Conduction Plane Research Articles

Slit-Slot Line and Its Application to Low Cross-Polarization Slot Antenna and Mutual-Coupling Suppressed Tripolarized MIMO Antenna

A slit-slot transmission line is devised, investigated, and applied to a slit-slot antenna and a co-located tripolarized slit-slot antenna array for 2.45 GHz multipolarization multi-input-multi-output (MIMO) applications. The slit-slot transmission line, with slit array etched on its conductive planes, is analyzed and characterized by using an equivalent circuit model and a graphical method based on simulations. Taking advantage of the features of a slit-slot transmission line, which include a shorter wavelength and a favorable current distribution for antenna applications, a slit-slot antenna, and a co-located tripolarized slot antenna array are presented and investigated by simulations and experiments. The effects of slits on the performances of the slit-slot antenna and the antenna array are explained. The simulated and measured results of fabricated prototypes show that the slits improve the cross-polarization of both the slit-slot antenna element and the antenna array around 5 dB, and that the isolation among the tripolarized slit-slot antenna array is improved by 14 dB, compared to the associated slot antennas. Furthermore, tripolarized slit-slot antenna array has an omnidirectional radiation patterns and low correlation which are favorable for MIMO applications.

A Low Profile, Dual-band, Dual Polarized Antenna for Indoor/Outdoor Wearable Application

A planar, low-profile, dual-band and dual-polarized antenna on a semi-flex substrate is proposed in this paper. The antenna is fabricated on Rogers substrate with a thickness of 3.04 mm and sized at $70.4 \times 76.14 \times 3.11$ mm3 ( $0.37\lambda _{0} \times 0.40\lambda _{0}\times 0.016 \lambda _{0}$ ) only. The circular polarization property is enabled in the global navigation satellite system (GNSS) L1/E1 (lower) band by introducing a complementary split ring resonator on the antenna patch. Meanwhile, the antenna operates in the second (upper) 2.45 GHz WLAN band is enabled by etching a U-shaped slot on its ground plane. This simultaneous, dual-band and dual-polarized operation enables the proposed antenna to be applied in the indoor/outdoor wearable application. To isolate the antenna against the influence of the human body, a multiband artificial magnetic conductor (AMC) plane is added on the reverse side of the dual-band radiator. Comparison of the antenna without AMC in free space and when evaluated on the chest of a human body backed by AMC showed improved gain; from 3–5.1 dBi in the lower band, and from 1.53–5.03 dBi in the upper band. Besides that, the front-to-back ratio of the AMC backed monopole antenna also improved from 11–21.88 dB and from 2.5–24.5 dB in the GNSS and WLAN bands, respectively. Next, the specific absorption rate (SAR) of the monopole antenna with and without the AMC plane is assessed. Evaluation results indicate that the maximum SAR value decreased by up to 89.45% in comparison with the antenna without AMC in the lower band. This indicates the effectiveness of the AMC array in increasing gain and FBR, besides reducing EM absorption in the human body.

A Multi-Stage Model for the Electromagnetic Shielding Effectiveness Prediction of an Infinite Conductor Plane With Periodic Apertures

This paper focuses on the shielding effectiveness (SE) prediction of the periodic aperture array on an infinite conductor plane against a plane electromagnetic wave with its wavelength much larger than the size of a unit cell of the array. Especially, the existing analytical expressions of SE are combined to cover the entire range of the aperture rate, which is defined as the ratio of the side length of the aperture to that of the unit cell. The combination is carried out by bridging the small aperture model and the wire mesh model. Then, a multi-stage model based on the piecewise function of the aperture rate is presented to calculate the SE for any aperture rate. The model is also extended to consider different wave polarization and incident angles. The results of the model are in good agreement with those from the full-wave simulation. The applicability of the model to a different thickness and aperture shape is discussed. In addition, the upper-limit frequency at which the model is no longer applicable is also analyzed.

A Flexible Tactile Sensor with Irregular Planar Shape Based on Uniform Electric Field.

