Left-hand Materials Research Articles

Single-port retroperitoneoscopic partial nephrectomy: Initial description and standardisation of technique.

Minimally invasive surgery has been established as the gold standard for the treatment of localised renal tumours. A retroperitoneal approach is a feasible option with advantages in posterior tumours and patients with previous abdominal surgeries. In this context, single-port retroperitoneoscopic partial nephrectomy (SPOR-PN) has not been widely explored and developed. We present this technique's description and our first results. We present a case series of nine patients undergoing SPOR-PN in a single institution. We used a multi-channel single-port access dispositive through a 35 mm incision below the 12th rib, a 30° two-dimensional laparoscope, curved graspers and needle drivers on the left hand and standard rigid material in the right hand. In all surgeries, we performed a complete renorrhaphy with the sliding-clip technique. The pain was evaluated through visual analogue scale (VAS) the day after surgery. Patients' age ranged from 44 to 78 years. The median RENAL score was 5p, and the mean surgical time was 134 min. We performed an 'off-clamp' procedure on three patients. Among the patients who had renal artery clamped, the median ischaemia time was 18 min. The median in-hospital stay time was 48 h. Median VAS the day after surgery was 2. None of the anatomical pieces had positive borders. Only one complication was reported (Clavien IIIa). SPOR-PN is a feasible minimally invasive and nephron-sparing technique. The advantages of this procedure may not be only a better cosmetic appearance but also less post-operative pain. Further development and larger studies are needed.

Calculation of Dispersion Characteristics of Finlines Loaded with Anisotropic Left and Right Hand Materials

In this paper, the edge-based finite element formula for calculating the dispersion characteristics of transmission lines loaded with anisotropic left handed materials and anisotropic right handed materials with electric field as working variable is derived, and the calculation is carried out by taking unilateral finline, bilateral finline and antipodal overlapping finline as examples. Firstly, the dispersion characteristics of three modes in three kinds of finlines are compared when the relative dielectric constant and permeability are fixed; Secondly, taking the unilateral fin line as an example, the changes of dispersion characteristics with the changes of relative dielectric constant and relative permeability in each direction are calculated. The calculation method and results derived in this paper further expand the application of anisotropic left handed and right handed materials in transmission lines, and also have great guiding significance for the use of finlines in microwave devices such as mixers, filters and resonators.

Hash Unit Cell Shape Used To Enhancement Gain and Bandwidth of Metasurface Antenna

In this paper, Low-profile, high gain and wideband antenna loaded with a single layer metasurface are proposed. The process of adding the metasurface layer depends on the Fabry Pérot technology, which required existing an air gap among the slot antenna and the metasurface layer. The metasurface layer consists of an array of 4 × 4 unit elements placed on a Roger Ro4003C substrate layer with a thickness of 2.5mm. Hash shape is used as a radiating element. The metasurface MS is acting as left-hand material in which both permittivity and permeability are negative, leading to negative refractive indexing. The emitted waves from the slot antenna are affected by a set of unit cells on the metasurface MS above the slot antenna because of the structure’s equivalent relative permeability and permittivity changes, and the slot antenna performance changes accordingly. The antenna works at a frequency of 6.75 GHz as a resonant frequency with an improvement in the bandwidth value for the metasurface antenna to get a value of 2.2 GHz instead of 390 MHz for the slot antenna. The proposed antenna has a 37 % bandwidth impedance starting at 4.7 GHz and ending at 6.9 GHz with a 7.43 dB gain value. The suggested antenna is useful for use with Wi-Fi applications.

Design of Compact Highpass Filter for 5G mm-wave Applications Using Complementary Split Ring Resonator

AbstractThis article presents a design of highpass filter (HPF) for millimeter-wave (mm-wave) applications using a square complementary split-ring resonator (SCSRR). A miniaturized size HPF filter is obtained by overlapping the Right-Hand (RH) and Left-Hand material. The arrangement of inter-digital parallel coupled capacitor and SCSRR offers low insertion loss, high selectivity with a sharp roll-off factor over a wide bandwidth of 15.9 GHz (from 34.1 to 50 GHz). Generally, SCSRR offers narrow passband/stopband however this prototype has a passband over a wide range of frequency. The proposed HPF has an appreciable agreement between simulated and fabricated results. Further, the filter is realized in the equivalent circuit model and their electrical elements functions are also discussed. This prototype has a cut-off frequency (fc) of 34.1 GHz with a maximum passband insertion loss of 1.45 dB. The fabricated area of the filter is 0.16λg × 0.09λg × λg and where λg is the guided wavelength at cutoff frequency fc.

