Asymmetric Plane Research Articles

Wideband asymmetric microstrip-fed circularly polarized antenna with monofilar spiral stub for WLAN application

A wideband circularly polarized printed antenna is proposed and fabricated, which employs monofilar spiral stubs and a slit in the asymmetrical ground plane which are fed by an inverted L-shaped microstrip feedline. The CP operation is realized by embedding an inverted-L shaped strip and modified ground plane and can be markedly improved by loading monofilar spiral stubs asymmetrically connected at the edge of the ground plane. After optimization, the measured results of the finally structure demonstrate that a 10-dB bandwidth of 67.6% from 4.6 to 9.3 GHz and a 3-dB axial-ratio bandwidth (ARBW) for circular polarization (CP) of 60.1% from 5 to 9.3 GHz could be achieved which could completely cover the WLAN (5.725-5.85 GHz) band. Therefore, the proposed antenna is suitable for circular polarization applications in C band. To explain the mechanism of broadband circular polarization operation, the analysis of magnetic fields distributions and a parametric study of the design are given. Compared to other recent works, a simpler structure, wider axial ratio and impedance bandwidths and a more compact size are the key features of the proposed antenna.

Methods of suppression of cross‐polarized power for the CPW‐fed monopole antenna

AbstractIn this article, we propose several techniques for radiation characteristics improvement of a coplanar waveguide‐fed monopole antenna with an asymmetric ground plane. Although utilization of an asymmetric ground plane provides wideband impedance characteristics, the cross‐polarization of the monopole antenna increases, resulting from the unbalanced horizontal currents of the ground plane. The proposed techniques, which include etching a notch at the feedline, embedding a slot array in the ground plane, and adding several conducting strips on the top and bottom planes, are used to suppress cross‐polarized power. From the simulated and measured results, it can be observed that the ratios of the maximum co‐polarized power to the maximum cross‐polarized power have been enhanced at the operating bands. The mechanisms of cross‐polarization suppression are explained by using current density distributions.

Compact microstrip-via-fed wideband circularly polarized antenna with monofilar spiral stub for C-band applications

A wideband circularly polarized printed antenna is proposed and fabricated, which employs monofilar spiral stubs and a slit in the asymmetrical ground plane which is fed by an asymmetrical microstrip feedline using a via. The CP operation is realized by embedding an inverted-L shaped strip and a modified ground plane and can be markedly improved by loading monofilar spiral stubs connected to the asymmetric feedline by means of a via. A parametric study of the key parameters is made and the mechanism for circular polarization is described. After optimization, the impedance bandwidth is approximately 3.6 GHz (4.4-8 GHz) and the 3 dB axial ratio bandwidth is approximately 3.3 GHz (4.7-8 GHz), which represent fractional bandwidths of approximately 58.1% and 52%, respectively. Therefore, the proposed antenna is suitable for circular polarization applications in C (4-8 GHz) band. Compared with other recent works, the simpler structure, wider axial ratio, impedance bandwidths, and more compact size are the key features of the proposed antenna.

A microstrip wideband monopole antenna for multisystem integration by utilizing stepped-impedance structure and L-shaped slot

In this article, a coplanar-waveguide (CPW)-fed dual-band antenna for applications of the multisystem integration has been demonstrated. The resonance analysis of the stepped-impedance (SI) monopole is presented by using the transmission-line analysis method. The frequency-response characteristics of the SI-monopole, such as the resonance condition and harmonic response, are systematically summarized. Furthermore, utilizing several simple techniques, such as bent feeding topology, asymmetric ground plane, and an L-shaped slot etched in the ground plane, a right-hand circularly polarized (RHCP) radiating wave at 1.57 GHz and a left-hand circularly polarized (LHCP) radiating wave at 2.33 GHz are excited for the applications of the global positioning system (GPS) and the satellite digital audio radio (SDAR) service system. After optimization of the geometrical parameters of the proposed antenna, the measured impedance bandwidths of a reflection coefficient less than −10 dB range from 1.40 to 2.98 GHz and from 4.48 to 6.27 GHz, and thus covers most of the commercial wireless communication systems, such as GPS, digital cellular system (DCS), personal communication system (PCS), international mobile telecommunications (IMT)−2000, wireless local area networks (WLAN), and long-term evolution (LTE) 2300/2600. The measured 3-dB axial ratio (AR) bandwidths are about 80 MHz at 1.57 GHz and 100 MHz at 2.33 GHz.

