Identical Patches Research Articles

Compact Filtering Patch Antenna Arrays for Marine Communications

A planar 2 × 2 filtering patch antenna array with high selectivity and wide stopband is investigated for marine communications. The 2 × 2 patch array is composed of a driven patch and four identical parasitic patches placed nearby. A forked-microstrip-line-coupled rectangular slot is used to excite the driven patch, while the neighboring parasitic patches are capacitively coupled by the driven patch. Owing to the hybrid feeding effect of the forked feed line, a radiation null can be generated at the lower band-edge. Simultaneously, another radiation null can be generated at the upper band-edge owing to the radiation cancellation effect between the driven patch and the parasitic patches. Consequently, no power dividing feeding network is required for the 2 × 2 array, and the quasi-elliptic bandpass filtering response is achieved without utilizing any complex filtering/non-filtering circuits. In addition, the proposed filtering array exhibits a wide stopband capable of suppressing the second-harmonic radiation effectively. Based on this 2 × 2 array, a larger 4 × 4 filtering array is further designed by just using a traditional four-way power dividing network. For validation, both of the 2 × 2 and 4 × 4 filtering patch arrays operating at 5.25 GHz are fabricated and tested. The measured results show that the two patch arrays have comparable impedance bandwidths of about 4.4%. The in-band peak gains are given by 11.1 and 15.5 dBi respectively, which are suitable for the long-distance shore-to-ship communications.

Millimeter-Wave Huygens’ Transmit Arrays Based on Coupled Metallic Resonators

A novel Huygens' transmit-array is proposed based on a coupled-resonator approach where two identical elliptical metallic patches with an elliptical hole separated by a dielectric substrate has been used to demonstrate millimeter-wave (mm-Wave) beam-forming for linear polarization. The proposed structure is simple and compatible with standard Printed Circuit Board (PCB) processes and utilizes a single dielectric substrate only. It is shown that by engineering the geometrical dimensions of the resonator, its electric (even-mode) and magnetic (odd-mode) resonances are excited in a balanced manner to achieve zero back-scattering in a large bandwidth. This operation principle of the proposed Huygens' cell is explained in details using both an insightful equivalent circuit model, as well as full-wave eigenmode analysis. Next, the proposed Huygens' cell is placed on top of a high gain 2D slot-array antenna, in its near-field, to engineer its aperture field distribution, where the resulting Huygens' transmit-array acts as a broadband phase plate. Several transmit-array prototypes designed around the 60 GHz frequency band are demonstrated and experimentally characterized in both their near and far-fields, to achieve difference pattern generation, beam expansion and beam steering as application examples, in addition to a uniform surface demonstrating its low-loss performance. Further discussions related to the unit cell size vs frequency bandwidth trade-offs and future extension to handling circular polarization are finally provided.

Design of Broadband High Gain Polarization Reconfigurable Fabry-Perot Cavity Antenna Using Metasurface

A broadband high gain polarization reconfigurable antenna based on metasurface has been presented. The antenna is composed of a planar metasurface, a slot antenna and an air cavity. The metasurface is made up of 64 identical patches, and all the patches are on the top surface of the substrate. The spatial equivalent circuit of the metasurface is discussed and two approximate calculation formulas of the equivalent circuit are obtained. The antenna can be reconfigured to linear polarization, left-hand and right-hand circular polarizations by adjusting the relative positions between the metasurface and the planar slot antenna. The gain of the antenna is improved. In order to verify these methods, the antenna is studied and designed to operate at around 11GHz. The simulated and measured results show that the 3dB axis ratio bandwidth is 10-12GHz (fractional bandwidth 18.18%) and maximum gain of 14.6dBi.

A Compact, Low-Profile, Wideband, Electrically Controlled, Tri-Polarization-Reconfigurable Antenna With Quadruple Gap-Coupled Patches

This communication presents a compact, low-profile, wideband, polarization-reconfigurable antenna with right-handed circular polarization (RHCP), left-handed circular polarization (LHCP), and linear polarization (LP) diversity. The antenna consisting of quadruple identical gap-coupled square patches possesses dual wideband degenerate modes, which could be properly allocated by controlling ON/OFF states of four p-i-n diodes integrated into an overlying specially engineered driven element to dynamically produce RHCP, LHCP, and LP radiations. Due to the collaboration between the gap-coupled patches and such a reconfigurable driven element, the proposed design could operate in a wide overlapped bandwidth of 7.1% in the three dynamical states while keeping a compact size of $0.56\lambda _{0}\,\,\times \,\,0.56\lambda _{0}$ and a low profile of $0.037\lambda _{0}$ . Benefiting from the advantages of low profile, compact size, and wideband operation in three polarization-reconfigurable states, the proposed antenna is quite suitable for space-limited, wideband, intelligent, and anti-interference wireless systems.