Tunable left-hand characteristics in multi-nested square-split-ring enabled metamaterials

Left-hand materials have drawn increasing attention from many disciplines and found widespread application, especially in microwave engineering. A sandwiched metamaterial consisting of multi-nested square-split-ring resonators on the top side and a set of wires on the back side is proposed. Scattering parameters are retrieved by high-frequency structure simulator (HFSS) software based on the finite element method. Effects of square-split-ring number on the left-hand characteristics containing negative values of permittivity, permeability, and refractive index have been intensively investigated. Simulated results show that obvious resonant left-hand characteristics could be observed within 8–18 GHz, and the resonant frequency counts are inclined to be in direct proportion to the square-split-ring number over 8–18 GHz. Besides, the proposed sandwiched metamaterial with three square-split-ring resonators and three wires presents the widest frequency band of left-hand characteristics in a range of 8–18 GHz. Further, electromagnetic field distributions demonstrated that the induced magnetic dipole dominates the resonant absorption. The multi-peak resonance characteristics of square-split-ring resonant structure are considered to be a promising candidate for selective-frequency absorption or modulation toward microwave frequency band.

Design of a slab waveguide using a graded index profile and a left hand material

In the present paper, we consider a pulse propagation in a slab waveguide structure having three layers. The guiding layer is assumed to have a linearly graded-index profile. Maxwell's equations are solved in the three layers and both electric and magnetic fields are written in terms of the asymmetry measure (a), the generalized frequency (V) and the generalized guide index (b). The dispersion properties are investigated for three waveguide arrangements: the first one has a left-handed material (LHM) cladding, the second one has a LHM substrate layer and the third has both surroundings as LHMs. The results show the proposed waveguide exhibits normal dispersion property in which b increases as V increases.

Design of a New Broadband Left-handed Material

The left-handed materials(LHM) are widely used in antenna, filter and other microwave devices due to its negative permittivity and negative permeability. This paper proposed a new kind of left-hand materials, by means of equivalent circuit analysis, electromagnetic simulation, and extract the equivalent electrical parameters, the results show that the structure realized double negative features in the 9.3 GHz to 14.2 GHz. At the same time, the real part of the equivalent negative refractive index is negative and the imaginary part is approximately to zero. The structure has the characteristics of low loss, wide frequency band and the technology is simple. It provides reference for the design of LHMs in microwave filed.

Intrinsic left-handed electromagnetic properties in anisotropic superconductors

Left-handed materials usually are realized in artificial subwavelength structures. Here, we show that some anisotropic superconductors such as Bi2Sr2CaCu2O8+δ, YBa2CuxOy, and La2−xSrxCuO4, are intrinsic left-handed materials. The condition is that the plasma frequency in the c axis, ωc, and in the ab plane, ωab, and the operating angular frequency, ω, satisfy ωc<ω<ωab. In addition, ω should be smaller than the superconducting energy gap to sustain superconductivity. We study the reflection and transmission of electromagnetic waves and reveal negative refraction and the backward wave with the phase velocity opposite to the direction of energy flux propagation. We also discuss possible approaches for improvement, making these properties feasible for experimental validation. Being intrinsic left-hand materials, the anisotropic superconductors are promising for applications in functional electromagnetic devices in the terahertz frequency band.

Dispersive multidomain pseudospectral time‐domain method for full‐wave analysis of radio‐frequency invisible cloaks

To implement full-wave simulation of electromagnetic wave impinging invisible cloaks, an efficient multidomain pseudospectral time-domain algorithm is developed in this study. The proposed method solves the same forms of Maxwell's equations in both the regular and cloaking areas, and then applies different methods to update the electric and magnetic field components, respectively. The new method requires less grid points per wavelength, meanwhile, the multidomain strategy relieves the complicated treatment of electric and magnetic field components based on Yee grids within finite-difference time-domain methods, and shows advantage of dealing with internal inhomogeneities within the cloaking materials. The results validated feasibility and efficiency of the proposed method in left-hand materials.

