Showing papers by "University of Electronic Science and Technology of China published in 1994"
TL;DR: In this article, the ϵ in PCM/PVDF matrix exhibits a broad relaxation peak at about 1KHz and it is possible that this is due to the αc relaxation of the polymer.
Abstract: 0-3 composite film of ferroelectric ceramics PCM and PZT in the matrix of a PVDF polymer has been studied in detail. The experimental results show that ϵ in PCM/PVDF and PZT/PVDF exhibits a broad relaxation peak at about 1KHz. It is possible that this is due to the αc relaxation of the polymer. Piezoelectric coefficient (d33, g33) of PCM/PVDF and PZT/PVDF were increased with weight fraction of ceramics from 40% to 80%. It was found that piezoelectric properties of PCM/PVDF were larger than that of PZT/PVDF, and the figure of merit in PCM/PVDF composite was highest about 15600.
28 citations
23 citations
TL;DR: In this paper, the frequency-domain impedance boundary condition used for a thin layer coating over perfect conductors is transformed to a time-domain boundary condition (TDIBC) for the case of ablique incident perpendicular-polarization plane wave, resulting in a partial differential equation in space and time.
Abstract: In this article, the frequency-domain impedance boundary condition used for a thin layer coating over perfect conductors is transformed to a time-domain impedance boundary condition (TDIBC) for the case of ablique incident perpendicular-polarization plane wave, resulting in a partial differential equation in space and time. Discretization of the TDIBC to effeciently handle the thin layer coating is presented in the context of the time-domain finite-difference (TDFD) technique. The TDFD solutions using our TDIBC are in good agreement with the analytical results. © 1994 John Wiley & Sons, Inc.
13 citations
TL;DR: In this paper, X-ray diffraction and electrical and diamagnetic analyses revealed that the 2223 phase was significantly enhanced by high-valence cation doping in BiSrCaCuO samples.
9 citations
TL;DR: In this paper, the interaction between electron beam and wave field of high harmonic gyrotron with inner slotted coaxial structure is analyzed and calculated in the presence of a cusp-injected system, beam voltage and length of resonator.
Abstract: The interaction between electron beam and wave field of high harmonic gyrotron with inner slotted coaxial structure is analysed and calculated in this paper. The optimum interaction efficiency is numerically illustrated for the 8th cyclotron harmonic TE81 π-mode atf0 = 35GHz. The influence of electron velocity distribution in cusp-injected system, beam voltage, and length of resonator on the efficiency is taken into consideration in numerical calculation. The results show that the inner slotted coaxial structure is good for an increase in the interaction efficiency.
5 citations
TL;DR: In this paper, a new technique for permittivity measurements of lossy dielectrics is presented based on the measurements of backscattering cross section and linear deviation (angular glint) of a two-point target, consisting of a conducting sphere with a dielectric one or a conducting one coated by the material under test.
Abstract: A new technique for permittivity measurements of lossy dielectrics is presented. It is based on the measurements of backscattering cross section and linear deviation (angular glint) of a two-point target, consisting of a conducting sphere with a dielectric one or a conducting one coated by the material under test. Because the linear deviation is proportional to the derivative of phase versus aspect angle, this technique overcomes the difficulty encountered in accurately measuring the phase in free space. Moreover, the choice of spherical targets, makes positioning less critical. The effectiveness of such a technique is verified by numerical simulations and measurements. © 1994 John Wiley & Sons, Inc.
5 citations
TL;DR: In this article, a new method for designing a directional coupler form the TE0, mode in a circular waveguide to the TE10 mode in rectangular waveguide is presented, which is used to design a 50 dB coupler for use in the sampling measurements of a very high power gyroklystron.
Abstract: A new method for designing a directional coupler form the TE0, mode in a circular waveguide to the TE10 mode in a rectangular waveguide is presented. This method is used to design a — 50 dB coupler for use in the sampling measurements of a very high power gyroklystron. By varying the rectangular waveguide size the suppression of the unwanted circular modes except the TE11 mode can be increased and by modifying the distance between the last two coupling holes the coupler directivity can be maximized. By using the coupling function φ(x) to make a second group of coupling holes we can greatly improve the suppression of the TE11mode. Some couplers with parameters d/2;100dB, p≳100 dB,p ≳100 dB for the TE11 mode and p > l0 dB for most of the other unwanted modes were designed by this method.
5 citations
TL;DR: In this paper, a transversely bianisotropic uniaxial medium, a generalization of the well-studied chiral material, can be fabricated by mixing metal helices in an isotropic host medium in such a way as to have the axes of all helices randomly oriented but perpendicular to a fixed direction.
