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Microwave Theory and Techniques, IEEE Transactions on

Issue 5 • Date May 1995

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Displaying Results 1 - 25 of 32
  • Effects of various suspended mounting schemes on mode characteristics of coupled slotlines considering conductor thickness for wideband MIC applications

    Page(s): 1106 - 1114
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    Propagation characteristics of fundamental and higher-order modes are determined in coupled slotlines with three suspended mounting schemes (pedestal, groove, inverse pedestal) for wideband applications of microwave and millimeter-wave integrated circuits. The analysis is based on a novel enhanced spectral domain approach (ESDA) that combines essentially the conventional spectral domain technique with the power conservation theorem. Numerical results, considering also the influence of finite conductor thickness, are presented for propagation constants and characteristic impedance of the fundamental modes. Effects of different suspended mounting schemes on cutoff frequencies of first higher-order even and odd modes are discussed in detail. Field profiles of the fundamental modes in coupled slotlines with and without pedestals are shown. The inherent mechanism of mode transition is explained with respect to different pedestal sizes, indicating that the monomode bandwidth can be extended by appropriately choosing the dimension of pedestal in coupled slotlines View full abstract»

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  • Generalized coupled interconnect transfer function and high-speed signal simulations

    Page(s): 1115 - 1121
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    A new expression for the coupled interconnect system transfer function has been derived under general linear generator and uncoupled load conditions, i.e., without any restrictions in circuit load impedance. High-speed-signals on coupled interconnects have been simulated using this transfer function. The simulation uses generalized interconnect circuit model parameters in which all line parameters are frequency dependent. The validity of the interconnect circuit parameters was confirmed previously using s-parameter measurements. High-speed signal simulation using this novel interconnect transfer function has been verified with time-domain measurements using an HP54121T high-speed sampling oscilloscope. This work accurately predicts coupled interconnect circuit responses. With this transfer function, signal integrity problems of high-performance VLSI circuits can be predicted in the design stage View full abstract»

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  • Shielding effect of a diaphragm in a packaged microstrip circuit

    Page(s): 1082 - 1086
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    The scattering of a diaphragm in a packaged microstrip line is investigated using the mode-matching method together with the method of lines. Instead of analyzing the discontinuity in the microstrip, this paper tackles the variation of the waveguide housing. The influences of the thickness and the depth of the diaphragm on the scatterings of the dominant mode and higher-order modes are analyzed based on a comparison of the modal power distributions. Finally, the shielding effect of a pair of closely spaced diaphragms is investigated View full abstract»

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  • A generic approach for permittivity measurement of dielectric materials using a discontinuity in a rectangular waveguide or a microstrip line

    Page(s): 1060 - 1066
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    A generic approach is proposed to accurately measure microwave and millimeter-wave properties of dielectric materials. This novel technique first determines the scattering parameters of a discontinuity containing a material having a wide range of complex dielectric permittivity ε that is known a priori (the direct problem). The discontinuity is embedded in a rectangular waveguide or a microstrip line. A unified theory, which is essentially based on a combination of the boundary integral equation technique with a modal expansion approach, is presented to tackle the direct problem. A class of generic diagrams are obtained for interrelating the dielectric permittivity ε to its S-parameters, and a simple analytical expression is deduced to solve the inverse problem. The proposed analytical formulation is easy to use and much more rapid than its iterative counterparts. It demonstrates a completely new and efficient strategy for accurate complex dielectric measurements View full abstract»

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  • MMIC-calibrated probing by CW electrooptic modulation

    Page(s): 1031 - 1036
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    This paper describes an electrooptic probing technique using a CW semiconductor-laser beam associated with a fast photodetector. Besides its simplicity, this technique presents some advantages over the sampling one thanks to the presence of a Fabry-Perot effect, namely an enhancement of the electrooptic interaction and a simple solution to the calibration problem. The good validity of the calibration method allows the application of this technique to S-parameter measurements. The S-parameter determination, in modulus and in phase, of an industrial MMIC by the electrooptic method is reported and compared with direct network analyzer measurements View full abstract»

