Periodic Structures and its
Applications in Antennas
Debabrata Kumar Karmokar
Student ID: 42660130
Principal Supervisor: Prof Karu Esselle
Associate Supervisor: Prof Michael Heimlich
Course: COMP901 Academic Presentation and Writing Skills
1/19
Outlines:
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What is a Periodic Structure?
Importance of Periodic Structures
What is a Leaky-Wave Antenna (LWA)?
Physics of LWA
Integration of Periodic Structures with
Microstrip LWA (MLWA)
Key Prior Research
Aims and Expected Outcome
Methodology
Task Plan, Current Position, and Progress
Conclusion
Department of Engineering, Faculty of Science
2/19
What is a Periodic Structures?
• Periodic structure is finite or infinite repetition of unit cells in
one, two or three dimensions
• Appear in nature in such forms as beehives, crystals, etc.
Fig. 2. A finite beam on periodic simple supports
(Mead D. J., 1996)
Fig. 1. A beehive
(http://oneida.uwex.edu/2011/06/30/building-beehive/)
Fig. 3. Uniform planar PBG
on microstrip substrate
Fig. 4. Periodic stubs on a microstrip line
(Pozar, D. M., 2005 )
(Gupta, S. K.)
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3/19
Importance of Periodic Structures
Big
Small
(a)
(b)
Fig. 5. Current magnitude distribution on the patches (a) without PBG and
(b) with PBG (Zhang et al., 2004)
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4/19
What is a Leaky-Wave Antenna (LWA)?
• LWA belong to the more general class of traveling wave antenna in
which the guided wave gradually leaks out into the surrounding
space to produce radiation
• A wide-band microwave antenna that radiates a narrow beam
whose direction varies with frequency
+x
Broadside
Substrate
Radiation
Microstrip line
Feed point
-z
Backfire
Fig. 6. The earliest example of
a leaky-wave antenna
+y
+z
Endfire
Ground Plane
Fig. 7. Basic microstrip leaky-wave antenna (MLWA)
(Oliner et al., 1993)
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5/19
First Higher Order Mode of Microstrip
Transmission Line (MTL) and Half-Width LWA
Microstrip line
W/2
W
h
Substrate
Ground Plane
Via
Fig. 8. Microstrip transmission line (MTL) and its first higher order mode
Department of Engineering, Faculty of Science
6/19
Dispersion Diagram of MTL
3.0
EH0
EH1
2.0
EH2
kc/ko
1.0
Radiation
region
0
0
10
20
30
40
Fig. 9. Dispersion curves for the lowest mode and the first two higher modes in microstrip line
(The microstrip line dimensions are: W = 3.00 mm, h = 0.635 mm, ϵr= 9.80) (Oliner et al., 1986)
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7/19
Physics of LWA
• A leaky-wave antenna supports a fast wave with 𝛽 < 𝑘0
x
Ey
z
Fig. 10. An aperture with an electric field Ey (x,z) on it at x=0 (Jackson et al., 2008)
The electric field Ey (x,z) on the aperture (x=0) that has the form of a leaky wave,
𝐸𝑦 0, 𝑧 = 𝐴𝑒 −𝑗𝑘𝑧 𝑧 --------------- (1)
Where the complex wavenumber of the leaky wave is given by 𝑘𝑧 = 𝛽 − 𝑗𝛼
The field in the air region above the aperture (x>0) is given by
𝐸𝑦 𝑥, 𝑧 = 𝐴𝑒 −𝑗𝑘𝑧 𝑧 𝑒 −𝑗𝑘𝑥 𝑥 ----- (2) 𝑘𝑥 = 𝛽𝑥 − 𝑗𝛼𝑥
Where the vertical wavenumber is 𝑘𝑥 = 𝑘02 − 𝑘𝑧2 1/2 ----- (3)
x
From Eq. 3 we get 𝛽𝛼 = −𝛽𝑥 𝛼𝑥
----- (4)
The radiation angle is given by 𝜃𝑟 = 𝑠𝑖𝑛−1 (𝛽/𝑘0 )
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θr
k0
kx
kz=β
8/19
Physics of LWA (contd.)
𝛽𝛼 = −𝛽𝑥 𝛼𝑥
----- (4)
 0
 0
x  0
 0
x  0
x  0
Fig. 11. Ray diagram of power flow in the air region (a) exponential growth
(b) exponential decay (Jackson et al., 2008)
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9/19
Physics of LWA (contd.)
Fig. 12. Ray diagram for a finite leaky-wave propagation
(Jackson et al., 2008)
Fig. 13. Field level of a typical leaky-wave having  / k0  3 / 2 and  / k0  0.02
Department of Engineering, Faculty of Science
(Jackson et al., 2008)
10/19
Physics of Leaky-Wave Antenna (contd.)
