Showing papers by "University of Electronic Science and Technology of China published in 1991"
Patent•
17 Sep 1991TL;DR: In this article, the CB-layer was introduced, where two kinds of semiconductor regions with opposite types of conduction are alternatively arranged, viewed from any cross-section parallel to the interface between the layer itself and the n + (or p + )-region.
Abstract: A semiconductor power device wherein the reverse voltage across the p + -regions(s) and the n + -regions(s) is sustained by a composite buffer layer, shortly as CB-layer. The CB-layer contains two kinds of semiconductor regions with opposite types of conduction. These two kinds of regions are alternatively arranged, viewed from any cross-section parallel to the interface between the layer itself and the n + (or p + )-region. Whereas the hitherto-used voltage sustaining layer contains only one kind of semiconductor with single type of conduction in the same sectional view. Design guidelines are also provided in this invention. The relation between the on-resistance in unit area Ron and the breakdown voltage V B of the CB-layer invented is Ron ocV B 113 which represents a breakthrough to the conventional voltage sustaining layer, whereas the other performances of the power devices remain almost unchanged.
517 citations
01 Aug 1991
TL;DR: In this paper, a new approach was proposed for numerical solution of integral equations describing transient scattering problems, where the idea is to first discretise in space, and then solve the resulting system of linear time-domain equations by carrying out a temporal Laplace transformation.
Abstract: A new approach was recently proposed for the numerical solution of integral equations describing transient scattering problems The idea is to first discretise in space, and then solve the resulting system of linear time-domain equations by carrying out a temporal Laplace transformation This approach combines the efficiency of the marching-on-in-time method with the stability and the accuracy of frequency-domain techniques The repeated solution of the Laplace-transformed system of linear equations thus obtained with the aid of iterative technique is considered Initial estimates are generated by marching-on-in-frequency and using a new extrapolation scheme The feasibility of this idea is demonstrated by solving electric-field integral equations for the total current along a straight thin-wire segment and the current density along a perfectly conducting cylinder
28 citations
TL;DR: In this article, anodic spark-deposited α-alumina films were reanodized in either borax aqueous solution or sulfuric acid solution for a short time to form an effective barrier layer at the pore base.
Abstract: α-Alumina films formed by anodic spark deposition in the melt of NaHSO4-KHSO4 mixture (200°C) exhibited a porous structure. It has been found that the porosity and amount of α-phase varied with anodic current density. By electrical measurements, films were found to exhibit a continuous open-pore structure, causing failure of humidity sensors. This problem can be overcome by reanodization of the anodicspark-deposited alumina films in either borax aqueous solution or sulfuric acid solution for a short time to form an effective barrier layer at the pore base. The modified anodic-spark-deposited alumina films showed highly sensitive response to water vapor change in the range of −76° to +20°C dew point with much improved long-term stability. The humidity characteristics of the α-alumina films were qualitatively explained in terms of the BET theory and condensation theory.
17 citations
TL;DR: In this article, the electrical properties of Sr0.5Ba0.3TiO3 in the presence of Nb2O5 as a donor, 3Li2O · 2SiO2 as a sintering agent, and Bi2O3 as a dopant have been studied.
Abstract: The electrical properties of Sr0.5Ba0.3TiO3 in the presence of Nb2O5 as a donor, 3Li2O · 2SiO2 as a sintering agent, and Bi2O3 as a dopant have been studied. When the compositions of the ceramics were 1 mol Sr0.7Ba0.3TiO3+ 0.5 mol% Nb2O5+ 2 mol% 3Li2O · 2SiO2+ 0.2 mol% Bi2O3, the ceramics were sintered at 1100°C and exhibited the following characteristics: apparent dielectric constant ɛ, 25000; loss factor tan δ, 2%; insulating resistivity ρj, 1010Ω· cm; variation of dielectric constant with temperature Δɛ/ɛ (−25° to +85°C), +10%, −14%. ɛ and tan δ show only small changes with frequency. The study shows this ceramic can be used in multilayer technology.
16 citations
01 Oct 1991
TL;DR: In this paper, a new method of constructing the projection matrix for array processing, using a uniform linear array in the single snapshot case, is presented, which is computationally simple, independent of the coherence of signal sources and beneficial to real-time processing.
Abstract: In the paper, a new method of constructing the projection matrix for array processing, using a uniform linear array in the single snapshot case, is presented. The method is computationally simple, independent of the coherence of signal sources and beneficial to real-time processing. Good performance can be obtained when the signal-to-noise ratio (SNR) is high. Simulation results show the effectiveness of the new method.
