Transcript Metamaterials CH5

Metamaterials CH5
Narrator:劉柏均
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.
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.
Experiment results: (P.161)
[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)
Return loss:[24]
Bidirectional:
Unidirectional:
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.
Part2: Dispersion NRI-TL media(P.165)
‧This inherently quasitransverse electromagnetic mode
(quasi-TEM) analysis is used to quickly and accurately
calculate the dispersion of the lowest pass-band and
several of the upper pass-bands.
Implementation: (P.165)
[31]
Calculations:[31]
[31]
Tmtl: Transfer matrix of uniform MTL.
w>>g
Where C,L are per-unit-length matrix.
Periodic structure(Bloch):
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.
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.
Preview
 Anisotropic grid monopole antenna.
 Resonance cone refraction effects in a low-profile antenna.
Thanks for comprehension.