CPW-Fed Wideband Circularly Polarized Printed Monopole Antenna With Open Loop and Asymmetric Ground Plane

A wideband circularly polarized (CP) printed monopole antenna with coplanar waveguide feeding is proposed. The antenna is composed of a rectangular monopole, an asymmetric ground plane, and a square-ring with an open gap at the bottom. By utilizing the asymmetric ground plane, CP radiation could be achieved at the upper band first. Then, a rectangular open loop is introduced to obtain wide-impedance bandwidth and broadband CP characteristic. The measured results demonstrate that the 10-dB impedance bandwidth reaches 96.5% (2.76 GHz, 1.48-4.24 GHz) and the 3-dB axial-ratio bandwidth is 63.3% (1.9 GHz, 2.05-3.95 GHz). In addition, parameter studies are performed, and surface current analysis is also given to show the operating mechanism of CP operation.

Development of a k–ω–ϕ–α turbulence model based on elliptic blending and applications for near-wall and separated flows

ABSTRACTA new turbulence model based on elliptic blending, termed as k − ω − ϕ − α model, is developed. This model uses the latest version of Wilcox's k − ω model in near-wall region and changes gradually to the model elsewhere. The capabilities of the present model are evaluated on near-wall and separation flows, i.e. the 2D fully developed channel flow, the asymmetric plane diffuser flow and the 2D backward-facing step flow, in comparison with available direct numerical simulation (DNS) and experimental data. The computational results are compared also to those from the popular model and the original model, and the present model is more stable than the model in complex flows. The present model provides indistinguishable velocity profiles and improved turbulent kinetic energy profiles compared to the model in the channel flow, while in the separation flows tested herein, the present model can obtain comparable results with the model, and both of them show improvements to some extent compared with the model.

Analysis of Microscopic Strain and Crystalline Structure in Ge/Ge1−X Sn x Fine Structures by Using Synchrotron X-ray Microdiffraction

We examined the formation of locally strained Ge nanostructures sandwiched between Ge1−x Sn x stressors using metal-organic chemical vapor deposition method. We have investigated the microscopic local strain and stress in the Ge/Ge1−x Sn x heterostructures using synchrotron microdiffraction and finite element method calculation. The microdiffraction measurement for an asymmetric lattice plane enables directly quantitative evaluation of the strain value of an individual Ge fine line structure with a few tens of nanometers width. An in-plane compressive strain value of 0.9% is achieved for a 30 nm-width Ge line with Ge1−x Sn x stressors, which corresponds to a compressive stress of 1.2 GPa.

Carbon-nanotube-assisted nanoepitaxy of Si-doped GaN for improved performance of InGaN/GaN light-emitting diodes

Using single-walled carbon nanotubes (SWCNTs) as nanomasks on an undoped GaN template, a significant biaxial stress relaxation was achieved in the subsequently-grown Si-doped n-GaN layer. Enhanced near band edge (NBE) emission intensity, similar free carrier concentrations, and the reduced peak width of the asymmetric (102) crystallographic plane all confirmed the suppression of threading dislocations due to the nanoepitaxial growth process. Temperature-dependent photoluminescence (PL) revealed improved internal quantum efficiency (IQE) of InGaN/GaN multi-quantum wells (MQWs) grown on this n-GaN layer. Furthermore, enhanced light output power and a remarkable reduction in efficiency droop were observed for the blue light-emitting diodes (LEDs), especially at higher injection currents. Our results emphasize the strong potential for SWCNTs as nanomasks in the heteroepitaxy of GaN-based devices without the exploitation of complicated lithography or etching processes.

Characterization of AlInN/AlN/GaN Heterostructures with Different AlN Buffer Thickness

Two AlInN/AlN/GaN heterostructures with 280-nm- and 400-nm-thick AlN buffer grown on sapphire substrates by metal-organic chemical vapor deposition (MOCVD) have been investigated by x-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) and Hall-effect measurements. The symmetric (0002) plane with respect to the asymmetric (10 $$\bar{1}$$ 2) plane in the 280-nm-thick AlN buffer has a higher crystal quality, as opposed to the 400-nm-thick buffer. The thinner buffer improves the crystallinity of both (0002) and (10 $$\bar{1}$$ 2) planes in the GaN layers, it also provides a sizeable reduction in dislocation density of GaN. Furthermore, the lower buffer thickness leads to a good quality surface with an rms roughness of 0.30 nm and a dark spot density of 4.0 × 108 cm−2. The optical and transport properties of the AlInN/AlN/GaN structure with the relatively thin buffer are compatible with the enhancement in its structural quality, as verified by XRD and AFM results.