11 citations
TL;DR: A fast algorithm is presented which computes the two-dimensional Hartley transform using the decimation in frequency decomposition and, due to its in-place property, it does not require midmemory devices or matrix transposition.
Abstract: A fast algorithm is presented which computes the two-dimensional Hartley transform. This algorithm is referred to as the split vector radix algorithm. It uses the decimation in frequency decomposition and, due to its in-place property, it does not require midmemory devices or matrix transposition. Its computational structure is simpler than that of the algorithm of L.Z. Chen (1983), and it is easy to program. Compared with the vector radix algorithm of R. Kumaresan and P.K. Gupta (1986), the proposed algorithm saves about 35% of the multiplication and 10% of the additions for the discrete Fourier transform (DFT) of a 4096*4096 real valued input sequence. >
10 citations
Patent•
06 Nov 1991TL;DR: In this article, a power semiconductor device contains a withstand voltage region between P+ and N+ regions and features that two kinds, other than one kind, of conducting materials are alternatively arranged to form a composite buffer layer (CB layer) as the withstand voltage regions.
Abstract: This power semiconductor device contains a withstand voltage region between P+ and N+ regions and features that two kinds, other than one kind, of conducting materials are alternatively arranged to form a composite buffer layer (CB layer) as the withstand voltage region. This invention also discloses a design specification for the composite buffer layer with different pattern. Such device has solved the contradiction between the improvement of conducting resistance and the withstand voltage for electronic devices.
8 citations
TL;DR: Fintushel and Stern as mentioned in this paper used equivariant Yang-Mills theory to define an invariant for Seifert-fibered homology spheres which, if positive, shows that the homology sphere cannot bound a Z 2-acyclic 4-manifold.
7 citations
TL;DR: In this article, a comparison of the temperature distribution along the full thermal path, including the active region, the substrate and the heat sink in an operating vertical double-diffusion MOS transistor (VDMOS), obtained by using a lumped thermal element model with a complete 2D numerical simulation by solving the heat flow and electrical current equations as well as Poisson's equation.
Abstract: This paper presents a comparison of the temperature distribution along the full thermal path, including the active region, the substrate and the heat sink in an operating vertical double-diffusion MOS transistor (VDMOS), obtained by using a lumped thermal element model with a complete 2-D numerical simulation by solving the heat flow and electrical current equations as well as Poisson's equation. The results from two approaches are shown to be in good agreement.
6 citations
TL;DR: In this paper, a dielectric structure of multi-layers, resting on an earthed plane in a uniform perpendicular field, has been developed for the special case of a simple conducting sphere, which is used to check the value of the field strength at the top of the sphere.
6 citations
TL;DR: In this paper, the radiation emitted by an elementary time-harmonic current placed vertically and in parallel in a chiral half-space bounded by a perfect conductor was studied using an exact formulation.
Abstract: The radiation emitted by an elementary time-harmonic current placed vertically and in parallel in a chiral half-space bounded by a perfect conductor is studied using an exact formulation. It is found that the coupled image principle holds for both cases.
01 Oct 1991
TL;DR: In this paper, a new method of complex ray expansion was employed to calculate the radar crosssection for hollow-pipe type targets with large apertures, such as engine intakes.
Abstract: A new method of complex ray expansion is employed to calculate the radar crosssection (RCS) for hollow-pipe type targets with large apertures, such as engine intakes. As a typical model, a curved hollow duct is analysed. The effectiveness and accuracy of the method can be verified from the investigation.
TL;DR: Numerical results for three complicated structures show that the developed CAD software is accurate, practical, and general.
Abstract: The analysis of the APTL has been completed by using a new, general recurrence matrix technique based on the method of lines. This new technique has laid the foundations for the analysis of the new type of planar structures. Numerical results for three complicated structures show that the developed CAD software is accurate, practical, and general.
TL;DR: In this article, a dual six-port network analyzer is employed to measure the scattering parameters of a transmission line filled with the material to be tested, and the measured data of the sixport ANA and the HP8510B agree well with each other by comparison.
Abstract: A six-port technique is presented for simultaneous measurement of complex permittivity and permeability of a given material. A dual six-port network analyzer is employed to measure the scattering parameters. The complex permittivity and permeability are computed from the scattering parameters of a transmission line filled with the material to be tested. Measured ϵr, μr, data for Teflon agree well with known values. The identical samples are measured with a six-port ANA and an automatic network analyzer, HP8510B. The measured data of the six-port ANA and the HP8510B agree well with each other by comparison.
01 Jan 1991
TL;DR: In this article, a modified nonlinear Schrodinger equation (MNLSE) was derived from the Maxwell equations in a nonlinear medium with the derivative-expansion procedure in the method of multi-scalesingular perturbation.
