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Microwave Theory and Techniques, IEEE Transactions on

Issue 5 • Date May 1989

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Displaying Results 1 - 18 of 18
  • A new approach to the RF power operation of MESFETs

    Page(s): 817 - 825
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    A large-signal numerical model for a MESFET is described which allows investigations of the behavior of these devices at X-band frequencies under large-signal conditions. The authors of numerical simulations are compared with those of the measurements and provide on improved understanding of the behavior of GaAs MESFETs that operate at microwave frequencies and with high power requirements. The analysis yields some indications about the optimum design of these devices.<> View full abstract»

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  • Transient analysis of multiple tuned injection-locked amplifiers with modulated input signal

    Page(s): 826 - 835
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    A method is presented for the dynamical investigation of reflection-type injection-locked amplifiers (ILAs) driven by modulated input signals. Its distinctive feature is to cover the large-signal analysis of high-order ILAs, allowing the use of broad-banding multiresonant structures. Small-parameter, stroboscopic, and congruence algebra techniques are combined to permit the calculation of output voltage transients directly in terms of amplitude and phase of the complex envelope, thus limiting the computational time required in CAD (computer-aided design) applications. Further, owing to the used black-box (scattering matrix) descriptions of the tank and coupling two-port, both linear and nonlinear subsystem identification can be performed in terms of measured data. As an example of the application of the method, a fourth-order ILA is analyzed, and results pertaining to binary phase-shift keyed (BPSK) modulated input signals are presented.<> View full abstract»

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  • Fast and accurate analytic formulas for calculating the parameters of a general broadside-coupled coplanar waveguide for (M)MIC applications

    Page(s): 843 - 850
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    Fast and accurate analytic formulas for calculating the quasistatic transverse electromagnetic (TEM) parameters of a general broadside-coupled coplanar waveguide (GBSC CPW) are presented. Simplicity, high speed of computation, and accuracy suggest the use of these formulas for (M)MIC CAD (monolithic) microwave integrated circuit computer-aided design programs. Numerical calculations are presented to investigate various electrical properties of the structure. An asymmetrical BSC CPW and the single CPW resulting from connecting the two coupled strips of the GBSC CPW at the input and the output ports are analyzed. Criteria are obtained to ensure the coplanar behavior of the structure.<> View full abstract»

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  • The complete spectrum of image line

    Page(s): 868 - 874
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    A derivation is presented of the complete orthonormalized spectrum, under LSA/LSM (longitudinal-section electric/magnetic) assumptions, for image line waveguiding structures by using a so-called method of partial wave phase shifts. The analysis is developed for the even LSM (TM/sup y/) polarization, having H/sub y/=0 and E/sub y/ as the main electric field component: the LSE analysis proceeds along dual lines. An arbitrary radiation field is described as a superposition of the LSM and LSE continua.<> View full abstract»

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  • Full vectorial finite element formalism for lossy anisotropic waveguides

    Page(s): 875 - 883
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    An efficient computer-aided solution procedure based on the finite-element method is developed for solving general waveguiding structures containing lossy, anisotropic materials. In this procedure a formulation in terms of the transverse magnetic field component is adopted and the eigenvalue of the final matrix equation corresponds to the propagation constant itself. Thus one avoids the unnecessary iterations which arise when using complex frequencies. To demonstrate the strength of the presented method, numerical results are shown for a rectangular waveguide filled with lossy anisotropic dielectric with off-diagonal elements in a permittivity tensor and compared with those obtained by the telegrapher equation method. The results are in excellent agreement both for phase and for attenuation.<> View full abstract»

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  • Characterization of microstrip lines near a substrate edge and design formulas of edge-compensated microstrip lines (MMICs)

    Page(s): 890 - 896
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    The proximity effects of microstrip lines near a substrate's edge present a problem for effectively designing high-packing-density MMICs (monolithic microwave integrated circuits). Proximity effects of this type are analyzed using the rectangular boundary division method. It is assumed that the cross-sectional dimensions of transmission lines in the MMICs are small compared with the wavelengths to allow the use of the quasi-TEM-wave approximation. Then, the concept of edge-compensated microstrip lines to keep the characteristic impedance constant near a substrate edge is introduced to circumvent the proximity effects and to expand the interconnection flexibility of microstrip lines on MMIC substrates. The practical design parameters of edge-compensated 50- Omega microstrip lines are given in the form of numerical data and simple polynomials for CASD (computer-aided design) work with a curve-fitting procedure. Results of capacitance measurements are compared with this theory with errors of about 1% resulting.<> View full abstract»

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  • Time-domain method of lines applies to planar guided wave structures

    Page(s): 897 - 901
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    A time-domain method for the analysis of wave propagation and scattering in a planar transmission structure is developed in which the concept of the method of lines is used. The analytical process incorporated along one of the three dimensions has been executed for each line independently (one-dimensional process) or for one set of lines (two-dimensional process), depending on whether or not the structure contains metallic strips at the dielectric interface boundary. A simple numerical example is presented as a demonstration of the above two processes of the method, and its validity is shown by comparison with other data.<> View full abstract»

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  • Multimode network description of a planar periodic metal-strip grating at a dielectric interface. III. Rigorous solution

    Page(s): 902 - 909
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    For pt.II see (ibid., vol.37, no.3, p.542-52, 1989). In pt.I the solution to the scattering problem posed by a plane-wave incident at an angle on a plane, periodic, metal-strip grating at a dielectric interface was formulated in terms of novel multimode equivalent network representations. The analytical phrasing followed in pt.I led to two Fredholm integral equations of the first kind with singular kernels. Here, the authors derive a rigorous analytical solution for one of the two integral equations derived in pt.I (see ibid., vol.37, no.3, p.534-41, 1989). Closed-form, rigorous, analytical expressions for the elements involved in the equivalent network representations derived are obtained. Numerical results obtained by using these rigorous equivalent network representations are presented for TE-mode and TM-mode incidence for the case in which the same dielectric is present on both sides of the grating as well as for the case in which the two dielectric media are different.<> View full abstract»

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  • Equivalent current density reconstruction for microwave imaging purposes

    Page(s): 910 - 916
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    Numerical computer simulations are used to study the possibilities of reconstructing the distribution of the equivalent current density vector in a domain with a known volume, inside which dielectric scatterers stand at arbitrary locations. An integrodifferential formulation of the three-dimensional electromagnetic inverse scattering is transformed into matrix form through the application of the moment method. A pseudoinversion algorithm overcoming ill-conditioned problems is used to obtain the distribution of the equivalent current density also in the case where the input data (i.e. the simulated values of the scattered field vector to be obtained in an observation domain) are affected either by Gaussian noise or by uniformly distributed errors. The results furnish information that could be used to devise a possible imaging method for detecting the locations and surface shapes of scattering objects.<> View full abstract»

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  • On the bandwidth of T-septum waveguide

    Page(s): 919 - 922
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    The single T-septum waveguide is analyzed using the Rayleigh-Ritz-Galerkin technique. The method is a variation of that used by previous groups with reported conflicting results. The results of the analysis agree closely with those of G.G. Mazumder and P.K. Saha (1985) and those of F.J. German and L.S. Riggs (ibid., vol.37, no.5, p.917-9, 1989).<> View full abstract»

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  • Transmission properties of a right-angle microstrip bend with and without a miter

    Page(s): 925 - 929
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    The transmission properties of a microstrip bend with and without a miter joint are investigated based on the waveguide model and using the Green's theorem approach. Unlike the conventional mode-matching technique, this approach does not require a modal description of fields inside the discontinuity region. Instead, the fields on the two sides of the discontinuity are related by applying the Green's theorem with an appropriate choice of an auxiliary function which plays the role analogous to that of the testing function in the method of moments. The selection of the auxiliary function is not systematic and involves good physical insight to the problem under study. Scattering parameters for the bend are presented which agree well with the quasistatic results at low frequencies. Significant improvement in the transmission properties is observed for the bend with a miter. It is noted that by themselves, the results provide an accuracy check for the more sophisticated integral equation approach which can handle arbitrarily shaped boundaries. Moreover, with a slight modification, this technique may be extended to study microstrip corners with an arbitrary miter.<> View full abstract»

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  • High-frequency MESFET noise modeling including distributed effects

    Page(s): 836 - 842
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    A microwave field-effect transistor (FET) noise analysis is presented including distributed effects caused by the wave propagation along the width of the gate. Using this model the noise characteristics of submicron gate MESFETs at frequencies beyond 20 GHz are evaluated. It is ascertained that in the case of well-designed quarter-micron low-noise MESFETs, distributed effects may be neglected. Common lumped approximations, on the other hand, are shown to produce noticeable deviations. An improved lumped model is proposed. The analysis presented can also be used with high-electron-mobility transistor (HEMT) devices after introducing adequate geometry and small-signal parameters View full abstract»

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  • The use of a single source to drive a binary peak power multiplier

