Image Guides Research Articles

Nonreciprocal coupling structure of a ferrite loaded dielectric image guide

A novel coupled image guide was designed and tested from 26.5 to 40 GHz. The nonreciprocal structure consisted of two dielectric image guides separated by a YIG/GGG ferrite film. Electromagnetic scattering matrix elements of the device were measured for the magnetic field applied perpendicular to the ferrite film plane. Nonreciprocal behavior in the scattering parameters was observed to be in agreement with analysis. The results indicated that various types of millimeter-wave passive devices could be realized in a planar geometry, such as isolators, filters, modulators, switches, and circulators.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analysis of coupling in image guide technology

Coupling for symmetrical and asymmetrical structures in image guide technology is described. Starting from T. Trinh and R. Mittra's analysis (ibid., vol. MTT-29, no.9, p.875-80, 1981), some improvements are proposed for treating strong coupling between an image guide and a ring resonator of any radius of curvature, by taking into account the field displacement effect, and, for a nonsymmetric coupler, the difference between the propagation constants of the straight and curved image guides. A comparison between this analysis and Trinh and Mittra's experiments is made. >

Inset dielectric guide mounting of a detector diode

Inset dielectric guide (IDG) is an alternative to dielectric guides such as image or insular guides for millimeter-wave and antenna applications. A simple detector diode mount is examined, and its performance in IDG is compared to that achieved when the same diode is mounted in a rectangular metal waveguide. The performance in IDG is good, although it is a little worse than in the waveguide due to some radiation from the diode mount. >

An efficient two-dimensional graded mesh finite-difference time-domain algorithm for shielded or open waveguide structures

A finite-difference-time-domain (FDTD) algorithm for the efficient full-wave analysis of a comprehensive class of millimeter-wave and optical waveguide structures is described. The algorithm is based on a two-dimensional graded mesh combined with adequately formulated absorbing boundary conditions. This allows the inclusion of nearly arbitrarily shaped, fully or partially lateral open or shielded guiding structures with or without layers of finite metallization thickness. Moreover, lossy dielectrics and/or lossy conductors are included in the theory. The algorithm leads to a significant reduction in CPU time and storage requirements as compared with the conventional three-dimensional eigenvalue FDTD mesh formulation. Dispersion characteristic examples are calculated for structures suitable for usual integrated circuits, such as insulated image guides, ridge guides, dielectric waveguides, trapped image guides, coplanar-lines and microstrip lines. The theory is verified by comparison with results obtained by other methods. >

Chemical modification of silicone elastomers for optics

Polysiloxanes with Si-H groups were chemically modified using vinyl compounds with phenyl, naphthyl, anthryl, andn-perfluorooctyl side groups by platinum catalysis (hydrosilylation). The introduction of aromatic groups increased the refractive index of poly(dimethyl siloxane) (n=1.403) up ton=1.70 depending on the degree of substitution and the kind of aromatic groups. Similarly, then-perfluorooctyl group reduced the refractive index to 1.35. Therefore, the chemical modification enabled us to obtain polysiloxanes with refractive indices between 1.35 and 1.70. The modifications affected the glass-transition temperature of polysiloxanes, and the effects were analysed. The modified polysiloxanes may be of use in fabrication of very flexible optical fibres for purposes such as sensors, image guides, data links and optical fibres for communications over very short distances.

Advance of Plastic Optical Fibers

AbstractPlastic optical fibers (so called POF) are already in wide use in a large number of fields. This paper gives an overview of the field including the advantages of plastic optical fibers, the various types of fibers and the materials in them.Then, the properties of three types of fibers which have recently been developed, are discussed. The first is fibers with a poly-methyl-methacrylate (PMMA) core, which have a low transmission loss. Another is heat resistant fibers for use in automobiles. And the third is the multi-fiber type for image guides. And finally, the applications of these fibers and their future prospect are discussed.

Analysis of leakage properties of periodic dielectric image guides

The leakage properties of dielectric image guides with periodic surface corrugations on their top or side walls are analysed. A finite-element method in conjunction with an improved perturbation technique is employed to calculate numerically the leakage constant of the lowest-order E11y, mode.

Propagation losses in dielectric image guides

The authors calculated the propagation losses of a dielectric image guide using the effective dielectric constant (EDC) method to a higher order of approximation. It was found that there exist a minimum in the waveguide attenuation that has not been alluded to in the literature, and also a peak in the imaginary parts of the transverse propagation constant relate to dimensional resonances within the waveguide. These results imply that the propagation losses will be lowered and the fields will be more effectively confined within the waveguide at frequencies close to the cutoff. >

Reduction of losses in dielectric waveguide Y-junctions with wide aperture angles

In this work, symmetrical Y-junctions made of rectangular dielectric guides are studied theoretically and experimentally. Using the effective dielectric constant method (EDCM), the dielectric guides are transformed into equivalent slab guides; after that, the junction is analysed as a discrete discontinuity located in a single plane transverse to the propagation axis. The experimental results agree very well with the theoretical predictions which indicate that there should be dimensions of the dielectric guide of the junction which optimize the transmission coefficient for a given angle and frequency. If wide aperture angles are required and image guides are used in making the junction, high losses appear; to diminish the former losses we have used Π guides in which the dielectric inside the window has a greater permittivity than the rest of the guide; metallic shields were also employed for the same purpose. These modifications improve the transmission coefficient, in some cases by nearly 5 dB

Higher order modes on usual waveguides

In the following paper some different kinds of microwave guides will be inspected under main aspect of higher order modes. The knowledge of these modes is important for field matching problems at discontinuities and for suppressing propagation of higher order modes by geometrical variations. In some cases it is sufficient to know their principal behaviour. They will be calculated in paper by the often used orthogonal expansion. This method allows to determine all kinds of waves: propagating, damping and complex waves. The following guides are inspected: 1. rectangular waveguides, 2. circular waveguides, 3. L-shaped waveguides, 4. double ridged rectangular waveguides, 5. unilateral finlines with one slot, 6. unilateral finlines with two slots, 7. shielded microstrip lines, 8. circular image guides, 9. rectangular waveguides with dielectric slab, 10. H-guides.

