摘要:

AbstractBy combining a ferrite‐type electromagnetic wave absorber and a lossy dielectric layer, an electromagnetic wave absorber with a super wideband characteristic can be realized. In this paper, a grid‐type ferrite absorber and a rubber ferrite loaded ferrite multilayered absorber are treated as a ferrite‐type absorber. When a lossy dielectric material is mounted in front of these ferrite‐type wave absorbers, the thickness of a lossy dielectric layer necessary for realization of a return loss of more than 20 dB at any frequency above 30 MHz was computed. It was found that the thickness is much less than that for the lossy dielectric attached to a single layer ferrite. Further, by means of a model experiment in the coaxial tube, the thickness of the lossy dielectric layer was proven to be smaller if a lossy dielectric is combined with the grid‐type ferrite absorber loaded with rubbe

ISSN:8756-663X    

DOI:10.1002/ecjb.4420780201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractFor the X‐ray free electron laser using stimulated transition radiation in periodic stacks of metal foils or polymer films, the effects considered are those that are due to: (1) the space charge of the relativistic electron beam; (2) multiple scattering of the electron beam passing through the stacks; and (3) both the space charge and multiple scattering simultaneously. Taking these respective effects into account in a Boltzmann transport equation, dispersion relations are derived and gain coefficients of the laser are calculated and compared. As a result, it is found that the effect of multiple scattering is large and it depends also on the magnitude of the electron beam energy, e.g., for the case of 50 GeV, the gain coefficient is decreased by several dB. The effect of the space charge is relatively small. Also, the gain coefficient generally decreases with the beam energ

ISSN:8756-663X    

DOI:10.1002/ecjb.4420780202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractUsually, the Poynting vector is considered to be a vector field expressing the power flow. However, in many textbooks on electromagnetics the following statements are given which cause confusion: (a) since an arbitrary vector field with zero divergence can be added without violating the energy conservation law, the Poynting vector is not a unique expression for the power flow; and (b) the Poynting vector has nonzero value near a charged magnet. Since it cannot be accepted that a power flow exists in such a space, the Poynting vector may not represent a power flow.Such statements which cause confusion come from the education in which the relativistic aspects of electromagnetic theory have not been considered seriously. This paper is intended to contribute to the electromagnetic education and presents: (a) a clear explanation for the fact that the electromagnetic theory is essentially relativistic; (b) an explanation why the Nukiyama vector does not replace the Poynting vector; (c) general conditions to be satisfied by a vector which can be added to the Poynting vector; and (d) the basis on which we take the Poynting vector as the only expression for the power flow density.

ISSN:8756-663X    

DOI:10.1002/ecjb.4420780203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper reports the optical control of microwave and millimeter‐wave active integrated antennas in which MESFETs are used as the optical control elements. Two types of circuits have been fabricated in which the change of the reactance by the photovoltaic effect of the FET is used. In one of them, the MESFET is used as a passive element which controls the electrical length of the slot antenna by means of the reactance change by optical illumination. It was confirmed that the resonant frequency of this antenna changes by 100 MHz in the × band. In the other circuit, the MESFET used in the oscillator for the active integrated antenna is illuminated optically. An optical tuning range of 63 MHz was observed in the × band. Further, for the latter circuit, a MESFET large signal model was used and the change of the operating frequency was investigated under an assumption of the changes due to optical illumination in the equivalent circuit parameter. It was found that the total of the shifts near the operating frequency of 10 GHz was about 60 MHz if the gate‐source capacitance and the drain‐gate capacitance are increased by 10 percent Hence, these parameters have an important role in the optical control. In addition, an FET structure to obtain a larger optical control range has been

ISSN:8756-663X    

DOI:10.1002/ecjb.4420780204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe influence of oxidation of an Al‐Cr‐Ni‐Ag multilayer metallization on the adhesion of Sn‐5wt%Sb solder was investigated. Oxidation of the multilayer metallization prevents the solder from wetting the multilayer metallization uniformly. The nonuniform wetting of the solder caused localization of thermal stress on the wetted regions and promoted differential degradation of the regions.The interface between Ni and Ag was oxidized when exposed to air without cooling to a low temperature. The nickel oxide at the interface prevented the formation of metallurgical bonds between the multilayer metallization and the molten solder. In some interface regions where the molten solder eliminated the nickel oxide either chemically or physically, the solder wetted the multilayer metallization but did not wet in the regions where the nickel oxide was not eli

ISSN:8756-663X    

DOI:10.1002/ecjb.4420780205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe paper proposes a new method for improving spectral purity of a crystal oscillator. It is based on the concept that loadedQcan be improved by employing negative resistance circuits. LoadedQcan be higher than unloadedQof the crystal resonator because the negative resistance circuit compensates losses in feedback circuit of the oscillator. This paper also proposes a new method for evaluation of loadedQof oscillator circuit. Practical measurement ofQshows that the proposed approach for improving loadedQleads to better spectral purity of crystal oscillator output.

