An ultra-wideband pattern reconflgurable antenna based on graphene coating

An ultra-wideband pattern reconfigurable antenna is proposed.The antenna is a dielectric coaxial hollow monopole with a cylindrical graphene-based impedance surface coating.It consists of a graphene sheet coated onto the inner surface of a cylindrical substrate and a set of independent polysilicon DC gating pads mounted on the outside of the cylindrical substrate.By changing the DC bias voltages to the different gating pads,the surface impedance of the graphene coating can be freely controlled.Due to the tunability of graphene＇s surface impedance,the radiation pattern of the proposed antenna can be reconfigured.A transmission line method is used to illustrate the physical mechanism of the proposed antenna.The results show that the proposed antenna can reconfigure its radiation pattern in the omnidirectional mode with the relative bandwidth of 58.5% and the directional mode over the entire azimuth plane with the relative bandwidth of 67%.

Ultra-broadband and polarization-independent planar absorber based on multilayered graphene

We propose an ultra-broadband and polarization independent planar absorber comprising multilayered graphene. The bandwidth of the proposed absorber is extended by increasing the number of layers of graphene, and it is polarization independent due to its symmetrical unit structure. The full wave simulation results show that an absorber with three graphenebased layers can efficiently harvest an electromagnetic wave with random polarization from 17.9 GHz to 188.7 GHz（i.e.,covering frequency regimes from K to D bands and relative bandwidth of - 165%）. The physical absorption mechanism of ultra-broadband absorption has been elaborated upon using the destructive interference method and multiple resonances approach in a multilayered medium. The proposed absorber can be used in many applications such as medical treatment,electromagnetic compatibility, and stealth technique.

Improving breakdown voltage performance of SOI power device with folded drift region

A novel silicon-on-insulator（SOI） high breakdown voltage（BV） power device with interlaced dielectric trenches（IDT） and N/P pillars is proposed. In the studied structure, the drift region is folded by IDT embedded in the active layer,which results in an increase of length of ionization integral remarkably. The crowding phenomenon of electric field in the corner of IDT is relieved by the N/P pillars. Both traits improve two key factors of BV, the ionization integral length and electric field magnitude, and thus BV is significantly enhanced. The electric field in the dielectric layer is enhanced and a major portion of bias is borne by the oxide layer due to the accumulation of inverse charges（holes） at the corner of IDT.The average value of the lateral electric field of the proposed device reaches 60 V/μm with a 10 μm drift length, which increases by 200% in comparison to the conventional SOI LDMOS, resulting in a breakdown voltage of 607 V.

All-dielectric three-element transmissive Huygens’ metasurface performing anomalous refraction

Metasurfaces have pioneered a new avenue for advanced wave-front engineering.Among the various types of metasurfaces,Huygens'metasurfaces are thought to be a novel paradigm for flat optical devices.Enabled by spectrally overlapped electric resonance and magnetic resonance,Huygens'metasurfaces are imparted with high transmission and full phase coverage of 2π,which makes them capable of realizing high-efficiency wave-front control.However,a defect of Huygens'metasurfaces is that their phase profiles and transmissive responses are often sensitive to the interaction of neighboring Huygens'elements.Consequently,the original assigned phase distribution can be distorted.In this work,we present our design strategy of transmissive Huygens'metasurfaces performing anomalous refraction.We illustrate the investigation of Huygens'elements,realizing the overlapping between an electric dipole and magnetic dipole resonance based on cross-shaped structures.We find that the traditional discrete equidistant-phase design method is not enough to realize a transmissive Huygens'surface due to the interaction between neighboring Huygens'elements.Therefore,we introduce an extra optimization process on the element spacing to palliate the phase distortion resulting from the element interaction.Based on this method,we successfully design unequally spaced three-element transmissive metasurfaces exhibiting anomalous refraction effect.The anomalous refractive angle of the designed Huygens'metasurface is 30°,which exceeds the angles of most present transmissive Huygens'metasurfaces.A transmissive efficiency of 83.5%is numerically derived at the operating wavelength.The far-field electric distribution shows that about 93%of transmissive light is directed along the 30°refractive direction.The deflection angle can be tuned by adjusting the number of Huygens'elements in one metasurface unit cell.The design strategies used in this paper can be inspiring for other functional Huygens'metasurface schemes.