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CH6 Resonance cone

Advisor: Prof. R.B.Wu Narrator: 劉柏均 Metamaterial ppt #4. CH6 Resonance cone. Index. Part1:Planar material, corner-fed, anisotropic grid antenna. Part2:Resonance cone refraction effects in a low-profile antenna. Part1:anisotropic grid antenna. Dipole antenna.

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CH6 Resonance cone

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  1. Advisor: Prof. R.B.Wu Narrator:劉柏均 Metamaterial ppt #4 CH6 Resonance cone

  2. Index • Part1:Planar material, corner-fed, anisotropic grid antenna. • Part2:Resonance cone refraction effects in a low-profile antenna.

  3. Part1:anisotropic grid antenna

  4. Dipole antenna Structure: feedline + two poles

  5. Monopole antenna Structure: similar to dipole antenna, but one of the poles is replaced with ground plane.

  6. Grid antenna(P.172) 1.The transmission and reflection of antenna form a cone shape in the space. 2.Orthogonal inductors and capacitors are embedded in the planar wire grid. 3.Dominant mode of EM-wave exhibits a fast phase reversal, resembling two-wire trans. line. 4.Second dominant mode resembles parallel-plate wave guide. 5.Two dominant modes are summed in the moment method simulation.

  7. CMA Diagram Wc: electron cyclotron frequency Wp: plasma frequency X^2+Y^2=const.: elliptic region X^2-Y^2=const.: hyperbolic region In the spatial coordinate, using partial differential eq. to describe the wave propagation of these categories of medium.

  8. Crystallography • Uniaxial: have one crystal axis(extraordinary,optic) that is different from the other two crystal axes (i.e. ni ≠ nj = nk). ,→Birefringence. • Biaxial: Index of three crystal axes are different.→Trirefrigence. • Anisotropy: is the property of being directionally dependent with index difference as measured along different axes.(iso: homogeneity in all dir.)

  9. Planar L-C grid over gnd.[1](P.174) 12X12 cells 2.5mm square (30cmX30cm macro cell)C=2pF L=5.6nH edge R=50 ohm. Not shown in the picture is non-edged large resistance 100 Kohm. 1.Using L-C grid to simulates anisotropic plasma. 2.Vertical current that pass shunt impedance produces vertical far field polarization.

  10. Result comparison…(Node V.) Wave generates from voltage source, has gone through several tens of unit cell of impedance. Thus the voltage is decreasing from the source to the upper right.

  11. Non-uniform grid with open-ended probe

  12. Cont.(Poynting vector) 1.The top one is simulation result of Poynting vector, and the bottom one is experiment result. 2.This is due to the non-uniformity (especially dense)in the near middle of the grid. 3.Poynting vector has approximate positive relationship with node voltage. (wave would naturally attenuate as propagating without active amplifier.)

  13. Non-uniformity along cone axis • Vertical current distribution which is weighted in favor of the feed point. • By experiment, we found that lower grid height near the feed point has higher directivity. • Solution: Sloped antenna, which strengthens the main lobe and reduces the side lobe. See next page!

  14. Comparison of experiment result:

  15. Double-sloped antenna Theoretically with higher directivity, but still under development.

  16. Part2: Resonance cone refraction effects in a low-profile antenna.

  17. Low-profile, six-macrocell antenna The difference between yellow and red region is that the sequence of L and C in a grid cell is interchanged. The transition region between the two media consisted of a row of cells such that each half of the cell had the characteristics of the adjacent medium.

  18. Refraction : most primary principle Refraction occurs whenever transition region is encountered.

  19. Predicted resonance pattern Simulation with refraction and ckt theorem as guildlines.

  20. Normalized node voltage With arrows indicates the Poynting vector (Power flow)direction.

  21. Explanation • The transition region act as stop band, which can strongly attenuate the waves that try to propagate across the region. • The macrocell points can be seen as pass band, equivalent to a internal director.

  22. Backward-wave propagation Power flow in neg. y-direction. With phase velo. In pos. y-direction.

  23. Spherical coordinates Θ=90 deg.→Pos. y velocity. Φ=90 deg.→In 2-D horizontal plane, but power flow definitely has reverse direction with phase velocity in meta. →Neg. y direction P vector.

  24. Conclusion1: • Part1:Planar material, corner-fed, anisotropic grid antenna: Relatively strong vertical currents are induced along the resonance cone line, exhibits a unidiectional horizontal-plane radiation pattern with main lobe approx. at the right angle to the reso. cone line.

  25. Result comparison…(Node V.) Strong vertical current at boundary of cone because the color is deeper(i.e. high voltage) at the boundary , with the same vertical impe. in comp. with other cells, thus stronger vertical current.

  26. Uni-dir. with right angle pattern

  27. Conclusion2: • Part2:Resonance cone refraction effects in a low-profile antenna: Use six-contiguous square region antenna , two touching squares with a common point at the source,but the cones never reach the edge of the array. Resulting in a pair of in phase induced point source thus unidirectional radiation.

  28. Radiation pattern:

  29. Thanks for comprehension

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