Efficient Microwave Guide Filters Ultrathin Switchable Microwave FilterBased on Graphene and Slot ArrayThe theory ofultrathin switchable microwave Filter contained of graphene sheet and slotarray is given Here, we design an ultrathin active filter utilizing grapheneAs theswitchable element, with metal slot arrays enabling a Band-pass feature Whenthe Fermi energy is adjusted, Rs decreases and graphene act more like aconductive Film which may ultimately change the communication between Grapheneand metal slot arrays the filter consists of a typical periodic cross slotArrays in ametal plate, above which is a large-area monolayerCVD graphenedeposited on silicon oxide covered silicon substrate to offer tenability ofelectromagnetic operation.To clearly testthe underlying mechanism of the proposed filter, the reflection coefficientsare depicted in Fig. 4. It can be seenthat a strong band-pass resonance, attributedTo thecross-slot array, occurs at approximately 14.
8 GHz inThe absenceof 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 crossslot and the electromagnetic response occurs around the slot enabling a passband oftransmission spectra while clearly rather lower density of current is observedinFig. 5 (b)when the Fermi level turns to 1.0eV, which point to the resonance has been seriously low by thechange of graphene surface resistance resulting from the application of gatevoltages.Fig.5 It is deserved to note that for the switchable filteronly frequencies near the resonance explain sharp transmission decrease at EF =1.
0eV?illustrating an improved tunability provided by the slot layerwhile similar actionis not observed in the off-resonant regions. Models havebeen 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 farless than that of HS at resonance, which reveals the importance of slot arraysin tunability and demonstrates the particular switching property of theproposed ultrathin filter at certain frequency Another case we concentrate onis that structured complementary cross-shaped graphene patches (CCGP) substitutesthe previous continuous graphene layer (CGL) since smaller area of graphene perunit cell in arranging may eliminate thetransmission waste due to the material loss.The transmission for this case is displayed in Fig. 7. The same switchingproperty is completed when EF=1.0eVbecause the conductive complementary graphene patch short out the capacitiveresponse associated with the cross slots. And there is an evidently but notlarge increase in transmission at resonance, indicating a reduction in materialloss. Furthermore, it can also be inferred from Fig.
6 and Fig. 7 that theinsertion loss at maximum transmission when EF=0eV may result from theinfluence of graphene minimum conductivity on the cross slotresonator layer which still influence the band-pass oscillation. In summary, we theoretically and numericallydemonstrate an ultrathin filter based on graphene and slot arrays which can beelectrically switched altering the transmission for microwave band via gate voltages.By changing the Fermi level of graphene, the band-pass resonance is seriously dampedachieving an off state of the switchable filter.