Efficient density of current is observed in Fig. 5

Efficient Microwave Guide Filters

 

Ultrathin Switchable Microwave Filter
Based on Graphene and Slot Array

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The theory of
ultrathin switchable 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 may 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.

Fig.5

 

 

It is deserved
 to note that for the switchable filter
only frequencies near the resonance explain  sharp transmission decrease at EF =1.0eV?illustrating an improved tunability provided by the slot layer
while similar actionis not observed in the off-resonant regions. Models have
been built to discuss the circumstance when 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 switching property of the
proposed ultrathin filter at certain frequency Another case we concentrate 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 evidently 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.