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Showing papers in "IEEE Transactions on Microwave Theory and Techniques in 1990"


Journal ArticleDOI
TL;DR: In this article, a robust algorithm for permittivity determination at frequencies corresponding to integer multiples of one-half wavelength in the sample is presented, and an error analysis yielding estimates of the errors incurred due to the uncertainty in scattering parameters, length measurement, and reference plane position is presented.
Abstract: The transmission/reflection method for complex permittivity and permeability determination is studied. The special case of permittivity measurement is examined in detail. Robust algorithms for permittivity determination that eliminate the ill-behaved nature of the commonly used procedures at frequencies corresponding to integer multiples of one-half wavelength in the sample are presented. An error analysis yielding estimates of the errors incurred due to the uncertainty in scattering parameters, length measurement, and reference plane position is presented. Equations for determining complex permittivity independent from reference plane position and sample length are derived. >

963 citations


Journal ArticleDOI
TL;DR: In this article, a direct three-dimensional finite-difference time-domain (FDTD) method is applied to the full-wave analysis of various microstrip structures and antennas.
Abstract: A direct three-dimensional finite-difference time-domain (FDTD) method is applied to the full-wave analysis of various microstrip structures. The method is shown to be an efficient tool for modeling complicated microstrip circuit components and microstrip antennas. From the time-domain results the input impedance of a line-fed rectangular patch antenna and the frequency-dependent scattering parameters of a low-pass filter and a branch-line coupler are calculated. These circuits were fabricated and the measurements made on them are compared with the FDTD results and shown to be in good agreement. >

646 citations


Journal ArticleDOI
TL;DR: In this article, the performance of an optoelectronic terahertz (THz) beam system was described, where the transmitter operation was based on the repetitive, sub-picosecond laser excitation of a Hertzian dipole antenna embedded in a charged coplanar line.
Abstract: The performance of an optoelectronic terahertz (THz) beam system is described. The transmitter operation is based on the repetitive, subpicosecond laser excitation of a Hertzian dipole antenna embedded in a charged coplanar line. With this transmitter electromagnetic beams of 1/2 cycle THz pulses at a repetition rate of 100 MHz are produced. The associated optoelectronic receiver is gated in synchronism with the excitation of the transmitter by subpicosecond pulses from the same laser source. With this receiver, the 10-nW beams of THz pulses were observed with a signal-to-noise ratio greater than 10000:1. Several sources contributing to the noise of the receiver are discussed, together with ways to reduce them. With an integration time of 125 ms, a signal-to-noise ratio of 1 is obtained for a THz beam with an average power of 10/sup -16/ W. The receiver operates in the sampling mode and has a time resolution of 0.5 ps. >

488 citations


Journal ArticleDOI
TL;DR: In this article, a method of miniaturizing branch-line 90 degrees hybrid and 180 degrees rat-race hybrid was proposed, which utilizes combinations of short high-impedance transmission lines and shunt lumped capacitors.
Abstract: A method of miniaturizing branch-line 90 degrees hybrids and 180 degrees rat-race hybrids is proposed The method utilizes combinations of short high-impedance transmission lines and shunt lumped capacitors The hybrids were fabricated on GaAs substrates and the validity and effectiveness of the method were confirmed through experiments at 25 GHz and 11 GHz The fabricated hybrids demonstrate excellent design accuracy at high frequencies, with a circuit size that is more than 80% smaller than that of conventional hybrids These hybrids are particularly suitable for uniplanar MMICs where necessary shunt connections are easily made >

426 citations


Journal ArticleDOI
TL;DR: In this paper, a method to determine the broadband small-signal equivalent circuit of field effect transistors (FETs) is proposed based on an analytic solution of the equations for the Y parameters of the intrinsic device and allows direct determination of the circuit elements at any specific frequency or averaged over a frequency range.
Abstract: A method to determine the broadband small-signal equivalent circuit of field-effect transistors (FETs) is proposed. This method is based on an analytic solution of the equations for the Y parameters of the intrinsic device and allows direct determination of the circuit elements at any specific frequency or averaged over a frequency range. The validity of the equivalent circuit can be verified by showing the frequency independence of each element. The method can be used for the whole range of measurement frequencies and can be applied to devices exhibiting severe low-frequency effects. >

