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Microwave Theory and Techniques, IEEE Transactions on

Issue 3 • Date Mar 1992

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Displaying Results 1 - 25 of 29
  • An analysis of a coupled-ring rotary joint design

    Page(s): 577 - 581
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    A theoretical and experimental analysis of a coupled-ring rotary joint design is described. A rotary joint of this type is commonly used for mechanically scanned, multichannel radars. The main goal of the analysis is to develop a better understanding for the transfer of energy through the joint's highly coupled rings. The author considers the geometry of a typical single channel and then describes a coupled transmission line model for the coupled-ring network. Using the model, the author determines the type of ring network needed for low channel loss and small rotational variations of this loss. Measurements on some test models support the predictions of the analysis View full abstract»

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  • 18-42 GHz experimental verification of microstrip coupler and open end capacitance models

    Page(s): 584 - 587
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    A cavity resonance technique is used to experimentally verify microstrip coupler and open end capacitance models over the frequency range of 18-42 GHz. In addition, these results are confirmed using an alternate version of the technique which directly determines open end discontinuity capacitance. In the second case, knowledge of substrate dielectric constant is not required, and the method also yields the microstrip relative effective dielectric constant View full abstract»

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  • InGaAs field-effect transistors with submicron gates for K-band applications

    Page(s): 429 - 433
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    Depletion mode InGaAs microwave power MISFETs with 0.7 μm gate lengths and 0.2 mm gate widths have been fabricated using an epitaxial process. The devices employed a plasma deposited silicon dioxide gate insulator. The RF power performance at 18 GHz, 20 GHz, and 23 GHz is presented. An output power density of 1.04 W/mm with a corresponding power gain and power-added efficiency of 3.7 dB and 40%, respectively, was obtained at 18 GHz. This is the highest output power density obtained for an InGaAs based transistor on InP at K-band. Record output power densities for an InGaAs MISFET were also demonstrated to the stable within 3% over 17 hours of continuous operation at 18 GHz View full abstract»

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  • Scattering at an offset circular hole in a rectangular waveguide

    Page(s): 587 - 592
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    A solution is given for the problem of scattering at an offset circular to rectangular junction and at a thick diaphragm, with an offset circular aperture, in a rectangular waveguide. The method used is mode matching for computing one discontinuity. The difficulty arising from the fact that the eigenmodes of the two waveguides are known in different coordinate systems is overcome by simple transformation for the evaluation of overlap integral between the eigenmodes of each waveguide. Experimental results validate this method View full abstract»

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  • High-performance in W-band monolithic pseudomorphic InGaAs HEMT LNA's and design/analysis methodology

    Page(s): 417 - 428
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    High-performance W-band monolithic one- and two-stage low noise amplifiers (LNAs) based on pseudomorphic InGaAs-GaAs HEMT devices have been developed. The one-stage amplifier has a measured noise figure of 5.1 dB with an associated gain of 7 dB from 92 to 95 GHz, and the two-stage amplifier has a measured small signal gain of 13.3 dB at 94 GHz and 17 dB at 89 GHz with a noise figure of 5.5 dB from 91 to 95 GHz. An eight-stage LNA built by cascading four of these monolithic two-stage LNA chips demonstrates 49 dB gain and 6.5 dB noise figure at 94 GHz. A rigorous analysis procedure was incorporated in the design, including accurate active device modeling and full-wave EM analysis of passive structures. The first pass success of these LNA chip designs indicates the importance of a rigorous design/analysis methodology in millimeter-wave monolithic IC development View full abstract»

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  • A multipole analysis of a dielectric loaded coaxial rectangular waveguide

    Page(s): 482 - 494
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    A multipole analysis of a coaxial rectangular waveguide whose inner conductor is circular is made in order to determine the TE and TM modes of the system. The analysis is based on using multipole (dipole, quadrupole etc.) electric and magnetic current sources to generate field solutions in the waveguide. These solutions are used to match the electromagnetic boundary condition in a homogeneous coaxial rectangular waveguide and to determine the TE and TM eigenvalues of the waveguide system. Eigenvalue results are compared with results of the generalized spectral domain method and to eigenvalue results for a ridged waveguide. Propagation in a coaxial rectangular waveguide is also studied when the coaxial rectangular waveguide is loaded with lossy inhomogeneous dielectric material. A variational formula is used to relate the TEM, TE, and TM modes of an empty coaxial rectangular waveguide to the propagation in the loaded inhomogeneous dielectric waveguide View full abstract»

