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Microwave Theory and Techniques, IEEE Transactions on

Issue 12  Part 1 • Date Dec. 1995

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Displaying Results 1 - 14 of 14
  • Measuring the permittivity and permeability of a sample at K/sub /spl alpha// band using a partially filled waveguide

    Publication Year: 1995 , Page(s): 2654 - 2667
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5230 KB)  

    A novel method of measuring the relative complex permittivity (/spl epsi/=/spl epsi/'-j/spl epsi/'') and relative complex permeability (/spl mu/=/spl mu/'-j/spl mu/'') of a material at K/sub /spl alpha// Band (26.5-40 GHz) using a partially filled waveguide (PFW) (rectangular) and a vector network analyzer (VNA) is presented. The method is based on 1) placing a material sample of length L/spl tilde/, width /spl alpha//spl tilde/ (waveguide width), and height d/spl tilde//spl les/b/spl tilde/ (b/spl tilde/ is the waveguide height) in a rectangular waveguide, 2) measuring the S-parameters of the sample using the VNA, and 3) inferring the /spl epsi/', /spl epsi/'', /spl mu/', and /spl mu/'' parameters by comparing the experimental S-parameters with numerically generated S-parameters. The paper presents a method of moments analysis and also a variational formulation of the scattering that occurs from a finite length sample that partially fills a waveguide. Formulas to calculate the complex Poynting power and energy in the waveguide are derived to check the degree to which the numerical solutions obey the conservation of complex power. Numerical methods to extract the material parameters from the S-parameter data are proposed. The experimental PFW S-parameters of a radar absorbing material are measured and its dielectric material parameters are inferred. View full abstract»

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  • Comment on "Are nonreciprocal bi-isotropic media forbidden indeed?"

    Publication Year: 1995 , Page(s): 2722 - 2724
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (403 KB)  

    For original paper see A.H. Sihvola, ibid., vol.43, pp.2160-2 (1995). In a recent paper, Sihvola has cast doubt on our claim that all bi-isotropic media must be reciprocal. We show that Sihvola's doubt has no rational basis. View full abstract»

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  • Simple and accurate solutions of the scattering coefficients of E-plane junctions in rectangular waveguides

    Publication Year: 1995 , Page(s): 2716 - 2718
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    Simple and accurate solution of the scattering coefficients of the E-plane right-angle bend in rectangular waveguide is presented. The solution is obtained by the mode-matching method in which the electromagnetic fields in waveguides are matched with those in junction section formed by a sectoral region. In the same procedure, the solutions of the scattering coefficients of the E-plane T-junction and the cross junction can be also obtained easily. By using the numerical results, the scattering properties of the dominant modes and higher-order modes in the E-plane right-angle bend are examined in detail View full abstract»

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  • Generators of magnetic groups of symmetry and commutation relations

    Publication Year: 1995 , Page(s): 2668 - 2675
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB)  

    A general procedure is given for determining the matrices [S], [Z], and [Y] of linear symmetrical multiports with gyromagnetic media. To obtain relations between the elements of the matrices, the color groups, the Curie principle, and the concept of gyrotropic symmetry (GS) and gyrotropic antisymmetry (GA) are used. Symmetries of the dc magnetic field are also considered. General properties of the multiports with GS and GA are discussed. Applications of the symmetry analysis are illustrated by two 3-D structures and some existent devices View full abstract»

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  • Numerical implementation and performance of perfectly matched layer boundary condition for waveguide structures

    Publication Year: 1995 , Page(s): 2676 - 2683
    Cited by:  Papers (32)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (788 KB)  

    This paper presents some numerical implementation issues and the performance of Berenger's perfectly matched layer (PML) boundary condition for modeling wave propagation in waveguide structures by the finite-difference time-domain (FDTD) method. The relation between the thickness and the conductivity profile of the perfectly matched layer is studied and a guideline for the selection of PML parameters is given. It is shown that the standard Yee's time-marching scheme results in virtually the same numerical solution as the exponential time-marching scheme. Numerical tests are provided for parallel-plate and rectangular waveguides and microstrip lines. It is found that PML is very effective in absorbing TEM and quasi-TEM waves, as well as nonTEM waves somewhat above cutoff frequencies, but ineffective in absorbing evanescent waves and nonTEM waves near cutoff frequencies. The reason for the ineffectiveness of PML for absorbing evanescent waves is explained. Comparative study of PML and Higdon's boundary condition shows that high-order Higdon's boundary condition can reach the same performance of 16-cell PML and can be adjusted for absorbing evanescent waves, but PML is in general more robust to implement. Performance of the boundary condition obtained by combining PML and Higdon's boundary condition is evaluated View full abstract»

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  • A quasi-closed form expression for the conductor loss of CPW lines, with an investigation of edge shape effects

    Publication Year: 1995 , Page(s): 2695 - 2701
    Cited by:  Papers (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    In previous work, we used a matched asymptotic technique to investigate the fields near an edge of a finitely conducting strip with nonzero thickness. It was demonstrated that with this asymptotic solution of the fields, the power loss in the region local to the edge could be determined accurately. In this paper, we will show how the accurate representation of the power loss can be used to obtain a closed form expression for the attenuation constant due to conductor loss of coplanar waveguide (CPW) structures. This expression is valid for an arbitrarily shaped edge and any conductor thickness. Results obtained with this expression are compared to and closely agree with both experimental results and other techniques found in the literature. We also investigated conductors with different edge shapes (45° and 90° edges) to explore their effect on the attenuation constant (or loss) of CPW structures View full abstract»

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  • Complex solitons in a superconductive medium

