Jianfeng Zhu

Compact Dual-Polarized UWB Quasi-Self-Complementary MIMO/Diversity Antenna With Band-Rejection Capability

A novel compact ultrawideband (UWB) multiple-input-multiple-output (MIMO) antenna system with dual polarization and band-rejection capabilities is proposed. The proposed MIMO antenna system consists of two quasi-self-complementary (QSC) antenna elements. The elements are arranged orthogonally and fed perpendicularly to obtain polarization diversity. High isolation can be achieved without additional decoupling structure owing to the inherent advantage of the self-complementary structure. Notched band at WLAN system can be realized by etching a bent slit in each of the radiating elements. Moreover, a four-element MIMO system is also proposed and investigated to fully reveal its potential use. Diversity performance in terms of envelope correlation coefficient (ECC) and the mean effective gain (MEG) ratio are studied. Measured results show that the proposed antenna has a wide bandwidth ranging from 3 to 12 GHz with band rejection at WLAN system and high port isolation (S12 ≤ -20 dB at most of the band), which demonstrate the proposed MIMO/diversity antenna system can be a good candidate for UWB applications.

Compact Quad-Mode Bandpass Filter Based on Quad-Mode DGS Resonator

In this letter, a quad-mode bandpass filter is built up based on a novel quad-mode defected ground structure (DGS) resonator which has two symmetric planes. The odd-/even-mode theory is applied to analyze the operating principle of the four resonances with their equivalent circuit models. The four resonances can be effectively tuned by adjusting the corresponding dimensions. The fabricated filter has a center frequency of 2.45 GHz and a wide stopband up to 7.8 GHz with a rejection below -30 dB, which extends to at least 30 GHz below -16 dB. Particularly, the filter exhibits an excellent attenuation slope of 302 dB/GHz in the upper passband transition.

Triple band-notched slot planar inverted cone antenna for UWB applications

A novel triple band-notched slot planar inverted cone antenna (SPICA) is proposed for UWB applications. The unnotched ultrawideband antenna is composed of a cone shaped radiating patch and a wide circularly slot on the ground plane. To obtain anti-interference characteristics, an elliptical complementary split ring resonator (ECSRR) was etched in the radiating patch and a parasitic V shaped strip was added adjacent to the upper edges of the cone shaped patch. This will result in triple notched bands at WiMAX, WLAN and X band satellite communication downlinks. The results show the antenna has a wide impedance bandwidth of 140% for SWR <; 2 from 2.2 to 12 GHz with triple undesired bands (WiMAX, WLAN and X-band satellite communication downlinks) rejected. Other advantages, such as stable omnidirectional radiation patterns, easy fabrication as well as compact size make the design applicable to UWB applications.

Independent Manipulating of Orthogonal-Polarization Terahertz Waves Using A Reconfigurable Graphene-Based Metasurface

Viewing the trend of miniaturization and integration in modern electronic device design, a reconfigurable multi-functional graphene-based metasurface is proposed in this paper. By virtue of the reconfigurability of reflection patterns, this metasurface is able to independently manipulate orthogonal linearly polarized terahertz wave. The building blocks of the proposed metasurface are series of graphene-strips-based unit-cells. Each unit-cell consists of two orthogonal graphene strips and a grounded substrate, which has anisotropic responses for each of orthogonal polarizations (x-polarized and y-polarized waves). The reflection phases of both x- and y-polarized waves can be controlled independently through separate electrical tuning. Based on the proposed metasurface, functionalities including beam splitting, beam deflecting, and linear-to-circular polarization converting using a shared aperture are numerically demonstrated and analyzed. Simulation results demonstrate excellent performance, which is consistent with the theorized expectations. This work paves the way for enhancing the miniaturization of modern electronic/optical devices and potentially has important applications in the next-generation information systems for communication, sensing, and imaging.

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.

Wide-Band Circularly Polarized ReflectarrayUsing Graphene-Based Pancharatnam-Berry Phase Unit-Cells for Terahertz Communication

A wide-band and high gain circularly polarized (CP) graphene-based reflectarray operating in the THz regime is proposed and theoretically investigated in this paper. The proposed reflectarray consists of a THz CP source and several graphene-based unit-cells. Taking advantages of the Pancharatnam Berry (PB) phase principle, the graphene-based unit-cell is capable of realizing a tunable phase range of 360° in a wide-band (1.4–1.7 THz) by unit-cell rotating, overcoming the restriction of intrinsic narrow-band resonance in graphene. Therefore, this graphene-based unit-cell exhibits superior bandwidth and phase tunability to its previous counterparts. To demonstrate this, a wide-band (1.4–1.7 THz) focusing metasurface based on the proposed unit-cell that exhibits excellent focusing effect was designed. Then, according to the reversibility of the optical path, a CP reflectarray was realized by placing a wide-band CP THz source at the focal point of the metasurface. Numerical simulation demonstrates that this reflectarray can achieve a stable high gain up to 15 dBic and an axial ratio around 2.1 dB over the 1.4–1.7 THz band. The good radiation performance of the proposed CP reflectarray, as demonstrated, underlines its suitability for the THz communication applications. Moreover, the design principle of this graphene-based reflectarray with a full 360° phase range tunable unit-cells provides a new pathway to design high-performance CP reflectarray in the THz regime.

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.

Ultrawideband MIMO/diversity antenna using CSRR structure for isolation enhancement

A novel compact ultra-wideband multiple-input-multiple-output (MIMO) antenna (of two elements) is proposed. Two circular radiating elements are arrange perpendicularly to reduce mutual coupling. By inserting a complementary split ring resonator (CSRR) in the ground plane, high isolation between two ports is further enhanced. Measured results show the proposed antenna has a wide impedance bandwidth from 3.1 to 10.6 GHz and good isolation (better than -20 dB at most of the band). Due to these highly desirable characteristics, the MIMO antenna is expected to be a good candidate for UWB application.

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.

60 GHz Dual-Circularly Polarized Planar Aperture Antenna and Array

This communication presents new designs of dual-circularly polarized (CP) planar aperture antenna and array for 60 GHz applications. First, a four-port planar aperture antenna with its feeding network is developed that exhibits wide impedance bandwidth, dual-CP radiation as well as high gain. Then, based on the proposed antenna, a new scheme of building a dual-CP array is proposed. With this new scheme that combines the power splitting network and series feeding method, four sequentially fed antenna elements are successfully combined to form a CP radiation array. The experimental results show that the −10 dB impedance bandwidths of the antenna and the array are more than 18.2% (55–66 GHz). While the 3 dB axial ratio bandwidths are from 54.2 to 64.3 GHz (17.2%) for the antenna and from 54.8 to 65 GHz (17%) for the array. The maximum gains achieved are 13.7 and 17.85 dBic for the antenna and array, respectively.