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1986 Vol. 8, No. 4
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Display Method:
1986, 8(4): 241-246.
Abstract:
In this paper, the horizontal radiation characteristics of dipole and loop antennas adjaeent to a rectangular cylinder reflector are calculated by the application of GTD. The magnitudes of the direct field, the reflected field and the diffracted field from the edges of the cylinder at the field point are calculated and compared. The effects of the dimension of the cylinder, of the relative position of the antennas with respect to the cylinder and of the method of feeding to the resultant field pattern are analyzed. Using the method described, optimum design can be carried out to obtain the optimum omnidireetional radiation charqacteristics of antennas with reflector of this kind.
In this paper, the horizontal radiation characteristics of dipole and loop antennas adjaeent to a rectangular cylinder reflector are calculated by the application of GTD. The magnitudes of the direct field, the reflected field and the diffracted field from the edges of the cylinder at the field point are calculated and compared. The effects of the dimension of the cylinder, of the relative position of the antennas with respect to the cylinder and of the method of feeding to the resultant field pattern are analyzed. Using the method described, optimum design can be carried out to obtain the optimum omnidireetional radiation charqacteristics of antennas with reflector of this kind.
1986, 8(4): 247-254.
Abstract:
In this paper, the two dimensional problems of the diffraction of the electromagnetic waves by a perfect eonductor are discussed, using the Savin s mapping function of the perturbed form to the boundary. The general method and asymptotic formulas used to solve the problems are presented. Especially, the concrete formulas for calculating O-order and 1-order asymptotie solutions are given for the cases of cylindrcal conductors.
In this paper, the two dimensional problems of the diffraction of the electromagnetic waves by a perfect eonductor are discussed, using the Savin s mapping function of the perturbed form to the boundary. The general method and asymptotic formulas used to solve the problems are presented. Especially, the concrete formulas for calculating O-order and 1-order asymptotie solutions are given for the cases of cylindrcal conductors.
1986, 8(4): 255-264.
Abstract:
The existing methods for designing two-dimensional digital filters are outlined anda new methodcomposite methodis proposed. This method has following advan-tages: (1) its computation cost is low; (2) it is easy to acquire lineur phase performance; ( 3 ) it is conient to be generalized to multi-dimensional ones; and so on. Some expe-rimental results show that it can get better results with lower computation cost than two-dimensional window method. Therefore, it applies no only to image processing systems or other computer systems for programming software, but also to some reseach work that involve two-dimensional or multi-dinensional digital filtering.
The existing methods for designing two-dimensional digital filters are outlined anda new methodcomposite methodis proposed. This method has following advan-tages: (1) its computation cost is low; (2) it is easy to acquire lineur phase performance; ( 3 ) it is conient to be generalized to multi-dimensional ones; and so on. Some expe-rimental results show that it can get better results with lower computation cost than two-dimensional window method. Therefore, it applies no only to image processing systems or other computer systems for programming software, but also to some reseach work that involve two-dimensional or multi-dinensional digital filtering.
1986, 8(4): 265-271.
Abstract:
In this report, interdiffusion of the p-IuP with Au-Zn Ti/Au, Pd/Au, and Ti/Pd/ Au at interface has been investigated by Auger electron spectroscopy and electron spectroscopy for chemical analysis. The surfaco morphology for the heat treatment are observed with scanning electron microscopy.It is found that the in-diffusion of Au is easier than that of Pd and Ti, and the out-diffusion of In is easier than that of P. The effects of the alloying temperature and time on the specific contact resistance of the p-InP/Zu-Zn system are studied. The lower specific contact resistance, c=2.4--2.710-4 cm2, is obtained when alloying at 450℃ for 2 min or at 350℃ for 30 min. these results indicate that the specific contact resistance strongly depends on the interface interdiffusion degree. The Zn in Au-Zn alloy distributes onto the most surface layer of the p-InP/Au-Zn system during evaporation process and heat treatment. It may be one of the reasons for the higher specific contact resistance.
In this report, interdiffusion of the p-IuP with Au-Zn Ti/Au, Pd/Au, and Ti/Pd/ Au at interface has been investigated by Auger electron spectroscopy and electron spectroscopy for chemical analysis. The surfaco morphology for the heat treatment are observed with scanning electron microscopy.It is found that the in-diffusion of Au is easier than that of Pd and Ti, and the out-diffusion of In is easier than that of P. The effects of the alloying temperature and time on the specific contact resistance of the p-InP/Zu-Zn system are studied. The lower specific contact resistance, c=2.4--2.710-4 cm2, is obtained when alloying at 450℃ for 2 min or at 350℃ for 30 min. these results indicate that the specific contact resistance strongly depends on the interface interdiffusion degree. The Zn in Au-Zn alloy distributes onto the most surface layer of the p-InP/Au-Zn system during evaporation process and heat treatment. It may be one of the reasons for the higher specific contact resistance.
1986, 8(4): 272-278.
Abstract:
A new technique called MOS constan t current quasistatic small-signal technique is given. Using this technique the quasistatic capacitance, high frequency capaeitanee and semiconductor surface potential of MOS capacitor can be measured simultaneously, and the low interface state distribution of Si/SiO2 system can also be rapidly and accurately determined. Due to the use of synchronous differential amplification technique with limited amplitude, the sensitivity of the new technique in measuring the interface state density is raised about an order of magnitude.