Tactility is an essential perception for intelligent equipment to acquire external information. It can improve safety and performance during human-machine interactions. Based on the uniqueness theorem of the electrostatic field, a novel flexible film tactile sensor that can detect contact position and be made into any plane shape is proposed in this paper. The tactile sensor included an indium tin oxide (ITO) film, which was uniformly coated on the polyethylene terephthalate (PET) substrate. A specially designed strong conductive line was arranged along the edge of the flexible ITO film, which has weak conductivity. A bias excitation was applied to both ends of the strong conductive line. Through the control of the shape of the strong conductive line, a uniform electric field can be constructed in the whole weak conductive plane. According to the linear relationship between position and potential in the uniform electric field, the coordinate of the contact position can be determined by obtaining the potential of the contact point in the weak conducting plane. The sensor uses a three-layer structure, including an upper conductive layer, an intermediate isolation layer, and a lower conductive layer. A tactile sensor sample was fabricated. The experiment results showed that the principle of the tactile sensor used for the contact position detection is feasible and has certain precision of position detection. The sensor has good flexibility, and can be made into any plane shape, and has only four wires. It is capable of covering large areas of robot arms, and provides safety solutions for most robots.

Propagation Loss Reduction Between On-Body Antennas by Using a Conductive Strip Line

This letter proposes a very simple solution to reduce the propagation loss between two antennas/sensors on body at 2.45 GHz by utilizing a flexible conductive strip line (CSL). The performance of the CSL is comparable to that of the free-access transmission line in the work by Tran et al. in some certain cases. The transmission improvement by the CSL is verified by measurement results on a perfect electrical conductor plane, on a phantom, and on a real body more than 20 dB for non-line-of-sight scenarios. Dimension parameters of the CSL are optimized so that the highest improvement by the CSL can be achieved and it is easy to be integrated into clothes. Moreover, the specific absorption rate is satisfied when the CSL is deployed near body.

Oxo- and Oxofluoroaluminates in the RbF-Al2O3 System: Synthesis and Structural Characterization.

Precise research on the RbF-Al2O3 system was carried out by means of combining X-ray powder diffraction, high-field solid-state NMR spectroscopy, and thermal analysis methods. α-Rb3AlF6, RbAlO2, Rb2Al22O34, and new phase, Rb2Al2O3F2, were identified in the system. The structure of this new rubidium oxofluoroaluminate was determined. It is built up from single layers of oxygen-connected AlO3F tetrahedra, those layers beeing separated by fluorine atoms. This type of structure exhibits a decent ionic conductivity at ambient temperature, 1.74 × 10-6 S cm-1. The similar structural arrangement of O3Al-O-AlO3 and FO2Al-O-AlO2F tetrahedra of the conduction planes in Rb2Al22O34 and Rb2Al2O3F2 were confirmed by 27Al NMR measurements. A thermal analysis of the RbF-Al2O3 system revealed that it can be defined as a pseudobinary subsystem of the more general quaternary RbF-AlF3-Al2O3-Rb2O phase diagram. From a phase analysis of individual phase fields, the mutual metastable behavior of all founded phases can be considered. It was observed that fluoro- and oxoaluminates exist together. Rb2Al2O3F2 is more stable under high temperature. Rubidium fluoro- and oxoaluminates are metastable precursors of the thermodynamically more stable structure of rubidium oxofluoroaluminate.

Buffer-Induced Current Collapse in GaN HEMTs on Highly Resistive Si Substrates

We demonstrate that the highly resistive Si substrate in GaN-on-Si RF HEMTs does not act as an insulator, but instead behaves as a conductive ground plane for static operation and can cause significant back-gate-induced current collapse. Substrate ramp characterization of the buffer shows good agreement with device simulations and indicates that the current collapse is caused by charge-redistribution within the GaN layer. Potential solutions, which alter charge storage and leakage in the epitaxy to counter this effect, are then presented.

VSIE-Based Domain Decomposition Method With Simplified Prism Vector Basis Functions for Planar Thin Dielectric-Conductor Composite Objects

A nonoverlapping and nonconforming volume-sur-face integral equation (VSIE) domain decomposition method (DDM) using simplified prism vector (SPV) basis functions is presented for complex electrically large composite planar thin dielectric-perfect electric conductor objects. Compared with the recently developed SPV-based VSIE, this scheme considerably accelerates the convergence of iterative solutions by an effective preconditioner resulted from the DDM. Moreover, this DDM does not require imposing continuity conditions at the interfaces between adjacent subdomains, and the use of discontinuous Galerkin approach allows the nonconforming volume discretizations. Due to the nonconforming nature, subdomains can be built up separately, resulting in a flexible and convenient geometrical modeling. For composite subdomains involving thin dielectric layers, the full/half SPV basis is applied so that, in comparison with the generally used Schaubert–Wilton–Glisson basis, the number of unknowns is remarkably reduced. Several numerical examples are reported to illustrate the efficiency and fast convergence of this scheme.

Gain enhanced circularly polarized antenna integrated with artificial magnetic conductor for S-band pico-satellites

A circularly polarized (CP) antenna integrated with an artificial magnetic conductor (AMC) plane is presented. The AMC plane is aimed at enhancing the gain of the CP antenna, besides reduced back-radiation, and avoiding radiation toward other high-frequency components on the CubeSat. It consists of a 3 × 3 array of diamond-shaped unit cells placed behind the complementary dipole-based antenna. To enable deployability and compact deployment size, the AMC structure is designed on a thin flexible Kapton film as substrate, whereas its metallic components are formed using Nickel conductive paint. Meanwhile, the CP antenna is designed on a thin Rogers RO4003C substrate and located on top of the AMC plane at a 20 mm distance. The combined structure operates at 2.4 GHz with satisfactory reflection and radiation performance. It is sized at 99 mm × 99 mm × 21.485 mm3, with 450 MHz (18%) of 10 dB impedance bandwidth and 250 MHz (10%) of 3 dB axial ratio bandwidth. The AMC plane also improved its gain from 3.05 dBi up to 5.35 dBi.

Miniaturized Band Pass Filter in Substrate Integrated WaveguideTechnology

Miniaturization is an important criteria in the selection of devices for next generation communication systems. A novel miniaturization technique for an inductive post filter is investigated in this paper. Miniaturization is not so popular in inductive post Substrate Integrated Waveguide (SIW) filter and so considerable amount of research is to be done in this domain. A band pass filter in SIW technology using inductive posts is realized and further analyses are carried out. The insertion loss in the pass band is found to be 0.5 dB and the return loss is 22 dB. In this paper, we investigate the use of slow wave technology for miniaturization. Unlike the conventional SIW, the slow wave SIW topology requires a double layer substrate with internal metallized vias introduced in the bottom layer connected to the bottom conductive plane. The number of rows of internal metallized vias was chosen based on a parametric study. The proposed miniaturization technique shows that the SIW filter is 21.6 % and 34.6 % miniaturized in size and area respectively. The response of the filter covers Ka band and hence is suitable for satellite communication application. A quality factor of 506 is achieved for the miniaturized filter.

High isolation circularly polarized (CP) antennas using compact soft surface

ABSTRACTA compact soft surface is proposed to improve an isolation of circularly polarized patch antennas in this article. The soft surface is generally made up of a periodically alternating perfect electric conductor and perfect magnetic conductor. The perfect magnetic conductor is implemented by the corrugation with a depth of quarter wavelength. The proposed compact soft surface is designed by a folded corrugation with a length of a quarter wavelength and the folded part is located below perfect electric conductor plane. Thus, the compact soft surface can be designed without any additional area above the ground plane. To verify its feasibility, mutual coupling and axial ratio of two circularly polarized antenna elements without and with the compact soft surface have been compared. This improved isolation results in small active reflection coefficient and wide beamwidth of active element pattern which would help to design wide scanning angle array.

Limiting Characteristics for Receiving Small Size Frame Antenna Matching Using Converter Negative Impedance

The limiting characteristics of electrically small-sized loop antenna matching by means of non-Foster's negative inductance are studied. Various options for including negative inductance in frame antenna structure are considered. The analytical limit expression for the operating frequency band of the small-sized loop antenna with the inclusion of negative inductance in the gap of the conductor frame is obtained. It is shown that for practical implementation the most convenient is the scheme with the inclusion of negative inductance between the conducting plane and the free output of the frame. Such inclusion of negative inductance causes small loss in width of the working frequency band compared with the inclusion of this inductance in the gap of the frame conductive plane, but EMF induced in the frame is twice as large. An integral expression is obtained for the maximum band matching of the small-sized loop antenna with the inclusion of negative inductance in grounded output, the integral in which is calculated numerically for various small-sized loop antenna quality factor and ratios between resonant frequency of the frame and operating frequency range. The results obtained are similar to Fano-Yula restriction for passive matching chains.

