Left-handed Waveguide Research Articles

Wireless Power Transmission Efficiency of Dipole Array Antenna using a Left-Handed Waveguide Slot Antenna as a Feeder

This paper proposes to transform microwaves for snow melting, which slightly leaking from the slotted waveguide, into electric power using a wireless power transmission technique for effective use. A combination of left-handed and right-handed waveguides is a method to melt snow evenly over a large area using microwaves. The left-handed waveguide, however, has large loss because of stubs. In order to evaluate the effect of the left-handed waveguide’s loss, this paper analyzed the wireless power transmission efficiency when the left-handed waveguide with a slot was set as the power transmission part, and a dipole array was placed above the left-handed waveguide as a power reception unit. The wireless power transfer efficiency was calculated using kQ product from S-parameters that were obtained by using the method of moments. The results clarified that the sum of the maximum efficiencies of the arrayed dipoles could be made larger than the maximum efficiency of one dipole.

Enhanced coupling coefficients of a thin-film waveguide grating with a double negative cover

We study the propagation of waves in waveguide gratings with a double negative cover. The waveguide grating is considered as a small perturbation to a perfect waveguide and the effects of index variations on the propagating modes in the grating region are studied. To describe the energy transfer between the modes of the original structure, two coupled-mode equations are derived using the perturbation method. General formulas for both longitudinal and transverse coupling coefficients of thin-film waveguide gratings are obtained, which can be used for both conventional and left-handed thin-film waveguide gratings. To emphasize the unusual properties of the left-handed waveguide gratings, we numerically obtain the coupling coefficients of waveguide gratings with a double negative cover and compare them with those of conventional waveguides. We show that the coupling coefficients of the left-handed waveguide gratings enhance more than 3 orders of magnitude. While the longitudinal coupling coefficient of a conventional waveguide is zero, we report that it is nonzero for a waveguide grating with a double negative cover. In particular, we show that for especial ratios of the substrate to cover permittivity, the coupling coefficient of the fundamental mode (m=0) only exists within a small frequency range.

Novel Capacitor-Loaded Substrate-Integrated-Waveguide Structure and Its Electronically Controlled Leaky-Wave Antenna Application

A capacitor-loaded slotted substrate-integrated waveguide structure is presented to realize a tunable composite right-/left-handed substrate-integrated waveguide structure. The capacitor-loaded slotted substrate-integrated waveguide structure is realized on a half-mode substrate-integrated waveguide structure to reduce the size. The inter-digital slots and varactor diodes are inserted to offer series-tunable capacitance of the composite right-/left-handed circuit model. A long slot is inserted to isolate DC bias, and the chip capacitors are mounted on the long slot to create a path for RF signal flow. Based on the tunable capacitor-loaded slotted substrate-integrated waveguide structure, an electronically controlled composite right-/left-handed leaky-wave antenna is designed. It is experimentally demonstrated that the direction of the main beam is continuously varied from +4° to −6° at 5.6 GHz as the bias voltage increases from 1 to 20 V.

Tunable Left-Handed Characteristics of Ferrite Rectangular Waveguide Periodically Loaded With Complementary Split-Ring Resonators

We propose, for the first time, a tunable left-handed (LH) waveguide consisting of an array of complementary split-ring resonators built on the broad wall of a rectangular waveguide filled with ferrite material. The left-handed behavior is caused by the negative permittivity of the complementary split-ring resonators together with the negative permeability of the transversely magnetized ferrite. The electromagnetic behavior of this structure is studied by means of an equivalent circuit model. From this model, the dispersion relation of the guide is derived and validated numerically by the finite element method. It is shown that this structure has a left-handed frequency band that can be tuned by changing the dc bias magnetic field applied to the ferrite. Compared to previous works, the fabrication requirements on this structure are not critical, which enhances its potential applicability.

Abruptly terminated planar left-handed material waveguide

The problem of guided mode reflection from an abruptly terminated planar metamaterial waveguide is studied by the variational technique. The theory is illustrated by examples of abruptly terminated three-layer waveguides with step permittivity and permeability profiles. Differences in the scattering characteristics for systems with metamaterials and usual media are discussed.

Broadband left-handed rectangular waveguide using a shorted stub and twisted E-plane posts

A broadband left-handed (LH) waveguide operating above the cutoff frequency is presented. The unit cell consists of one-shorted stub and two-twisted posts. The structure induces double loops in the surface currents, resulting in enhanced inductance which broadens the negative permeability region. To analyze the LH properties of the structure, a 2-port network cross-connected equivalent circuit is derived. The measured results of the LH waveguide constructed with five unit cells in an X-band are in good agreement with simulated data and show a good transmission property as well as a broad LH fractional bandwidth of 26.5%. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:835–840, 2013; View this article online at wileyonlinelibrary.com. DOI: 10.1002/mop.27419

Proper and improper modes of the left-handed material waveguides

The guided, complex, and virtual modes of the planar left-handed material waveguides are studied. The modal dispersion and field distributions are analyzed for the systems with step and parabolic profiles of dielectric permittivity and magnetic permeability. It is shown that anomalously high magnitudes of the magnetic fields may be observed in such structures. Effects of material nonlinearity and spatial dispersion are discussed.