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  • An analysis of the large-signal characteristics of AlGaAs/GaAs heterojunction bipolar transistors

    Page(s): 465 - 474
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    The large-signal characteristics of AlGaAs/GaAs heterojunction bipolar transistors are reported. A harmonic balance analysis technique is used for their analysis. This is based on equivalent circuit extractions using approximate physical equations for constraining the fitted solutions and for describing certain circuit element value bias trends. Class A and Class AB large signal behavior was measured and modeled satisfactorily. Power saturation is shown to occur due to the input signal entering the cutoff or the saturation region of the HBT operations. This is illustrated by time-dependent current/voltage waveforms and the power dependence of large-signal equivalent circuit elements. Depending on device bias and matching conditions the main courses of nonlinearities in device output may be caused by the nonlinearities in transconductance, input conductance, and base-collector capacitance View full abstract»

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  • Modeling of discontinuities in general coaxial waveguide structures by the FDTD-method

    Page(s): 547 - 556
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    The finite-difference time-domain (FDTD) method is used to model generalized coaxial waveguide structures with discontinuities. The cross section of the waveguide consists of a closed outer conductor and one or two inner conductors of arbitrary shape. The cross section can have any number of dielectric materials with losses. The singular field-behavior near sharp edges is explicitly included in the finite-difference scheme. Any kind of discontinuity can be handled: changes in cross-section as well as changes of material parameters. From the time-domain data, frequency-domain data (S-parameters) are obtained using Fourier-transform techniques View full abstract»

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  • Ka-band high efficiency power amplifier MMIC with 0.30 μm MESFET for high volume applications

    Page(s): 563 - 566
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    A single-ended three-stage MESFET power amplifier designed for high-volume, low-cost applications shows an average of 15-21% power added efficiency in Ka-band with 100-150 mW of power output over 30-35 GHz. Δ<S21 with power saturation, an important parameter in phased array applications, is also reported. Efficiencies as high as 28% were measured on good wafers with high on-wafer repeatability under power drive View full abstract»

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  • Analysis of superconducting microwave structures: application to microstrip lines

    Page(s): 499 - 508
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    An accurate analysis for the microwave and millimeter-wave transmission lines, which include the high Tc superconductor materials, is presented. This analysis is based on blending a full electromagnetic wave model with London's equations and the two-fluid model. It is capable of fully characterizing the transmission lines, including obtaining the current distributions inside the superconducting material, the electromagnetic fields, the power handling capability, and the quality factor. A simplified model based on the TM-mode solution is also presented. The solution is obtained using the finite-difference scheme. This approach is employed in investigating the superconducting microstrip structure. Results showing current distributions and quality factors are presented. Variations of the line characteristics with the strip width are also presented. The possibility of developing empirical relations for the current carrying capacity as functions of the critical current density and the critical magnetic flux density is also demonstrated View full abstract»

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  • Complex images of an electric dipole in homogeneous and layered dielectrics between two ground planes

    Page(s): 595 - 600
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    Simple closed-form expressions are derived for the vector and scalar potentials of a horizontal electric dipole in homogeneous and layered dielectrics between two ground planes. For the homogeneous dielectric case, an infinite number of dipole images due to the top and bottom ground planes are replaced by a few complex dipole images. For the layered dielectric case, the dipole images due to both the dielectric interfaces and the ground planes are replaced by a few complex dipole images. In addition, the waveguide modes of LSE and LSM types trapped by the two ground planes, and the surface wave modes of LSE and LSM types trapped by the dielectric slabs, both excited by the dipole, are included in the closed-form expressions. The accuracy of the closed-form expressions is confirmed by the numerical integration of spectral integrals View full abstract»

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  • A frequency-dependent FDTD method for biological applications

