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Metamaterials CH5

Narrator: 劉柏均. Metamaterials CH5. Theory:2-D LC Network Model. For interpretation of the reason why NRI is different from conventional TL. “Planar Negative Refractive Index Media Using Periodically L–C Loaded Transmission Lines”

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Metamaterials CH5

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  1. Narrator:劉柏均 MetamaterialsCH5

  2. Theory:2-DLCNetworkModel For interpretation of the reason why NRI is different from conventional TL. “Planar Negative Refractive Index Media Using Periodically L–C Loaded Transmission Lines” George V. Eleftheriades, Senior Member, IEEE, Ashwin K. Iyer, Student Member, IEEE, and Peter C. Kremer KVL Wave eq.: KCL

  3. Further extensions: In conventional TL: → → In NRI materials: Z=1/jωC, Y=1/jωL →

  4. Application of LHM • Phase shifter • Overcome diffraction limit

  5. Topic1:Phase shifter • Phase shifter seen in Fig. 1 offers some significant advantages compared to standard delayTLs: it is more compact in size, it can achieve a positive or a negative phase shift while occupying the same short physical length and it exhibits a linear, flatter phase response with frequency, leading to shorter group delays.

  6. 2-D cell periodic analysis “Compact Linear Lead/Lag Metamaterial Phase Shifters for Broadband Applications” Marco A. Antoniades, and George V. Eleftheriades,IEEE Unit cell with symmetric structure, satisfying: Bloch wave fcn: Product of phase factor and periodic fcn. Mentioned before in Kenneth’s presentation.

  7. Phase shift per unit cell(matched) As It can be simplified as: Critical pt is intersection of +,-curve: f=0.9GHz

  8. What if unmatched? Stop band occurs!!! Where

  9. Topic2:Diffraction limit • A conventional lens focuses only the propagating waves, resulting in an imperfect image of the object. • The evanescent waves with strong attenuation , carries the details smaller than wavelength of the object.

  10. e.g. A light source lying along y-axis consists of a continuum of plane waves: propagates at an angle with the optical z axis given by the direction cosine= kz/k. Propagation wave with components s.t. Evanescent waves has strong attenuation at path from the object to the image. Minimum resolvable feature (by Fourier transform)

  11. Solution to overcome it. With NRI materials, evanescent waves can be restored to a larger bandwidth: Then (the diffraction limit) becomes smaller.

  12. Thanks for comprehension.

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