On the Effects of Structural Coupling on Piezoelectric Energy Harvesting Systems Subject to Random Base Excitation

The current research investigates the novel approach of coupling separate energy harvesters in order to scavenge more power from a stochastic point of view. To this end, a multi-body system composed of two cantilever harvesters with two identical piezoelectric patches is considered. The beams are interconnected through a linear spring. Assuming a stochastic band limited white noise excitation of the base, the statistical properties of the mechanical response and those of the generated voltages are derived in closed form. Moreover, analytical models are derived for the expected value of the total harvested energy. In order to maximize the expected generated power, an optimization is performed to determine the optimum physical and geometrical characteristics of the system. It is observed that by properly tuning the harvester parameters, the energy harvesting performance of the structure is remarkably improved. Furthermore, using an optimized energy harvester model, this study shows that the coupling of the beams negatively affects the scavenged power, contrary to the effect previously demonstrated for harvesters under harmonic excitation. The qualitative and quantitative knowledge resulting from this analysis can be effectively employed for the realistic design and modelling of coupled multi-body structures under stochastic excitations.

An ultra-compact four-port 4 × 4 superwideband MIMO antenna including mitigation of dual notched bands characteristics designed for wireless network applications

In this manuscript, four-port multiple-input-multiple-output (MIMO) superwideband antenna with mitigation of interfering bands is reported. The presented antenna comprises four identical patches which are placed orthogonal to each other. Rectangular ground plane to placed below the radiating patch forming monopole configuration and reduces the overall size of the antenna. Size reduction of antenna also has no change in wide operating bandwidth of the proposed antenna and interfering bands. Interfering bands which include WiMAX, LTE43 and WLAN are suppressed by using T-C shaped stubs/slots on the radiating patch and it is also worth noting that no separate isolation technique is used to achieve isolation between the radiating elements. Also, the inter-radiating patch maintains isolation of more than 20 dB with ECC (Envelope Correlation Coefficient) being less than 0.02 and TARC (Total Active Reflection Coefficient) less than 20 dB in operating bands. Single element, 2 × 2 MIMO, and 4 × 4 MIMO antenna is fabricated and confirms good agreement with simulated results.

A Symmetrically Stacked Planar Antenna Concept Exhibiting Quasi-Isotropic Radiation Coverage

This letter presents a symmetrically stacked planar antenna (SSPA) featuring switchable quasi-omnidirectional and omnidirectional radiation patterns to accomplish a quasi-isotropic radiation coverage. The proposed antenna consists of two identical planar patch antenna elements. By separately controlling the phase of the two excitation ports, the comprised antenna collectively emulates either an electric dipole mode or a magnetic dipole mode. Collectively, these two complementary dipoles enable a full spherical coverage with a simulated far-field gain variation lower than 6.8 dB. In actual usage scenarios, the proposed antenna can encapsulate various RF circuits and components between the two antennas due to the ground planes functioning as electromagnetic shielding structures. Studies confirm that quasi-isotropic characteristics are preserved for highly integrated user scenarios.

Isogeometric FE-BE coupling approach for structural-acoustic interaction

This paper introduces two NURBS (Non-Uniform Rational B-Splines)-based Isogeometric FE (Finite Element)-BE (Boundary Element) coupling approaches, i.e. DCM (Directed Coupling Method) and SICM (Symmetric-Iterative Coupling Method), to solve the structural-acoustic interaction problems. IGA (IsoGeometric Analysis) can eliminate the substantial geometrical errors and time-consuming meshing steps. Meanwhile, CAD (Computer Aided Design) only makes use of surface representations to model geometrical objects, which is naturally combined with BEM (Boundary Element Method). Therefore, the IGABEM (Isogeometric Boundary Element Method) simulates the acoustic domain described by the Helmholtz equation, while structures are discretized by using the Isogeometric Reissner-Mindlin shell elements that only require C0-continuity across the element boundaries, which simplifies the continuity enforcement between patch boundaries. The main strategy of two coupling approaches is to establish the transformation of interface boundary conditions, that is, the sound pressure is converted to the force boundary conditions of shell structure. The reliability and accuracy of DCM are verified by analytical solutions or Lagrange-based coupling method. By using the model with six identical bi-quartic NURBS patches, the geometric singularity of the spherical surface is eliminated, and the accuracy is significantly improved. It is found that the interaction between the fluid and structure is closely related to the physical properties of the fluid. Compared with Lagrange model, IGA method has much higher accuracy and convergence. SICM method is introduced for the first time to deal with the structure-sound interaction problem. Although SICM fails near the natural frequency of the structure, it has the advantage of generating symmetric coupling matrix, which greatly reduces the dimension of the matrix. Finally, a complex toroidal shell subjected to the mixed structural-acoustic loads, including the plane acoustic wave and the concentrated load, is investigated.