Abstract: The transversely bianisotropic uniaxial medium, a generalization of the well-studied chiral material, can be fabricated by mixing metal helices in an isotropic host medium in such a way as to have the axes of all helices randomly oriented but perpendicular to a fixed direction. In the present consideration, based on the concept of characteristic waves and the method of angular spectral expansion, field representations in this class of medium are developed. The analysis reveals that the solutions of source-free Maxwell's equations for transversely bianisotropic uniaxial medium can be expressed in sum-integral forms of circular cylindrical vector wave functions. The addition theorem of vector wave functions for transversely bianisotropic uniaxial medium can be straightforwardly derived from that of vector wave functions for isotropic medium. Applications of the proposed theory to electromagnetic scattering are presented.
5 citations
TL;DR: In this paper, a methodology for the analysis of superconductive interconnects is described, where the time-domain impedance boundary condition (TDIBC) of a superconductor is obtained from its frequency-domain counterpart.
Abstract: A methodology is described for the analysis on superconductive interconnects. First, the time-domain impedance boundary condition (TDIBC) of a superconductor is obtained from its frequency-domain counterpart. Next, discretization of the TDIBC is presented in the context of the finite-difference—time-domain (FDTD) technique. The FDTD solutions for a superconductive parallel-plate transmission line are in good agreement with the exact solutions. Finally, the transmission property of a superconductive via is analyzed by the FDTD method. © 1994 John Wiley & Sons, Inc.
4 citations
TL;DR: An alternative wave-function theory based on the spline approximation of the undetermined angular-spectrum amplitudes in homogeneous anisotropic media is developed and is applicable to scalar, vector, and tensor fields in homogeneity anisotrop media and any bounded coordinate systems.
Abstract: An alternative wave-function theory based on the spline approximation of the undetermined angular-spectrum amplitudes in homogeneous anisotropic media is developed. The scattering of a scalar wave by an anisotropically coated cylinder is considered as an illustrative example. Numerical results for a bi- static radar cross section are presented for both transverse electric and transverse magnetic polarizations to validate our wave-function theory. The present method is applicable to scalar, vector, and tensor fields in homogeneous anisotropic media and any bounded coordinate systems.
3 citations
TL;DR: In this article, the magnetic-wall approximation for their slots, shielded coplanar waveguides (SCPWs) and semienclosed CPWs (SECPWs) are analyzed through an intensive use of elliptic function transformation.
Abstract: On the magnetic-wall approximation for their slots, shielded coplanar waveguides (SCPWs) and semienclosed CPWs (SECPWs) are analyzed through an intensive use of elliptic function transformation. CAD-oriented formulas for the quasi-TEM parameters of SCPWs and SECPWs, including their coupled versions, are derived. The comparison of the results calculated here with previous ones show 2% accuracy for formulas in the practical situation where the slots are not too wide, e.g., s / (s + 2w) ≥ 0.2 for an SCPW. © 1994 John Wiley & Sons, Inc.
TL;DR: The perturbed field by a dielectric sphere near a grounded plane bounding a uniform field is given so as to fill the gap between the solution of the case where the sphere was resting on the grounded plane and the case when the sphere is away from the ground plane.
Abstract: The perturbed field by a dielectric sphere near a grounded plane bounding a uniform field is given so as to fill the gap between the solution of the case where the sphere is resting on the grounded plane and the case where the sphere is away from the grounded plane We can now calculate the perturbed field when the sphere is located near the grounded plane The case of a conducting sphere is studied and used as a check
TL;DR: In this article, the frequency dependence of the RCS of an arbitrarily shaped simple scatterer is given, based on which model measurement of RCS can be made with testing equipment unchanged, even though the size of the model is sometimes scaled down with respect to that of the prototype.
Abstract: The frequency dependence of the RCS of an arbitrarily shaped simple scatterer is given, based on which model measurement of RCS can be made with testing equipment unchanged, even though the size of the model is sometimes scaled down with respect to that of the prototype. © 1994 John Wiley & Sons, Inc.
21 Dec 1994
TL;DR: In this article, a general model for target detection in clutter using multi-look multifrequency polarimetric SAR measurements only for the pixel under test is established, based upon this model, typical polarIMetric covariance matrix parameters at several bands are used to illustrate the procedures to optimize frequencies and polarizations.
Abstract: In this paper, we are investigating the optimization of frequencies and polarizations from the viewpoint of target detection in SAR images. Frequency and polarization diversity provided by multifrequency polarimetric SAR opens new ways for more robust detection of ground stationary man-made targets in complex clutter. Due to the scene inhomogeneity, the scattering characteristics of the area within each SAR resolution cell may be nonuniform. Each nonuniform pixel have multiple elementary scattering centers belonging to several classes. Radar returns for each pixel are contributions of the collective interactions of electromagnetric waves scattered by all scattering centers within the pixel. Multifrequency polarimetric measurements for each pixel makes it possible to decorrelate signals from different classes of scatterers within the resolution cell. For the general target-plus-clutter versus clutter case, in this paper is established a general model for target detection in clutter using multi-look multifrequency polarimetric SAR measurements only for the pixel under test. Based upon this model, typical polarimetric covariance matrix parameters at several bands are used to illustrate the procedures to optimize frequencies and polarizations for target detection in clutter.