Surface modes coupling in one-dimensional metamaterial photonic crystals with defects

We have investigated optical properties of one-dimensional (1D) photonic crystals (PC) composed of alternating layers of a right hand material (RHM) and a left hand material (LHM). The RHM dielectric function is frequency independent and the LHM (metamaterial) dielectric function and magnetic susceptibility are described according to the Drude model. P- or S polarized electromagnetic waves are considered to shine onto the 1D PC in the attenuated total reflectivity geometry to explore the coupling of light with the plasmons at the surfaces of the metamaterial layers. The metamaterial surface supports plasmons which in the single layer structure couple to form the symmetric and antisymmetric modes. These surface plasmons form a bulk mode in the multilayer system. The presence of a defect, which is obtained by varying the right hand layer thickness, at the middle of the layer structure, shows interesting features; the amplitude of the electric field at the defect site is enhanced and highly localized.

Design of a novel negative refractive index material based on numerical simulation

This paper presents a novel metamaterial constructed with wires, spheres and hollow slabs (WSHS), which simultaneously exhibits negative permittivity and permeability. An electromagnetic wave simulation is performed based on the proposed metamaterial and shows that a negative refractive index is achieved for this metamaterial. Adjusting the lattice constant of the unit cell is an easy way to manipulate the frequency of negative index of this structure. A left-hand material prism is designed composed of metamaterial unit cells and the simulation on the proposed prism proves the left-hand behavior of the designed metamaterial.

Fredholm's equations for subwavelength focusing

Subwavelength focusing (SF) is a very useful tool that can be carried out with the use of left hand materials for optics that involve the range of the microwaves. Many recent works have described a successful alternative procedure using time reversal methods. The advantage is that we do not need devices which require the complicated manufacture of left-hand materials; nevertheless, the theoretical mathematical bases are far from complete because before now we lacked an adequate easy-to-apply frame. In this work we give, for a broad class of discrete systems, a solid support for the theory of electromagnetic SF that can be applied to communications and nanotechnology. The very central procedure is the development of vector-matrix formalism (VMF) based on exploiting both the inhomogeneous and homogeneous Fredholm's integral equations in cases where the last two kinds of integral equations are applied to some selected discrete systems. To this end, we first establish a generalized Newmann series for the Fourier transform of the Green's function in the inhomogeneous Fredholm's equation of the problem. Then we go from an integral operator equation to a vector-matrix algebraic one. In this way we explore the inhomogeneous case and later on also the very interesting one about the homogeneous equation. Thus, on the one hand we can relate in a simple manner the arriving electromagnetic signals with those at their sources and we can use them to perform a SF. On the other hand, we analyze the homogeneous version of the equations, finding resonant solutions that have analogous properties to their counterparts in quantum mechanical scattering, that can be used in a proposed very powerful way in communications. Also we recover quantum mechanical operator relations that are identical for classical electromagnetics. Finally, we prove two theorems that formalize the relation between the theory of Fredholm's integral equations and the VMF we present here.

The Study on the Periodic Left-Handed Materials of Convex-SRRs Structure

The split ring resonators is the basic structure unit ,it is important constituent part of periodic left-handed materials (LHMs).The convex split ring resonators (convex-SRRs) structure is the new SRRs, the new periodic LHMs are made of convex-SRRs structure unit.The convex-SRRs structure is arranged periodically 3 * 4 matrix along XOY plane and arranged periodically 3 * 2 * 1 matrix along the YOZ plane. These convex-SRRs structure units in space periodic aligned to the prism shape, the new artificial materials come into being.In order to prove that the convex-SRRs structure periodic materials are left-handed materials (LHMs), the microwave transmission and negative refractive are simulated using the materials of convex-SRRs structure prism. First the permeability and permittivity of convex-SRRs structure materials are negative value by simulation the microwave transmission, this is the symbol of the left hand material properties. Second by simulation, prism’s experiment of convex-SRRs structure materials has a negative refractive effect, These simulations demonstrate that the materials of convex-SRRs structure periodic arrangement are LHMs.