ISSN:8756-663X    

DOI:10.1002/ecjb.4420780206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractTo investigate the infl uence of electrode material on arc discharge, a dc 30‐V, 3‐ω resistive circuit was interrupted 30 times using an Ag, Cu, or Ag‐Cu combination electrode and the arc duration and optical spectra of light emitted from the arcing area nearby cathode were evaluated. Then, the relationship between the number of breaking operations and arc duration in the breaking arc and that between the number of breaking operations and some kinds of detected spectra and their intensity were investigated.The arc duration was longer when an Ag cathode was used than when a Cu cathode was used. When a Cu anode and Ag cathode combination was used, only the Ag spectrum was observed. When an Ag anode and Cu cathode combination was used, only the Cu spectrum was observed when there were few breaking operations. However, when there were many breaking operations, the Ag spectrum also was observed at the end of arcing. When the number of operations reached 30, the Ag spectrum also was observed at the beginning of arcing and its intensity was high.It is believed that the aforementioned phenomena are due to the vapor pressure difference between two materials, the difference between two breaking arc characteristics, and the volume of transferred ma

ISSN:8756-663X    

DOI:10.1002/ecjb.4420780207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractPlasma parameters of Ar/SiH4plasma were measured as a function of dc bias in a double‐tubed coaxial line‐type microwave plasma chemical vapor deposition (CVD) apparatus. The results indicate that it is possible to control the ion bombardment energy without affecting either the gas phase reaction or ion flux density incident to the substrate. Hydrogenated amorphous silicon films were deposited as a function of the ton bombardment energy and characteristics of the deposited films were investigated. The results indicate that the ion bombardment improves film density, bonding characteristics of hydrogen, and optical band gap but increases the concentration of dangling bonds due to Ar ion implantation. The ion bombardment not only causes the heating of the films but also induces sputtering and ion implantat

ISSN:8756-663X    

DOI:10.1002/ecjb.4420780208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe image sticking effect in a thin‐film transistor activated liquid crystal display (TFT‐LCD) was related to the transmittance drift caused by dc voltage applied to liquid crystal (LC) cells. Using the electrooptical property of LC, the transmittance drift was calculated based on the drift of the residual dc potential which causes the image sticking effect. The transmittance drift calculated using the experimental result of the residual potential shift agreed with the measured transmittance drift. It was concluded that this calculation method was effective in analyzing the image sticking effect of LC ce

ISSN:8756-663X    

DOI:10.1002/ecjb.4420780209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractObservation of Shapiro step is important for evaluation of the Josephson junction. This theoretical characteristic is given by a nonlinear differential equation with the normalized frequency ω based on the current driven resistively shunted junction (RSJ) model as a parameter [14]. Although this model provides good agreement with the experimental results, the number of operations for the numerical solution of the equation is excessive. Hence, discussions of the experimental results by means of theoretical values are difficult. As a result, a proposal of a simple approximate equation which can describe the theoretical characteristics only with ω is considered extremely useful. In the high temperature superconducting junction extensively studied recently, theIcRnproduct is large and ω<0.1 is expected. For ω<0.1, the current amplitude of Shapiro step decreases excessively. In practice, Shapiro steps are often not observed at a high‐temperature superconducting junction. This is considered to be caused by the ω<0.1 measurement condition. It is important for evaluation of the junction to investigate this problem. No detailed analysis has been carried out for the region with ω<0.1. On the other hand, since ω<0.1 is the ideal operating condition of the Josephson mixer, understanding of the characteristics is important from the application point of view. In this paper, understanding of the theoretical characteristics for ω<0.1, the derivation of the approximate equation and the condition in which Shapiro step cannot be observed are investigated. The analysis results and the experimental values are compared, and the effectiveness of the analysis is

ISSN:8756-663X    

DOI:10.1002/ecjb.4420780210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY