Metallic Patches Research Articles

DUAL-BAND BANDSTOP FILTERS BASED ON ULTRA THIN FREQUENCY SELECTIVE SURFACES

In this paper, we present designs for terahertz filters with two independent stopbands based on periodic metallic resonant structures patterned on the dielectric substrate. Two simple and thin structures are proposed to realize required characteristics for single-polarized and dual polarized filter designs. To realize single polarized one, a unit cell of the proposed periodic structure consists of two sets rectangular shape conducting metal patches patterned on the top of the dielectric substrate, and the dual-band response is due the lattice resonances observed in the unit cell. To realize dual polarized filter design, a modified unit cell is considered with additional patches on the bottom of the dielectric substrate. The patches on the bottom layer are the same ones as on the top layer but orthogonally oriented. For this case, polarization-independent frequency response can be obtained after geometric optimization of the unit cell because the top and the bottom layers resonantly interact with only the TE or TM incident plane wave to minimize cross coupling effects between the layers. In order to intensively understand the transmission performance of the proposed filters, a large number of simulations using integral equation method are performed based on the different values for permittivity, period of the unit cell, dielectric thickness, and geometric dimensions. The electric field distributions are analyzed to understand the mechanism of the resonance behavior.

Analytical Modeling of Microwave Transmission Through Metasurfaces Made of Perforated Metal Plates, Arrays of Metal Patches, and Wire Grids

Analytical Modeling of Microwave Transmission Through Metasurfaces Made of Perforated Metal Plates, Arrays of Metal Patches, and Wire Grids

Design of a transmissive dual-frequency polarization rotator for linearly polarized electromagnetic wave

This paper presents the design of a transmission-type dual-frequency polarization rotator for linearly polarized electromagnetic wave. The rotator facilitates polarization conversion for incident waves at any azimuth angle ϕ at two specific frequency points, resulting in a transmission wave with a counterclockwise rotation of 2ϕ. The proposed polarization rotator structure comprises three metal layers separated by two dielectric substrates. It includes two large rectangular metal patches positioned orthogonally along the x- and y-axes, respectively, as well as two small rectangular metal patches also positioned orthogonally along the x- and y-axes, respectively. The upper and lower metal layers act as the receiving and radiation ends, respectively. The transmitting and receiving ends are interconnected through coaxial metal holes. Remarkably, polarization conversion efficiencies exceeding 0.95 and 0.94 at 12 and 17 GHz, respectively, are achieved, and these high conversion efficiencies remain consistent as the azimuth angle of incidence changes. Furthermore, experimental results obtained from fabricated samples align well with the simulation ones, thus validating the effectiveness of the proposed polarization rotator. The proposed transmissive dual-frequency polarization rotator exhibits good practical application prospects in mobile satellite communications, GNSS, WLAN, etc.

THIẾT KẾ VẬT LIỆU BIẾN HOÁ PHÂN CỰC CHÉO BĂNG THÔNG RỘNG LÀM VIỆC TRONG VÙNG TẦN SỐ THz

A broadband and lightweight polarization converter is proposed for applications in the THz frequency region. The proposed design has a metasurface structure with the dielectric layer modified to a hollow structure to obtain a lightweight design. The unit cell consists of two opposite arcs resonator patches and a continuous metal patch separated by the polyimide substrate layer. The simulated results indicate that the proposed polarized converter achieves a polarization conversion ratio above 93% in the frequency range from 1.6 THz to 5.8 THz with a relative bandwidth of 113.5%.

Multifunctional metasurface for Terahertz wavefront manipulation based on the combination of vanadium dioxide and graphene

In this paper, we propose a multifunctional wavefront control metasurface based on vanadium dioxide (VO2) and graphene. The unit cell structure contains a VO2 substrate, three rectangular metal strips as the bottom layer, orthogonal graphene strips as the top layer, and an intermediate layer consisting of a split ring resonator and circular metal patches. The desired performances can be achieved by changing the parameters of the split ring resonator in the middle layer, as well as controlling the phase transition state of VO2 and the Fermi level of graphene. When VO2 is in the insulating phase and the Fermi level of graphene is 1 eV, a transmissive metasurface is established, which realizes cross-polarization conversion, anomalous refraction, focusing lens, and orbital angular momentum generation at the frequency of 0.63 THz by changing the geometric sizes of the unit cell. When VO2 is in the metal phase and the Fermi level of graphene is 0.01 eV, a reflective metasurface can be achieved, which realizes terahertz beam splitting, radar cross section, and anomalous reflection of a single beam at the frequency of 0.63 THz. This multifunctional wavefront control metasurface treating the combination of VO2 and graphene exhibits significant application prospects in terahertz transmission, imaging, and communication.

Ultra-broadband high-efficiency cross-polarization conversion and amplitude-phase manipulable multi-functional wavefront manipulation based on terahertz metasurface

Drawing upon the physical phenomenon of polarization transformation, this paper proposes an ultra-broadband, high-efficiency linear polarization converter composed of a metallic grating, an L-shaped metallic patch, and a dielectric substrate. The polarization conversion properties have been scrutinized using the finite element numerical simulation software CST. The computational outcomes reveal that the polarization converter operates within the frequency range of 0.5 THz to 1.8 THz, exhibiting a relative bandwidth of 113%, a transmission coefficient exceeding 0.87, a polarization conversion efficiency approaching 100%, and a phase coverage spanning 360°. Furthermore, a Fabry–Perot interference model was established utilizing Matlab to corroborate the concurrence between the theoretical analysis and the numerical findings. The polarization converter metasurface amalgamates both phase and transmission amplitude variations to accomplish not only a two-dimensional focusing lens operating between 1.55 THz and 1.65 THz, but also a spatial imaging capability utilizing transmission amplitude variation within the 0.5 THz to 1.15 THz range. The outcomes demonstrate that the devised metasurface exhibits ultra-broadband and high transmission efficacy, thus providing novel insights for the versatility of terahertz wave polarization and phase manipulation.

Bulk Electrosynthesis of Patchy Particles with Highly Controlled Asymmetric Features.

Asymmetric modification of particles with various patches of different composition and size at predefined positions is an important challenge in contemporary surface chemistry, as such particles have numerous potential applications, ranging from materials science and (photo)catalysis to self-assembly and drug delivery. However, approaches allowing the synthesis of this kind of complex objects in the bulk of a solution in a straightforward way are currently lacking. In this context, bipolar electrochemistry (BE) is a powerful technique for the asymmetric modification of conducting objects. Herein, this approach is used for the highly controlled modification of particles with different metal patches, generated at specific locations of isotropic objects. The synthesis is carried out in the bulk of the solution and leads to predefined patterns of increasing complexity, including even a specific chiral arrangement of the patches.

A compact high gain filtering patch antenna for multiband wireless system

A novel compact multilayer patch antenna is designed for triple-band operation with filtering characteristics. The multiband antenna with filtering characteristics is necessary to suppress adjacent band interference. Further, it brings higher out-of-band suppression without deteriorating the in-band gain. This filtering antenna offers size compactness, high gain, and high selectivity with reduced interference. On exciting the antenna, the electromagnetic (EM) coupling takes place from feed to patch through the slotted ground. Then the magnetic field reaches its maximum at the middle of the rectangle patch while the electric field reaches its maximum at the edges. These fields couple with the ‘U’ shaped metallic loops and bring field distribution in it and thus contribute to dual-band resonance at 2.45GHz and 4.15GHz. For better impedance matching, the two ‘U’ shaped metallic loops are employed. The additional middle band at 3.25GHz is attained through the employment of a split rectangular ring around the center patch. The bottom ground is etched with a bent horizontal slot to achieve proper positioning of the lower resonance. The modified CRLH feeding structure is adopted in this antenna to realize radiation null between operating bands. The dimension of the CRLH branches decides the positioning of radiation nulls in the spectrum of interest. This null reduces the interband interference and it is an important feature for any multiband communication system. The usage of via between patch and feed increases the electrical length of an antenna and thus provides size miniaturization. Whereas the position of the via in the patch decides the impedance matching. thus multiple iterations of simulation were done to optimize the via position for better impedance matching. The designed antenna has a compact dimension of 0.21λo × 0.21λo. The realized triple bands have −10dB impedance bandwidth of 180MHz (2.31 to 2.49GHz), 350MHz (3.1 to 3.45GHz), and 850MHz (3.6 to 4.45GHz) with a maximum gain of 5.2dB. Thus the multi-layer antenna not only has proven to be multiband but also incorporated filtering characteristics to lessen interband interferences. The proposed antenna would be beneficial in a multiband wireless system that supports services such as Wifi, WiMAX, and 5G. The antenna is the perfect candidate for the unmanned ariel vehicle (UAV) to be used in emergency and military applications.

Direction independent broad-band wide angle metamaterial absorber for “K” band applications

Abstract In this work, the design of broadband, wide-angle, direction-independent metamaterial (MM) electromagnetic wave (EM) absorber for K-band frequency application is investigated and validated experimentally. The unit cell of the metamaterial absorber consists of four 90° rotated L-shaped metallic patches imprinted on a dielectric substrate backed by a metallic sheet. The structure yield absorption in the broad frequency ranges from 22.5 to 29.3 GHz for both TE and TM polarized waves with more than 90 % absorptivity having a wide fractional bandwidth of (6.8 GHz) 25.8 %. The structure is four-fold symmetric and hence yields polarization insensitivity for different angles of polarization under both TE and TM polarized waves. The structure is also investigated under oblique incidence where the 80 % absorptivity holds up to 45° incident angles for both TE and TM waves. The absorption mechanism is explained with the help of top and bottom surface current distribution, induced electric field, and parametric analysis. To verify the resonance in the structure, characteristic mode, and equivalent circuit analysis have been carried out and presented. A prototype of the absorber has been fabricated and simulated results are validated with measured results. Measured results are showing good agreement with the simulated responses. The novelty of the proposed absorber lies in its unique metallic pattern on a λ 0/8 (concerning the canter frequency of absorption bandwidth) thin FR-4 substrate while showing the wide absorption bandwidth and direction independence to normal and oblique incidence. The compact nature of the absorber and broadband response with good polarization insensitivity at normal and oblique incidence makes it commercially suitable for the reduction of radar cross section (RCS) in stealth applications at the K-band.

Flat-topped Beams using Phase Compensation based on Low-profile Transmitarray

This paper proposes a method to add an additional phase compensation to conventional phased arrays to achieve flat-topped beam forming, which can convert the spherical waves emitted by common conical horn antennas into cylindrical flat-topped beams, at the same time, there is also a certain power enhancement. A centrosymmetric unit composed of four layers of F4B and metal patches is designed. By changing the value of the parameters, a 360∘ phase change can be achieved, and it has the advantages of small size and low-profile. To validate the design concept, a prototype of the transmitarray (TA) was designed, fabricated, and measured by calculating the phase distribution of the front. The measurement results show that the designed TA can achieve flat-topped beams at 5.2GHz, the maximum gain is 1.15dB higher than that of the horn antenna, and the flat-topped range is about ±10∘. The results are in good agreement with the simulation within the test range.

Low infrared emissivity and broadband wide-angle microwave absorption integrated bi-functional camouflage metamaterial with a hexagonal patch based metasurface superstrate.

This work proposed and demonstrated a bi-functional metamaterial to implement the multispectral camouflage in infrared and microwave bands. Aiming at integrating broadband, wide-angle and low infrared emissivity into one structure, the bi-functional structure is made up of three metasurface layers with different functions. Specifically, a metasurface superstrate based on hexagonal metallic patch was deployed to achieve a low infrared emissivity and a high transmittance of microwave simultaneously. In the framework of equivalent circuit model, the bi-functional structure was designed and optimized. A dielectric transition layer was introduced into the structure to obtain better microwave absorption performances. A sample of such structure was prepared based on optimized geometric parameters and tested. The simulated and measured results indicate that the novel hexagonal patch metasurface superstrate significantly reduces infrared emissivity and the measured emissivity of the structure is about 0.144 in 8-14µm infrared band. Meanwhile, the multilayered structure has a broadband absorption band from 2.32 GHz to 24.8 GHz with 7 mm thickness and is equipped with good angular stability under oblique incidence. In general, the method and specific design proposed in this work will benefit utilizing metasurface to implement bi-functional microwave and infrared camouflage materials with outstanding performances, which are promising for extensive applications.