A new technique called MOS constan t current quasistatic small-signal technique is given. Using this technique the quasistatic capacitance, high frequency capaeitanee and semiconductor surface potential of MOS capacitor can be measured simultaneously, and the low interface state distribution of Si/SiO2 system can also be rapidly and accurately determined. Due to the use of synchronous differential amplification technique with limited amplitude, the sensitivity of the new technique in measuring the interface state density is raised about an order of magnitude.
1986, 8(4): 279-286.
Abstract:
A sensitive linear sensor, which is suitable for ineasuring humidity of elastic dielectric on conveyer, is presented. A programmable counter is used to improve the measuring accuracy. The dynamic test of this system has been completed on the conveyer in Shanghai Coking Factory. The experimental results are in good agreement with the actual humidity of the coking coal.
A sensitive linear sensor, which is suitable for ineasuring humidity of elastic dielectric on conveyer, is presented. A programmable counter is used to improve the measuring accuracy. The dynamic test of this system has been completed on the conveyer in Shanghai Coking Factory. The experimental results are in good agreement with the actual humidity of the coking coal.
1986, 8(4): 287-292.
Abstract:
In this paper, an assupmtion to explain emission properties of the La-WC cathode and its resistance to poisoning of oil vapour is presented and was demonstrated by experiments. In the operating temperature range of the La-WC cathode, lanthanum would react chemically with tungsten carbide and form La2C3. La2C3 is a kind of good emissive material with a work function approximate to lanthanum's and can also combine with lanthanum into an eutectic. The eutectic is easy to wet the tungsten matrix and migrate over its surface to form a thin emission film. As a result, the cathode emission is greatly increased. In addition, the La-Wc cathode has capability to resist poisoning of oil vapour is for the reason that the carbon from the oil vapour reacts with the lanthanum in the eutectie and forms La2C3, which is also a good emissive material.
In this paper, an assupmtion to explain emission properties of the La-WC cathode and its resistance to poisoning of oil vapour is presented and was demonstrated by experiments. In the operating temperature range of the La-WC cathode, lanthanum would react chemically with tungsten carbide and form La2C3. La2C3 is a kind of good emissive material with a work function approximate to lanthanum's and can also combine with lanthanum into an eutectic. The eutectic is easy to wet the tungsten matrix and migrate over its surface to form a thin emission film. As a result, the cathode emission is greatly increased. In addition, the La-Wc cathode has capability to resist poisoning of oil vapour is for the reason that the carbon from the oil vapour reacts with the lanthanum in the eutectie and forms La2C3, which is also a good emissive material.
1986, 8(4): 309-315.
Abstract:
The field matching method for calculating the capacitance of a rectangular coaxial strip transmission line is presented. The method is not only simple, easy to use and commonly adaptive but also efficient for reducing the calculating error.
The field matching method for calculating the capacitance of a rectangular coaxial strip transmission line is presented. The method is not only simple, easy to use and commonly adaptive but also efficient for reducing the calculating error.
1986, 8(4): 316-320.
Abstract:
The majority of literatures dealing with digital signal processing ignore the effect of oscillator instabilities. This will in some cases lead to an inadmissible design mistake.In this paper, Monte Carlo computer simulation is used to estimate the effect of oscillator instabilities on signal processing. The key link of this method is generating high quality random number sequence simulating the phase noice of oscillator. The case of pulse compression performance is discussed as an example in order to clarify:(1) the effect of oscillator instabilities on pulse compression performance, and (2) the requirement of oscillator frequency stability when the tolerance of the system performance is known. Finally, some computer simulation examples are given which will provide as reference data for engineering designers.
The majority of literatures dealing with digital signal processing ignore the effect of oscillator instabilities. This will in some cases lead to an inadmissible design mistake.In this paper, Monte Carlo computer simulation is used to estimate the effect of oscillator instabilities on signal processing. The key link of this method is generating high quality random number sequence simulating the phase noice of oscillator. The case of pulse compression performance is discussed as an example in order to clarify:(1) the effect of oscillator instabilities on pulse compression performance, and (2) the requirement of oscillator frequency stability when the tolerance of the system performance is known. Finally, some computer simulation examples are given which will provide as reference data for engineering designers.
1986, 8(4): 293-302.
Abstract:
The limitation of far region Fresnel-Kirchhoff formula in transient problem is diseussed. Under the excitation of an impulse, the radiation field has to be evaluated in terms of precise Fresnel-Kirchhoff formula; otherwise, some important transient features would be lost.
The limitation of far region Fresnel-Kirchhoff formula in transient problem is diseussed. Under the excitation of an impulse, the radiation field has to be evaluated in terms of precise Fresnel-Kirchhoff formula; otherwise, some important transient features would be lost.
1986, 8(4): 303-308.
Abstract:
In this paper, it is clarified that as the term, the impulse response of aperture antennas in the f ar-field region, is used, the far-field region is referred to the actual signal exciting an antenna, not to the Dirac delta function exerted on an antenna for deducing the impulse respose, and that the applicable distance range of the impulse response in the far-field region is determined by the frequency range of the exciting signal.
In this paper, it is clarified that as the term, the impulse response of aperture antennas in the f ar-field region, is used, the far-field region is referred to the actual signal exciting an antenna, not to the Dirac delta function exerted on an antenna for deducing the impulse respose, and that the applicable distance range of the impulse response in the far-field region is determined by the frequency range of the exciting signal.
