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Advanced Metamaterials: Leaky Wave Antennas and NRI-TL Media Analysis

Dive into the fascinating world of metamaterials with a focus on leaky wave antennas and the analysis of NRI-TL media. Explore the implementation, dispersion, and experimental results, along with insightful conclusions and future perspectives in the field. Discover bidirectional and unidirectional antenna features, dispersion characteristics, and implementation techniques for enhanced performance.

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Advanced Metamaterials: Leaky Wave Antennas and NRI-TL Media Analysis

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  1. Metamaterials CH5 Narrator:劉柏均

  2. Index • Part1:Leaky-wave antenna: are of much concern due to its highly directivity, fast-wave structure (d<<l) . • Part2:Dispersion of NRI-TL media, discussed with Sievenpiper’s “mushroom” structure.

  3. Part1:Implementation of LWA(P.160) [5] The dimensions are given for a printed structure at 15 GHz on a 20 mil substrate of e , = 3.

  4. Experiment results: (P.161) [5]

  5. Another similar structure:[23] Fig1 Fig2 Fig3 Satisfying the following relationship: cos(bd)=cos(kd)+Xsin(kd)/2Z bd: phase delay of unit cell. kd: phase delay of TL segment. X=1/wC reactance due to series capa. Z: characteristic impe. q=arcsin(b/k)

  6. Return loss:[24] Bidirectional: Unidirectional:

  7. Conclusion: • Slot antenna is actually a bidirectional antenna, unwanted direction can be suppressed by ground plane. • However, ground plane may produce parasitic TEM waves which would limit the VSWR(Voltage standing wave ratio) bandwidth. Recently, an approximately unidirectional antenna has been inspired by old bidirectional ones, harnessing phase cancelling technique.

  8. Part2: Dispersion NRI-TL media(P.165) ‧This inherently quasitransverseelectromagnetic mode (quasi-TEM) analysis is used to quicklyand accurately calculate the dispersion of the lowest pass-bandand several of the upper pass-bands.

  9. Implementation:(P.165) [31]

  10. Calculations:[31] [31] Tmtl: Transfer matrix of uniform MTL. w>>g Where C,L are per-unit-length matrix. Periodic structure(Bloch):

  11. Result:(P.166) For simplicity, via and patch edges are loaded with lumped inductor(L=11.6nH) and capacitor(C=2pF): By MTL, Im part of propagation const. gd ranges from (0.125p)j to (0.066p)j.For consistency with experiment result of super lens, taking the sign that will induce exponential growth. Center of stop band=1.38GHz ,with leakage due to mismatch(reflection) loss.

  12. Conclusion • The cause of superlens can be analyzed by FEM(finite-element method). That is,devided the antenna into finite numbers of unit cells of mushroom structure,and calculating an unit cell’s voltage and current, the other ones’s voltage and current can be inferred from Bloch’s recursive relationship.

  13. Preview • Anisotropic grid monopole antenna. • Resonance cone refraction effects in a low-profile antenna. Thanks for comprehension.

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