Flame Made Nanopowder Processing Results in Low Temperature Sintering of β'’-Al2O3 Thin Films (50 µm) with TiO2 and ZrO2 Addition

β’’-Al2O3 is used commercially as a Na+ conducting ceramic electrolyte for its high ionic conductivity (0.2-0.3 S cm-1 at 300°C) and low materials’ costs. However, for batteries using β'’-Al2O3, about half of the cell resistance arises from the electrolyte itself because traditionally processed electrolyte materials are 1-2 mm thick. One can anticipate dramatic drops in cell resistance at <100 µm. However, traditional high sintering temperatures of 1600 °C/0-4 h cause rapid and excessive Na2O loss driving formation of the β- rather than β'’-Al2O3 phase lowering ionic conductivities limiting final properties. Known methods of β'’-Al2O3 sintering commonly involve covering the sample with the same powder to reduce Na2O loss. The quality (phase, particle size, particle morphology, etc.) of the starting powder has been shown to have a strong effect on β’’-Al2O3 sintering behavior. In line with our latest success of using flame made nanopowders (NPs) to minimize the external energy input for sintering Li7La3Zr2O12, Li+ conducting ceramic electrolyte known for its difficulty in sintering, we show that the same can be achieved for β’’-Al2O3. In this study, β’’-Al2O3, TiO2 and ZrO2 NPs were produced by liquid-feed flame spray pyrolysis (LF-FSP). The NPs were then processed to green films (80 µm) by tape casting such that β'’-Al2O3 with 0, 1, 2, and 3 wt.% of TiO2 addition is produced. TiO2 was selected to aid sintering as Al3+ vacancies generated by Ti4+ doping promote the sintering process. Furthermore, low melting point (1050-1150 °C) Na2O-TiO­2 line compounds form inducing liquid phase sintering. As expected, superior densification of β'’-Al2O3 films occurs with increasing TiO2 wt. %. Near full densities are reached at ≥ 1360 °C/2 h with 2 and 3 wt. % added TiO2. However β’’-Al2O3 content reaches only ~65 wt.% and the orientation of the c-axis is perpendicular to the film surface per XRD. The preferred conduction plane is perpendicular to the c-axis reducing net conductivity. Also, the large grain sizes seen in the 2 and 3 wt. % TiO2 samples suggest liquid phase sintering. To perturb grain reorientation during liquid phase sintering, and also pin grain boundaries to reduce grain growth, we introduced 10 wt. % of ZrO2 with 2 and 3 wt.% TiO2. The added ZrO2 may also reduce Na2O loss rate by reducing surface exposure of β’’-Al2O3. Sintering of the aforementioned samples both reduces final grain sizes and degrees of c-axis orientation. Furthermore, nearly full densities could be accessed at 1320 °C/2 h with 85 wt.% β'’-Al2O3. Ionic conductivities obtained equal those reported by others. Our approach is scalable and economical for mass producing β'’-Al2O3 films. Furthermore, the combination of nanopowders with selected additives allows sintering β'’-Al2O3 at 1320 °C, the lowest ever reported. Work supported on NSF subcontract from Na4B to University of Michigan and by a give from Mercedes-Daimler.

High‐gain broadside dipole planar AMC antenna for 60 GHz applications

A novel 60 GHz high-gain planar artificial magnetic conductor (AMC) antenna is proposed. The prototype of the antenna is a dipole structure with a broadband input impedance match. Parasitic patches and a novel AMC plane are successively used to enhance its broadside gain. The antenna has a compact size of 7.5 mm × 8 mm, including the modified AMC plane. Simulated and measured results both show the antenna has good properties of return losses better than 10 dB, stable peak gains up to 10.9 dBi and favourable radiation patterns from 57 to 64 GHz, which all denote that it is fit for 60 GHz wireless portable communication systems.

Closed formulae for the wave number of the TM0 mode guided by a dielectric-coated plane conductor

ABSTRACTSimple closed formulae are derived for the wave number of the TM0 mode guided by a plane conductor coated with a dielectric slab, for the first time. Finite conductivity and dielectric loss are accounted for. So is the retardation effect of colliding electrons, in order to extend the frequency-range of the proposed formulae beyond 1 THz. Those formulae are applied in two examples.

