Analysis of Guided and Leaky Tm0n and Te0n Modes in Circular Dielectric Waveguide

Yang, Siming; Song, Jiming

doi:10.2528/pierb15120802

Cited by 8 publications

(6 citation statements)

References 31 publications

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“…2, 3, 4 and depicted in Table 1. This is in accordance to a plethora of publications (e.g., [37,49]), which prove that surface waves above their cut-off (actually turn-on) may exhibit a bifurcation to a proper and an improper branch. However, the first dominant mode (#1 in Table 1) remains in the improper quadrant B 4 , when either its β z /k 0 is less or greater than 1, because it is not reaching any possible bifurcation point.…”

Section: Leaky and Surface Modessupporting

confidence: 91%

See 1 more Smart Citation

Space and Leaky Wave Radiation From Highly Lossy Biological Cylindrical Human-Limps Models

Mitsalas¹,

Kaifas²,

Kyriacou³

2021

PIER B

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The continuous and discrete radiation spectrum of a highly dielectric constant structure with extremely high losses is revisited herein. This work is motivated by the need of efficient electromagnetic power extraction from antenna-sources implanted into the human body. As the dielectric constant of biological tissues varies between 35 and 80 with a conductivity increasing from 0.5 to 2 S/m with frequency, the involved propagation and particularly radiation phenomena cannot be described by the current state of the art published research. Since the scope of the biomedical applications refers to the communication or energy transfer between an implanted device and an external one, the problem to be addressed involves primarily the near field and secondary the farradiated field. Many of human body parts as the hands, legs, torso, and neck can be modeled as cylinders. Indicatively, a non-magnetic infinite cylinder with an average dielectric constant ε r1 = 58.1 and conductivity σ = 1.69 S/m is considered, with focus on the hand with average radius 2.75 cm. Although a plethora of excellent publications elaborates both analytically and numerically on the radiation from dielectric cylinders including losses, there is not any work studying rods with so high dielectric constants and extremely high losses (loss tangents around unity or higher), while most of them are dealing with the far field rather than near field. Classical works reveal radiation due to the discrete surface and leaky modes as well as a continuous spectrum, while complex modes appearing as quadruplets are found responsible for only energy storage. These are indications of discrete modes transitions as dielectric losses are increased. It is herein proved that indeed increasing losses are causing not only mode transition but also a change in their nature as surface or leaky, while the complex mode quadruplet breaks resulting in radiation in both the near and far fields, while losses have significant effects in the continuous spectrum (sky or space wave). These phenomena are exploited to serve the main purpose of this paper aiming to devise a physical mechanism supporting efficient energy and signal transferring inwards or outwards a highly lossy, high dielectric constant cylinder. The novelty of the proposed methodology stems from a Wiener-Hopf based non-meromorphic Kernel factorization resulting in a field product representation. This is composed of well defined individual terms with each one of them building on a specific pole-mode. The proposed formulation is found to be equivalent to the generalized "multiplicative" and "additive" steepest descent methods regarding the far field evaluation, but additionally is capable of providing the near field as well. The latter feature supports important biomedical applications. Due to the huge extent of the subject and in order to facilitate the continuous spectrum, the analysis is restricted to the excitation by an infinitesimal electric dipole positioned at the origin and oriented along the axis of the cylinder. S...

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Section: Leaky and Surface Modessupporting

confidence: 91%

“…( 5) via Davidenkos technique [47,48]. Toward this direction, the work of Yang and Song [49] provides useful methods in order to derive initial guesses in the vicinity of cut-off frequencies.…”

Section: Alternative Evaluation Of Near and Far Fieldmentioning

confidence: 99%

Space and Leaky Wave Radiation From Highly Lossy Biological Cylindrical Human-Limps Models

Mitsalas¹,

Kaifas²,

Kyriacou³

2021

PIER B

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“…The curves in Figs. 12-14 resemble the known results obtained numerically by other authors (see, e.g., [7]).…”