    Publication Year: 1995 , Page(s): 2710 - 2713
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    We show analytically that a type-II superconductor may support short-range electromagnetic spatial solitons with a complex propagation constant. A theoretical model based on the Ginzburg-Landau theory is used. Analytical results for the complex solitons predict unique features that cannot be found in conventional solitons in normal (asuperconductive) media View full abstract»

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  • Analysis of rectangular waveguide junctions by the method of lines

    Publication Year: 1995 , Page(s): 2649 - 2653
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    A novel discretization on two crossed line systems is introduced in the method of lines to analyze junctions in rectangular waveguides. This discretization is one-dimensional and replaces the two-dimensional discretization otherwise necessary for such structures. Hence the matrices encountered are small compared with other approaches. Equivalent circuits for the right-angle E-plane corner and scattering parameters for the asymmetric T-junction are presented, which agree very well with literature View full abstract»

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  • Graphite millimeter-wave waveguide and mirror for high temperature environments

    Publication Year: 1995 , Page(s): 2684 - 2688
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (548 KB)  

    A graphite helix corrugated waveguide with a miter mirror has been fabricated and used for 135 GHz pyrometer measurements on a high temperature plasma arc furnace. The guide has an internal diameter of 3.81 cm, a length of 123 cm, and a corrugation of 32 grooves/inch. One end of the guide was sealed with a Teflon window having moth eye surfaces to reduce reflections. The room temperature insertion loss of this guide assembly for HE11 mode propagation and launch was measured to be 0.5±0.1 dB. It was used successfully in a high temperature environment where the miter mirror end reached incandescent temperatures in access of 1200°C. High temperature graphite surface corrosion typically increased the insertion loss to 1.2±0.2 dB but did not significantly affect the beam divergence View full abstract»

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  • An improved modal expansion method for two cascaded junctions and its application to waveguide filters

    Publication Year: 1995 , Page(s): 2719 - 2722
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    An improved modal expansion method is described for the scattering matrix of a cascaded network which consists of an enlargement junction combined with a reduction junction. The new method can significantly reduce computation time and requirement of computer memory. Application to iris coupled waveguide cavity filters is demonstrated. Numerical results for a rectangular waveguide cavity filter are given View full abstract»

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  • Investigation of periodic structures in a fin line: a space-spectral domain approach

    Publication Year: 1995 , Page(s): 2708 - 2710
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    The space-spectral domain approach (SSDA) is utilized for the analysis of the unilateral fin line with periodically varying slot patterns. Two new type of structures in a unilateral fin line with sinusoidally and triangularly varying slot patterns are investigated using this approach View full abstract»

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  • Multilayer asymmetric aperture-coupled broadside microstrip lines and their quasi-static and dynamic analyses

    Publication Year: 1995 , Page(s): 2702 - 2707
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    This paper describes new multilayer aperture-coupled broadside microstrip lines suitable for miniaturized microwave and millimeter-wave integrated circuits. Spectral-domain method is used for detailed investigations of these structures, and both quasi-static and dynamic results are presented to illustrate the need of a full-wave analysis for accurate circuit designs at high frequencies. The new transmission lines possess many desirable features, such as flexibility in circuit design and ability to optimize various transmission lines' characteristics, as well as miniaturization by using thin dielectric layers. Besides having the inherent properties of large ratios for the mode characteristic impedances and effective dielectric constants found in broadside-coupled structures, we also found that the studied coupled transmission lines can have equal mode effective dielectric constants for certain values of the structural parameters View full abstract»

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  • Quasi-TEM study of microshield lines with practical cavity sidewall profiles

    Publication Year: 1995 , Page(s): 2689 - 2694
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    This paper presents the quasi-TEM characteristics of microshield lines with practical cavity sidewall profiles. A conformal mapping method is used for the derivation of the electrical parameters of the structures. In this study, numerical results for the characteristic impedances of air-suspended microshield lines with both positive and negative sidewall slopes are presented. Simple and explicit CAD-oriented expressions are proposed for the design and analysis of rectangular-shaped microshield line. Comparisons are made between the results obtained by these formulas and by a standard numerical technique. Furthermore, the sensitivities of the electrical parameters of a rectangular-shaped microshield line to an imperfect sidewall etching process, leading to nonvertical sidewall profiles, are also examined View full abstract»

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  • On the computation of complex modes in lossless shielded asymmetric coplanar waveguides

    Publication Year: 1995 , Page(s): 2713 - 2716
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    We compute complex modes in lossless shielded asymmetric coplanar waveguides (CPWs) using the spectral domain technique. The slot asymmetry is found to significantly affect the existence of the complex modes. These modes are found to exist at low microwave frequencies even when using materials with a low permittivity. We found that waveguide modes degenerate into complex modes more frequently than CPW (π) and slotline (c) modes. When the structures are highly asymmetrical and when the dielectric substrates are thick or have a high permittivity, the degeneration of lower-order c-modes into complex modes is detected. Other forms of mode conversion, where a waveguide mode is converted to a c-mode, are also observed, especially in highly asymmetric structures and when using dielectric materials of a high permittivity or of a large thickness. Numerical convergence of the complex modes' propagation constants is also examined View full abstract»

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The IEEE Transactions on Microwave Theory and Techniques focuses on that part of engineering and theory associated with microwave/millimeter-wave components, devices, circuits, and systems involving the generation, modulation, demodulation, control, transmission, and detection of microwave signals. This includes scientific, technical, and industrial, activities. Microwave theory and techniques relates to electromagnetic waves usually in the frequency region between a few MHz and a THz; other spectral regions and wave types are included within the scope of the Society whenever basic microwave theory and techniques can yield useful results. Generally, this occurs in the theory of wave propagation in structures with dimensions comparable to a wavelength, and in the related techniques for analysis and design..

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