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  • Microwave interactions in semiconductor multiple-quantum-well heterostructures utilizing a coplanar-strip geometry device

    Page(s): 1122 - 1127
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    A novel device design utilizing a multiple-quantum-well heterostructure conduction channel with an oxide-isolated overlying coplanar-strip transmission line has been constructed. These devices exhibit negative differential conductance in their dc characteristics for current transport in the plane of the quantum-well layers, originating from the change in mobility of the heated electrons within the quantum-well structure. This device design has permitted the observation of nonlinear conduction properties using these multiple-quantum-well heterostructures at microwave frequencies View full abstract»

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  • Microwave circuit analysis and design by a massively distributed computing network

    Page(s): 1087 - 1094
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    The advances in microelectronic engineering have rendered massively distributed computing networks practical and affordable. This paper describes one application of this distributed computing paradigm to the analysis and design of microwave circuits. A distributed computing network, constructed in the form of a neural network, is developed to automate the operations typically performed on a normalized Smith chart. Examples showing the use of this computing network for impedance matching and stabilizing are provided View full abstract»

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  • Complex power and mode coupling in circular chirowaveguides

    Page(s): 1182 - 1186
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    The total power carried by two (or more) modes of lossless circular chirowaveguides is shown to be complex in general, both above and below cutoff. This is explained by the coupling between modes which, in turn proves the lack of orthogonality, at least in the power sense View full abstract»

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  • A W-band source module using MMIC's

    Page(s): 1010 - 1016
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    A W-band source module providing 4-GHz tuning bandwidth (92.5-96.5 GHz) has been developed. This module consists of three MMIC chips: a 23.5 GHz HBT VCO, a 23.5-94 GHz HEMT frequency quadrupler and a W-band three-stage HEMT output amplifier, all fabricated in TRW production lines. It exhibits a measured output power of 3 dBm at 94-95 GHz and a 3-dB tuning bandwidth greater than 3 GHz, with a phase noise of -92 dBc/Hz at 1 MHz offset. This work demonstrates a new and efficient way to implement high performance W-band source. Its wide tuning bandwidth with good phase noise performance, as well as design simplicity, makes this approach attractive for many W-band system applications View full abstract»

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  • Non-leaky coplanar (NLC) waveguides with conductor backing

    Page(s): 1067 - 1072
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    In this paper, we present a structure called a non-leaky coplanar (NLC) waveguide with conductor backing. It is a multilayered structure with two possible configurations. The spectral domain approach with a complex root searching procedure is used to investigate leakage phenomena. The simulation results confirm that the leakage in conductor-backed coplanar waveguide (CBCPW) occurs in the form of wave in the parallel plate waveguide with infinite width. The results show that the leakage in the multilayered structure can be removed if the geometrical and material parameters of the structure are chosen appropriately. Experiments were carried out to investigate the transmission of these structures. It was found that the resonance in the transmission of finite-width conductor-backed coplanar waveguide (FW-CBCPW) is caused by the energy leakage from the dominant CPW mode. The resonance is eliminated in the NLC waveguides. These NLC waveguides are feasible and practical in the uniplanar MMIC design due to their planar nature View full abstract»

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  • Mixed potential integral equation technique for hybrid microstrip-slotline multilayered circuits using a mixed rectangular-triangular mesh

    Page(s): 1162 - 1172
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    In this paper, a mixed potential integral equation (MPIE) formulation for hybrid microstrip-slotline multilayered circuits is presented. This integral equation is solved with the method of moments (MoM) in combination with Galerkin's method. The vector-valued rooftop functions defined over a mixed rectangular-triangular mesh are used to model the electric and magnetic currents on the microstrip and slotline structures. An efficient calculation technique for the quadruple interaction integrals between two cells in the system matrix equation is presented. Two examples of hybrid microstrip-slotline circuits are discussed. The first example compares the simulation results for a microstrip-slotline transition with measured data. The second example illustrates the use of the simulation technique in the design process of a broadband slot-coupled microstrip line transition View full abstract»

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  • The effects of covering on complex wave propagation in gyromagnetic slotlines

    Page(s): 1100 - 1105
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    The evolution of complex leaky waves in partially open gyromagnetic slotlines into complex modes in a shielded slotline is presented. Given a particular stratified gyromagnetic slotline with two sidewalls present, four types (Types I-IV) of guided structures are defined and investigated, depending upon the four possible combinations of top and bottom covers. The behavior of the complex solutions is discussed for the partially open gyromagnetic slotlines. Initially, the slotline of Type I, which lacks both top and bottom covers, shows that no coupling exists among various pairs of leaky waves. By adding only a top cover into Type I, the resultant slotline of Type II exhibits certain coupling between different sets of leaky waves. Similarly, by adding only a bottom cover into Type I, the resultant slotline of Type III shows that certain strong leaky waves of Types I and II now become weak leaky waves. From these numerical experiments, we deduce that the complex modes supported by Type IV, which is completely shielded, can be the result of the mode coupling of the two previously found leaky waves in Types II and III waveguides, respectively. Therefore, the formation of complex modes in shielded slotline is related to the effects of covering on mode coupling of the various leaky waves of the partially open slotlines View full abstract»

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  • Validation of a nonlinear transistor model by power spectrum characteristics of HEMT's and MESFET's

    Page(s): 1046 - 1052
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    The bias dependence of the power output spectrum and the generation of intermodulation products from different HEMT's and MESFET's at large signal excitation is studied and compared with simulated values. An extended HEMT/FET model suitable for small and and negative Vds (with a drain voltage dependence of the peak transconductance in the unsaturated drain current region, and at negative drain voltage), is also proposed. Good agreement between simulated and measured power spectrum up to at least the fourth harmonic is demonstrated for HEMT and MESFET devices from different manufacturers. Measured and simulated intermodulation products are also in good agreement, which confirm the validity of the model View full abstract»

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  • Dispersion and attenuation characteristics of coplanar waveguides with finite metallization thickness and conductivity

    Page(s): 1128 - 1135
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    A new approach of modifying the conventional spectral-domain approach is proposed for an analysis of the coplanar waveguide whose signal strip and ground planes have finite thickness and conductivity. By introducing suitable equivalent sources in the slot and signal strip regions, the problem can be significantly simplified by reducing the two-dimensional numerical integration into the one-dimensional one, thus it can be treated as easily as the conventional spectral-domain approach. By this modified approach, both the phase constant and attenuation constant can be determined simultaneously without using the assumption that the metallization thickness is much larger or smaller than the skin depth. In this work, comparison with published theoretical and experimental results is presented to check the accuracy of the new approach's results. In particular, the effective dielectric constant εeff and attenuation constant a of a coplanar waveguide with finite metallization thickness and finite conductivity are discussed in detail, together with the current distributions along the signal strip and ground planes View full abstract»

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  • Full-wave characterization of a through hole via in multi-layered packaging

    Page(s): 1073 - 1081
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    A full-wave analysis is presented for the propagation characteristics of a through hole via connecting two semi-infinitely long transmission lines in multi-layered packaging environment. The current distribution on the via and a section of transmission line is solved under the thin wire approximation by the moment method and the scattering parameters are extracted by the matrix pencil method. The Green's function in multilayer packaging environment is derived by applying the image theory and evaluated by the help of the Poisson summation formula. Numerical results are included to investigate the frequency dependent propagation characteristics for via structures with various geometrical parameters, e.g., the via height, wire diameter, and distance between two ground planes. The excitation of the radial waves due to the current distribution on the via is also discussed in detail View full abstract»

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  • Nonlinear models for the intermodulation analysis of FET mixers

