Showing papers in "IEEE Transactions on Microwave Theory and Techniques in 1980"
TL;DR: In this paper, approximate design formulas for bandpass filters using parallel coupled stripling stepped impedance resonators (SIR) are derived, taking into account the arbitrary coupling length as well as quarter-wavelength coupling.
Abstract: Approximate design formulas for bandpass filters using parallel coupled stripling stepped impedance resonators (SIR) are derived. The formulas take into account the arbitrary coupling length as well as quarter-wavelength coupling. Some advantages of this filter are its abilities to control spurious response and insertion loss by changing the structure of the resonator. Using the design formulas two experimental filters were designed and fabricated and their performances closely matched design data.
784 citations
TL;DR: In this article, a probe technique for the determination of dielectric properties of semisolid materials and living tissues in situ is described experimentally and theoretically, based on an antenna modeling theorem.
Abstract: A novel probe technique for the determination of dielectric properties of semisolid materials and living tissues in situ is described experimentally and theoretically. This method, based on an antenna modeling theorem, offers unique advantages over conventional dielectric measurements techniques including 1) an ability to perform living (in vivo) tissue dielectric measurements, 2) elimination of the need for tedious sample preparation, 3) the ability to obtain continuous dielectric property data from below 0.1 GHz to above 10 GHz, and 4) the ability to process data on a real time basis. Results of system performance evaluation via measurements of standard liquid dielectric and in vivo tissue data are presented.
622 citations
TL;DR: In this paper, a simple method for formulating the dyadic Green's functions in the spectral domain is presented for generalized printed transmission Iines which contain several dielectric layers and conductors appearing at several Dielectric interfaces.
Abstract: A simple method for formulating the dyadic Green's functions in the spectral domain is presented for generalized printed transmission Iines which contain several dielectric layers and conductors appearing at several dielectric interfaces. The method is based on the transverse equivalent transmission line for a spectral wave and on a simple coordinate transformation. This formulation process is so simple that often it is accomplished almost by inspection of the physical cross-sectional structure of the transmission line. The method is applied to a new versatile transmission line, a microstrip-slot Iine, and some numerical results are presented.
567 citations
TL;DR: In this paper, a MESFET model is presented that is suitable for use in conventional, time-domain circuit simulation programs, and the parameters of the model are evaluated either from experimental data or from more detailed device analysis.
Abstract: A MESFET model is presented that is suitable for use in conventional, time-domain circuit simulation programs. The parameters of the model are evaluated either from experimental data or from more detailed device analysis. The model is shown to be more complete than earlier models, which neglect transit-time and other effects. An integrated circuit (IC) design example is discussed.
461 citations
TL;DR: In this paper, the effects of fringing fields on the capacitance of a circular microstrip disk are studied with the dual integral equation formalism for practical microstrip circuits when the substrate thickness is small.
Abstract: The effects of fringing fields on the capacitance of a circular microstrip disk are studied with the dual integral equation formalism for practical microstrip circuits when the substrate thickness is small. Approximations as well as exact numerical evaluations are made in the calculation of the capacitance. With a seminumerical approach, an approximate formula for the capacitance is obtained and shown to yield accurate results with the simple use of a calculator. Asymptotic lower bound and exact numerical computations are also carried out. The various techniques are illustred and compared with numerical results.
169 citations
TL;DR: In this article, the analysis of a microstrip line covered with a low-loss sheet material is presented, and the results show that the characteristics of such a line are drastically affected by high dielectric constant.
Abstract: The analysis of a microstrip line covered with a low-loss sheet material is presented in this paper. Numerical results show that the characteristics of a microstrip covered with a thick sheet of high dielectric constant are drastically affected. The effect is more for small values of W/h ratio. A closed-form expression for the dielectric loss of a multilayer structure is derived.The extension of present method to high-loss materials is also discussed. Numerical and experimental results for effective dielectric constant of a microstrip covered with low- and high-loss sheet materials are compared and found to be in good agreement.