Design of three‐dimensional filtering balun with inherent complete ground and enhanced stopband rejection

A novel design approach of three-dimensional filtering balun with inherent complete ground and enhanced stopband rejection is proposed. The whole structure consists of a horizontal feeding plane, a vertically mounted plane, and three ports. By arranging the double-sided parallel-strip line filter symmetrically on the two sides of the vertical plane, the frequency selectivity and complete ground are effectively synthesised. By inserting a rectangular conductor plane with two crossed slots into the middle of the vertical plane, the balanced-to-unbalanced conversion and stopband rejection are significantly enhanced. For demonstration, an experimental filtering balun is fabricated. The measurement agrees well with the simulation, achieving a wide upper stopband under −15 dB from 3.77 to 9.74 GHz.

RESONANT CHARACTERISTICS OF CIRCULAR HTC SUPERCONDUCTING PRINTED ANTENNA COVERED WITH A DIELECTRIC LAYER

—Effects of a superstrate layer on the resonant frequency and bandwidth of a high Tc superconducting (HTS) circular printed patch are investigated in this paper. For that, a rigorous full-wave spectral analysis of superconducting patch in multilayer configuration is described. In such an approach, the spectral dyadic Green's function which relates the tangential electric field and currents at various conductor planes should be determined. Integral equations are solved by a Galerkin's moment method procedure, and the complex resonance frequencies are studied with basis functions involving Chebyshev polynomials in conjunction with the complex resistive boundary condition. To include the superconductivity of the disc, its complex surface impedance is determined by using London's equation and the model of Gorter and Casimir. Numerical results are compared with experimental results of literature as well as with the most recent published calculations using different methods. A very good agreement is obtained. Finally, superstrate loading effects are presented and discussed showing interesting enhancement on the resonant characteristics of the superconducting antenna using combinations of Chebyshev polynomials as set of basis functions.

Triple-band tunable perfect terahertz metamaterial absorber with liquid crystal

We report a compact triple-band tunable perfect terahertz metamaterial absorber (TMA) at the subwavelength scale of thickness, which is composed of a planar metallic disk resonator array above a conductive ground plane separated with liquid crystal (LC) mixture. The calculations of terahertz absorption spectra demonstrate triple near-unity absorption bands in the gap plasmonic resonance coupling regime. Three resonance frequencies of the absorber exhibit continuous linear-tunability as changing the refractive index of LC. Remarkably, each peak absorbance of the triple bands maintains at a level of beyond 99% in the whole tuning operation, and the absorbance can remain more than 90% over a wide range of incident angles. Our work suggests that the LC tunable absorber scheme has the potential to overcome the basic difficulty to perform simultaneously multiband spectral tuning and near-unity absorbance with wide angle of incidence and weak polarization dependence. The proposed LC-tunable multiband perfect TMA is promising in the application of biomolecular spectra-selective terahertz imaging and sensing.

Propagational characteristics in a warm hybrid plasmonic waveguide

We theoretically analyze the properties of guided modes in a warm planar conductor–gap–dielectric (CGD) system. The latter consists of a high index dielectric, separated from a warm metallic plasma with a low index nano-sized dielectric layer (gap) by using the hydrodynamic model coupled to Maxwell's equations. The effects of thermal pressure on the confinement and the propagation losses of Hybrid Plasmon Polariton (HPP) modes are studied. We found that the thermal effect leads to a reduction in the effective refractive index as well as in the propagation losses of the HPP mode. Furthermore, the cutoff thickness in the warm CGD waveguide is found to be smaller than that in a cold CGD waveguide. The results may be useful in understanding the essential physics of active/passive Plasmonic devices and chip-scale systems.

A novel method of measurement of loss in a track of a turn of a planar transformer for induction heating applications

The new trend in power converters is to design planar magnetic components aimed at low profile. However, at high frequencies, the AC losses induced in the planar inductor and transformer windings become significant due to skin and proximity effects. This paper presents the design of a high-frequency planar transformer (HFPT) for an induction heating system. The aim of this design is to adapt the levels of voltage and current from the inverter to the resonant tank characteristics. We propose a planar structure of Litz in the primary of our HFPT to reduce the AC resistance of the planar conductor. The Litz structure is obtained with a technique of the turn’s division in four tracks and their intersection so that the current passes all over the turn.For the single secondary turn, the choice of the section is based on an analytical study compared to a 2D finite element modeling (FEM), and is determined according to the shape that represents fewer losses and responds to our needs.2D finite element modeling (FEM) was performed for three different primary turns’ structures; full coil, a turn with four parallel tracks and our Litz planar turn; to minimize losses. Simulation results show that the planar Litz conductor can lead to a lower AC resistance. The performance of this Litz structure is also verified by measurements on experimental prototypes.