357 citations


Journal ArticleDOI
TL;DR: In this paper, an approximate model based on measured probe impedances from 1 to 18 GHz with samples consisting of water, methanol, and dioxane-water mixtures is evaluated.
Abstract: Dielectric measurements using a probe consisting of a coaxial transmission line with an open-circuit end placed against the sample are discussed. For the 2.99- or 3.6-mm (OD) probes considered, a simple lumped parameter model shows errors above 1 GHz that increase greatly with frequency. An approximate model based on measured probe impedances from 1 to 18 GHz with samples consisting of water, methanol, and dioxane-water mixtures is evaluated. This model is more accurate than the lumped-parameter model and is better suited for calibration of the automatic network analyzer (ANA). The errors introduced in dielectric measurements by the use of approximate models for the probe are discussed. The technique succeeds because of partial cancellation of errors in modeling the probe in ANA-based measurements. >

241 citations


Journal ArticleDOI
TL;DR: In this paper, an analytic lumped-element small-signal models of directly and externally modulated analog fiber-optic links are derived and compared with the performances of these modulation techniques.
Abstract: Analytic lumped-element small-signal models of directly and externally modulated analog fiber-optic links are derived. Incremental modulation efficiency is defined and used to compare the performances of these modulation techniques. In experiments to optimize link RF-to-RF gain and noise figure, the measurements obtained agreed with calculations to within approximately=1 dB. The externally modulated link was operated with two different impedance matching circuits. With a low-pass match the bandwidth was 150 MHz, and the link transducer gain was 1 dB; with a bandpass match the bandwidth was 22 MHz, the link transducer gain was 11 dB, and the noise figure was 6 dB. The directly modulated link was operated with a low-pass match. In this case, the bandwidth was 1 GHz, the link transducer gain was -14 dB, and the noise figure was 33 dB. These experimental results were achieved with no amplification,. >

227 citations


Journal ArticleDOI
TL;DR: The use of optically controlled devices to perform a range of circuit functions is reviewed in this article, where the optical control of amplifier performance is discussed and future directions for research in this area are discussed.
Abstract: The use of optically controlled devices to perform a range of circuit functions is reviewed. The optical control of amplifier performance is discussed. The optical control of two- and three-terminal oscillators and optically pumped mixers is discussed. Among the active devices treated are Gunn and IMPATT oscillators; MESFET and HEMT amplifiers, oscillators, and mixtures; and diode mixers. Future directions for research in this area are discussed. >

217 citations


Journal ArticleDOI
TL;DR: In this paper, the impact of ground-to-ground spacing on dispersion and radiation losses in coplanar waveguides is investigated, and their effects on loss and dispersion are described.
Abstract: The coplanar waveguide (CPW) structure is subdivided into five classes based on substrate thickness, backside metallization, and ground plane width. Radiation and guided modes are studied in each class, and their effects on loss and dispersion are described. For coplanar waveguides, dispersion due to interaction with surface wave parallel-plate modes in the substrate strongly depends on the ground-to-ground spacing (W+2G). If this spacing is small compared to dielectric wavelength and substrate thickness, both dispersion and radiation losses are minimized. In finite ground plane cases, small ground-to-ground spacing compared to substrate thickness is necessary to avoid the excitation of the microstrip mode and to minimize the deviation of the CPW mode from the odd mode of the ideal line. Limitations on the reduction of (W+2G) come from conductor loss, which imposes a minimum width requirement on the center conductor. If substrate thickness is to be kept large compared with this dimension, it is inevitable that, at high frequencies, the operation of the CPW will not be below the cutoff frequency of surface wave modes. However, the interaction of the CPW mode with surface wave modes is negligible for integrated circuit applications when ground-to-ground spacing is small compared with dielectric wavelength. >

210 citations


Journal ArticleDOI
TL;DR: In this paper, a mode-matching analysis of lossy planar transmission lines is presented, where the metallic layers are treated in the same way as the remaining waveguide subregions, with each of them characterized by its complex dielectric constant.
Abstract: A mode-matching analysis of lossy planar transmission lines is presented. This method uses a modified mode-matching technique developed for travelling-wave FET analysis. The metallic layers are treated in the same way as the remaining waveguide subregions, with each of them characterized by its complex dielectric constant. This leads to a fully self-consistent description of the conductor losses. In contrast to the usual perturbation methods, it includes metallic loss by a self-consistent description without any skin-effect approximation. The analysis holds for arbitrarily high losses and also for metallization dimensions smaller than the skin depth. The approach is validated by comparison with previous experimental and theoretical work. Monolithic microwave integrated circuit (MMIC) microstrip and coplanar lines are investigated. The variation in propagation characteristics for typical metallization thickness is studied and the consequences with regard to MMIC design are discussed. For the coplanar waveguides (CPWs) significant deviations compared to the conventional assumption of lossless zero-thickness strips are found. >