158 citations
TL;DR: In this article, state-of-the-art information on losses of single and coupled microstrip lines is summarized along with the effect of dispersion, and a rough comparison is made between the losses of microstrip and that of several other types of lines used in microwave integrated circuits.
Abstract: This article summarizes state-of-the-art information on losses of single and coupled microstrip lines. Conductor loss, substrate loss (for pure dielectric or magnetic materials), and radiation loss are considered along with the effect of dispersion. Finally, a rough comparison is made between the losses of microstrip and that of several other types of lines used in microwave integrated circuits.
158 citations
TL;DR: In this paper, a generalized study for the resonant modes of a dielectric rod resonater placed between two parallel conducting plates is presented, where the cutoff conditions and dispersive properties of the resonator are investigated.
Abstract: This paper describes a generalized study for the resonant modes of a dielectric rod resonater placed between two parallel conducting plates. Dielectric and conductor losses are ignored. It is shown that there are two resonant states in this resonator, trapped and leaky states. In order to determine the cutoff and resonat frequencies in the trapped state, numerical results are given for the cutoff conditions and dispersive characteristics of a dielectric rod waveguide. The field patterns for the hybrid modes are also presented. For the resonant modes in the leaky state, it is shown to be useful to introduce a complex angular frequency. Numerical results are given for the various modes with different values of the dielectric constant. Generalized mode charts covering both states and including the cutoff conditions are presented. The existence of both states has been verified by experiments.
157 citations
TL;DR: In this article, a novel synthesis technique is developed for two-port networks which possess finite real frequency transmission zeros, where the low-pass prototype is synthesized in the form of a network with complex conjugate symmetry where the real frequency transmissions are extracted from both ends and realized by simple resonators separated by phase shifters.
Abstract: A novel synthesis technique is developed for two-port networks which possess finite real frequency transmission zeros. The low-pass prototype is synthesized in the form of a network with complex conjugate symmetry where the real frequency transmission zeros are extracted from both ends and realized by simple resonators separated by phase shifters. The remaining transmission zeros are realized by the central part of the filter in the form of a cross-coupled double array. This prototype is particularly suitable for designing waveguides bandpass filters and each real frequency transmission zero is independently tunable. Furthermore, in the case of the most complex transfer function with all possible types of transmission zeros, the realization requires only one type of coupling which is necessary in the important case of TE/sub011/ cylindrical mode cavity resonators. The general synthesis technique is given and the process illustrated by a nontrival example. Additionally, from the results of a computer program based upon the synthesis techniques, the important differences between the possible prototype forms for the same transfer function resulting from extracting the transmission zeros in different orders are cited.
144 citations
TL;DR: In this paper, the spectral domain analysis is applied for deriving despersion characteristics of dominant and higher order modes in fin-line structures, and the characteristic impedance is calculated based on the powervoltage definition.
Abstract: The spectral domain analysis is applied for deriving despersion characteristics of dominant and higher order modes in fin-line structures. In addition to the propagation constantant, the characteristic impedance is calculated based on the power-voltage definition. Numerical results are compared for different choices of basis functions and allow to estimate the accuracy of the solution.
143 citations
TL;DR: In this article, the authors provide basic information on the design of ring-type radiators for tissue heating and the experimental results for a unit designed to operate in the TM modes at 2.45 GHz.
Abstract: Ring-type microstrip antennas appear to offer important advantages in medical therapy when used for local tissue heating. In designing these radiators, the properties of a microstrip covered with layers of lossy dielectric representing various tissue layers have to be taken into account. This paper provides basic information on design of ring-type radiators for tissue heating and the experimental results for a unit designed to operate in the TM modes at 2.45 GHz. The radiator is well matched when spaced 1.3-3 mm from muscle tissue or muscle tissue covered by a thin layer of fat tissue. A limited volume of muscle tissue is heated at a greater rate than the fat layer as shown by a thermographic technique.
