Weijun Hong

WiFi band-stop FSS for increased privacy protection in smart building

This paper proposes a periodic double ring strip frequency selective surface (FSS) with dual-band stop behavior. The FSS elements are designed to be etched on the transparent coating of glass substrate in smart buildings, which acts as a dual-band notch filter on 2.45GHz and 5.4GHz to avoid the leakage of WiFi signal outside the building. All the simulation parts are simulated by using High Frequency Structure Simulator (HFSS). The proposed FSS possesses 450MHz and 960MHz bandwidth with insertion loss more than -10dB around the two central operating frequencies 2.45GHz and 5.45GHz, respectively. Furthermore, the unit-cell structure provides a stable performance for both TE and TM polarizations with incident angles 0°-60°. A prototype of the proposed FSS is fabricated and measured. Good agreement between the simulated and measured results is obtained.

Control of the Spin Angular Momentum and Orbital Angular Momentum of a Reflected Wave by Multifunctional Graphene Metasurfaces

Three kinds of multifunctional graphene metasurfaces based on Pancharatnam–Berry (PB) phase cells are proposed and numerically demonstrated to control a reflected wave’s spin angular momentum (SAM) and orbital angular momentum (OAM) in the terahertz (THz) regime. Each proposed metasurface structure is composed of an array of graphene strips with different deviation angles and a back-grounded quartz substrate. In order to further help readers have a deeper insight into the graphene-based metasurfaces, a detailed design strategy is also provided. With the aid of the designed graphene elements, the proposed metasurfaces can achieve the full 360° range of phase coverage and provide manipulation of SAM and OAM of a circularly polarized (CP) wave at will. More importantly, simultaneous control of these two momentums can also be realized, and in order to demonstrate this function, a THz spin-controlled OAM beam generator with diverse topological charges is created, which can provide one more degree of freedom to improve the channel capability without increasing the bandwidth compared to a linearly polarized (LP) OAM beam. Numerical results verify the proposed graphene metasurfaces, which pave the way for generating spin OAM vortex waves for THz communication systems.

Manipulating of Different-Polarized Reflected Waves with Graphene-based Plasmonic Metasurfaces in Terahertz Regime

A graphene-based plasmonic metasurface which can independently control different polarized electromagnetic waves with reasonably small losses in terahertz regime is proposed and demonstrated in this paper. This metasurface is composed of graphene based elements. Owing to anisotropic plasmonic resonance of the graphene-based elements, the reflected phases and magnitudes of orthogonally polarized waves can be independently controlled by varying dimensions of the element. Four types of graphene-based plasmonic metasurfaces with different reflected phases distributions are synthesized and simulated, exhibiting diverse functions such as polarized beam splitting, beam deflection, and linear-to-circular polarization conversion. The simulation results demonstrate excellent performances as theoretical expectation. The proposed graphene-based plasmonic metasurface can be applied to realize extremely light-weight, ultra-compact, and high-performances electromagnetic structures for diverse terahertz applications.

Reconfigurable Multifunctional Metasurface Hybridized with Vanadium Dioxide at Terahertz Frequencies

Driven by the continuous demand for system integration and device miniaturization, integrating multiple diversified functions into a single metasurface hybridized with the tunable metaparticle is highly demanding at terahertz (THz) range. However, up to now, because of the limitation of the tunable metaparticle at terahertz range, most of the metasurfaces feature a single function only or process similar functionalities at a single frequency. A reconfigurable multifunctional metasurface which can realize the switch of transmission and reflection and manipulate the linearized polarization state of electromagnetic waves simultaneously over a controllable terahertz frequency range based on the vanadium dioxide was designed for the first time in the paper. The numerical result demonstrates the validity of the appropriately designed metasurface. Simulation results show that the reconfigurable and multifunctional performance of this metasurface can be acquired over 1.59 THz to 1.74 THz without re-optimizing or re-fabricating structures, which effectively extends the operating frequencies. The proposed metasurface holds potential for electromagnetic wave manipulation and this study can motivate the realization of the wideband multifunctional metasurface and the software-driven reconfigurable metasurface at terahertz frequencies.