188 citations


Journal ArticleDOI
Thomas E. Darcie1, G.E. Bodeep1
TL;DR: In this article, the design and performance of multichannel amplitude-modulated (AM) vestigial-sideband (VSB) lightwave cable television (CATV) systems are described.
Abstract: The design and performance of multichannel amplitude-modulated (AM) vestigial-sideband (VSB) lightwave cable television (CATV) systems are described. Requirements on linearity and noise are derived, and factors limiting the performance of the laser transmitters and receivers are discussed. For the high-performance lasers the carrier-to-noise ratio and composite second- and third-order distortions are acceptable for video trunk systems. Impairments because of fiber reflections and dispersion and mode partition fluctuations in the laser are discussed. Feedforward, feedback, and predistortion are discussed; difficulties with each prevent immediate application. The use of LiNbO/sub 3/ external modulators and high-power solid-state lasers is considered. The third-order distortion and insertion loss of the modulator more than counteract the high available laser power (100 mW), making this alternative unattractive unless a third-order linearizer can be implemented. >

Journal ArticleDOI
TL;DR: An efficient local mesh refinement algorithm, subdividing a computational domain to resolve fine dimensions in a time-domain-finite-difference (TD-FD) space-time grid structure, is discussed in this paper.
Abstract: An efficient local mesh refinement algorithm, subdividing a computational domain to resolve fine dimensions in a time-domain-finite-difference (TD-FD) space-time grid structure, is discussed. At a discontinuous coarse-fine mesh interface, the boundary conditions for the tangential and normal field components are enforced for a smooth transition of highly nonuniform held quantities. >

Journal ArticleDOI
TL;DR: In this article, a SPICE model for modeling GaAs MESFET devices more accurately is discussed, in particular small-signal parameters are accurately modeled over a wide range of bias conditions.
Abstract: A SPICE model for modeling GaAs MESFET devices more accurately is discussed. In particular, small-signal parameters are accurately modeled over a wide range of bias conditions. These results were achieved by modifying the model equations of H. Statz et al. (see IEEE Trans. Electron. Devices, vol.3, no.2, p.160-9, 1987) to better represent the variation of I/sub ds/ as a function of the applied voltage. The model applies over a large range of pinch-off voltages, allows size scaling of devices, and is suited for modeling R/sub ds/ changes with frequency. The Statz equations are used to represent diode characteristics and capacitive components of the model. >

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate the optical generation and transmission of a microwave signal by the mixing of two high-quality optical signals from diode-laser-pumped Nd:YAG ring lasers.
Abstract: Demonstrated is the optical generation and transmission of a microwave signal by the mixing of two high-quality optical signals from diode-laser-pumped Nd:YAG ring lasers, resulting in a narrow microwave line width (less than 5 kHz line width at 3 dB and less than -115 dBc/Hz at 300 kHz from line center) and broad microwave tunability (DC to 52 GHz). A III-V semiconductor waveguide with a doping superlattice active region is used to optoelectronically provide 20 dB of amplitude control and up to 5 pi of phase shift. This approach can be straightforwardly implemented using integrated optics and fiberoptic links for control of phased-array antenna elements. >

Journal ArticleDOI
TL;DR: In this paper, a numerical inversion of the Laplace transform is proposed for the analysis of lossy coupled transmission lines with arbitrary linear terminal and interconnecting networks. But the inversion technique is equivalent to high-order, numerically stable integration methods.
Abstract: A novel method based on numerical inversion of the Laplace transform is presented for the analysis of lossy coupled transmission lines with arbitrary linear terminal and interconnecting networks. The formulation of the network equations is based on a Laplace-domain admittance stamp for the transmission line. The transmission line stamp can be used to formulate equations representing arbitrarily complex networks of transmission lines and interconnects. These equations can be solved to get the frequency-domain response of the network. Numerical inversion of the Laplace transform allows the time-domain response to be calculated directly from Laplace-domain equations. This method is an alternative to calculating the frequency-domain response and using the fast Fourier transform to obtain the time-domain response. The inversion technique is equivalent to high-order, numerically stable integration methods. Numerical examples showing the general application of the method are presented. It is shown that the inverse Laplace technique is able to calculate the step response of a network. The time-domain independence of the solution is exploited by an efficient calculation of the propagation delay of the network. >