Finite-Difference Analysis of Rectangular Dielectric Waveguide Structures

A class of dielectric waveguide structures using a rectangular dielectric strip in conjunction with one or more layered dielectrics is analyzed with a finite-difference method formulated directly in terms of the wave equation for the transverse components of the magnetic field. This leads to an eigenvalue problem where the nonphysical, spurious modes do not appear. Moreover, the analysis inclndes hybrid-mode conversion effects, such as complex waves, at frequencies where the modes are not yet completely bound to the core of the highest dielectric constant, as well as at frequencies below cutoff. Dispersion characteristic examples are calculated for structures suitable for millimeter-wave and optical integrated circuits, such as dielectric image lines, shielded dielectric waveguides, insulated image guides, ridge guides, and inverted strip, channel, strip-slab, and indiffused inverted ridge guides. The numerical examples are verified by results available from other methods.

A Completely Theoretical Design Method of Dielectric Image Guide Gratings in the Bragg Reflection Region

This paper presents a new and completely theoretical accurate method for the design of dlelectic image guide gratings. Our method is based on a network approach that can easily analyze, with satisfactory approximations, the interaction of dielectric step discontinuities. These are the fundamental constituents of our gratings. Measurements on a filter modeled at X-band show excellent agreement with the design characteristics.

Rigorous Hybrid-Mode Analysis of the Transition from Rectangular Waveguide to Shielded Dielectric Image Guide

The transition waveguide to shielded and dielectric image guide is analyzed by the rigorous hybrid-mode field expansion technique where higher order mode coupling effects are taken into account directly, also below the corresponding cutoff frequency. The solution of the related eigenvalue problem includes waves with a complex propagation constant although the guide is assumed to be lossless. Calculated diagrams of the propagation constant as a function of frequency, as well as of the permittivity, illustrate the complicated mode conversion between evanescent modes, complex waves, backward waves, and propagating waves. For the three-dimensional scattering problem, the calculated magnitude of the input reflection coefficient agrees well with measurements, whereas the transmission-line theory applied to this structure leads to wrong results.

A Broad-Band Directional Coupler for Both Dielectric and Image Guides (Short Papers)

A four-port directional coupler is presented for use in dielectric and image guides. Simple design equations are derived and the subsequent results are in good agreement with theory. Broad-band performance has been achieved over the entire conventiortal waveguide bandwidth (26-40 GHz).

Analysis of Low-Loss Broadside-Coupled Dielectric Image Guide Using the Mode-Matching Technique (Short Papers)

The solutions of electromagnetic field equations of the broad-side-coupled dielectric image guide are derived using the mode-matching technique. The even- and odd-mode dispersion characteristics are presented as a function of the dimensional parameters of the guide for the low-loss mode for which the principal electric field is parallel to the metal image planes.

Directly Connected Image Guide 3-dB Couplers with Very Flat Couplings

The design and evaluation of the directly connected image guide 3-dB directional coupler is described. These couplers have several useful features as a component for millimeter-wave integrated circuits because of broadband and flat coupling characteristics, mechanical stability, and compactness. The bandwidth of the directly connected image guide coupler with proper dimensions and the nearly optimixed value of h extends to about 28 percent under the tolerance limits of +-0.25 dB of deviation in coupling from 3 dB. Furthermore, experimental verification has been performed, and, hence, the usefulness of the proposed directly connected couplers with appropriate tapered sections was confirmed, even at frequencies where higher modes could be excited.

Field Distribution in the Trapped Image Guide

ABSTRACT An efficient analytical method for accurate calculation of the field distribution in trapped image guide is presented. Based on the Weber-Schafheitlin integral, the method yields field distributions which are compared with measured data at Ku-band.

Coupling Between Microstrip Line and Image Guide through Small Apertures in the Common Ground Plane

A design theory is described for coupling between microstrip line and image guide through small coupling holes in a common ground plane. A five-slot Chebyshev coupler is designed based on coupling through a rectangular slot. The theoretical results are compared with experimental results.

Comments on "Hollow Image Guide and Overlayed Image Guide Coupler"

The authors of the above paper failed to acknowledge several publications dedicated to the same subject. The so-called hollow image guide has already been studied by the E.D.C. method with the name of pi guide, as well as another dielectric structure named T guide [2]. The same paper shows a good agreement between the theoretical and the experimental results which were measured by means of a movable electric field probe with the end of the dielectric waveguides finished in a short circuit.

Complex waves on shielded lossless rectangular dielectric image guide

Waves with complex propagation constants occur in the modal spectrum of shielded rectangular dielectric image guides, although the guide is assumed to be lossless. Dispersion characteristics are presented, calculated by a rigorous mode-matching technique. Plots of power flow show that the energy supported by such a complex wave returns to the plane of excitation.