Numerical study of a structure containing left-handed material waveguide

In this paper a waveguide structure consisting of a pair of left-handed material (LHM) and dielectric slabs inserted in vacuum is investigated theoretically. Maxwell’s equations are used to determine the electric and magnetic fields of the incident waves at each layer. Snell’s law is applied and the boundary conditions are imposed at each layer interface to calculate the reflected and transmitted powers of the structure. Numerical results are illustrated to show the effects of frequency, angle of incidence and LHM thickness on the transmitted power when the refractive index of the dielectric layer changes. The same procedure is repeated to show the variation of the transmitted power with the change in the mentioned parameters under different values of dissipation factor of the lossy LHM. Consequently, two cases of the LHM are considered, loss-less case and loss case. The results obtained, are in agreement with the law of conservation of energy.

Composite right-/left-handed coplanar waveguides loaded with split ring resonators and their application to high-pass filters

In this study, it is demonstrated that coplanar waveguides periodically loaded with split ring resonators (SRRs) and shunt connected elements can be applied to the synthesis of composite right-/left-handed transmission lines with very good high-pass filter characteristics. By balancing the line and forcing the characteristic impedance around the transition frequency to be in the vicinity of 50 Ω, a broad transmission band with low insertion losses is obtained. Owing to the presence of the transmission zero to the left of the left-handed band, severe cut-off is also obtained. A prototype high-pass filter device has been designed, fabricated and characterised to illustrate the possibilities of the approach.

Beam-Scanning Performance of Leaky-Wave Slot-Array Antenna on Variable Stub-Loaded Left-Handed Waveguide

Metamaterial is an artificial material in which the effective phase constant can be controlled by the internal physical periodic structure of the transmission line. Effective phase constant is designed to be of any value, which may be small, large, approximately zero, or negative, attained by changing the dimensions of the periodic structure. Miniaturization of the antenna and wide design flexibility of radiation patterns can be expected from the use of metamaterials. In this work, we developed a leaky-wave slot-array antenna on a variable stub-loaded left-handed waveguide. The radiation pattern of the fabricated antenna was measured and the characteristics of the left-handed transmission line were observed. Moreover, performance of beam-scanning by changing the length of the stubs on the waveguide was confirmed experimentally.

Guided modes in a symmetric five-layer left-handed waveguide

The guided modes are investigated in a symmetric five-layer slab waveguide with a core of negative refractive index material surrounded by four normal dielectrics. The graphical method is applied to determine the guided optical modes. The left-handed material waveguide supports both oscillating and surface guided modes. For oscillating guided modes the fundamental mode can be supported. Mode double-degeneracy appears and some modes are absent in the five-layer waveguide. High-order surface guided modes exist due to the oscillating electric field in the inner claddings. Energy flux for the oscillating and surface guided modes is also discussed in detail.

Sub-diffraction negative and positive index modes in mid-infrared waveguides

We characterize a strongly anisotropic waveguide consisting of alternating 80 nm layers of n(+)-InGaAs and i-AlInAs on InP substrate. A strong increase in the transverse magnetic (TM) reflection at lambda = 8.4 microm corresponds to a characteristic low-order mode cutoff for the left-handed waveguide. The subsequent decrease of TM reflection at lambda = 11.5 microm represents the onset of right-handed no-cutoff light guiding. Good qualitative agreement is found when the experimental results are compared to finite element and transfer-matrix frequency domain simulations.

The mode characteristics of a symmetrical slab waveguide with single-negative-material cladding

The propagating characteristics of a symmetrical three-layer slab waveguide with mu-negative (MNG) media are studied in detail. It is found the MNG waveguide can propagate not only quick waves but also slow waves of TE0 and TE1 modes. The properties of this guided mode are different from those of the left-handed waveguide and the conventional waveguide. In MNG slab waveguide, the region of effective refractive index of the guided mode is wider than those of the other two. In addition, the TE0 fundamental guided mode does not exist at all, while the higher-order TE guided modes and all TM guided modes do exist. However the surface wave of TE0 and TE1 modes can emerge under a certain condition. The propagation constant of higher-order TE mode is greater than that of the TM mode of the same order. Two TE modes of the same order can coexist in the MNG, which is closely related to the structural parameters. The energy fluxes of two TE modes are oppositely directed inside and outside the inner layer, therefore the total energy flux can be negative.