Asymmetrically CPW-fed octagonal sierpinski UWB fractal antenna

An asymmetrically CPW-fed octagonal Sierpinski fractal antenna is designed for ultrawideband applications. It comprises of a second iterative fractal radiating patch, microstrip feedline and asymmetrical coplanar waveguide ground planes. An impedance bandwidth of 3.73 GHz to more than 20 GHz is achieved. Stable radiation patterns and desirable gain characteristics are observed. The simulated and experimental results are found to be in good agreement. The designed antenna structure has advantages of wide bandwidth and miniaturized dimensions over already reported UWB antenna structures. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1738–1745, 2016

COMPACT TRI-BAND DUAL-POLARIZED PLANAR MONOPOLE ANTENNA WITH ASYMMETRICAL GROUND PLANE AND LOADED STUB

This paper presents a compact tri-band dual-polarized planar monopole antenna, which is linearly polarized in the lower and middle bands and circularly polarized in the higher band. The antenna is printed on a substrate with an asymmetrical ground plane and a loaded vertical stub. The vertical stub and asymmetrical ground plane are mainly used to make the antenna obtain circular polarization performance in the higher band. The antenna has been built and tested. Its measured 10-dB impedance bandwidths are 2.39-2.54 GHz, 3.38-4.12 GHz, and 4.57-6.04 GHz, which can fully cover all the 2.4/5.2/5.8 GHz WLAN bands, all the 2.4/5.5 GHz Wi-Fi bands, and 3.5/5.5 GHz WiMAX bands. In the higher band, the measured 3-dB axial-ratio bandwidth is 5.4-5.83 GHz.

Contouring two-sided asymmetric plane maximum-thrust nozzles

The results of the optimal contouring of asymmetric plane nozzles under some additional constraints are presented. One of the constraints is due to the asymmetric arrangement of the unknown nozzles relative to the combustion chamber exit. The investigation is based on the numerical integration of the Reynolds-averaged Navier–Stokes equations and direct optimization methods using genetic algorithms and the representation of the optimized contours in the form of the Bernstein–Bezier curves.

Casting innovative aerospace design case studies in the parameter analysis framework to uncover the design process of experts

Traditional aerospace design methods offer quick and efficient ways to generate new designs, but such that often resemble previous ones. For truly innovative design, however, a different approach is needed. This paper suggests that a general conceptual design method called ‘parameter analysis’ (PA) may be used for teaching and practicing innovative aerospace design. To support this proposition, we investigate four diverse, innovative and unique case studies, all carried out by very experienced aerospace designers: the ‘dam busting’ bouncing bomb of World War II, the Gossamer Condor human-powered plane of the 1970s, the asymmetric Boomerang twin-engine plane of the 1990s and the SpaceShipOne suborbital spacecraft of the early 2000s. The paper elaborates on how the methodology of case-study research has been adapted and applied to provide the evidence supporting the research hypothesis, and presents the results of analyzing the case studies. It shows that the expert aerospace designers followed a thought process similar to PA, even if unknowingly, where the similarity was measured by counting the number of PA characteristics that could be shown to exist in the case studies. Advantages and limitations of the research methodology are also discussed.

A novel CB ACS-fed dual band antenna with truncated ground plane for 2.4/5 GHz WLAN application

A novel conductor backed asymmetric coplanar strip (CBACS) fed dual band antenna which is suitable for wireless local area network is presented in this paper. The proposed antenna is composed of inverted L-shaped exciting strip, a lateral ground plane and a modified truncated ground plane on the backside with overall dimension of about 25mm×17.5mm×1.6mm. The proposed design comprises monopole patch with asymmetric coplanar ground plane with conductor backing exhibit dual band of response with measured bandwidth of return loss ≤−10dB is 2.30–2.55GHz and 4.06–6.65GHz which cover all the WLAN bands (2.4/5.2/5.8GHz). The parametric studies indicate that operating frequencies and wider bandwidth are determined by the dimension of the ground plane at the top and bottom. The proposed antenna covers IEEE 802.11a/b/HYPERLAN-2/RFID band with good radiation characteristics. The measurement of proposed antenna that has been printed on an FR4 substrate with dielectric constant 4.4 yields good conformity between simulated results. The proposed structure is simulated using the method of moment based electromagnetic solver IE3D version 15.10.

The first case of actinide triple helices: pH-dependent structural evolution and kinetically-controlled transformation of two supramolecular conformational isomers.

The first actinide triple helices, including two supramolecular conformational isomers of uranium(VI), have been synthesized with the aid of a flexible V-shaped ligand and a rigid aromatic base. The isomers exhibit an intriguing pH-dependent structural evolution and a kinetically-controlled transformation via a novel conformational rearrangement of the organic base.

