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Periodic Structures and its Applications in Antennas

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 . Outlines:. What is a Periodic Structure?

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Periodic Structures and its Applications in Antennas

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  1. Periodic Structures and its Applications in Antennas Debabrata Kumar Karmokar Student ID: 42660130 Principal Supervisor: Prof KaruEsselle Associate Supervisor: Prof Michael Heimlich Course: COMP901 Academic Presentation and Writing Skills

  2. Outlines: • 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

  3. 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. 4. Periodic stubs on a microstripline (Pozar, D. M., 2005 ) Fig. 3. Uniform planar PBG on microstrip substrate (Gupta, S. K.) Department of Engineering, Faculty of Science

  4. Importance of Periodic Structures Big Small Fig. 5. Current magnitude distribution on the patches (a) without PBG and (b) with PBG (Zhang et al., 2004) Department of Engineering, Faculty of Science

  5. 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 - z Endfire Backfire Ground Plane + y Fig. 6. The earliest example of a leaky-wave antenna (Oliner et al., 1993) Fig. 7. Basic microstrip leaky-wave antenna (MLWA) Department of Engineering, Faculty of Science

  6. First Higher Order Mode of Microstrip Transmission Line (MTL) and Half-Width LWA Microstrip line h Substrate Via Ground Plane W Fig. 8. Microstrip transmission line (MTL) and its first higher order mode W/2 Department of Engineering, Faculty of Science

  7. 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) Department of Engineering, Faculty of Science

  8. Physics of LWA • A leaky-wave antenna supports a fast wave with x Fig. 10. An aperture with an electric field Ey(x,z) on it at x=0 (Jackson et al., 2008) Ey The electric field Ey (x,z) on the aperture (x=0) that has the form of a leaky wave, z --------------- (1) Where the complex wavenumber of the leaky wave is given by The field in the air region above the aperture (x>0) is given by ----- (2) Where the vertical wavenumber is ----- (3) x ----- (4) From Eq. 3 we get k0 θr kx The radiation angle is given by kz=β Department of Engineering, Faculty of Science

  9. Physics of LWA (contd.) ----- (4) Fig. 11. Ray diagram of power flow in the air region (a) exponential growth (b) exponential decay (Jackson et al., 2008) Department of Engineering, Faculty of Science

  10. 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 and (Jackson et al., 2008) Department of Engineering, Faculty of Science

  11. Physics of Leaky-Wave Antenna (contd.) The radiation angle is given by 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

  12. 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 half-width MLWA Fig. 17. ML over a ground plane with periodic lattice of apertures (Gagnon et al., 2006) (Li et al., 2010) Department of Engineering, Faculty of Science

  13. Key Prior Research Department of Engineering, Faculty of Science

  14. 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 Department of Engineering, Faculty of Science

  15. Aims and Expected Outcome (contd.) Fig. 18. Half-width MLWA: endfire to backfire scanning capability (Expected outcome of this research) Department of Engineering, Faculty of Science

  16. 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

  17. Task Plan, Current Position, and Progress We are here • 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

  18. Conclusion • 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

  19. Q & A Department of Engineering, Faculty of Science

  20. Department of Engineering, Faculty of Science

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