    Page(s): 1037 - 1045
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    An accurate, detailed analysis program has been developed for intermodulation distortion (IMD) simulation of FET mixers. This program is very efficient at calculating the IMD from multiple RF inputs. We have proposed a simplified nonlinear model for IMD analysis of FET gate mixers. The accuracy of the simplified model has been verified experimentally using two different MESFET mixers and one HEMT mixer at X band. All the tests show good agreement between measured results and the calculated results for second- and third-order IMD. The simplified model is based on modeling the derivative of the device transconductance by a sum of a Gaussian function and a linear function of the gate voltage. Drain bias dependence is ignored. The advantage of this model is that it can be used for both MESFET and HEMT mixers, and its fitting parameters can be easily determined from a nonlinear characterization of the devices at low frequencies View full abstract»

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  • Partial-boundary element method for analysis of striplines with arbitrary cross-sectional dielectric in multi-layered media

    Page(s): 1153 - 1161
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    A new method of analysis called the partial-boundary element method (p-BEM) is proposed for the analysis of striplines with arbitrary cross-sectional dielectric in multi-layered media. By using a Green's function that satisfies the boundary conditions of a relevant structure with multi-layered media and introducing a concept of the equivalent charge density, the p-BEM formulates a potential integral and boundary integral equations only on partial-boundaries such as the surface of the arbitrary cross-sectional dielectric. The number of the equations needed to be formulated is much less than in the conventional BEM. Numerical results of analysis are presented for two kinds of striplines: 1) with a rectangular dielectric ridge and 2) with an embedded rectangular dielectric in three-layered media View full abstract»

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  • A novel monolithic HBT-p-i-n-HEMT integrated circuit with HBT active feedback and p-i-n diode variable gain control

    Page(s): 1004 - 1009
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    We report the world's first functional MMIC circuit integrating HBT's, HEMT's, and vertical p-i-n diodes on a single III-V substrate. The 1-10 GHz variable gain amplifier monolithically integrates HEMT, HBT, and vertical p-i-n diode devices has been fabricated using selective MBE and a merged processing technology. The VGA offers low-noise figure, wideband gain performance, and good gain flatness over a wide gain control range. A noise figure below 4 dB was achieved using a HEMT transistor for the amplifier stage and a wide bandwidth of 10 GHz. A nominal gain of 10 dB was achieved by incorporating HBT active feedback techniques and 12 dB of gain control range was obtained using a vertical p-i-n diode as a varistor, all integrated into a compact 1.5×0.76 mm2 MMIC. The capability of monolithically integrating HBT's, HEMT's, and p-i-n's in a merged process will stimulate the development of new monolithic circuit techniques for achieving optimal performance as well as provide a foundation for high performance mixed-mode multifunctional MMIC chips View full abstract»

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  • A comprehensive study of numerical anisotropy and dispersion in 3-D TLM meshes

    Page(s): 1173 - 1181
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    This paper presents a comprehensive analysis of the numerical anisotropy and dispersion of 3-D TLM meshes constructed using several generalized symmetrical condensed TLM nodes. The dispersion analysis is performed in isotropic lossless, isotropic lossy and anisotropic lossless media and yields a comparison of the simulation accuracy for the different TLM nodes. The effect of mesh grading on the numerical dispersion is also determined. The results compare meshes constructed with Johns' symmetrical condensed node (SCN), two hybrid symmetrical condensed nodes (HSCN) and two frequency domain symmetrical condensed nodes (FDSCN). It has been found that under certain circumstances, the time domain nodes may introduce numerical anisotropy when modelling isotropic media View full abstract»

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  • Proviso on the unconditional stability criteria for linear twoport

    Page(s): 1197 - 1200
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    The proviso imposed by Rollett [1962] on the well-known stability criteria for linear twoports is examined and redefined as the requirement that at least one set of immittance parameters must have no RHP (right-half plane) poles. It is shown that the proviso can be interpreted as the extreme cases of a newly introduced proviso that requires that the S-parameters defined for at least one pair of arbitrary positive reference impedances have no RHP poles. The new proviso means that the twoport must be stable for at least one pair of arbitrary positive resistance terminations. Since S-parameters are much easier to measure than immittance parameters at microwave frequencies and their direct measurability is an indication of the absence of RHP poles, the new proviso allows us to apply the stability criteria to measured circuits less consciously of the proviso View full abstract»