    Page(s): 532 - 539
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    A frequency-dependent finite-difference time-domain (FD)2 TD method for calculating the response of pulses in plasma or water has recently been described. This method is an advance over the traditional finite-difference time-domain (FDTD) method in that it allows for the frequency dependence of these two media. The modification of the (FD)2TD method to obtain broadband frequency information in 3D biological applications is discussed. The implementation of this method is described, and its accuracy is verified by comparison with analytic solutions using the Bessel function expansion. The use of this method is illustrated by an example of the 3D simulation of a hyperthermia treatment using two applicators over a frequency range of 40 to 200 MHz View full abstract»

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  • Parameter extraction technique for HBT equivalent circuit using cutoff mode measurement

    Page(s): 574 - 577
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    A parameter extraction method based on the S-parameter measurements of the heterojunction bipolar transistors (HBTs) biased to cutoff is proposed. This method is applied to confirm the results for the RF probe pad and interconnection pattern parasitics obtained from the special test structures, and to determine some of the device capacitances of the HBT. The remaining device parameters are extracted by the S-parameter measurements of the devices biased to the active mode. The extraction technique gives good agreement between the equivalent circuit and the measured S-parameters of the HBT including probe pads and interconnections View full abstract»

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  • Microstripline-slotline transition analysis using the spectral domain technique

    Page(s): 515 - 523
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    A spectral domain analysis of the microstripline-slotline transition is presented. The equivalent circuit of the transition is obtained. Elements of the equivalent circuit are determined from the residue theorem. The reflection loss of the transition is determined using the present theory and is found to agree with the experimental data View full abstract»

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  • Computation of the dispersion characteristics of a shielded suspended substrate microstrip line

    Page(s): 581 - 584
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    The dispersion characteristics of a shielded suspended substrate microstrip line are calculated using five different sets of basis functions for the current distributions. Their comparison leads to the more suitable basis functions for the acquisition of fast and accurate results for frequencies up to 100 GHz View full abstract»

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  • Moment method formulation of thick diaphragms in a rectangular waveguide

    Page(s): 592 - 595
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    A method of determination of the electrical characteristics of two thick apertures in a rectangular waveguide is presented. The coupled integral equations resulting from the boundary condition of the magnetic field at the four interfaces are transformed into matrix equations using the method of moments. The numerical data on reflection and transmission coefficients are evaluated. A comparison of theoretical and experimental results is presented View full abstract»

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  • Large signal modeling of HBT's including self-heating and transit time effects

    Page(s): 449 - 464
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    A physically based, large signal heterojunction bipolar transistor (HBT) model is presented to account for the time dependence of the base, collector, and emitter charging currents, as well as self heating effects. The model tracks device performance over eight decades of current. The model can be used as the basis of SPICE modeling approximations, and to this end, examples are presented. A thesis for the divergence of high frequency large signal SPICE simulations from measured data is formulated, including a requisite empirical equation for the base-collector junction capacitance View full abstract»

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  • A 100-element planar Schottky diode grid mixer

    Page(s): 557 - 562
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    The authors present a Schottky diode grid mixer suitable for mixing or detecting quasi-optical signals. The mixer is a planar bow-tie grid structure periodically loaded with diodes. A simple transmission line model is used to predict the reflection coefficient of the grid to a normally incident plane wave. The grid mixer power handling and dynamic range scales as the number of devices in the grid. A 10-GHz 100-element grid mixer has shown an improvement in dynamic range of 16.3 to 19.8 dB over an equivalent single-diode mixer. The conversion loss and noise figure of the grid are equal to those of a conventional mixer. The quasi-optical coupling of the input signals makes the grid mixer suitable for millimeter-wave and submillimeter-wave applications by eliminating waveguide sidewall losses and machining difficulties. The planar property of the grid potentially allows thousands of devices to be integrated monolithically View full abstract»

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  • Analysis of a wide resonant strip in waveguide

    Page(s): 495 - 498
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    An analysis has been developed to calculate the susceptance due to a wide resonant strip on the transverse plane of a rectangular waveguide. The theory is based upon a variational form for the susceptance, where the current distribution is determined by the moment method. Accurate results have been obtained for the wide strips as confirmed by the measurements View full abstract»

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  • A 16 element quasi-optical FET oscillator power combining array with external injection locking