Abstract: A modified nonlinear Schrodinger equation (MNLSE), which is defined as the equationobtained by putting some higher-order terms (the higher-order dispersion and nonlinearity)into a nonlinear Schrodinger equation (NLSE), has been derived from the Maxwell equationsin a nonlinear medium with the derivative-expansion procedure in the method of multi-scalesingular perturbation. Meanwhile its two equivalent expressions are given. First, the firstfourth-order perturbed equations of the Maxwell equations in a source-free nonlinear mediumwaveguide are obtained. Then, in the special case of the monomode waveguide, the third-or-der perturbed equation solution is the NLSE, and the fourth-order one is MNLSE. Carefulinvestigation shows that the MNLSE obtained with the reductive perturbation technique (Y.Kodama and A. Hasegawa, IEEE J. Quantum Electron, QE-23(1987), 510)should be corrected.
TL;DR: In this article, the dyadic Green's function in the Fourier transform spectral domain for a microstrip patch on an anisotropic substrate in a shielding rectangular waveguide is presented, and numerical data for resonant frequencies are provided using Galerkin's method in the spectral domain and Parseval's theorem.
Abstract: The dyadic Green's function in the Fourier-transform spectral domain for a microstrip patch on an anisotropic substrate in a shielding rectangular waveguide is presented. Numerical data for resonant frequencies are provided using Galerkin's method in the spectral domain and Parseval's theorem.
TL;DR: In this paper, the dispersion characteristics of the dominant mode in the suspended slotlines on magnetized ferrite and anisotropic dielectric substrates have been obtained by applying the transverse equivalent transmission line in the spectral domain and the Galerkin method.
Abstract: The dispersion characteristics of the dominant mode in the suspended slotlines on magnetized ferrite and anisotropic dielectric substrates have been obtained. The solution is obtained by applying the transverse equivalent transmission line in the spectral domain and the Galerkin method. Numerical results are presented which could be used in designing directional couplers and isolators.
TL;DR: Using a back-to-back rectangular waveguide-fin-line transition, the influence of mounting grooves and serration patterns of fin-lines on the transmission characteristics was investigated experimentally as mentioned in this paper.
Abstract: Using a back-to-back rectangular waveguide-fin-line transition, this paper investigates experimentally the influence of mounting grooves and serration patterns of fin-lines on the transmission characteristics. The experimental results are useful to design the rectangular waveguide-fin-line transition and other fin-line circuits.
01 Nov 1991
TL;DR: Wang et al. as discussed by the authors described the preparation of PbTiO3 thin film by DC single-target magnetron reactive sputtering, which hasn't been reported yet up to now in China and abroad.
Abstract: Preparation of PbTiO3 thin film by DCsingle-target magnetron sputteringYang Bangchao Wang Juyong Jia Yuining and Huang YongliMAterial Science and Engineering Department University ofElectronic Science and Techno1or of ChinaChengdu, 61 0054 China)This paper describes the preparation of PbTiO3 thin film by DC single-target magne—tron reactive sputtering, which hasn't been reported yet up to now in China and abroad.After many experiments the best Pb/Ti area ratio of the target has been found under aspecified sputtering condition. The samples obtained are heat—treated to 600°C and theX-ray diffraction patterns of them are observed. The authors have succeeded in prepari-ng almost transparent and light yellow perovskite—type PbTiO3 with resistivity of 1O'cm
TL;DR: In this article, it was shown that Riblet's results break down when the inner conductor becomes a strip, and the solution of the rectangular coaxial line with a general cross-inner conductor was proposed.
Abstract: The structure of the rectangular coaxial line is of simple symmetry: however, its exact analysis is difficult. Riblet solves this problem by making use of the degenerate Ryperelliptic integral [3]. Here we point out that his results break down when the inner conductor becomes a strip. We solve this latter case and offer the solution of the rectangular line with a general cross-inner conductor.
TL;DR: In this paper, a circular coaxial line with a cross of unequal arms as the inner conductor is presented, and two parameters at their disposal to adjust the line characteristics more freely.
Abstract: Presented here is a circular coaxial line with a cross of unequal arms as the inner conductor to enable us to have two parameters at our disposal to adjust the line characteristics more freely.
TL;DR: In this article, the angular spectrum of an antenna horn in the Fresnal region is decomposed into plane waves with the fast Fourier transform algorithm and the waves diffracted from a reflection grating are superposed as a diffracted beam.