Miniaturized SIW Cavity Tri-Band Filter Design

This letter presents a novel tri-band filter design using an ultraminiaturized substrate-integrated waveguide (SIW) cavity operated at evanescent mode. Two miniaturized SIW cavities in a face-to-face form are vertically stacked to build the proposed tri-band filter. The top and bottom metal layers form the cavity’s broadside walls, and the middle layer possesses three identical patches which are formed by evenly trisecting a circular patch. These patches are shorted to the cavity’s bottom wall through one, two, or four via-holes. The patches together with the host cavity exhibit three frequency-distinct resonances that create the filter’s triple passbands. The resonance frequencies are independently controlled, and six passband-edge transmission zeros are created for good selectivity. The filter size is only $0.22\,\,\lambda _{d} \times 0.22\,\,\lambda _{d}$ , and the measured in-band minimum insertion losses are 2.31, 2.25, and 3.01 dB for the first, second, and third bands, respectively. It is believed that the proposed tri-band filter has obtained the best circuit area efficiency in the SIW tri-band filter category.

Wide Transmission Band Frequency-Selective Rasorber Based on Convoluted Resonator

This letter proposes a wide transmission band frequency-selective rasorber (FSR) based on a convoluted resonator (CR). The FSR consists of a two-layered metallic structure with an air gap in the middle. At the top layer, the lumped-resistor-loaded metallic dipole with a CR inserted into the center is applied to generate wide absorption and transmission bands. At the bottom layer, the wideband frequency-selective surface is realized by a triple-layer metallic structure, in which two layers of identical square patches are coupled through a layer of the square aperture. The full-wave simulation results show that the wide transmission band with low insertion loss and wide absorption band are realized. To validate the performance of the proposed FSR, the prototypes are fabricated and measured, and reasonable agreement between the simulated and measured results is obtained. The measured results show that the transmission band with insertion loss less than 1 dB is covered from 9.00 to 12.63 GHz with 33.5% relative bandwidth. Compared with the previous FSRs with wide transmission band, the proposed FSR yields the widest relative bandwidth, better oblique performance, and simpler design.

Effects of the Size, the Number, and the Spatial Arrangement of Reactive Patches on a Sphere on Diffusion-limited Reaction Kinetics: A Comprehensive Study.

We investigate how the size, the number, and the spatial arrangement of identical nonoverlapping reactive patches on a sphere influence the overall reaction kinetics of bimolecular diffusion-limited (or diffusion-controlled) reactions that occur between the patches and the reactants diffusing around the sphere. First, in the arrangement of two patches, it is known that the overall rate constant increases as the two patches become more separated from each other but decreases when they become closer to each other. In this work, we further study the dependence of the patch arrangement on the kinetics with three and four patches using the finite element method (FEM). In addition to the patch arrangement, the kinetics is also dependent on the number and size of the patches. Therefore, we study such dependences by calculating the overall rate constants using the FEM for various cases, especially for large-sized patches, and this study is complementary to the kinetic studies that were performed by Brownian dynamics (BD) simulation methods for small-sized patches. The numerical FEM and BD simulation results are compared with the results from various kinetic theories to evaluate the accuracies of the theories. Remarkably, this comparison indicates that our theory, which was recently developed based on the curvature-dependent kinetic theory, shows good agreement with the FEM and BD numerical results. From this validation, we use our theory to further study the variation of the overall rate constant when the patches are arbitrarily arranged on a sphere. Our theory also confirms that to maximize the overall rate constant, we need to break large-sized patches into smaller-sized patches and arrange them to be maximally separated to reduce their competition.