    Page(s): 475 - 481
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    The authors present analysis, design and experimental results of a 16 element planar oscillator array for quasi-optical power combining. Each element in the array consists of a single FET oscillator with an input port for injection of the locking signal and an output port which is connected to a patch radiator. The array is synchronized using a 16-way power dividing network which distributes the locking signal to the oscillating elements. The array is constructed using a two-sided microstrip configuration, with the oscillators and feed network on one side of a ground plane, and the patch radiators on the opposite side. An effective radiated power (ERP) of 28.2 W CW with an isotropic conversion gain of 9.9 dB was measured at 6 GHz. For an injected power of 10.3 dBm, a locking range of 453 MHz at a center frequency of 6.015 GHz was obtained; a bandwidth of 7.5%. Because of the simple nature of the individual oscillator elements, this approach is well suited to MMIC implementation View full abstract»

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  • Alternative field representations and integral equations for modeling inhomogeneous dielectrics

    Page(s): 604 - 608
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    New volume and volume-surface integral equations are presented for modeling inhomogeneous dielectric regions. In particular, it is shown that materials with nontrivial permeability and permittivity can be modeled using a single unknown equivalent current or field component. The integral equations result in more efficient numerical implementations and should be useful in a variety of electromagnetic applications View full abstract»

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  • Criteria for the onset of oscillation in microwave circuits

    Page(s): 566 - 569
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    A commonly used criterion for oscillator startup is demonstrated not to be universally valid. In order to investigate startup conditions, the Nyquist stability criterion is written in terms of microwave quantities. It is shown that widely available microwave CAD can be used to create Nyquist stability plots. Since the Nyquist criterion gives only global stability information, a convenient graphical criterion is developed to determine whether an oscillation will start up near a particular resonance frequency View full abstract»

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  • A general approach for the S-parameter design of oscillators with 1 and 2-port active devices

    Page(s): 569 - 574
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    A circular function that serves as a basis for deciding if a circuit will continuously oscillate is introduced. The circular function is derived from the signal flow graph of the circuit including the external load. Any node in the flow graph can be split into two nodes, one of which contains incoming branches and the other of which contains outgoing branches. The circular function is then the transfer function between the two nodes, and it can be measured or simulated by looking at the reflection coefficient of a circulator inserted at the node that was originally split. Oscillations occur when the circular function is unity. The stability of these oscillations is determined by considering the behavior of the circular function as the circuit saturates. The circular function can be applied to one-port oscillators that use negative resistance devices and to feedback oscillators containing transistors, and it reduces to previously published results for specific circuit topologies. To verify the practicality of this approach two 30 GHz HEMT oscillators were designed and tested View full abstract»

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  • Pulse propagation in superconducting coplanar striplines

    Page(s): 509 - 514
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    The phenomenological loss equivalence method (PEM), the enhanced two-fluid model for thin-film superconducting materials, and the dynamical calculation of radiation losses in planar structures are used-in the context of a linear filter approach-to model attenuation and dispersion of ultrafast pulses in coplanar striplines. The numerical simulation of this modeling shows excellent agreement with experimental results available in the literature. Simple relationships between the peak attenuation and delay time of the propagation pulse, and penetration depth at absolute zero and conductivity at critical temperature may open the possibility of using pulse distortion to characterize thin-film, high-temperature superconducting materials View full abstract»

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  • On the quasi-TEM and full-wave approaches applied to coplanar multistrip on lossy dielectric layered media

    Page(s): 524 - 531
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    The characteristic parameters of coplanar multistrip lines embedded in multilayered lossless/lossy substrates are commonly computed by using either quasi-TEM or full-wave model. Several methods are provided in the literature to deal with this type of structure. A comparative study of quasi-TEM and rigorous solutions is carried out in order to establish criteria for the validity of the quasi-TEM approach. Reliable quasi-TEM and full-wave numerical data have been properly generated by applying an enhanced spectral domain analysis. The authors conclude that the quasi-TEM model yields satisfactory results for many MIC and MMIC practical cases. However, significant errors arise when high conductivity substrates are involved in MMIC applications. A discussion about the computation of the dynamic modal characteristic impedance is also reported, showing how the insertion of the modal orthogonality can save computational effort in a lossy multiport system View full abstract»

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Aims & Scope

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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