    Page(s): 929 - 931
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    The binary power multiplier (BPM) recently proposed by Z.D. Farkas (ibid., vol.MTT-34, p.1036, 1986) requires a pair of radio frequency inputs whose phases are set independently. In this note, a method is presented in which a single source may be used to drive a BPM. Phase coding occurs at the course input, where the power is low and phase switching is straightforward. There is a loss in energy of about 25% but only a small reduction in peak power View full abstract»

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  • Bandwidth properties of rectangular T-septum waveguides

    Page(s): 917 - 919
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    The transmission line modeling (TLM) method is applied to rectangular T-septum waveguides for the determination of the separation between the hybrid TE10 and hybrid TE20 modes. While previous analysis have predicted a wider bandwidth for this class of waveguiding structure than is available with conventional ridged waveguide, they have not been in agreement on the exact bandwidth properties. This discrepancy is resolved, and the apparent cause of error in previously published results is pointed out. The results obtained are in agreement with those presented by G.G. Mazumder and P.K. Saha (1985) View full abstract»

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  • Analysis of a centered-inclined waveguide slot coupler

    Page(s): 884 - 889
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    Integral equations are developed for a centered-inclined coupling slot (including the effect of finite wall-thickness of the common broad-wall) and the slot-aperture electric intensity field is found using the method of moments. Numerical results for resonant length, backscattered wave amplitude, and phase variation off-resonance are presented over a range of values of the waveguide b dimension, wall thickness, slot width, and frequency. It is shown that the resonant length is relatively insensitive to slot tilt, θ, for a standard-height X-band waveguide, whereas its dependence on θ is significant for reduced-height waveguides. The phase variation of scattered TE10 waves in both waveguides off-resonance is less for wider slots and smaller b dimensions. Shunt-series coupling slots exhibit greater phase variation off resonance when compared to a centred-inclined coupling slot. Also, the former has a longer resonant length for a smaller b dimension and for a wider slot. Thus the centred-inclined slot coupler possesses superior characteristics. The higher-order mode coupling between a centred-inclined slot coupler and a pair of straddling radiating slots in the branch waveguide is significant View full abstract»

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  • Optimized method for obtaining permittivity and conductivity profiles of microwave materials

    Page(s): 922 - 925
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    An iterative method for obtaining the distribution of the relative permittivity εr(z) or electrical conductivity σ(z) of microwave semiconducting materials is presented. The semiconducting material is fitted in a rectangular waveguide which is terminated by a variable short circuit. The reflection coefficients of the system are measured at a single frequency and at different positions of the moving short. The measured coefficients are used in the iterative process of solving the inverse problem by obtaining the functional gradient. The method takes into account continuous and discontinuous profiles View full abstract»

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  • Theory of magnetostatic waves in moving ferrite films and applications to rotation rate sensing

    Page(s): 851 - 859
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    A first-order field theory for electromagnetic waves in moving ferrites and ferrite thin films is presented. The dominant effect of the motion is found to be the Doppler-shifted frequency observed in the moving frame. This gives rise to an anomalously large shift in wavenumber, due to the dispersive nature of the ferrite medium. Because of the large effect, it is suggested that a moving-medium experiment using magnetostatic waves could be used to distinguish between various competing forms for the dispersion term in the Fresnel-Fizeau coefficient. The results of the field theory are discussed with relation to relative and absolute rotation rate sensing. The author describes how magnetostatic waves could be used to measure relative rotation rates if confined to propagate around the perimeter of a rotating disk. Since the phase shift would be established in the time required to propagate around the disk, the response time could be significantly shorter than conventional tachometers. An experiment with counterpropagating magnetostatic waves is suggested to clarify the effect of a magnetic medium on the magnitude of the Sagnac effect View full abstract»

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  • Modeling ferrimagnetic resonators

    Page(s): 860 - 867
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    The impedance matrix for an arbitrary n-port ferrimagnetic resonator is derived by applying Poynting's theorem to a region of space surrounding the resonator. Simplifications to the impedance matrix for low-loss (Q>≈100) ferrite material make it possible to obtain an equivalent circuit model for the resonator, which can be used with most computer-based circuit simulation programs. The circuit model for the general-case polymodal ferrimagnetic resonator consists of a network of single-pole resonators, each of which has a possible non-frequency-dependent, nonreciprocal phase shift. The components of the circuit model are described in terms of the properties of the ferrite material, and the coupling strength of the microwave circuit to the magnetostatic modes of the ferrimagnet. The method is demonstrated in three simple examples, including a one- and two-port loop coupled filter, and a ferrimagnet in a waveguide 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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