Design of SWB MIMO Antenna with Extremely Wideband Isolation

This paper presents a compact planar multiple input multiple output (MIMO) antenna for super wide band (SWB) applications. The presented MIMO antenna comprises two identical patches on the same substrate. Dimensions of the MIMO antenna are 0.17λ × 0.20λ × 0.006λ mm3, with respect to the lowest resonance of 1.30 GHz. The SWB antenna was manufactured using F4B substrate having a dielectric constant of 2.65 that provides a percent impedance bandwidth and bandwidth ratio of 187% and 30.76:1, respectively. The mutual coupling between the antenna elements is suppressed by placing a T-shaped corrugated strip in the mid of two antenna elements. The proposed MIMO antenna exhibits maximum diversity gain of 10 dB, low mutual coupling (<−20 dB), low envelope correlation coefficient (ECC < 0.02), efficiency >80%, and low reflection coefficient (<−10 dB) in the SWB frequency range (1.30 GH–40 GHz). The presented antenna is a good candidate for SWB applications. The designed antenna has been experimentally validated, and the simulated results were also verified.

Design of a dual-band terahertz metamaterial absorber using two identical square patches for sensing application.

A dual-band terahertz metamaterial absorber composed of two identical square metallic patches and an insulating medium layer on top of a continuous metallic ground is demonstrated. Two resonance peaks (labeled A and B) with near 100% absorbance are obtained, of which peak A derived from the localized resonance of the two square patches has a line-width of 0.2571 THz and quality factor of 6.9156, while peak B which resulted from the hybrid coupling of the localized resonance of the two square patches and surface lattice resonance of the device has a very narrow line-width of 0.0083 THz and large quality factor of 296.2771. Narrow line-width and large quality factor have important prospects in sensing application. Based on this, the sensing performance of the device is explored; it is revealed that peak B exhibits highly sensitive sensing ability (including a sensing sensitivity of 1.9010 THz per RIU and figure of merit of 229.04) in terms of the surrounding index. In addition, the influence of structural parameters on the absorption performance is discussed to further verify the formation mechanism of these two absorption peaks.

Design of frequency selective rasorber with wide transmission/absorption bands

This paper presents a high-frequency transmissive frequency selective rasorber (FSR) with wideband transmission/ absorption properties. It is synthesized by placing a resistive sheet on top of a bandpass frequency selective surface (FSS) separated by an air spacer. The unit cell of resistive sheet comprises the resistor-loaded central tortuous Jerusalem cross. Its central tortuous cross, acting as a parallel LC resonator with a high inductance and a low capacitance, is utilized to realize a wide pass-band with low insertion loss by cutting off resistive sheet’s lossy path over a wide frequency band. The bandpass FSS adopts a triple-layer coupled structure, in which two layers of identical capacitive metallic patches are coupled through an intermediate inductive wire grid. A second-order pass-band with high selectivity is realized by this bandpass FSS. Simulation results show that the fractional bandwidth of the 1 dB transmission band and the 10 dB absorption band is 19.6% and 107.9%, respectively. Meanwhile, since its periodicity is only 8 mm, the proposed FSR also shows good angular and polarization stabilities. A good agreement between the measured and simulated results validates the proposed FSR design.

The Effect of Perimenopausal Transdermal Estradiol and Micronized Progesterone on Markers of Risk for Arterial Disease.

The arterial effects of hormone therapy remain controversial. This study tested the effects of transdermal estradiol plus intermittent micronized progesterone (TE + IMP) in healthy perimenopausal and early postmenopausal women on several mechanisms involved in the pathophysiology of arterial disease. Healthy perimenopausal and early postmenopausal women, ages 45 to 60 years, were enrolled in this randomized, double-blind, placebo-controlled trial. Women were randomized to receive TE (0.1 mg/day) + IMP (200 mg/day for 12 days) or identical placebo patches and pills for 12 months. Outcomes included: change in stress reactivity composite z-score (combining inflammatory, cortisol, and hemodynamic responses to a standardized psychological laboratory stressor); flow-mediated dilation (FMD) of the brachial artery (an index of vascular endothelial function); baroreflex sensitivity; and metabolic risk (presence of the metabolic syndrome or insulin resistance), all assessed at baseline and at months 6 and 12. Of 172 women enrolled, those assigned to TE + IMP tended to have higher resting baroreflex sensitivity than those assigned to placebo across the 6- and 12-month visits. Although treatment groups did not differ in terms of the other prespecified outcomes, a significant treatment-by-age interaction was found for FMD and stress reactivity such that an age-related decrease in FMD and increase in stress reactivity were seen among women assigned to placebo but not those assigned to TE + IMP. Women on TE + IMP also had lower resting diastolic blood pressure, lower levels of low-density lipoprotein cholesterol, and higher baroreflex sensitivity during stress testing. TE + IMP tended to improve cardiac autonomic control and prevented age-related changes in stress reactivity and endothelial function among healthy perimenopausal and early postmenopausal women.

