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Efficient Microwave Guide Filters


Ultrathin Switchable Microwave Filter
Based on Graphene and Slot Array

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The theory
of ultrathin exchangeable microwave Filter contained of graphene sheet and slot
array is given here, we design an ultrathin active filter utilizing graphene As
the switchable element, with metal slot arrays enabling a Band-pass feature.
When the Fermi energy is adjusted, Rs decreases and graphene act more like a
conductive Film which maybe ultimately change the communication between Graphene
and metal slot arrays, the filter consists of a typical periodic cross slot Arrays
in a metal plate, above which is a large-area monolayer CVD graphene deposited
on silicon oxide covered silicon substrate to offer tenability of
electromagnetic operation. To clearly test the underlying mechanism of the proposed
filter, the reflection coefficients are depicted in Fig. 4.  It can be seen that a strong band-pass
resonance, attributed to the cross-slot array, occurs at approximately 14.8 GHz
in The absence of gate voltages in which graphene is at Dirac point.



It is checked
in Fig. 5 (a) that the heavy surface current exists along the edge of cross
slot and the electromagnetic response occurs around the slot enabling a passband
of transmission spectra while clearly rather lower density of current is
observed in Fig. 5 (b) when the Fermi level turns to 1.0eV, which point to the
resonance has been seriously low by the change of graphene surface resistance
resulting from the application of gate voltages.




It is deserved
 to note that for the switchable filter
only frequencies near the resonance explain  sharp transmission decrease at EF =1.0eV?explain  an improved  provided by the slot layer inspite  similar work  is not observed in the off-resonant regions.
Models have been establish  to explain  the circumstance while  only a single layer graphene (SLG) sheet is
utilized without slot arrays The lowering  in transmission of the SLG sheet is far less
than that of HS at resonance, which reveals the importance of slot arrays in
tunability and demonstrates the particular changing  property of the proposed ultrathin filter at specific
 frequency Another case we focus  on is that structured complementary cross-shaped
graphene patches (CCGP) substitutes the previous continuous graphene layer
(CGL) since smaller area of graphene per unit cell in arranging  may eliminate the transmission waste  due to the material loss. The transmission for
this case is displayed in Fig. 7. The same switching property is completed when
EF=1.0eV because the conductive complementary graphene patch short out the capacitive
response associated with the cross slots. And there is an clearly  but not large increase in transmission at resonance,
indicating a reduction in material loss. Furthermore, it can also be inferred
from Fig. 6 and Fig. 7 that the insertion loss at maximum transmission when
EF=0eV may result from the influence of graphene minimum conductivity on the   cross slot
resonator layer which still influence  the band-pass oscillation.

 In summary, we theoretically and numerically
demonstrate an ultrathin filter based on graphene and slot arrays which can be
electrically switched altering the transmission for microwave band via gate voltages.
By changing the Fermi level of graphene, the band-pass resonance is seriously damped achieving an off state of the
switchable filter.  

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