CPW-fed dual-band MIMO antenna based on harmonic resonance with high isolation

In this paper, a dual-band CPW-fed MIMO antenna is designed and analyzed. Fundamental resonance of the coplanar stepped impedance resonator (CSIR) produces the 1st operating band, while its harmonic resonance and the resonance of the rectangular slot line resonator (RSLR) construct the 2nd band. The port-to-port isolation within the 2nd band is high since it works at the harmonic resonant frequency of the CSIR. The bandwidth of the 2nd band can be easily tuned in a very wide range by adjusting the resonant frequency of the RSLR. Finally, a hexagon 3-port dual-band MIMO antenna is designed and fabricated with isolation higher than 30 dB and 40 dB within the two operating bands, respectively.

Remote Video Interception System Implemented on USRP

With the development of the technology, life is filled with increasing information equipment. When they work, a great deal of information will be radiated. For the leaked information, an interception system is built with USRP (Universal Software Radio Peripheral), and the line synchronization signal was extracted with a method called cepstrum. Compared with the method of autocorrelation, the new method is more conducive to find the interval between the neighboring peaks. And the system has more obvious advantages compared to the traditional system composed of AD (Analog-Digital) and DSP (Digital Signal Process) devices. It is small in size, inexpensive, reconfigurable, and it is convenient to operate. The results of experiments indicate that 16 fonts can be reconstructed clearly. It fully reflects its superior performance.

A 2.4GHz Circular Polarization Rectenna with Harmonic Suppression for Microwave Power Transmission

A novel circular polarization rectenna with multi-orders harmonic suppression is proposed in this paper. The circular polarization is realized by corner perturbation on a rectangular radiation patch, and enhanced by a diagonal slim slot etched at the center of the patch. An open stub connects to the transmission line is used to suppress harmonics. The realized results show that the antenna obtained -18dB return loss at 2.4GHz, and -7dB, -20dB and -20dB suppression on second to fourth harmonic frequency bands respectively. With a voltage doubling rectifier circuit connecting to the output of the antenna, 75% of RF-to-DC conversion efficiency is achieved.

A Novel Design of Broadband Metamaterial Absorber Based on Sine-Curved-Surface Substrates

A cross-band dual-layer metamaterial absorber with properties of broad bandwidth is presented in this paper. Different from the previous methods to broaden the absorption width, this letter proposes a novel design of the structure of dielectric substrates with sine-curved shape surfaces. The proposed structure consists of two layers of dielectric substrate which exhibits as periodic sine-curved shape. Several closed ring resonators (CRRs) wrap on the top curved-surfaces of both the layers of the dielectric substrate in a unit cell. This approach for expanding absorption bandwidth is confirmed by numerical simulations in which the multiband absorbers can couple to a wideband absorber. With the parametric optimization method, the bandwidth-enhanced absorptions occur across C and X band. Comparing the absorption performances of the proposed structure with planar substrate situation by simulated results, we find the bandwidth of the sine-curved-surface absorber is widened. The full width at half maxima (FWHM) bandwidth is greater than 4GHz and the absorption peak is over 95% in the whole frequency range. This specific periodic curved surface structure provides a new idea for widening bandwidth of metamaterial absorbers.

A Circular Polarized Rectenna with Out-of-Band Suppression for Microwave Power Transmission

A novel circular polarized rectenna with out-of-band suppression is proposed in this paper. The circular polarization is realized by corner perturbation on a rectangular radiation patch and enhanced by a diagonal slim slot etched at the center of the patch. An open stub connecting to the quarter wavelength impedance transformer is used to suppress out-of-band wave through harmonics notching. The results of simulations and experiments agree very well, which show that the rectenna obtained −19 dB return loss at 2.4 GHz and −15.5 dB, −18.1 dB, and −11.4 dB suppression on second, third, and fourth harmonic frequency bands, respectively. The reflection coefficient in overall out-of-band, up to 10 GHz, is limited up to −3 dB. Integrated with a voltage doubling rectification circuit, the proposed rectenna can obtain 75.5% RF-to-DC conversion efficiency.

Conformal array design on arbitrary polygon surface with transformation optics

A transformation-optics based method to design a conformal antenna array on an arbitrary polygon surface is proposed and demonstrated in this paper. This conformal antenna array can be adjusted to behave equivalently as a uniformly spaced linear array by applying an appropriate transformation medium. An typical example of general arbitrary polygon conformal arrays, not limited to circular array, is presented, verifying the proposed approach. In summary, the novel arbitrary polygon surface conformal array can be utilized in array synthesis and beam-forming, maintaining all benefits of linear array.