Journal ArticleDOI
TL;DR: In this article, the equivalent capacitances of coplanar waveguide discontinuities on multilayered substrates are calculated using a three-dimensional finite-different method, which can be applied to more complicated structures such as interdigitated capacitors, air bridges, and waveguide transitions.
Abstract: Equivalent capacitances of coplanar waveguide discontinuities on multilayered substrates are calculated using a three-dimensional finite-different method. The application of the method is demonstrated for open ends and gaps in microstrip and coplanar waveguides, as well as for more complicated structures such as interdigitated capacitors. The main advantage of the method is its flexibility in treating multilayered substrates and different conductor configurations. It can therefore be applied to more complicated structures such as interdigitated capacitors, air bridges, and waveguide transitions. The effect of conductor metallization thickness and shielding walls is also taken into account. Good agreement between the calculated data and measurements up to 25 GHz in the case of coplanar structures indicates the validity of the static analysis even for high frequencies. >

Journal ArticleDOI
TL;DR: In this article, a full-wave analysis of metal-insulator-semiconductor (MIS) structure micron coplanar transmission lines on doped semiconductor substrates is carried out using a finite-difference time-domain approach.
Abstract: A full-wave analysis of metal-insulator-semiconductor (MIS) structure micron coplanar transmission lines on doped semiconductor substrates is carried out using a finite-difference time-domain approach. Metal conductor loss is taken into account in the analysis. Line parameters and electromagnetic field distributions are calculated over a wide frequency range involving slow-wave and dielectric quasi-transverse-electromagnetic mode limits. Measurements of these line parameters, varying substrate resistivity from 1 to 1000 Omega -cm, in the frequency range up to 40 GHz are also presented, and these agree with the analysis quite well. On the basis of these results, an equivalent circuit line model is induced and some considerations on the relationship between line structure and properties made. >

Journal ArticleDOI
X. Yuan1
TL;DR: In this article, the hybrid moment and finite element methods are used to obtain 3D scattering and/or absorption from inhomogeneous, arbitrarily shaped objects, where the surface of an object is approximated by triangles and the volume of the object is estimated by tetrahedrons.
Abstract: The hybrid moment and finite element methods are used to obtain 3-D scattering and/or absorption from inhomogeneous, arbitrarily shaped objects. The surface of the object is approximated by triangles and the volume of the object is approximated by tetrahedrons. The electrical parameters are assumed constant in each tetrahedron. The Galerkin testing procedure is used. To avoid contaminations of spurious mode, a divergenceless vector basis function is used in finite elements. The calculated internal field and scattered field for a homogeneous sphere, a layered sphere, and a lossy prolate spheroid are compared with Mie series solutions and other numerical techniques. The accuracy and rate of convergence of the solution are discussed. >

Journal ArticleDOI
TL;DR: In this article, two techniques are presented for the analysis of electromagnetic radiation and scattering from finite microstrip structures, based on two different formulations, viz. the volume-surface and surface-surface formulations.
Abstract: Two techniques are presented for the analysis of electromagnetic radiation and scattering from finite microstrip structures. The two techniques are based on two different formulations, viz. the volume-surface and surface-surface formulations. In the volume-surface formulation the finite-sized dielectric is replaced by an equivalent volume polarization current whereas the conducting plates are replaced by equivalent surface currents. For the surface-surface formulation the surface covering the dielectric volume is replaced by equivalent electric and magnetic currents and the conducting plates by surface electric currents. Both techniques can be utilized for the analysis of arbitrarily shaped finite microstrip structures. The techniques are quite accurate, and they are utilized to validate each other. Typical numerical results are presented to demonstrate the agreement between these two solution techniques. >

Journal ArticleDOI
TL;DR: In this paper, the problem of modeling GaAs MESFETs for calculations of intermodulation and spurious responses is examined, and it is shown that an adequate model must express not only the absolute I/V characteristics of the device, but also the derivatives of those characteristics.
Abstract: The problem of modeling GaAs MESFETs for calculations of intermodulation and spurious responses is examined. It is shown that an adequate model must express not only the absolute I/V characteristics of the device, but also the derivatives of those characteristics. It is demonstrated that these derivatives are dominant in determining intermodulation levels, and that the common approaches to modeling MESFETs do not model those derivatives very well. Finally, a new model for the MESFET gate I/V characteristic (the dominant nonlinearity in most FETs) that is accurate through at least the third derivative is proposed. >