Ultra-low radar cross-section realized by metasurface with nonuniform elements

A novel checkerboard metasurface is proposed to realize broadband ultra-low radar cross-section reduction (RCSR). The metasurface element is a non-uniform array which contains two uniform subarrays composed of 3 × 6 metallic patches. The reflection phases of the two subarrays can be compensated each other. Based on this characteristic, the non-uniform element reflects two orthogonally polarized waves with a phase difference shrinking to 180 ± 20° in a wideband from 11.2 to 23.0 GHz. When the non-uniform elements are arranged into a checkerboard structure, two co-polarized reflective waves with phase difference of 180 ± 20° are then generated for arbitrary polarized incident waves, resulting in an ultra-low RCS reduction. Simulation results show that the proposed checkerboard metasurface achieves at least 15 dB RCS reduction from 11.2 to 23 GHz (69%) for normal incident waves. The experimental results are good agreement with the simulations.

Direction control of electromagnetic beam scattering by physically stacked cascaded coding metasurfaces

Coded metasurfaces build a bridge between the physical world and digital worlds, making it possible to manipulate electromagnetic waves and implement programmable metamaterials through digitally coded sequences. This “digital metasurface” based on binary digital logic greatly simplifies the design process of the metasurface and improves the flexibility of regulating electromagnetic waves. Based on the principle of Fourier convolution addition, a physical superposition cascaded metasurface is designed. The metasurface unit consists of three dielectric substrates and four “H”-shaped copper metal patch boards. The addition of most coding metasurfaces is to add two basic coding metasurfaces through the addition rules between digital codes to obtain a new coding sequence, and the new coding sequence has the characteristics of the previous two coding sequences. We propose a physically superimposed cascaded encoding metasurface. By physically superposing two different sequences of metasurfaces, the cascaded metasurface formed after superposition also has the characteristics of the first two basic coding sequences. We experimentally verified the proposed idea using two different dielectric materials, and there was good consistency between the experiment and simulation, thereby verifying the consistency of the metasurface cascade and the phase-encoding element surface addition principle. This design approach has potential applications in multifunctional photonic devices.

Multi-polarized Fabry-Pérot resonator cavity using multilayer partially reflective metasurface in X-Band

In this paper, we propose a multi-polarized Fabry-Pérot resonator cavity (MPFPRC) by integrating the multilayer partially reflective metasurface (MPRM), the feed of multi-polarized slot coupling patch antenna and the reflective ground in X-Band. The MPRM consists of first-layer square metal patches, second-layer metal ground with square slots, third-layer square metal patches and fourth-layer partially reflective patches. Based on the MPRM, the proposed MPFPRC is capable of transforming 0°, 45° and −45° linearly polarized (LP) waves emitted by the feed into LP beam, left-handed circularly polarized (LHCP) beam and right-handed circularly polarized (RHCP) beam, respectively. Finally, the designed MPFPRC is simulated, processed and measured. The experimental results verify that the −3 dB gain bandwidth of LP is 9.1–10.2 GHz, the −3 dB gain bandwidth and 3 dB axial ratio bandwidth of the LHCP are 9.0–10.0 GHz and 9.2–10.0 GHz, and the −3 dB gain bandwidth and 3 dB axial ratio bandwidth of the RHCP are 9.0–10.0 GHz and 9.3–10.0 GHz.

Synthesis of Polarization-Independent Perfect Anomalous Reflectors via Modulated Metasurfaces and an Analytical Design Model

A systematic approach to the synthesis of polarization-independent metasurfaces for anomalous reflection is presented. A fast analytical procedure is laid out to analyze the electromagnetic (EM) behavior of an impedance-modulated metasurface for arbitrary angles of incidence and reflection, subsequently serving as a means to provide the necessary impedance profile for reflection toward a specific direction, while capturing all propagation mechanisms, including surface waves (SWs) and nonlocal effects. We apply this procedure to design a metasurface for reflecting a normal incident wave to a different reflection angle, where the synthesized impedance is approximated by a discrete design, based on orthogonal metallic patches. This is done to provide control of both cases of incident wave polarization, while the unit cell analysis and extraction of equivalent impedance is easily performed by a full-wave computational eigenmode analysis of the unit cell. The unit cell design is performed by a simple fine-tuning process with minimal geometric modifications, and the actual discrete metasurface design is proven to agree well with the continuous model. The validity of the synthesis approach is perfectly demonstrated by the fabrication and experimental verification of a model design.