Bandwidth Enhancement Technique of the Meandered Monopole Antenna

A small dual-band monopole antenna with coplanar waveguide (CPW) feeding structure is presented in this paper. The antenna is composed of a meandered monopole, an extended conductor tail, and an asymmetrical ground plane. Tuning geometrical structure of the ground plane excites an additional resonant frequency band and thus enhances the impedance bandwidth of the meandered monopole antenna. Unlike the conventional monopole antenna, the new resonant mode is excited by a slot trace of the CPW transmission line. The radiation performance of the slot mode is as similar as that of the monopole. The parametrical effect of the size of the one-side ground plane on impedance matching condition has been derived by the simulation. The measured impedance bandwidths, which are defined by the reflection coefficient of −6 dB, are 186 MHz (863–1049 MHz, 19.4%) at the lower resonant band and 1320 MHz (1490–2810 MHz, 61.3%) at the upper band. From the results of the reflection coefficients of the proposed monopole antenna, the operated bandwidths of the commercial wireless communication systems, such as GSM 900, DCS, IMT-2000, UMTS, WLAN, LTE 2300, and LTE 2500, are covered for uses.

Design of a compact CPW-feed asymmetric elliptical slot ultrawideband antenna for high gain

ABSTRACTA compact, CPW‐feed slot antenna for ultrawideband applications is proposed. The antenna uses an elliptical patch as radiating element and an asymmetric slotted ground plane to provide a measured usable bandwidth of 120% (2.81–11.2 GHz). The asymmetric slot in the ground plane creates an extra inductive reactance which neutralizes the capacitive effect of the open ended elliptical patch and results into wider impedance matching. To improve the gain of the proposed antenna, a three metallic layer frequency selective surfaces (FSSs) of overall thickness 3.5 mm and with a stop band (transmission < −20 dB) of 8.3 GHz (2.6–10.9 GHz) is proposed. With the FSS, there is a 4–5 dBi improvement in the antenna peak gain and the back lobes are reduced by around 10 dBi. The measured and simulated results are in good agreement. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:314–319, 2015

Numerical Investigation of Flow in an Asymmetric Plane Diffuser Using a Multi-Scale Turbulence Model

The flow in an asymmetric plane diffuser was simulated using both the multiscale turbulence model based on the variable interval time average method and the standardk-εmodel based on the Reynolds average method. The numerical method used in this simulation is an unstructured staggered mesh scheme. The capability of the multi-scale model to simulate flow in an asymmetric plane diffuser has been validated. Pressure coefficient, frictional resistance coefficient and mean velocity profiles downstream are in agreement with experiments. Moreover, the results predicted by the multi-scale model are better than that predicted by the standardk-εmodel. The computational results show that the multiscale turbulence model can successfully simulate this type of separated flow.

Study on applying a flexibility-assisted array air bag imprinting processing technology in the development of linear gradient imprinting and simulating an asymmetric imprinting plane

This study proposed an innovative flexibility-assisted array air bag imprinting technology. It developed a linear gradient imprinting process, and used a geometric model and Matlab software for simulation in order to deduce the plane equation of the asymmetric imprinting process. This study also discussed the imprinting plane of the linear gradient imprinting processing technology. In the experiments, this study adopted the pyrometric cone micro structure array as the die characteristic shape, and used the UV curing mechanism to conduct experiments on a flexibility-assisted array air bag imprinting process. The experimental results suggest that, the innovative flexibility-assisted array air bag imprinting technology, as proposed in this study, can successfully conduct linear gradient imprinting processes. Meanwhile, the asymmetric imprinting method, as deduced using the geometric method proposed in this study, can successfully predict the imprinting parameters of the asymmetric imprinting process.

CPW-Fed Monopole Antenna for Multiple System Integration

In this work, a coplanar-waveguide (CPW)-fed monopole antenna for multiple wireless communication system integration is developed. A rectangular monopole antenna and a feeding structure are fabricated on the same plane of the substrate to simplify circuit processing and position alignment. Simply tuning one of the CPW ground-plane widths, which results in an asymmetrical ground plane structure, enhances the impedance bandwidth and excites the circular polarization at 1.57 GHz. To cover the operation bandwidth of the wireless local area network (WLAN) system, a parasitic inverted-L radiating strip is shorted to the ground plane. The measured impedance bandwidth of a S11 <; -10 dB ranges from 1.37 to 2.82 GHz, and thus covers most commercial wireless communication systems, such as GPS, DCS, PCS, IMT-2000, WLAN, and LTE. The measured 3-dB axial-ratio bandwidth is about 3.8% with respect to 1.56 GHz.