TL;DR: In this paper, the third-order intermodulation distortion generated in a MESFET amplifer is analyzed by means of the Volterra series representation, which enables direct analytical determination of the nonlinear elements from small-signal measurements.
Abstract: Third-order intermodulation distortion generated in a MESFET amplifer is analyzed by means of the Volterra series representation. A transistor model is used which enables direct analytical determination of the nonlinear elements from small-signal measurements. The four nonlinearities considered are the gate capacitance, transconductance, drain feedback capacitance, and output conductance. Volterra transfer functions are derived for a simplified model and closed-form expressions for the third-order intermodulation ratio and intercept point are determined. The equations show the dependence of distortion on frequency, terminating impedances, and transistor parameters. Principal sources of distortion are identified and the influence of device parameters and network terminations is investigated. Experimental verification on specific MESFET amplifiers, with 2-mu m and 1-mu m gate devices, comparing predicted and measured intermodulation products for various load conditions is presented.
TL;DR: In this paper, the match and isolation properties of planar electrically symmetric n-way hybrid power dividers/combiners are studied, which resemble the Wilkinson hybrid, are named the "radial" hybrid, and the "fork" hybrid.
Abstract: The match and isolation properties of two types of planar electrically symmetric n-way hybrid power dividers/combiners, which were recently introduced in the literature, are studied. These hybrids, which resemble the Wilkinson hybrid, are named the "radial" hybrid, and the "fork" hybrid because of their geometry. Optimum values of their isolation resistances are given to maximize the match and isolation at band center. The power dissipation requirement in the isolation resistors is also discussed. It is shown that the use of two stages of quarter-wave lines and isolation resistors, rather than only one stage as was originally proposed, improves the match and isolation considerably as well as reduces the power dissipation requirements.
TL;DR: In this article, measurements of the noise characteristics of a variety of gallium-arsenide field effect transistors at a frequency of 5 GHz and temperatures of 300 K to 20 K are presented.
Abstract: Measurements of the noise characteristics of a variety of gallium-arsenide field-effect transistors at a frequency of 5 GHz and temperatures of 300 K to 20 K are presented. For one transistor type detailed measurements of dc parameters, small-signal parameters, and all noise parameters (T/sub min/, R/sub opt/, X/sub opt/ g/sub n/) are made over this temperature range. The results are compared with the theory of Pucel, Haus and Statz modified to include the temperature variation. Several low-noise ampifiers are described including one with a noise temperature of 20 K over a 500-MHz bandwidth. A theoretical analysis of the thermal conduction at cryogenic temperatures in a typical packaged transistor is included.
TL;DR: In this paper, an analytical expresion for the efficiency of the gyrotron traveling wave amplifier is derived for the case of non-fundamental cyclotron harmonic interaction, which scales the efficiency with respect to the modes and parameters of operation.
Abstract: An analytical expresion for the efficiency of the gyrotron traveling wave amplifier is derived for the case of nonfundamental cyclotron harmonic interaction. It scales the efficiency with respect to the modes and parameters of operation. This relation, together with a general linear dispersion relation, also derived in the present paper, gives the characteristics and optimum operation conditions of the gyrotron traveling wave amplifier.
TL;DR: In this article, an ultrawide-band amplifier was developed that covers the frequency range from 350 MHz to 14 GHz with a minimum gain of 4 dB at an output power of 13 dBm.
Abstract: An ultrawide-band amplifier module has been developed that covers the frequency range from 350 MHz to 14 GHz. A minimum gain of 4 dB was obtained across this 40:1 bandwidth at an output power of 13 dBm. The amplifier makes use of negative and positive feedback and incorporates a GaAs MESFET that was developed with special emphasis on low parasitics. The transistor has the gate dimensions 800 by 1 mu m. The technology and RF performance of the GaAs MESFET are discussed, as are the design considerations and performance of the single-ended feed-back amplifier module.