Abstract: According to the angular-spectrum method, a radiation beam of an antenna horn in the Fresnal region is decomposed into the plane waves with the fast Fourier transform algorithm and the waves diffracted from a reflection grating are superposed as a diffracted beam. Compared with the reflected beam from the same size mirror, the radiation half width of the diffracted beam from a grating is narrower and its lateral shape is shift. These performances have been experimentally verified at Ka-band by: (1). The relative diffraction efficiencies in the first order with two triangular gratings which is put along propagating direction of a beam produced by a conical lens-horn. (2). H-plane lateral width with power—3dB lapsed of the focus beam from a grating and a mirror in a grating spectrometer for millimeter waves (25–100 GHz).
TL;DR: In this paper, an electric dipole located along an arbitrary direction in the presence of a chiral slab is formulated using matrix analysis in conjunction with Fourier transform techniques, and the dyadic Green's function of such a structure may be determined for further investigation.
Abstract: Radiation of an electric dipole located along an arbitrary direction in the presence of a chiral slab is formulated using matrix analysis in conjunction with Fourier transform techniques. Moreover, dyadic Green's function of such a structure may be determined for further investigation porpose.
TL;DR: In this article, anodic spark-deposited α-alumina films were reanodized in either borax aqueous solution or sulfuric acid solution for a short time to form an effective barrier layer at the pore base.
Abstract: α-Alumina films formed by anodic spark deposition in the melt of NaHSO4-KHSO4 mixture (200°C) exhibited a porous structure. It has been found that the porosity and amount of α-phase varied with anodic current density. By electrical measurements, films were found to exhibit a continuous open-pore structure, causing failure of humidity sensors. This problem can be overcome by reanodization of the anodicspark-deposited alumina films in either borax aqueous solution or sulfuric acid solution for a short time to form an effective barrier layer at the pore base. The modified anodic-spark-deposited alumina films showed highly sensitive response to water vapor change in the range of −76° to +20°C dew point with much improved long-term stability. The humidity characteristics of the α-alumina films were qualitatively explained in terms of the BET theory and condensation theory.
TL;DR: In this paper, the radiation loss formula in planar waveguides with graded-index profile is given and some numerical results for the bending loss in bent step-index slab waveguiders are shown and compared with other previous work.
Abstract: In this paper, the radiation loss formula in bent planar waveguides with graded-index profile is given and some numerical results for the bending loss in bent step-index slab waveguides are shown and compared with other previous work.
TL;DR: It is shown that the techniques of the phase and amplitude control of SAR patterns result in more selectively and effectively heating of tumors situated eccentrically and deeply within bodies of patients.
Abstract: This paper discusses a type of annular phased array system--H-Horn APA. The phase and amplitude control of power deposition patterns for this system are theoretically analyzed at a frequency of 200 MHz. The formulas for calculating E-field and SAR for this APA system are derived, and can be applied to other type APA systems. Models of computerized tomography (CT) scans from liver and lung regions have been used, respectively, for predicting optimization of E-field and SAR patterns in the case of the relative phase and amplitude changes. It is shown that the techniques of the phase and amplitude control of SAR patterns result in more selectively and effectively heating of tumors situated eccentrically and deeply within bodies of patients. The APA hyperthermia described in this paper shows great promise, and it looks very useful for developing clinical applications.
TL;DR: In this article, the main section of a broadband TEM cell (BTEM cell) can be mapped into a cylinder via conformal transformation in three dimensions, and the outer conductor is approached by using an upper rectangular conductor from above and by a lower rectangular conductor from below; then the maximum and minimum values of characteristic impedance are calculated.
Abstract: The main section of a newly appearing broadband TEM cell (BTEM cell) can be mapped into a cylinder via conformal transformation in three dimensions. Its outer conductor is approached by using an upper rectangular conductor from above and by a lower rectangular conductor from below; then the maximum and the minimum values of characteristic impedance are calculated. The average of the two extreme values is in good agreement with the actual characteristic impedance when the flared angles is small.
TL;DR: In this article, the authors developed a general multilayer dielectric sphere model in the toroidal coordinates and gave the analytical electrostatic solution when it is excited by a uniform field.
Abstract: We develop a general multilayer dielectric sphere model in the toroidal coordinates and give the analytical electrostatic solution when it is excited by a uniform field. The special case of the electrostatic result of an incomplete conducting sphere can be obtained simply. It is in agreement with the published result. We have also found that the coating dielectric film on the conducting sphere surface can remarkably reduce distortion on the external homogeneous field when the normalized dielectric constant is from 1–5.
TL;DR: In this paper, the special cases of a general coaxial rectangular line with square outer conductor and inner cross conductor of equal arms are solved analytically by means of conformal transformations.
Abstract: The special cases of a general coaxial rectangular line with square outer conductor and inner cross conductor of equal arms are solved analytically by means of conformal transformations.