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REFRACTION EXPERIMENTS IN WAVEGUIDE ENVIRONMENTS. 指導教授 吳瑞北 學生 許宗堯. OUTLINE. Review : resonator, negative refraction Measurement technique The axially symmetric SRR, the omega SRR, and the S ring Solid-state structure. REVIEW. Waveguide miniaturization---subwavelength resonator

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refraction experiments in waveguide environments

REFRACTION EXPERIMENTS IN WAVEGUIDE ENVIRONMENTS

指導教授 吳瑞北

學生 許宗堯

outline
OUTLINE
  • Review : resonator, negative refraction
  • Measurement technique
  • The axially symmetric SRR, the omega SRR, and the S ring
  • Solid-state structure
review
REVIEW
  • Waveguide miniaturization---subwavelength resonator
    • The phase delay of the forward-wave can be completely compensated by the phase advance of backward-wave.
review1
REVIEW
  • DNG metamaterial has negative refraction

ENG DNG MNG DPS

review2
REVIEW
  • For normally incident wave
    • n2 is real, wave number is also real
    • n2 is pure imaginary, wave number is also pure imaginary → the wave is strongly attenuated inside the slab
  • For obliquely incident wave
    • Boundary condition :
      • kx1 = kx2
    • dispersion relation
review3
REVIEW

DNG

uniaxial MNG

measurement techniques
MEASUREMENT TECHNIQUES
  • Many variations of rings and rods have been devised to achieve negative permittivities and permeabilities
  • Various geometries….
    • driving criteria:
      • increase the bandwidth, reduce the losses, yield stable and repeatable results in measurements
  • Main ring used now : the edge-coupled SRR, the broadside SRR , the axially symmetric SRR, the omega SRR ,and the S ring.
slide9

all the rings exhibit a frequency dispersive permittivity response, in addition to the required frequency-dispersive permeability response

  • However, the interesting region of permittivity response where negative values are achieved is usually much higher in frequency than the region where the permeability is negative, making this effect not usable
measurement techniques1
MEASUREMENT TECHNIQUES
  • Transmission level can be measured without many difficulties.
  • The first step to perform transmission measurements on metamaterials is to obtain a proper incident beam
  • an approximated plane wave can be created by eliminating the interference from the external environment as much as possible
ppw configuration
PPW CONFIGURATION
  • slab aperture D = 5 cm
  • Frequency : around 10GHz
  • Far-field limit = =17 cm
  • Distance >17 cm
ppw configuration1
PPW CONFIGURATION
  • The position of the sample is a result of a trade-off between incidence and reception
  • far enough:
    • the wave front exiting the waveguide coupler has enough space to flatten out and to approach a plane-wave front while it has to be far enough from the reception to minimize all near-field effects
  • close enough
    • the tapering effect of the absorbers cannot be avoided, and neither can the Gaussian far-field distribution due to the aperture source
measurements of various ring
MEASUREMENTS OF VARIOUS RING
  • the axially symmetric SRR, the omega SRR, and the S ring
axially symmetric srr
AXIALLY SYMMETRIC SRR
  • Set of specific dimensions resonant and plasma frequencies
    • fmo ≈ 8 GHz,fmp ≈ 9 GHz, and fep ≈ 11 GHz
  • These frequencies are directly related to the thicknesses of the metallizations, the gaps, and other geometric parameters in the design of the SRR
transmission level of axially symmetric srr
TRANSMISSION LEVEL OF AXIALLY SYMMETRIC SRR
  • a stand alone peak between 8.2 and 8.7 GHz at a refraction angle of about −30◦
omega srr
OMEGA SRR
  • peform both negative values of permittivities and permeabilities
  • Transmission band is between 12GHz to 13.2GHz
omega srr1
OMEGA SRR
  • the refracted beam is seen to bend at an angle of about -27◦corresponding to an effective index of refraction of about −1.7
  • It should also be mentioned that the losses of the prism at 12.6 GHz are smaller than 14 dB, which is acceptable
s ring
S RING
  • S ring does not require the addition of a rod to exhibit a negative permittivity at similar frequencies to where it exhibits a negative permeability
  • The second important feature of this ring is that its shape can be easily modified to achieve desired frequency responses
slide20

dash line: permittivity

solid line: permeability

solid state structure
SOLID-STATE STRUCTURE
  • A major drawback in most metamaterials realized to date is the losses that they exhibit
  • Various causes have been identified as a possible origin of losses, one of them being mismatch
  • Another major drawback of most of the current implementations of negative metamaterials is their mechanical fragility
solid state structure1
SOLID-STATE STRUCTURE
  • A way that appears to avoid both drawbacks is to realize a solid-state metamaterial
  • mechanical standpoint
    • it is less fragile
  • electromagnetic standpoint
    • it exhibits less mismatched boundaries
transmission level of solid state structure
TRANSMISSION LEVEL OF SOLID-STATE STRUCTURE
  • The insertion losses : we have measured the transmission power with and without the metamaterial sample
    • Without the metamaterials samples, the corresponding value at 8.85 GHz is −9.8 dBm
    • return loss at the incident interface is less than 5 dB

the original solid-state structure