Journal ArticleDOI
TL;DR: In this article, an analysis of the AC resistance in a microstrip structure for any metallization thickness by deriving the current distribution over the strip cross section is presented, and the analysis uses the separation of variables technique and the Green's function method.
Abstract: The AC resistance of the strip in a microstrip structure is compared with that of an isolated strip for better understanding of the conductor loss mechanism. An analysis is presented of the AC resistance in a microstrip structure for any metallization thickness by deriving the current distribution over the strip cross section. The analysis uses the separation of variables technique and the Green's function method. It shows that the skin current of the strip is concentrated toward the ground plane in a microstrip structure. In the extreme case, the AC resistance of the strip can be twice as high as the AC resistance of the same isolated strip. The imperfect ground plane also adds to the total conductor loss of a microstrip line. For a wide strip over a lossy ground plane at high frequency, the ground plane surface current distribution is concentrated directly under the strip, and the ground plane AC resistance can be as large as the strip AC resistance. Therefore, the total AC resistance at the microstrip line can be four times as high as that of an isolated strip conductor. >

Journal ArticleDOI
TL;DR: In this paper, a technique for simultaneously measuring the real and imaginary parts of both the permittivity and the permeability of a given material is discussed, where a gap in a coaxial line is filled with the material under test, and the S-parameter (S/sub 11/ and S/sub 21/) measurement is made on the gap, taking into account higher-order modes excited at the discontinuity.
Abstract: A technique for simultaneously measuring the real and imaginary parts of both the permittivity and the permeability of a given material is discussed. A gap in a coaxial line is filled with the material under test. Complex permittivity and permeability are computed from the S-parameter (S/sub 11/ and S/sub 21/) measurement made on the gap, taking into account higher-order modes excited at the discontinuity. Measured epsilon /sub r/ and mu /sub r/ data for several materials are presented from 45 MHz up to 18 GHz. This technique shows good agreement between calculated and generally accepted values. >

Journal ArticleDOI
TL;DR: In this article, a review of phase and frequency synchronization of active MMIC based transmit/receive modules is presented, and particular emphasis is placed on the synchronization of oscillators through the use of an indirect subharmonic optical injection locking technique.
Abstract: A review of various methods of phase and frequency synchronization of active MMIC based transmit/receive modules is presented, and particular emphasis is placed on the synchronization of oscillators through the use of an indirect subharmonic optical injection locking technique. In this approach, the nonlinear behavior of large-signal modulated laser diodes and solid-state oscillators is exploited to extend the bandwidth of the synchronizing link to the millimeter-wave frequency range. Experimental results of the phase and frequency coherency of two 21.5 GHz FET oscillators are reported. Optimum performance is achieved at a subharmonic factor of 1/4, with a locking range of 84 MHz and a phase noise degradation of only 14 dB. The phase coherency measurement of two injection-locked oscillators points to a phase shift, which is introduced as a result of the frequency detuning between the slave and master oscillator signals. A scheme to correct for this phase error is presented. >

Journal ArticleDOI
TL;DR: In this article, a planar millimeter-wavelength whispering gallery dielectric resonator (DR) was used for the design of W-band directional filters and power combiners.
Abstract: The utilization of planar millimeter-wavelength whispering gallery dielectric resonator modes for the design of W-band directional filters and power combiners is studied. The device presented combines the output power of several millimeter-wavelength devices in a single step by means of whispering gallery dielectric resonator (DR) modes. At millimeter wavelengths the cylindrical DRs used on their conventional TE, TM, or hybrid modes are impractically small. When used in their whispering gallery modes (WGMs) these cylindrical DRs have dimensions larger than normal for millimeter wavelength. After a description of the WGM phenomena, both electromagnetic and circuit parameters of these resonators are defined when they are coupled with transmission lines. The analysis based on the ring resonator model makes it possible to predict the theoretical responses of any devices. Experimental results obtained for directional filters and for power combiners in W-band are given. >

