application (Ref No.
MW1257)

50. Important References
• Y. Tawk, and C. G. Christodoulou, Member, IEEE, A New Reconfigurable
Antenna Design for Cognitive Radio
• Elham Ebrahimi, James R. Kelly, Peter S. Hall, Integrated Wide-Narrowband
Antenna for Multi-Standard Radio, IEEE TRANSACTIONS ON ANTEN-NAS
AND PROPAGATION, VOL. 59, NO. 7, JULY 2011
• J. Liang, C Chiau, X. Chen and C.G. Parini, Study of a Printed Circular Disc
Monopole Antenna for UWB Systems", IEEE Transactions on Antennas and
Propagation, vol. 53, no. 11, November 2005, pp.3500-3504.
• C.A. Balanis, Antenna Theory and Analysis, 2nd ed., Wiley, New York, 1997
D. M. Pozar, Microwave and RF Design of Wireless System, Wiley, New
York, 2001.
• CST’s user manual “www.cst.com”