The surface mode supported by an asymmetrical waveguide containing left-handed materials

The propagating characteristics of surface mode supported by an asymmetrical three-layer waveguide containing left-hand materials are studied in detail. The forward and the backward surface modes have been identified respectively through the slope of dispersion curve and the total energy flux of the structure. Research shows that anti-symmetry mode corresponds to forward surface wave. Furthermore, to symmetry mode, the type of surface mode depends on the distribution of the electric field in the left-handed layer. It is found that, the conversion between backward surface wave and forward surface wave is realizable by varying the thickness of the left-handed layer and the permittivity of the substrate.

Variable magnetic and electric resonances for split-ring resonators as left-handed materials in free space

Electric and magnetic resonances of split-ring resonators (SRRs) as left-hand materials (LHM) were studied in a free space. Different copper thicknesses were designed to tune the electromagnetic resonance frequencies of SRRs. While the split gap width was varied, double-negative responses in SRRs were investigated in detail. Even both electric and magnetic resonance frequencies became higher as copper thickness was decreased, the electric resonance frequency increased much more higher with the increasing of the split gap width.

Anderson localization in bi-layer array with compositional disorder: Conventional photonic crystals versus metamaterials

The localization length has been derived for one-dimensional bi-layered structures with random perturbations in the refractive indices for each type of layers. Main attention is paid to the comparison between conventional materials and those consisting of mixed right-hand and left-hand materials. It is shown that the localization length is described by the universal expression for both cases. The analytical results are confirmed by numerical simulations.

Applications of BPNN in Analyzing LHM Elemental Basic Structure

Based on the back propagation multi-layer forward feed neural network, the neural network model is built for the dielectric sensitive structural parameters between the equivalent permittivity and the equivalent permeability, which is used to analyze the basic left-hand materials(LHMS) structural. The experimental results show that the analysis time is 145.535648 seconds and the training mean error is 0.000113426 while adopting the scaled conjugate gradient method. The results are coincident with these ones by the full wave method, satisfying the engineering demand, reducing the faults caused by thickness resonance in the traditional numerical analysis method, realizing the coexistence between the high analysis precision and the high efficiency of the left-hand materials.

Propagation Characteristics of a Novel NRD Guide with Double-Layer LHM Slab

A new waveguiding structure based on NRD (Nonradiative Dielectric) guide with a double-layer LHM (Left Hand Material) slab is carefully investigated. Rigorous multi-mode network treatment combining with mode matching method is carried out to analyze the propagation characteristics of the structure. Theoretical analysis results reveal that depending on the choice of permittivity and permeability of the two dielectric slabs, the guiding structure is of series distinct and interesting properties, such as anomalous dispersion, opposite polarization modes coupling, and the existence of complex mode. Besides, the new configuration can also be used as a leaky wave antenna working in the dominant or the first higher order mode. All these particular features create various applications in electromagnetic engineering.

Relativistic energy loss and induced photon emission in the interaction of a left-handed sphere with an external electron beam

Relativistic energy loss and photon emission in the interaction of a coated sphere containing a left-handed material with an external electron beam are studied based on the classical electrodynamics. Both of electric modes and magnetic modes are not only found in the spectra of energy loss and photon emission for different combinations of electron velocity and sphere radius, the new excitation modes can be also observed. Our results show that different excitation modes for the left-hand materials and the structure information of coated sphere can be explored by scanning transmission electron microscopy (STEM).

Fabricating Metal Patterned Ceramic Substance by Tape-Casting

Tape-casting technology is introduced to fabricate metal-arrayes patterned ceramic substance containing periodic multilayer silver wire structure in the low dielectric constant ceramic matrix for microvave bandgap materials and left hand material application. One important advantage of the metal patterned ceramic substance comparing with the periodic structures fabricated on the printed circuit boards (PCB) using a shadow mask/etching technique is that complex multilayer structure can be designed and fabricated in the ceramic body as well as on the surface by the tape-casting process, while the shadow mask/etching technique technology can only design patterns on the surface of printed circuit boards. An Hp8720ES network analyzer was used to measure the transmission properties of the metal patterned ceramic substance. The experimental result shows some novel properties at X-band microwave frequencies. The metal patterned ceramic substance can be used in the microwave communication, such as microwave antenna.