Journal ArticleDOI
TL;DR: In this article, a numerical approach that aims to detect, by means of interrogating microwaves, the locations and the dielectric permittivities of unknown inhomogeneous cylindrical objects of arbitrary cross sections that might be present inside a fixed area of interest is proposed.
Abstract: A numerical approach that aims to detect, by means of interrogating microwaves, the locations and the dielectric permittivities of unknown inhomogeneous dielectric cylindrical objects of arbitrary cross sections that might be present inside a fixed area of interest is proposed. An illumination is assumed with the electric field vector polarized along the cylindrical axis. The two-dimensional Lippman-Schwinger integral equation of electromagnetic scattering is transformed into matrix form by the moment method. The system obtained is solved by using a pseudoinversion algorithm to overcome ill-conditioning problems. The first-order Born approximation is also applied when the dielectric inhomogeneities are weakly scattering. Computer simulations have been performed by means of a numerical program. Results show the capabilities and limitations of the proposed approach. >

Journal ArticleDOI
TL;DR: In this article, a generalization of the full vector finite-element formulation in terms of the electric and magnetic fields is proposed, where the necessary conditions on the tangential field components and the additional conditions on normal field components are automatically satisfied by the trial functions.
Abstract: Propagation analysis of chirowaveguides, i.e. waveguides including chiral media, are calculated using a generalization of the full vector finite-element formulation in terms of the electric and magnetic fields. The formulation permits numerous inhomogeneous waveguide structures of arbitrary linear composition, including chiral media, to be analyzed without any nonphysical, spurious modes. In the proposed formulation both the necessary conditions on the tangential field components and the additional conditions on the normal field components are automatically satisfied by the trial functions. In this way the dimension of the resulting sparse generalized eigenvalue problem is significantly reduced. The straightforward extension to the novel class of chirowaveguides, which exhibit a number of interesting new features, demonstrates the versatility of the formulation. The advantageous numerical properties are thus preserved. Numerical examples on both metal and dielectric chirowaveguides are given. The finite-element results are compared with exact solutions, and the correspondence is found to be excellent. >

Journal ArticleDOI
TL;DR: In this paper, a full-wave spectral-domain analysis is applied to the characterization of multiport microstrip discontinuities using the moment method to find the currents in the microstrip circuits and subsequently the scattering parameters of the junctions.
Abstract: A full-wave spectral-domain analysis is applied to the characterization of multiport microstrip discontinuities. This method uses the moment method to find the currents in the microstrip circuits and subsequently the scattering parameters of the junctions. In this approach, all the physical effects are considered, including radiation and surface waves. The numerical results for a T- and a cross-junction are presented and agree well with the quasi-static values at low frequencies. The S-parameters of a T-junction are further compared with the measured results, with excellent agreement. The utilization of a shaped T-junction as a broadband equal-power divider is also discussed. >

Journal ArticleDOI
TL;DR: In this paper, a time-domain network analyzer which uses optoelectronic techniques for on-wafer monolithic microwave and millimeter-wave integrated-circuit measurements is described.
Abstract: Progress in the application of ultrafast optics to microwave and millimeter-wave techniques using picosecond photoconductors is reviewed. The generation, control, and characterization of pulsed and high-frequency waves using a frozen wave generator, an impulse excited resonator, and a spectral filter are discussed. A time-domain network analyzer which uses optoelectronic techniques for on-wafer monolithic microwave and millimeter-wave integrated-circuit measurements is described. >

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the effect of different modes of low-frequency oscillation and the extrinsic circuit required for stabilization on high-frequency power generation of resonant tunneling diodes.
Abstract: Stability criteria for resonant tunneling diodes are investigated. Details of how extrinsic elements, such as series inductance and parallel capacitance, affect the stability are presented. A GaAs/AlAs/InGaAs/AlAs/GaAs double-barrier diode is investigated, showing the effect of different modes of low-frequency oscillation and the extrinsic circuit required for stabilization. The effect of device stabilization on high-frequency power generation is described. The main conclusions of the paper are: (1) stable resonant tunneling diode operation is difficult to obtain, and (2) the circuit and device conditions required for stable operation greatly reduce the amount of power that can be produced by these devices. >

Journal ArticleDOI
TL;DR: In this article, the authors proposed a leaky-wave antenna structure on partially dielectric-loaded open guiding structures, where the dispersion curve doubles back because it connects a complex nonspectral (leaky-wave) solution with a real spectral solution.
Abstract: Most modes on partially dielectric-loaded open guiding structures are purely bound in some frequency range and leaky in another. The transition region between them is complicated and interesting, including a section where the dispersion curve doubles back because it connects a complex nonspectral (leaky-wave) solution with a real spectral (bound-wave or surface-wave) solution. The physical nature of this type of transition region is discussed qualitatively, where some anomalous features are considered; then numerical values for a specific example, a recently proposed novel leaky-wave antenna structure, are presented. >