Planar patch antenna system with high isolation for full‐duplex applications

In this Letter, a differential-fed planar antenna system is presented with large isolation between transmission and reception ports for full-duplex applications. The proposed system contains two antenna pairs, each of which is composed of two identical single-ended microstrip patch antennas operating at 12 GHz. Each element in the array is fed 180° out-of-phase by utilising rat-race hybrid couplers making the whole system differential-fed. The patch antenna array and the hybrid ring couplers are designed on two separate substrate materials with the ground plane in between. Simulation results show high isolation S 21 < − 70 dB through the entire band of interest while measured results approach S 21 < − 50 dB in a reflective environment. The design also exhibits good impedance matching, reasonable gain values, and high efficiency.

Habitat fragmentation promotes malaria persistence.

Based on a Ross-Macdonald type model with a number of identical patches, we study the role of the movement of humans and/or mosquitoes on the persistence of malaria and many other vector-borne diseases. By using a theorem on line-sum symmetric matrices, we establish an eigenvalue inequality on the product of a class of nonnegative matrices and then apply it to prove that the basic reproduction number of the multipatch model is always greater than or equal to that of the single patch model. Biologically, this means that habitat fragmentation or patchiness promotes disease outbreaks and intensifies disease persistence. The risk of infection is minimized when the distribution of mosquitoes is proportional to that of humans. Numerical examples for the two-patch submodel are given to investigate how the multipatch reproduction number varies with human and/or mosquito movement. The reproduction number can surpass any given value whenever an appropriate travel pattern is chosen. Fast human and/or mosquito movement decreases the infection risk, but may increase the total number of infected humans.

Steady vortex patch with polygonal symmetry for the planar Euler equations in a disc

In this paper, we construct two types of vortex patch equilibria for the two-dimensional Euler equations in a disc. The first type is called the “N+1 type” equilibrium, in which a central vortex patch is surrounded by N identical patches with opposite signs, and the other type is called the “2N type” equilibrium, in which the centers of N identical positive patches and N negative patches lie evenly on a circle. The construction is performed by solving a variational problem for the vorticity in which the kinetic energy is maximized subject to some symmetry constraints, and then analyzing the asymptotic behavior as the vorticity strength goes to infinity.

High Gain of Directional Ultra-Wideband Array Antenna Using Flat Reflector Structure for Microwave Imaging

UWB array antenna with high gain is proposed. The 4 × 1 array antenna consists of four identical copper circular patches are appropriately connected using quarter-wavelength transformer transmission line. The array elements and its feed network are properly optimized to have a high gain performance over wide range bandwidth frequencies. New additional flat reflector with distance of 20 mm enhances the proposed antenna gain. UWB antenna performance with reflector is better than UWB antenna without reflector structure. Antenna with reflector recorded wider operated bandwidth; 1.9GHz-10.6GHz with higher gain ranged from 3.5dB until 14.2dB compared with without reflector antenna operated from 2.2GHz to 10.6GHz with lower gain ranges of 1.9dB to 9.8dB. The reflector structure enhanced the antenna gain by 50% where the average gain throughout operated frequency for antenna with reflector and antenna without reflector is 10.2dB and 6.8dB respectively. Dimensions of 80 mm × 45 mm is considered as small UWB array antenna. The high gain and wide operator bandwidth of proposed antenna finds it very suitable to be integrated in human brain microwave imaging system due to ability of the wide signal with high energy penetrating human head structure.

Crystallization, vitrification, and gelation of patchy colloidal particles

We present the phase diagrams for neutral patchy colloidal particles whose surface is decorated by different number of identical patches, where each patch serves as an associating site. The hard-core Lennard-Jones (LJ) potential and associating interaction are incorporated into the free energies of patchy particles in phases of the fluid (F), random close packing (RCP), and face-centered-cubic (FCC) crystal. A rich phase structure of patchy particles with F-F, F-RCP, and F-FCC transitions can be observed. Meanwhile, the sol-gel transition (SGT) characterizing the connectivity of patchy particles is also investigated. It is shown that, depending on the number of patches and associating energy, the F-F transition might be metastable or stable with respect to the F-RCP and F-FCC transitions. Meanwhile, the critical temperatures, critical densities, triple points, and SGT can be significantly regulated by these factors.