Final Presentation for ESP Design Project 2110

1. ESP2110
WIFIANTENNA DESIGN PROJECT
Picture from [1], p. 353

2. Contents
Introduction
1. Fabrication, design and parts
2. Reason for choice
Theory
1. Loop
2. Archery-target antenna
3. Impedance matching
4. VSWR
User design and future considerations
Performance analysis
Field testing
Conclusion
Credits

3. Introduction
Fabrication
Archery target antenna
Parasitic elements
 Main back reflector
 Front annular reflector
 Center small reflector
 Wooden back base for physical support
Driven element
 Z-shape
 1λ circular loop

4. Design overview
 Basic design and dimensions
from existing literature
 Optimum dimensions
derived mainly from
experimentation and
occasionally FD-TD method
 Modifications not tested
before include
1. the addition of secondary
rim
2. use with specified driven
element
Picture modified [2], p. 227

5. Back Reflector

6. Front + center reflector

7. 1λ circular loop

8. Introduction
Reason for choice
 Good match with project
requirement
 Relatively small size for its
Performance
 Flexibility with modifications :
 type of driven element used
 configuration of reflectors
Characteristics
required
Archery-target
Antenna
High gain √
High directivity √
Fixed, narrow band √
WIFI frequency band √

9. Loop theory
1λ circular loop
Radiation pattern
Pictures modified from [3]

10. 4:1 delay line type coax Balun
 1λ loop feedpoint impedance (Ω) ≈ 80-150
 L = 1/2λ
Causes 180° phase shiftas desired
Provides balanced input
Balun theory
Pictures from [5] and [6]

11.  Endoresonance antenna: open cavity
 Can be considered similar to waveguide
operation (resonant modes)
Archery-target antenna theory
Pictures from [1], p. 19

12. Archery-target antenna theory
 Influence of sub-reflector size
Small
Large
Pictures modified from [7], p. 4

13. Archery-target antenna theory
 Evolution of front reflectors
Maintaining backfire effect while
enlarging aperture size
Increasing directivity with
secondary rim on reflectors

14. Archery-target antenna theory
 Estimated radiation plot and directivity
Graphs from [2], p. 226

15. Impedance matching
 Determine lengths x1 and x2 using software Smith v3.10

16. Smith chart andVSRW of antenna with original
1λ line segment
Impedance matching

17. Practical approach to impedance matching
 Since Smith chart of antenna line segment is favourable
 And accuracy loss due to connectors and small physical
length of λ
 Take x1 ≈ 0
Impedance matching

18. Impedance matching
New Smith’s Chart andVSWR with stub

19. User design &
future considerations
User design
 Handle/ portable
 Rigid back wooden support
 Weather resistant due to lacquered wood
Future considerations
 Selective frequency using translucent aperture
 Increase aperture efficiency by using better dielectric
 Wider bandwidth using main conical
reflector and a smaller centre reflector
Pictures from [8], p. 115

20. Performance analysis
-80
-60
-40
-20
0
20
40
60
80
100
120
RSSI
signalQuality
2m
• RSSI -10 to 15
• Signal Quality 100
25m
• RSSI -50
• Signal Quality 80
2m
• RSSI -10 to 15
• Signal Quality 100
Loop A (Directed)
Loop A
Loop B
Loop B (Opposite)
2m
• RSSI -35
• Signal Quality 100
25m
• RSSI -58
• Signal Quality 80
2m
• RSSI -37
• Signal Quality 97

21. Field hunting

22. Field hunting – Objective A

23. Field hunting – Objective A

24. Field hunting – Objective B

25. Field hunting – Objective B

26. Field hunting – Objective C

27. Field hunting – Objective C

28. Field hunting - Summary

29. Conclusion
Fabrication
 Our antenna is durable and portable
 Well suited for the Objective
Overall Performance
 Up to standard for field testing
 Good Signal Quality

30. References and Credits
 [1]A. Kumar, H.D. Hristov, Microwave cavity antennas , Norwood, MA : Artech
House , 1989
 [2] M.Vidmar, “An Archery-TargetAntenna”, MicrowaveJournal, Vol. 48, No. 5,
pp.222-230, May 2005.
 [3] J. Bernhard, E.Michielssen and L. C.Godara, Eds., “Antenna Parameters,
Various Generic Antennas and Feed Systems, and Available Software”, in
Handbook of antennas in wireless communications , Boca Raton, FL : CRC Press,
2002, ch. 5, sec. 3.2
 [5]T.Tribuzio. (2011, Mar. 2). About Balun [Online]. Available:
http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=3767
 [6]A.Vernucci. (2011, Mar. 2). A Simple 50-ohmSingle-Band Balun [Online PDF].
Available: www.qsl.net/i0jx/balun.pdf
 [7] M. Rayner,A.D. Olver,A.D. Monk, “FD-TD design of short backfire antennas”,
IEE Proc.-Microw.Antennas Propag., Vol. 144, No. 1, pp. 1-6, Feb 1997
 [8] G. S. Kirov, “Design of Short Backfire Antennas”, IEEE Antennas Propagat.
Mag.,Vol. 51, No. 6, pp. 110-120, Dec 2009