Resonator-Loaded Waveguide Notch Filters with Broad Tuning Range and Additive-Manufacturing-Based Operating Frequency Adjustment Procedure

This article presents a new class of ring-resonator-loaded waveguide notch filters with a broad tuning range, low cost, and improved performance. The proposed approach employs a complementary asymmetric split-ring resonator coupled to a microstrip transmission line and excited in a rectangular waveguide. An equivalent circuit model is proposed to explain the working principle of the proposed notch filter. The adjustment of the operating frequency is based on the additive manufacturing of a metallic copper patch allocated on the microstrip transmission line, which enables extensive tuning capabilities and consistent performance with minimum variations across the tuning window. For demonstration purposes, a filter employing a WR-28 waveguide and photolithography-manufactured resonator is prototyped and experimentally validated. The measured results indicate a broad 8 GHz tuning range with a consistent insertion loss, ranging from 23.4 to 31.4 GHz. An inverse regression model is constructed using measurement data obtained for tuning patches of various sizes, which allows for determining the relationships between the operating frequency and the copper patch size. The resulting calibration curve enables rapid filter tuning to the required frequency by inserting metallic patches of the model-predicted size.

Design and analysis of ultra-wideband four-port MIMO antenna with DGS as decoupling structure for THz applications

The growing demand for high-speed communication has resulted in developing terahertz (THz) antennas that operate at high-frequency, high-speed, and high data rates. An ultra-broadband functioning four port THz multiple input and multiple output (MIMO) antenna with a defective ground plane as a decoupling structure is proposed in this study. A rectangular metallic patch was changed by integrating parasitic components onto the radiator with the lowered ground plane on a polyamide substrate to obtain the ultra wideband THz frequency operating antenna. The designed THz antenna has been transformed into a MIMO antenna by replicating horizontally and vertically with the separation of 0.08 λ and 0.01 λ, respectively (λ computed at 2 THz). The proposed THz MIMO antenna operates in the 2–10.7 THz frequency range and has an overall substrate dimension of 40 μm x 46 μm × 2 μm. The proposed antenna equivalent circuit is designed to validate the impedance bandwidth of the antenna. The designed THz MIMO antenna has isolation better than 20 dB across the impedance bandwidth. The isolation enhancement is achieved by creating alternate current channels through the defected ground structure of the antenna. The proposed THz MIMO antenna's MIMO diversity features are studied and determined to be ECC < 0.001, DG is about 10 dB, TARC < -10 dB, MEG < -3 dB, and CCL < 0.2 bps/Hz over the antenna's operational frequency.

A Switchable Frequency Selective Rasorber with a Broad Transmission Window at the X-Band

This paper proposes a switchable polarization-insensitive frequency selective rasorber (FSR) within the X-band. The FSR comprises a lossy layer, a lossless layer, and an intermediate air layer. The lossy layer consists of metal patches, folded wires, and lumped resistors, while the lossless layer is formed with square and cross patches loaded with PIN diodes. An equivalent circuit model (ECM) has been developed to analyze and verify the working principle of the system. By altering the state of the PIN diodes, it is feasible to switch between absorbing and transmitting modes. In the rasorber mode, the switchable FSR attains a transmission window ranging from 10.13 to 12.27 GHz with a minimum insertion loss below 2 dB and a broad absorption band covering 5.79–15.37 GHz. When switched to absorber mode, the passband is negated, and the FSR exhibits a low transmission band from 10.68 to 18.00 GHz. This innovation can improve the omni-directional stealth capability and battlefield survivability of radar systems, possessing substantial research importance and practical applications.

A Novel High-Isolation Dual-Polarized Patch Antenna with Two In-Band Transmission Zeros.

In this study, we present a novel dual-polarized patch antenna that exhibits high isolation and two in-band transmission zeros (TZs). The design consists of a suspended metal patch, two feeding probes connected to an internal neutralization line (I-NL), and a T-shaped decoupling network (T-DN). The I-NL is responsible for generating the first TZ, and its decoupling principles are explained through an equivalent circuit model. Rigorous design formulas are also derived to aid in the construction of the feeding structure. The T-DN realizes the second TZ, resulting in further improvement of the decoupling bandwidth. Simulation and experimental results show that the proposed antenna has a wide operating bandwidth (2.5-2.7 GHz), high port isolation (>30 dB), and excellent efficiency (>85%).

Effect of coupling on the performance a periodic leaky wave patch antenna

This article demonstrates the effect of coupling between two metal strips and the substrate width of a periodic leaky wave patch antenna operating at 80 GHz. Increasing the width of the substrate and the distance between the metal patches results in directional radiation and a good reflection coefficient in the 72-86 GHz band.