TL;DR: A multiple-scattering formalism is developed for the determination of four effective parameters for bi-isotropic composites in the resonance range and the degenerative two- and three-effective-parameter cases are discussed in some detail.
Abstract: A multiple-scattering formalism is developed for the determination of four effective parameters for bi-isotropic composites in the resonance range. Two models, the truncated quasicrystalline approximation and the dynamic Maxwell-Garnett model, are presented to calculate the effective parameters of general discrete random composites. All the results recover the Maxwell-Garnett mixing formula at low frequency. The degenerative two- and three-effective-parameter cases are also discussed in some detail due to the practical importance of these composites and the requirement of the inherent unity of the formalism.
TL;DR: In this paper, the boundary value problem of an elliptical chirowaveguide is rigorously formulated by constructing the elliptical cylinder vector wave functions, and the influence of chirality parameter both on the propagation axial constant and on the attenuation constant, are illustrated for the first several modes.
Abstract: The boundary value problem of an elliptical chirowaveguide is rigorously formulated by constructing the elliptical cylinder vector wave functions. Influence of chirality parameter both on the propagation axial constant and on the attenuation constant, are illustrated for the first several modes. © 1994 John Wiley & Sons, Inc.
TL;DR: In this paper, high quality indium tin oxide (ITO) films were deposited on k9 glass in a dc magnetron triode system using reactive sputtering in Ar+O2 with a negative substrate bias.
TL;DR: In this paper, the current density inside the conductors of a lossy circular two-wire transmission line was analyzed under the quasi-TEM assumption, and the exact expressions for the ac resistance and internal inductance at an arbitrary frequency were derived.
Abstract: In this article, under the quasi-TEM assumption, through an exact electromagnetic field analysis, we give an analytic solution for the current density inside the conductors of a lossy circular two-wire transmission line, and finally obtain the exact expressions for the ac resistance and internal inductance at an arbitrary frequency. © 1994 John Wiley & Sons, Inc.
TL;DR: In this paper, the sintering and properties of non-ohmic SrTiO3 ceramics in the presence of Nb5+ as a donor dopant and Li+ as an acceptor dopant, were studied.
Abstract: The sintering and properties of non-ohmic SrTiO3 ceramics in the presence of Nb5+ as a donor dopant and Li+ as an acceptor dopant and sintering agent have been studied. Different sintering parameters, such as sintering temperature, sintering time, cooling rate, and the ambient atmosphere at the cooling stage, were investigated. The changes induced by each parameter on the electrical properties have been discussed. The segregation of lithium at the grain boundaries is mainly fulfilled at the cooling stage. The correct slow cooling rate and oxygen atmosphere are both favourable to the segregation of lithium at the grain boundaries, and thus result in an improvement of non-linear I–V characteristics. The lithium content and different lithium salts (Li2CO3, LiNO3, LiF) were also investigated.
TL;DR: In this paper, the Schwartz-Christoffel transformation is used to transform the charged conducting closed cylinder into an internal problem by making use of some symmetries, if any, of the field.
Abstract: Classical solutions to the charged conducting closed cylinder are external transformations of the closed boundary to a circle, or the real axis of another plane. By making use of some symmetries, if any, of the field, we can change this external into an internal problem by the Schwartz-Christoffel transformation, resulting in easier and better solutions.
TL;DR: In this article, the angular spectrum of spontaneous emission in a two-dimensional undulator free-electron laser is analyzed theoretically, and it is shown that the s-th harmonic spontaneous emission power density can be greatly enhanced by using a 2D undulator, for which l = s, so the harmonic number can be selected by selecting l.
Abstract: The angular spectrum of spontaneous emission in a two-dimensional undulator free-electron laser is analyzed theoretically. Numerical calculation shows that thes-th harmonic spontaneous emission power density can be greatly enhanced by using a two-dimensional undulator, for whichl=s, so the harmonic number can be selected by selectingl. Therefore, the higher harmonic operation of a free-electron laser can be realized selectively.
TL;DR: In this paper, the rotational degenerated coordinate system is employed to express the field in both series and integral form, which is convenient for numerical calculation, and the picture of images follows readily.
Abstract: The static problem of two contacting conducting spheres of different radii has been studied by many authors for many years, mainly from the physical intuition of electric images. In this paper we employ the rotational degenerated coordinate system to express the field in both series and integral form, which is convenient for numerical calculation, and the picture of images follows readily.