TL;DR: In this paper, it was shown that the mutual interaction is due to contradirectional (or backward) waves in the secondary arm, so that multi-aperture interactions are manifested as elimination of the self-interactions of the individual apertures.
Abstract: Bethe's small aperture coupling theory, modified by Cohn for large coupling apertures, is improved by including correction terms obtained by averaging the fields over the large aperture. Additionally, inclusion of nonempirical thickness correction factors derived previously by McDonald give coupling formulas which result in theoretical predictions for multiaperture couplers substantially in exact agreement with experiment (correcting small discrepancies previously noted by the author in a 1968 paper). This agreement is now so close that it becomes possible both to identify and explain the mutual interaction effects between closely spaced apretures in multiaperture couplers. It is shown that the mutual interaction is due to contradirectional (or backward) waves in the secondary arm, so that multiaperture interactions are manifested as elimination of the self-interactions of the individual apertures (since the high directivity of typical multiaperture couplers implies negligible backward wave amplitude).
TL;DR: In this article, a new type of highly stabilized GaAs FET oscillator using a dielectric resonator and a stabilization resistor in the feedback circuit has been developed, which has a high external quality factor Q/sub ex/ for more than 1000 MHz with no hysteresis phenomena.
Abstract: A new type of highly stabilized GaAs FET oscillator using a dielectric resonator and a stabilization resistor in the feedback circuit has been developed. The oscillator fabricated with a microwave integrated circuit has a high external quality factor Q/sub ex/ for more than1000 with no hysteresis phenomena. The microwave characteristics of the GaAs FET oscillator has revealed 1) high efficiency of 20 percent with 70-mW output power at 11.85 GHz, 2) a wide tuning range more than1000 MHz, 3) a wide oscillation frequency from 9 to 14 GHz with same MIC pattern by using five dielectric resonators of different sizes, 4) a high-frequency stability as low as /spl plusmn/ 150kHz in the tempature range from -20 to + 60/spl deg/ C, and 5) low FM noise of 0.07 Hz/ /spl radic/Hz at off-carrier frequency of 100kHz.
TL;DR: In this paper, mode-matching technique is employed for computing the propagation constants and field distributions of an inverted strip dielectric waveguide, and the results derived in this manner are further improved by using variational formulas expressly designed for open Dielectric Waveguides.
Abstract: The mode-matching technique is employed for computing the propagation constants and field distributions of an inverted strip dielectric waveguide. The results derived in this manner are further improved by using variational formulas expressly designed for open dielectric waveguides. Illustrative numerical results are presented and compared with an experimental measurement as well as those based on approximate methods found in the literature.
TL;DR: In this paper, it was shown that a gyrotron oscillator operating in a slightly tapered magnetic field can attain an efficiency of approximately 1.7 times higher than that obtainable in a constant magnetic field.
Abstract: It is shown that a gyrotron oscillator operating in a slightly tapered magnetic field can attain an efficiency of ~78 percent, approximately 1.7 times higher than that obtainable in a constant magnetic field. Extensive numerical data have been tabulated and a convenient parameter is introduced to generate numerical efficiency scaling relations through which optimum operating conditions are clearly exhibited. Conditions for reaching the high efficiency operating regime are also studied and numerically illustrated.
TL;DR: In this article, a low-cost easily fabricated millimeter-wave line scanner is described, which consists of a 1mm x 1mm silicon dielectric rod with a metal grating (periodic structure) on the upper surface and p-i-n diodes mounted on the sidewall.
Abstract: The design and experimental findings for a low-cost easily fabricated millimeter-wave line scanner is described. This antenna consists of a 1-mm x 1-mm silicon dielectric rod with a metal grating (periodic structure) on the upper surface and p-i-n diodes mounted on the sidewall. A narrow 8/spl deg/ beam is radiated from the grated (perturbed) surface at an angle dependent on the guide and perturbation spacing. The beam angle is switched over a 10/spl deg/ angle by application of a dc forward current through the p-i-n diode modulators.