Anisotropic Left-Handed and μ-Negative Slab Waveguides: Physics and Device Applications

We study the properties of various anisotropic left-handed slab waveguides. The analysis is extended to anisotropic μ-negative slab waveguides. The possible existence of the plasmon modes in various anisotropic slab waveguide configurations is discussed. An FDTD program is developed to investigate the potential device applications of these anisotropic structures. A new signal detector and a two-channel harmonic separator multiplexer are designed employing the μ-negative slab waveguide.

Guided modes in left-handed waveguides

We investigate basic properties of linear guided modes in a waveguide slab with the core of a material with simultaneously negative effective permittivity and permeability surrounded by a normal dielectric cladding. The existence and dispersion of all possible types of guided modes have been studied in detail. We demonstrate that the two orthogonally polarized, TE and TM slow guided modes, with the same frequency and the same wave number can exist simultaneously. Their group velocities, however, can be parallel or anti-parallel.

Demonstration of Negative Refraction in a Cutoff Parallel-Plate Waveguide Loaded With 2-D Square Lattice of Dielectric Resonators

A 2D negative-refractive index metamaterial is proposed and investigated, which is composed of a parallel-plate waveguide loaded with a square lattice of disc-type dielectric resonators. Collective and macroscopic behavior of the dielectric resonator lattice under the fundamental TE resonance gives negative effective permeability, whereas the parallel-plate waveguide below the cutoff for TE modes provides negative effective permittivity. Thus, the double-negative condition for the propagated waves with the appropriate polarizations can establish the left-handedness. Equivalent-circuit models are shown to give a good insight into the physical mechanism of the guided waves. Numerical simulation of the 2D dispersion diagram verifies the existence of the left-handed (LH) guided modes along with the isotropic characteristics. A triangular prism of the proposed LH structure that is sandwiched by the right-handed parallel-plate waveguides is designed and fabricated to directly observe the negative refractive index of the LH waveguide. The numerical and experimental results validate the negative refraction for the proposed structure.

SCATTERING AND RADIATION CHARACTERISTICS OF STEP DISCONTINUITY IN LEFT-HANDED SLAB WAVEGUIDE OPERATING IN EVANESCENT SURFACE MODE

The scattering and radiation characteristics of a step discontinuity in left-handed (LH) slab waveguide operating in evanescent surface mode of TE and TM polarization are analyzed by a method, which combines the rigorous mode-matching method with the multi-mode network theory. In the analysis the radiation problem is transformed into a propagation problem so as to tremendously simplify the calculation procedure. The dispersion properties of the grounded planar LH slab waveguide for both ordinary and evanescent surface modes are examined, from which the left-hand property of the operating mode is testified. The relative scattered power and radiation pattern of the step are given for the first time, from which the backward radiation of the stepped LH guide is clearly demonstrated. The frequency scanning characteristics of the step under consideration in this paper are just opposite to that of the ordinary antenna, which makes the considered structure promising candidate for new type of planar antennas.

Localization of light in a lamellar structure with left-handed medium : the Light Wheel

A rigorous analysis of the contra-directional coupling between a left-handed waveguide and a right-handed waveguide shows that such a structure supports twin modes with complex (conjugate) propagation constants. Using evanescent coupling or a source inside one of the waveguides, the twin modes can be excited. In this case, light rotates inside the lamellar structure forming an exotic mode : the light wheel. The structure can finally be seen as a new type of cavity and can be used for beam reshaping.

Analysis of left-handed rectangular waveguides with dielectric-filled corrugations using the asymptotic corrugation boundary conditions

The asymptotic corrugation boundary conditions are employed to analyse left-handed rectangular waveguides with dielectric-filled transverse corrugations. The dispersion relations as well as the field expressions in the waveguide and the corrugation are derived. An equivalent multiport network model for the case of the two-walled corrugated waveguide is presented, and can easily be reduced to the one-walled case. Compared to the rather sophisticated full-wave solution, the asymptotic solution proves to provide accurate results within a wide frequency band. The limitations of the asymptotic boundary conditions are investigated to determine the range of validity of the presented solution.

Left-handed transmission characteristics of rectangular waveguides periodically loaded with ferrite

A left-handed rectangular waveguide periodically filled with tangentially magnetized ferrite medium has been proposed, and backward wave characteristics in the structure have been confirmed numerically by using a mode-matching method. The operational frequency is selected to be below the cutoff frequency for a dominant TE/sub 10/ mode in a rectangular waveguide where the effective permittivity is negative. The obtained results show that there exist backward-wave modes in the negative permeability frequency region where magnetostatic surface wave modes can be supported, and the field profiles have a sinusoid-like form composed of a series of exponentials in each section. In addition, three-dimensional full-wave simulation is demonstrated, which shows that unexpected excitations of magnetostatic surface wave mode transversely propagating along a surface of the ferrite layer near the input port plays a role of a transformer from a guided TE/sub 10/ mode to the backward wave mode and vice versa near the output port.