Multimode Network Theory Research Articles

High-Contrast Gratings based Spoof Surface Plasmons.

In this work, we explore the existence of spoof surface plasmons (SSPs) supported by deep-subwavelength high-contrast gratings (HCGs) on a perfect electric conductor plane. The dispersion relation of the HCGs-based SSPs is derived analyt- ically by combining multimode network theory with rigorous mode matching method, which has nearly the same form with and can be degenerated into that of the SSPs arising from deep-subwavelength metallic gratings (MGs). Numerical simula- tions validate the analytical dispersion relation and an effective medium approximation is also presented to obtain the same analytical dispersion formula. This work sets up a unified theoretical framework for SSPs and opens up new vistas in surface plasmon optics.

Frequency selective characteristics of gratings with arbitrary profiles composed of left-handed materials

The frequency selective surface (FSS) of gratings with arbitrary profiles composed of left-handed materials is systematically analysed by a method that combines the staircase approximation and the multimode network theory with the rigorous mode matching procedure. The effects of different periodic groove profiles, such as rectangle, ellipse and trapezoid on the reflection characteristics of the FSS are carefully studied and compared with each other. The variations of the frequency selective characteristics with dielectric loss and the comparisons between left-handed and right-handed gratings are also presented with the physical explanations of the related phenomena.

Investigation on a Novel Leaky Wave Antenna with Double Radiation Beam Composed of Left-handed Slab Loaded Hybrid Waveguide using Planar Technology

A novel leaky wave antenna with double radiation beam composed of left-handed slab loaded hybrid waveguide using planar technology is proposed in this paper and its leaky characteristics are investigated with a method that the multimode network theory is combined with mode-matching method. The study of dispersion curves reveals that the proposed antenna structure supports two leaky modes corresponding to the forward and the backward radiations respectively. It demonstrates that the proposed antenna is of desirable property that can radiate both forward and backward directions simultaneously with quite simple and flexible configuration. Extensive numerical results of leaky characteristics with different structural parameters of the antenna are given to provide useful guidelines for the design of the new antenna.

Scattering Characteristics of Dielectric Periodic Structure Composed of Left-handed Materials with Arbitrary Oblique Incidence

Scattering characteristics of monolayer and multilayer dielectric periodic structure composed of left-handed materials (LH-DPS) with plane wave arbitrary oblique incidence are carefully analyzed using a method which combines multimode network theory with the rigorous mode matching method. Our analysis results reveal that the arbitrary oblique incident angles and relative position between different LH-DPS have great effects to the scattering characteristics of LH-DPS which different from the situation of dielectric periodic structure composed of right-handed materials (RH-DPS). The reasons why the reflection characteristics of the LH-DPS are totally different from those of the RH-DPS with arbitrary oblique incidence are also given. The present quantitive investigation provides guidelines for the design of the monolayer and multilayer dielectric frequency selective surfaces for millimeter wave applications.

Complete Polarization Conversion Characteristics of Dielectric Grating Composed of Left-Handed Materials

The TE/TM polarization conversion characteristics of dielectric grating composed of left-handed materials for the case of plane wave oblique incidence are carefully investigated by a method which combines the multimode network theory with the rigorous mode matching method. It is indicated that complete polarization conversion between TE and TM modes can be realized using left-handed gratings. This can hardly achieve in the conventional right-handed gratings. Comparisons of polarization conversion properties between right-handed gratings and left-handed gratings are given with physical explanations. This unique merit of left-handed periodic structure is of important significance for accurate design of new millimeter wave TE/TM polarization converters.

Scattering characteristics of a new dielectric periodic array composed of left‐handed gratings

AbstractThe scattering characteristics of a new dielectric periodic array composed of left‐handed gratings are carefully investigated by a method which combines the multimode network theory with the rigorous mode matching method. The variations of the frequency selective characteristics with the number of periodic layers are presented and comparisons of scattering properties between the left‐handed and right‐handed periodic arrays are also shown with some explanations. Guidelines for accurate design of the millimeter wave frequency selective surface are given. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 266–269, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23076

Analysis of Coupling and Radiation Properties for an Improved Dielectric Waveguide Directional Coupler Utilizing a Tapering Left-Handed Slab Core

The coupling and radiation characteristics of an improved dielectric waveguide directional coupler with a tapering left-handed slab core located in the coupling region are analyzed by the staircase approximation method, which combines the building block approach and multi-mode network theory with a rigorous mode-matching procedure. Particular attentions are directed toward the radiation characteristics under different structural parameters of the coupler. Numerical results indicate that the proposed coupler is very promising by shortening the coupling length significantly while keeping the radiation loss at a low level.

Realization of complete polarization conversion using periodic structure composed of left‐handed materials

AbstractThe polarization conversion characteristics of dielectric periodic structure composed of left‐handed materials for the case of plane wave oblique incidence are carefully investigated by a method which combines the multimode network theory with the rigorous mode matching method. It is indicated that complete polarization conversion between TE and TM modes can be realized using left‐handed gratings. This can hardly achieve in the conventional right‐handed gratings. This unique merit of left‐handed periodic structure is an important significance for accurate design of new millimeter wave polarization converters. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2862–2864, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22826

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.

A NEW FREQUENCY SELECTIVE SURFACE COMPOSED OF LEFT-HANDED MATERIALS

The frequency selective characteristics of a new dielectric periodic structure composed of left-handed materials (LHM) are carefully studied by a method which combines the multimode network theory with the rigorous mode matching method. The variations of the frequency selective characteristics with structure parameters and dielectric loss are presented and comparisons for the frequency selective properties between RHM and LHM gratings are also shown with some explanations. Guidelines for accurate design of the LHM dielectric frequency selective surface are given.