TL;DR: In this article, the spectral-domain technique is used to determine both wavelength and characteristic impedance of the fin line of millimeter-wave waveguarded wavegates, and design curves are presented for practical millimeterwave fin line structures.
Abstract: This paper presents an analysis of the fin line. The spectral-domain technique is used to determine both wavelength and characteristic impedance. Numerical results are compared with known data for ridged waveguide slab-loaded waveguide, and slotline. Design curves are presented for practical millimeter-wave fin line structures.
TL;DR: In this paper, a novel microwave integrated circuit (MIC) 180/spl deg/ hybrids (magic-T's) suitable for MIC are described, which make use of the two orthogonal modes (even and odd) of the coupled slot lines, and, therefore, have special port location.
Abstract: Novel microwave integrated circuit (MIC) 180/spl deg/ hybrids (magic-T's) suitable for MIC are described. They make use of the two orthogonal modes (even and odd) of the coupled slot lines, and, therefore, have special port location, which is quite different from that of the conventional 180/spl deg/ hybrids such as a rat-race. That is, the two-ports, which correspond to the E-arm and the H-arm of the well-known waveguide magic-T, can be located on the same side, opposite to the other two ports. This feature is of a great practical advantage when applied to an MIC, because the crossing of the transmission lines can be omitted when this type of magic-T is applied to balanced-type circuits such as balanced mixers. Satisfactory experimental results at a center frecuency of 6 GHz are given. The isolation between the E- and the H-ports is better than 30 dB over an octave band, and the frequency sensitivity of the coupling is almost flat in the frequency range from 2 to 10 GHz.
TL;DR: In this paper, a systematic and intuitive procedure is proposed to derive the variational (or stationary) principle for non-seff-adjoint electromagnetic problems with various boundary conditions.
Abstract: A systematic and intuitive procedure is proposed to derive the variational (or stationary) principle for non-seff-adjoint electromagnetic problems with various boundary conditions Several physical interpretations of this principle in terms of generalized reactions, time-average stored energy, and reactive powers, respectively, are discussed in detail This general variational principle which makes the generalized reactions a stationary value is actually an extension of the least action principle in physics The applications of the principle to establish the variational expressions for a waveguide, a cavity resonator, and a Ioasy one-dimensional inhomogeneous slab are presented
TL;DR: In this paper, the results of a numerical solution for open microstrip transmission line with finite-width dielectric are presented for a quasi-TEM computational model, based on moment methods using equivalent source models for the free and bound charges existing on boundary surfaces.
Abstract: The results of a numerical solution for open microstrip transmission line with finite-width dielectric are presented for a quasi-TEM computational model. The related solution is based on moment methods using equivalent source models for the free and bound charges existing on boundary surfaces. Characteristic impedance and velocity of propagation are presented in graphical form for estimating the effects of dieletric truncation on microstrip circuits and for related circuit design.
TL;DR: In this article, the asymptotic properties of the fundamental mode HE/sub 11/ inside a large waveguide of finite surface impedances are discussed and the analysis applies to corrugated waveguides, certain optical fibers and wave-guides with metal walls coated by a dielectric layer.
Abstract: The asymptotic properties of the fundamental mode HE /sub 11/ inside a large waveguide of finite surface impedances are discussed. The analysis applies to corrugated waveguides, certain optical fibers and wave-guides with metal walls coated by a dielectric layer. It is shown that for k-->/spl infin/ the HE /sub 11/ mode has the following two properties: it is polarized in one direction and the field vanishes at the boundary. Because of these properties, it is useful in the design of microwave feeds, since it minimizes cross-polarization and edge illumination at the aperture. It is also useful for long distance communication because of its low attenuation constant. Both the far field of a feed and the attenuation constant are discussed. It is shown that rectangular apertures have negligible cross-polarization over wider bandwidth than circular apertures. Furthermore, if the medium inside a waveguide is Iossless, so that power is lost only at the boundary, then the attenuation constant is very small, it is asymptotic to (ka)/sup -2/ for large ka, where k= 2 pi/lambda and a is a characteristic dimension of the waveguide. A rectangular waveguide consisting of four metal plates coated with thin dielectric layers is shown to be attractive for long distance communication, because of its simplicity of fabrication and its low attenuation.