Section: De Analysis In the Complex Domainsupporting

confidence: 86%

“…However, rigorous mathematical proof of the existence of complex waves in a DR remains, to the best of our knowledge, one of fundamental unsolved problems of the theory of electromagnetic wave propagation in open waveguides. This statement may be indirectly validated by considering, e.g., a recent publication [7] that contains a comprehensive reference list on this topic. Typical approaches developed by many authors searching for complex waves are reduced to numerical solution in the complex domain of dispersion equations (DEs) associated with symmetric waves in a DR (in many cases using commercial solvers) or incorrect replacement of the initial DEs by simplified equations employing various approximations or asymptotic expansions (see, e.g., [8] and [9]).…”

Section: Introductionmentioning

confidence: 99%

On a Rigorous Proof of the Existence of Complex Waves in a Dielectric Waveguide of Circular Cross Section

Shestopalov¹,

Kuzmina²

2018

PIER B

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Existence of symmetric complex waves in a dielectric rod (DR)-a dielectric waveguide of circular cross section-is proved by analyzing functional properties of the dispersion equations (DEs) using the theory of functions of several complex variables and validating the existence of complex roots of DE. A closed-form iteration procedure for calculating the roots in the complex domain supplied with efficient choice of initial approximation is proposed. Numerical modeling is performed with the help of a parameter-differentiation method applied to the analytical and numerical solution of DEs.

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“…Among the few studies on this aspect, in [8] the condition of leaky cutoff β = α was first introduced for the fundamental leaky mode of a microstrip line, as the boundary between a low-frequency, reactive regime (where β < α) and a high-frequency, radiative regime (where β > α). The same condition was also derived in [9] by means of a simple effective-dielectric-constant approach, and has been applied over the years to a number of cases, such as microstrips operated on higher leaky modes [10], circular dielectric rods and waveguides [11], [12], Goubau lines [13], modified microstrip lines [14], etc.…”

Section: Introductionmentioning

confidence: 97%

The Transition Between Reactive and Radiative Regimes for Leaky Modes in Planar Waveguides Based on Homogenized Partially Reflecting Surfaces

Fuscaldo

Burghignoli

Galli

2020

IEEE Trans. Microwave Theory Techn.

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The gradual transition from a reactive to a radiative regime is studied for leaky modes supported by multilayered planar open waveguides. The so-called leaky cutoff condition, i.e., the frequency for which the leaky phase constant β equals the leaky attenuation constant α, originally introduced for microstrip lines and other printed structures, is investigated here with the aim of providing detailed information on the relative amount of reactive and radiative attenuation for leaky modes excited by finite sources and propagating as cylindrical waves along general planar waveguides. Analytical results are derived on the basis of a lossy parallel-plate-waveguide model and are validated through full-wave numerical simulations of two-dimensional leaky-wave structures based on grounded slabs covered with lossless or lossy partially reflecting surfaces (including, e.g., graphene layers) that can be treated as homogenized sheets. An analysis of the complex wave impedance of the considered leaky modes is also provided, in order to assess the frequency ranges where a good input matching can be expected for practical sources. In this regard, an ad hoc impedance matching network is designed and fullwave validated for a specific case to show that is indeed possible to achieve a good impedance matching below cutoff in practical designs.

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Analysis of Guided and Leaky Tm0n and Te0n Modes in Circular Dielectric Waveguide

Cited by 8 publications

References 31 publications

Space and Leaky Wave Radiation From Highly Lossy Biological Cylindrical Human-Limps Models

Space and Leaky Wave Radiation From Highly Lossy Biological Cylindrical Human-Limps Models

On a Rigorous Proof of the Existence of Complex Waves in a Dielectric Waveguide of Circular Cross Section

The Transition Between Reactive and Radiative Regimes for Leaky Modes in Planar Waveguides Based on Homogenized Partially Reflecting Surfaces

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