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2D planar EBG structure Ch11, Ch12

2D planar EBG structure Ch11, Ch12. 學生 : 王冠中 教授 : 吳瑞北. Above resonance, the surface is capacitive and supports TE waves. Near ω0, the surface impedance is much higher than the impedance of free space, and the material does not support bound surface waves.

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2D planar EBG structure Ch11, Ch12

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  1. 2D planar EBG structure Ch11, Ch12 學生 :王冠中 教授 :吳瑞北

  2. Above resonance, the surface is capacitive and supports TE waves Near ω0, the surface impedance is much higher than the impedance of free space, and the material does not support bound surface waves. Below resonance, the surface is inductive and supports TM waves

  3. the high-impedance surface also has unusual reflection-phase properties. the tangential magnetic field is small, even with a large electric field along the surface magnetic conductor The image currents in the ground plane are in-phase with the antenna current, rather than out of phase,

  4. finite-element numerical model • . The calculation yields the allowed frequencies for each wave vector.

  5. MEASURING TM a pair of small monopole antennas oriented normally with respect to the surface, TE

  6. REFLECTION PHASE

  7. MEASURING

  8. DESIGN PROCEDURE a is the lattice constant, g is the gap between the plates, w is the width of the plates, and ε1 and ε2 are the dielectric constants of thesubstrate and the material surrounding the surface For a square lattice F = 1, for a triangular lattice F =√ 3, and for a hexagonal grid of capacitors F = 1/ √ 3.

  9. The inductance of a high-impedance surface is determined entirely by its thickness.

  10. TUNABLE IMPEDANCE SURFACES

  11. REFLECTIVE-BEAM STEERING • we calculate the required reflection phase gradient, as described by Eq. (11.18); • select a frequency; • and then calculate the corresponding voltages for each biasline based on a previously measured calibration table.

  12. the surface is about 3.75 wavelengths square and operates at about 4.5 GHz. The surface can steer a reflected beam over ± 40◦ for both polarizations. • Wider steering angles would be possible with a larger surface.

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