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1992 Vol. 14, No. 2
Display Method:
1992, 14(2): 113-119.
Abstract:
The continued traction tactics for cryptanalysis based on Legendre theorem of continued fraction are proposed.
The continued traction tactics for cryptanalysis based on Legendre theorem of continued fraction are proposed.
1992, 14(2): 120-126.
Abstract:
A method based on spatial filter preprocessing is presented to enhancethe resolution of the existing spectrum estimation algorithms. The effective signal-to-noise ratio (SNR) and the accuracy of autocorrelation estimation are significantly improved through use of this method. The method is applied to array processing in the signal snapshot case. Simulation results are presented to illustrate the improved performance achieved by the new method as compared with that obtained by the other existing algorithms.
A method based on spatial filter preprocessing is presented to enhancethe resolution of the existing spectrum estimation algorithms. The effective signal-to-noise ratio (SNR) and the accuracy of autocorrelation estimation are significantly improved through use of this method. The method is applied to array processing in the signal snapshot case. Simulation results are presented to illustrate the improved performance achieved by the new method as compared with that obtained by the other existing algorithms.
1992, 14(2): 127-133.
Abstract:
The fixed frame length maximum correlation method which is the optimum method in a binary symmetric channel has been proved. With Poisson distribution, the frame sync acquisition probability is obtained and followed by computer simulation. By Markov modeling techniques, the probability and the mean time into lock mode are given. Finally, it is shown that the optimum frame sync method is far superior to conventional, and it is very useful in practice.
The fixed frame length maximum correlation method which is the optimum method in a binary symmetric channel has been proved. With Poisson distribution, the frame sync acquisition probability is obtained and followed by computer simulation. By Markov modeling techniques, the probability and the mean time into lock mode are given. Finally, it is shown that the optimum frame sync method is far superior to conventional, and it is very useful in practice.
1992, 14(2): 134-141.
Abstract:
First, the linear theories of frequency stability in nearly sinusoidal feedback oseil-lators are simply reviewed. Then, the describing function method and determining equation approach are applied to obtain new expressions for the oscillation-frequency and the oscillation-amplitude stability of nonlinear nearly sinusoidal feedback oscillators. Finally, the differences of the expressions of oscillation-frequency stability derived from describing function method and determining equation approach are presented, and the relationship between descri- bing function method and determining equation approach is studied.
First, the linear theories of frequency stability in nearly sinusoidal feedback oseil-lators are simply reviewed. Then, the describing function method and determining equation approach are applied to obtain new expressions for the oscillation-frequency and the oscillation-amplitude stability of nonlinear nearly sinusoidal feedback oscillators. Finally, the differences of the expressions of oscillation-frequency stability derived from describing function method and determining equation approach are presented, and the relationship between descri- bing function method and determining equation approach is studied.
1992, 14(2): 142-148.
Abstract:
The zero-voltage quasi-resonant boost switching DC-DC converter have been investigated by using the time averaging equivalent circuit approach of periodically switching linear networks. The DC steady state and the AC small signal characteristics of the converter are also given.
The zero-voltage quasi-resonant boost switching DC-DC converter have been investigated by using the time averaging equivalent circuit approach of periodically switching linear networks. The DC steady state and the AC small signal characteristics of the converter are also given.
1992, 14(2): 149-155.
Abstract:
The dual space theory is introduced for extracting the natural frequencies of a radar target from a measured response. The theory not only contains Prony method,SVD method and E pulse method, but also gives a new scheme-the Combination Operation(CO) method, which is shown to be more insensitive to random noise and to estimation of modal contents. Verification of the CO mehtod is accomplished by comparing the numerical results with those of the other three methods. The applicability of CO method to a conducting sphere is also demonstrated.
The dual space theory is introduced for extracting the natural frequencies of a radar target from a measured response. The theory not only contains Prony method,SVD method and E pulse method, but also gives a new scheme-the Combination Operation(CO) method, which is shown to be more insensitive to random noise and to estimation of modal contents. Verification of the CO mehtod is accomplished by comparing the numerical results with those of the other three methods. The applicability of CO method to a conducting sphere is also demonstrated.
1992, 14(2): 156-162.
Abstract:
The boundary-element method is used for the investigation of horn antennas, and the input standing-wave property, aperture field, near field and far field of horn antennas are studied throughly. The obtained results are in good agreement with data available in the literatures. Some examples are given to show the validity and usefulness of this approach.
The boundary-element method is used for the investigation of horn antennas, and the input standing-wave property, aperture field, near field and far field of horn antennas are studied throughly. The obtained results are in good agreement with data available in the literatures. Some examples are given to show the validity and usefulness of this approach.
1992, 14(2): 163-169.
Abstract:
Based on the quasi-measured values of tropospheric refraction,it is discussed that the exponential atmospheric model is reasonable, and according to the stable fea-ture of refractivity at 9 km above sea level, a simplified method to predict tropospheric range error is presented, and the accuracy of which is discussed. Besides, some new parameters for linear regression of tropospheric refraction are given, the improvement in prediction ef range error is distinct.
Based on the quasi-measured values of tropospheric refraction,it is discussed that the exponential atmospheric model is reasonable, and according to the stable fea-ture of refractivity at 9 km above sea level, a simplified method to predict tropospheric range error is presented, and the accuracy of which is discussed. Besides, some new parameters for linear regression of tropospheric refraction are given, the improvement in prediction ef range error is distinct.
1992, 14(2): 170-175.
Abstract:
One of the most diffuculties in designing ICRH antenna is how to analyse and estimate the electric forces on it when so high a plasma current disappears rapidly as the plasma disruption occurs. In this paper, a means to analyse and calculate these forces isgiven.
One of the most diffuculties in designing ICRH antenna is how to analyse and estimate the electric forces on it when so high a plasma current disappears rapidly as the plasma disruption occurs. In this paper, a means to analyse and calculate these forces isgiven.
1992, 14(2): 176-183.
Abstract:
The electron optical column for variable rectangular-shaped beam lithography system DJ-2 is described, with emphasis on the analysis of optical configuration and shaping deflection compensation. In this column the variable spot shaping is performed with a minimum number of lenses by a more reasonable optical scheme. A high-sensitivity electrostatic shaping deflector with serial parallel-plates is employed for high-speed spot shaping. With the accurate linear and rotational approaches, the spot current density of over 0.4 A/cm2 is obtained, with a tungsten hairpin cathode, and the edge resolution is better than 0.2 m within 2 X 2 mm field size.
The electron optical column for variable rectangular-shaped beam lithography system DJ-2 is described, with emphasis on the analysis of optical configuration and shaping deflection compensation. In this column the variable spot shaping is performed with a minimum number of lenses by a more reasonable optical scheme. A high-sensitivity electrostatic shaping deflector with serial parallel-plates is employed for high-speed spot shaping. With the accurate linear and rotational approaches, the spot current density of over 0.4 A/cm2 is obtained, with a tungsten hairpin cathode, and the edge resolution is better than 0.2 m within 2 X 2 mm field size.
1992, 14(2): 184-189.
Abstract:
Two methods for improving the equidriving power-frequency characteristics of broadband high power klystrons are presented. One is that a comb-line bandpass filter with attenuation properties is inserted between the TWT driver and the klystron for compensating the gain-frequency characteristics of the klystron to get the required equidriving gain-frequency characteristics. The other is that a reactive element is connected with the input cavity to change its resonance frequency f0 and QL and then to improve the gain-frequency characteristics of the klystron.
Two methods for improving the equidriving power-frequency characteristics of broadband high power klystrons are presented. One is that a comb-line bandpass filter with attenuation properties is inserted between the TWT driver and the klystron for compensating the gain-frequency characteristics of the klystron to get the required equidriving gain-frequency characteristics. The other is that a reactive element is connected with the input cavity to change its resonance frequency f0 and QL and then to improve the gain-frequency characteristics of the klystron.
1992, 14(2): 190-198.
Abstract:
An AC small-signal transistor model incorporating 8 nonlinearities using Taylor series representations is described. Based on this method, a nonlinear distortion-analysis program has been developed. It is used to compute the third-order intermodulation distortion IMs. The relations between IM3 and the operating frequency, emitter and base widths, emitter line current density and doped impurity concentration on base are obtained.
An AC small-signal transistor model incorporating 8 nonlinearities using Taylor series representations is described. Based on this method, a nonlinear distortion-analysis program has been developed. It is used to compute the third-order intermodulation distortion IMs. The relations between IM3 and the operating frequency, emitter and base widths, emitter line current density and doped impurity concentration on base are obtained.
1992, 14(2): 199-202.
Abstract:
The concept of multilayer set and its representation are introduced. Two examples of its application in graphic layout design are discussed.
The concept of multilayer set and its representation are introduced. Two examples of its application in graphic layout design are discussed.
1992, 14(2): 203-207.
Abstract:
The effects of finite word length in LMS adaptive noise canceller are discussed. The theoretical formula of output signal-to-noise ratio involving quantization noise and round-off noise are derived. If the variation of input weak signal can be reflected by certain word length, the output SNR mainly depends on the word length of adaptive operations.
The effects of finite word length in LMS adaptive noise canceller are discussed. The theoretical formula of output signal-to-noise ratio involving quantization noise and round-off noise are derived. If the variation of input weak signal can be reflected by certain word length, the output SNR mainly depends on the word length of adaptive operations.
1992, 14(2): 208-211.
Abstract:
The design principles and structure, characters of a kind of pulse Cunndiode, microwave circuit and pulse modulator are described. The performances of the developed pulse Gunn oscillator are as follows: in the frequency range of 3-4 GHz, the maximum pulse power is 20W, the highest efficiency is 5% and the maximum pulse duration ratio is less than 1%.
The design principles and structure, characters of a kind of pulse Cunndiode, microwave circuit and pulse modulator are described. The performances of the developed pulse Gunn oscillator are as follows: in the frequency range of 3-4 GHz, the maximum pulse power is 20W, the highest efficiency is 5% and the maximum pulse duration ratio is less than 1%.
1992, 14(2): 212-216.
Abstract:
A basic scheme for detecting subsurface targets with EM pulse of nanoseconds and an especially developed travelling-wave antenna of high quality are described. The antenna is a sort of sector antenna with structure of three layers, which possesses higher radiation efficiency and better travelling-wave properties. A fine resolution graphic system and a high speed display are employed in terminal processing. Metal pipes burried about 1m under the earth can be detected and clearly displayed. High resolution and burried about lm under short processing time of the system, compared with other similar devices make it suitable for engineering use.
A basic scheme for detecting subsurface targets with EM pulse of nanoseconds and an especially developed travelling-wave antenna of high quality are described. The antenna is a sort of sector antenna with structure of three layers, which possesses higher radiation efficiency and better travelling-wave properties. A fine resolution graphic system and a high speed display are employed in terminal processing. Metal pipes burried about 1m under the earth can be detected and clearly displayed. High resolution and burried about lm under short processing time of the system, compared with other similar devices make it suitable for engineering use.
1992, 14(2): 217-220.
Abstract:
A modified C-V method for determination of charge density in LB mono-film is presented. The inaccuracy problem of the conventional C-V method is overcome entirely The method is proved to be applicable by determining the charge density in the monofilm.
A modified C-V method for determination of charge density in LB mono-film is presented. The inaccuracy problem of the conventional C-V method is overcome entirely The method is proved to be applicable by determining the charge density in the monofilm.
1992, 14(2): 221-224.
Abstract:
A systematic study of TiO2 ceramic boundary layer capacitor (BLC) ismade. TiO2 ultrafine powder microdoped with Nb5+, Ba2+ is prepared by spray drying. The relations between the dielectric properties of TiO2 and the sintering temperature, measuring conditions are studied. The mechanism of TiO2 ceramic BLC is illustrated.
A systematic study of TiO2 ceramic boundary layer capacitor (BLC) ismade. TiO2 ultrafine powder microdoped with Nb5+, Ba2+ is prepared by spray drying. The relations between the dielectric properties of TiO2 and the sintering temperature, measuring conditions are studied. The mechanism of TiO2 ceramic BLC is illustrated.