TL;DR: In this paper, simple approximate design equations are derived for an even degree (n /spl ges/ 6) low-pass inverter capacitance prototype filter having single transmission zeros at both real and imaginary frecuencies.
Abstract: Simple approximate design equations are derived in this paper for an even degree (n /spl ges/ 6) low-pass inverter capacitance prototype filter having single transmission zeros at both real and imaginary frecuencies. This is achieved by utilizing one or two additional couplings. The transmission zeros improve considerably the passband group delay and increase the skirt selectivity compared to those of the ordinary Chebyshev prototype. An exact and more complicated method based on the known generalized Chebyshev rational function approximation is also presented for the comparison. The prototype with one additional coupling is utilized to realize narrow-bandpass printed circuit filters consisting of half-wave resonators.
TL;DR: In this article, a dielectric waveguide is proposed for use in millimeter-wave integrated circuits, and a simple analysis for dispersion characteristics is developed, which agrees reasonably with measured data.
Abstract: A novel dielectric waveguide is proposed for use in millimeter-wave integrated circuits, and a simple analysis for dispersion characteristics is developed. Numerical results agree reasonably with measured data. Radiation loss of this waveguide at curved sections are proven to be considerably Iess than those of the image guide. As an application of this waveguide, a leaky-wave radiator has been tested.
TL;DR: In this paper, an accurate variational treatment of the diffraction of TE and TM waves by an abrupt transverse discontinuity in a dielectric waveguide, such as the mirror of a double heterostructure (d.h.) injection laser, or the end plane of an antenna for millimeter waves, under the assumption of small aspect ratio was presented.
Abstract: This paper presents an accurate variational treatment of the diffraction of TE and TM waves by an abrupt transverse discontinuity in a dielectric waveguide, such as the mirror of a double heterostructure (d.h.) injection laser, or the end plane of a dielectric slab antenna for millimeter waves, under the assumption of small aspect ratio. A matrix representation of the Green's function is derived analytically, in the limit of small efective frequency, for the TE case. For the TM case, the complication introduced by the discontinuity of the transverse electric field across the dielectric interface is discussed in detail. The numerical examples refer to the d.h. laser configuration. Both transverse directions (perpendicular as well as parallel) to the junction are studied. The effect of mode coupling at the mirror of a LOC laser as well as the effect of an antireflection coating are investigated.
TL;DR: In this paper, an integral equation formulation of the problem in terms of the transverse dyadic Green's function and expanding the fields irradiated by a short dipole was employed to solve the integral equations.
Abstract: Analysis of the near-field irradiation of prolate spheroidal models of humans and animals by a short electrical dipole is described. The method of solution involves an integral equation formulation of the problem in terms of the transverse dyadic Green's function and expanding the fields irradiated by a short dipole in terms of the vector spherical harmonics. The extended boundary condition method (EBCM) is employed to solve the integral equations. The power distribution and the average specific absorption rate (SAR) are calculated and plotted as a function of the separation distance. It is shown that for a dipole placed along the major axis of the spheroidal (k-polarization), and for a very short separation distance, d= 0.15 lambda, the relative power values at both ends of the spheroid are about 40 compared with the ratio of 15 in the planewave exposure case. Furthermore, the calculated average SAR values as a function of the separation distance were found to oscillate around the constant value obtained from the planewave irradiation case. Differences between the near-and far-field exposure cases occurred only at separation distances shorter than 0.5 lambda where the magnitudes of the electric and magnetic energy densities are higher than the time-average radiation power density.