INVESTIGATION ON EFFECTS OF LEFT-HANDED MATERIALS ON FREQUENCY SELECTIVE CHARACTERISTICS OF DIELECTRIC PERIODIC STRUCTURES

The effects of left-handed materials (LHM) on frequency selective reflection and transmission characteristics of dielectric periodic structures are carefully investigated using a method which combines the multimode network theory with the rigorous mode matching method. In addition, the effects of LHM dielectric loss on the selective properties are also given. It has been shown that the selective behavior of periodic structures can be modified by adding LHM layers above and below the periodic layer.

A very compact dielectric waveguide directional coupler utilizing a double‐negative slab core

AbstractA novel dielectric waveguide directional coupler with a double‐negative slab lies in the coupling region is analyzed by the staircase approximation method, which combines the building block approach and multimode network theory with a rigorous mode‐matching procedure. Particular attention is directed toward the coupling characteristics under different structural and constitutive parameters of the coupler. Numerical results indicate that the transition and coupling length of the proposed coupler is only 70% and 42% of related lengths in the conventional coupler, respectively. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1545–1548, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22491

A New Dielectric Grating Antenna with Large Leakage Constant for Millimeter-Wave Applications

The leakage properties of a new dielectric grating leaky wave antenna are carefully examined by an approach of combining the multimode network theory with the mode-matching method. A systematic comparison is given for the leaky characteristics of the n = −1 space harmonic of TM mode polarization between the present antenna and the traditional one. It has been found that the former is not only of lower conductor loss, but also of larger leakage constant than the latter. As a result, the dimension of the antenna could be largely reduced, which is of practical significance for some applications. Extensive numerical results of the radiation characteristics are given to establish useful guidelines for the design of the new grating antenna. Furthermore, special features such as cancellation or resonance effects are high-lighted and discussed. Physical insights for the mathematical findings are also presented.

Frequency selective characteristics of a new dielectric periodic structure composed of left‐handed materials

AbstractThe frequency selective characteristics of a new dielectric periodic structure composed of left‐handed materials (LHM) are carefully investigated by a method, which combines the multimode network theory with the rigorous mode matching method. The variations of the frequency selective characteristics with structure parameters are presented and comparisons of propagation properties between right‐handed materials and LHM gratings are also shown with some explanations. Guidelines for accurate design of the left‐handed dielectric frequency selective surface are given. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 421–424, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22153

Multi-mode network analysis for discontinuities in parallel-plate waveguides partially filled with multi chiral rods

The reflection and transmission characteristics of the guided modes in parallel-plate waveguides partially filled with one or multi chiral rods have been investigated by a method, which combines the multimode network theory with a rigorous mode matching procedure. The formulas of the reflection and transmission coefficient matrix are derived. The numerical results for different cases are presented and have indicated that the chirality parameters and the gometrical dimensions of the chiral rods have significant influence on the reflection and transmission characteristics of the guided modes.

Scattering and radiation characteristics of step discontinuity in a double‐negative (DNG) slab waveguide operating in the evanescent surface mode

AbstractThe scattering and radiation characteristics of a step discontinuity in a double‐negative (DNG) slab waveguide operating in the evanescent surface mode are analyzed by a method which combines the rigorous mode‐matching method with multimode 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 DNG slab waveguide for ordinary and evanescent surface modes are examined, from which the left‐hand property of the operating mode is verified. The relative scattered power and radiation pattern of the step discontinuity are given for the first time, from which the backward radiation of the stepped DNG guide is clearly demonstrated. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1085–1088, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21607

Leaky Characteristics of Modified NRD Guide with Finite Parallel Plate Length

Leaky wave characteristics of modified NRD (Nonradiative Dielectric) guide with parallel plate length are systemically investigated. A technique is used to investigate the leaky property of the guide structure, whichis formulated by effectively combining the multimode network theory with the mode-matching method. In the paper, two phenomena are carefully studied: First, the asymmetric position of the dielectric rod generates a leaky hybrid mode that could produce cross talk between components of the circuit. Second, when the length of metallic plate is finite, another type of leaky mode creates which influences and even couples to the normal leaky guide mode under appropriate circumstances.

Scattering of Chiral Periodic Structure

We propose, develop, and implement an exact method to analyze the scattering of chiral periodic structure. The method combines the building block approach of multimode network theory with a rigorous mode-matching procedure. Symmetry properties of the structure are employed to simplify the analysis. Numerical results are given to discuss physical properties of the structure. At low frequencies, when only two Floquet modes can propagate in chiral period layer, the scattering of plane waves by the chiral periodic structure acts approximately as the scattering of plane waves by a uniform chiral slab with parameters equal to the average of those for the periodic layer. At higher frequencies, we find anomalous coupling regions known as Wood's anomalies and are explained by the excitation of and reradiation of leaky waveguide modes in the periodic layer.

Analysis of Dielectric Periodic Structures with Multi-Mode Network Method

The transmission characteristics of several dielectric periodic guiding structures are analyzed in this paper with a method, which the rigorous mode matching method is combined with the multimode network theory. The precision and effectiveness of the present method are verified by experimental data.

A novel leaky NRD guide with a double-layer dielectric slab

A new leaky nonradiative dielectric guide with a double-layer dielectric slab is investigated in this paper by combining a multimode network theory with a mode-matching method. Numerical results show that proper selection of the permittivities can vary the leakage constant over a wide range. A leakage constant larger than 10% of free-space wavenumber can be obtained easily without entering the cutoff region. Leaky-wave antennas with shorter length and medium gain can thus be developed. In addition, the present leaky guide possesses the advantages of simple fabrication and physical stability. Extensive numerical results are provided to guide the antenna designs.