TL;DR: In this paper, the phase and frequency locking of microwave, millimeter wave power combining were analyzed and summarized in an all-round way, and the results of numerical calculations and the relations of phase to phase locking model and oscillator parameters were given.
Abstract: The phase and frequency locking of microwave, millimeter wave power combining were analysed and summarized in an all-round way. The master/slave phase locking of cavity oscillators, the peer phase locking of mutually coupled oscillators, and the peer phase locking of ring-connected multiple oscillators were investigated. The results of numerical calculations, and the relations of phase to phase locking model and oscillator parameters were given. And the cavity and space power combining aspects for microwave and millimeter wave were presented.
TL;DR: Based on the high frequency approximation theory, the complex ray expansion of plane wave is derived in this paper, and the results obtained may be regarded as the basis of the numerical expansion of the plane wave, which has been used successfully in some problems.
Abstract: Based on the high frequency approximation theory, the complex ray expansion of plane wave is derived. The results obtained may be regarded as the basis of the numerical expansion of plane wave, which has been used successfully in some problems.
TL;DR: It is proposed firstly that the original phase and the time-delay are the main factors which affect the measuring resolution of the multitone complex envelope method and three possible ways to eliminate these effects are given.
Abstract: It is proposed firstly that the original phase and the time-delay are the main factors which affect the measuring resolution of the multitone complex envelope method. The effects of these factors are analysed and checked by the computer simulation. Finally, three possible ways to eliminate these effects are given.
TL;DR: Using kinetic coupling mode theory of three waves, the effect of longitudinal momentum spread in ion-ripple laser (IRL), which is an advanced new scheme to generate tunable-coherent radiation with frequency ranging from microwaves to x-rays, is investigated in this paper, which shows that the growth rate of IRL falls off rapidly with increasing momentum spread, and the momentum spread causes linear damping of beam space charge wave, weakening the beam-radiation mode coupling and lowering the output radiation frequency apart from broadening the radiation spectrum.
Abstract: Using kinetic coupling mode theory of three waves, the effect of longitudinal momentum spread in ion-ripple laser (IRL), which is an advanced new scheme to generate tunable-coherent radiation with frequency ranging from microwaves to x-rays, is investigated. For a Gaussian distribution in beam longitudinal momentum, the results show that the growth rate of IRL falls off rapidly with increasing momentum spread, and the momentum spread causes linear damping of beam space-charge wave, weakening the beam-radiation mode coupling and lowering the output radiation frequency apart from broadening the radiation spectrum. The dispersion relation and phase matching conditions are also obtained.
TL;DR: Analysis approach and formulas for the transmission properties of uniform multiconductor interconnecting buses in high-speed integrated circuits are presented and a tapered bus system can be analyzed as a set of cascaded uniform buses with slightly different strip widths.
Abstract: Analysis approach and formulas for the transmission properties of uniform multiconductor interconnecting buses in high-speed integrated circuits are presented in this article. And further, by using a network approach, a tapered bus system can be analyzed as a set of cascaded uniform buses with slightly different strip widths. Obtained results are in good agreement with the experimental data.
TL;DR: In this paper, the relationship between received laser power and the product of the signal noise ratio and the bandwidth of the receiver is derived, and their corresponding curves are given, thus facilitating operation mode comparison and performance determination.
TL;DR: The linear relationship between Doppler centroid and range walking in spaceborne SAR data is analyzed, and a new method, so called amplitude correlation method, is proposed, which has much less computation burden and is able to give higher estimation accuracy for a quasi-Homogeneous scene or a non-homogeneous scene.
Abstract: The linear relationship between Doppler centroid and range walking in spaceborne SAR data is analyzed, and a new method to estimate Doppler centroid is proposed, which is so called amplitude correlation method. Compared with clutter-lock method which is widely used now, the new method has much less computation burden and is able to give higher estimation accuracy for a quasi-homogeneous scene or a non-homogeneous scene. This is clearly verifled by the experimental results of estimating Doppler centroid for SEaSAT-A raw data.
TL;DR: In this paper, a new millimeter-wave microstrip Gunn oscillator is introduced, consisting of fin line and microstrip with microstrip as the output-port transmission line, which can be mechanically frequency tuned.
Abstract: The frequency of a microstrip oscillator is difficult to tune. A new millimeter-wave microstrip Gunn oscillator is introduced in this Letter. Consisting of fin line and microstrip with microstrip as the output-port transmission line, this Gunn oscillator can be mechanically frequency tuned. A Ka-band oscillator of this structure is developed. The tuning bandwidth of this oscillator can reach 7.5 GHz or more with an output power of more than 70 mW. © 1994 John Wiley & Sons, Inc.