The radiation angle is given by
𝜃𝑟 = 𝑠𝑖𝑛−1 (𝛽/𝑘0 )
Fig. 14. Normalized complex propagation constant for
a microstrip line (Line dimensions are: W = 11 mm,
h = 0.508 mm, ϵr= 2.2) (Liu et al., 2008)
Department of Engineering, Faculty of Science
11/19
Integration of Periodic Structures
with microstrip LWA (MLWA)
Fig. 16. Reconfigurable half-width MLWA
Fig. 15. (a) The 3D view of the periodic
half-width MLWA
(b) The layout of this periodic halfwidth MLWA
Fig. 17. ML over a ground plane with periodic
lattice of apertures (Gagnon et al., 2006)
(Li et al., 2010)
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12/19
Key Prior Research
References
Approach
Yuanxin, L., X. Quan, et al. (2011). "The HalfWidth Microstrip Leaky Wave Antenna With the
Periodic Short Circuits." Antennas and
Propagation, IEEE Transactions on 59(9): 34213423.
Series of short circuits with long
rectangular guide
2.
Park, W.-Y. and S. Lim (2011). "Multi-Beam
Leaky-Wave Antenna: Design, Analysis, and
Experiments." Electromagnetics 31(4): 247-257
Right-/left-handed meta surface with
defected ground surface
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3.
Kempel, L., E. Rothwell, et al. (2011).
Theoretical analysis of a varactor-loaded halfwidth leaky-wave antenna. General Assembly
and Scientific Symposium, 2011 XXXth URSI
Application of varactors with half-width
leaky-wave antenna
•
Ouedraogo, R. O., E. J. Rothwell, et al. (2011).
"A Reconfigurable Microstrip Leaky-Wave
Antenna With a Broadly Steerable Beam."
Antennas and Propagation, IEEE Transactions on
59(8): 3080-3083
Connection of lumped capacitors at the
free edge of the antenna through
computer controlled switch
1.
4.
Contributions
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One beam steered from -80 to
+100
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Another beam is fixed at 590
(Frequency range: 3.9 to 4.2 GHz)
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Main lobe scans from 1440 to
410
Poor radiation in broadside
The varactor controls the
complex wavenumber
Same pointing direction of the
main lobe across 1 GHz
Obtained the placement of
main beam at several selected
angles
No position of main beam at
backfire and endfire
Optimizer failed to fiend
switching configuration at -800
Gain is comparatively lower at
broadside
13/19
Aims and Expected Outcome
• To design 1D, 2D and 3D periodic structures capable of
supporting the leaky-wave antennas
• To make more energy efficient antenna using PBG
structures
• To integrate these periodic structures with leaky-wave
antennas
• Designing leaky-wave antennas that can scan the main
beam from endfire to back fire
• To develop leaky-wave theory in connection to solid state
PBG theory
• To provide experimental evidence supporting the claims in
the proposed branch
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14/19
Aims and Expected Outcome (contd.)
Fig. 18. Half-width MLWA: endfire to backfire scanning capability
(Expected outcome of this research)
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15/19
Methodology
• Calculation of initial dimensions of the periodic
structure
• Mathematical modelling of the antenna system
• Analysis of the modelled system
• Optimization methods development
• Observation of the electric current distribution
• Study the effect of change in geometry of the periodic
structures
• Fabrication and testing of entire assembly
• Post processing of measured and simulated results
• Comparison of the simulated results with practical data
Department of Engineering, Faculty of Science
16/19
1/09/2014
1/03/2014
1/09/2013
Task Name
Task 1- Literature Review
Task 2- Research Equipment and Software Training
Task 3- Mathematical Modeling
Task 4- Integration of Periodic Structure
Task 5- Simulation
Task 6- Data Analysis
Task 7- Fabrication
Task 8- Post Processing
We are here
Task 9- Summarization
Task 10- Thesis Writing and Submission
1/03/2013
1/09/2012
1/03/2012
Task Plan, Current Position, and Progress
Progress:
 Basic knowledge on LWA
 Prior research and scope in the field from journals and conference papers
 Training on CST Microwave Studio and HFSS
Department of Engineering, Faculty of Science
17/19
Conclusion
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MLWA provide excellent properties
Low profile, minimal weight, simple fabrication
MLWA have wide range of applications
Number of limitations in the previous research
– Broadside scanning
– Endfire and backfire scanning
• Successful completion of this project should
overcome most of the limitations
• Development of a novel periodic leaky-wave
antenna for continuous scanning from endfire to
backfire through broadside
Department of Engineering, Faculty of Science
18/19
Q&A
Department of Engineering, Faculty of Science
19/19
Department of Engineering, Faculty of Science
20/19