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  • Analysis and design of a novel noncontacting waveguide backshort

    Page(s): 1023 - 1030
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    A new noncontacting waveguide backshort has recently been developed for millimeter- and submillimeter-wave frequencies. The design consists of a metal bar with rectangular holes cut into it, which is covered with a dielectric layer to form a snug fit with the broadwalls of a waveguide. It is mechanically rugged and can be readily fabricated for frequencies from 1-1000 GHz. This paper presents a technique for the theoretical characterization of the backshort, using an approach that combines the mode-matching method and a set of coupled space-domain integral equations. The convergence characteristics of the analysis are included, along with a set of general design guidelines View full abstract»

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  • Ferrite phase shifters using stress-insensitive garnet materials

    Page(s): 1017 - 1022
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    Stable hysteresis characteristics of ferrimagnetic materials are critical to the RF performance of microwave ferrite toroidal phasers. Particularly troublesome are the magnetostrictive characteristics where the hysteresis properties are altered by stress. This paper presents the results of a study addressing Mn+3 substitutions in garnets to improve the resultant magnetostrictive characteristics in order to achieve stress-insensitive performance in waveguide toroidal phasers View full abstract»

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  • Rigorous and numerically efficient computation of the irrotational electric and magnetic eigenfunctions of complex gyrotron cavities

    Page(s): 1187 - 1195
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    For the modal analysis of complex gyrotron cavities, complete sets of eigenfunctions of the corresponding completely shielded cavity are required. In this contribution, it is shown that the generalized scattering matrix method which is well-known for the computation of the resonance modes can also be applied to the calculation of the irrotational electric and magnetic eigenfunctions. The irrotational eigenfunctions are computed for some circularly symmetrical structures. The validity of the method is checked by investigating a spherical cavity for which the analytical solution is known. Furthermore, a special subdivision of tapered cavity sections is presented which considerably improves the numerical efficiency of the method. For a standard gyrotron cavity, the field in the source region is computed with and without making use of irrotational electric eigenfunctions. It is demonstrated that the accuracy and the numerical efficiency of the modal expansion of the cavity field in the source region is improved if these eigenfunctions are included in the analysis View full abstract»

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  • Static capacitance of some multilayered microstrip capacitors

    Page(s): 1144 - 1152
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    A new unified model, the modified Wolff model (MWM) is presented to determine the lumped capacitance of rectangular, circular, hexagonal and triangular patches on the single layer substrate and under the multilayer condition. Effect of the top shield on the lumped capacitance has also been determined. The MWM is the combination of Wolff-Knoppick model, TTL technique and single layer reduction (SLR) technique, The results of MWM have been compared against the results of SDA, FEM, dual integral method and other forms of the variational methods with accuracy between 0.5-5% for most shapes under various conditions. The present model has accuracy of SDA and other rigorous formulations. No single method has been used in the literature to determine the lumped capacitance of patches of several shapes under the multilayer and shielded condition. The MWM is fast even on the desktop computer. Thus, the model is suitable for a unified CAD for the MMIC applications View full abstract»

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  • A low-voltage, high-power T/R-switch MMIC using LC resonators

    Page(s): 997 - 1003
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    A novel T/R switch is proposed for high-power/low-distortion operation at a low control voltage. LC-resonant switches composed of inductors, capacitors, and switch FET's are incorporated in TX and RX arms to provide a reverse control scheme that removes the rf-voltage limitation in the transmit mode, A 1.9-GHz LC-resonant T/R switch MMIC with a total FET periphery of 3.36 mm exhibits 3rd IMR less than -40 dB for an input power up to 31 dBm when controlled at a V/-2 V. This MMIC occupies an area as small as less than 2×2 mm, This will make it possible to implement advanced T/R-switches at PCS and ISM frequencies below 5 GHz 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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