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1989 Vol. 11, No. 6
Display Method:
1989, 11(6): 561-568.
Abstract:
Based on Evans spatial smoothing preprocessing scheme, a new approach aalled two-direction spatial smoothing preprocessing method is presented. It is proved that the decor-relation, the effective aperture and the maximum number of distinguishable coherent signals (when array size is given) of the new method are better than those of the Evans method. Simulation results give a comparison between the eigenvector spectrums produced by the two methods.
Based on Evans spatial smoothing preprocessing scheme, a new approach aalled two-direction spatial smoothing preprocessing method is presented. It is proved that the decor-relation, the effective aperture and the maximum number of distinguishable coherent signals (when array size is given) of the new method are better than those of the Evans method. Simulation results give a comparison between the eigenvector spectrums produced by the two methods.
1989, 11(6): 569-575.
Abstract:
A new method is presented to analyze the multilayer electrically thick circular microstrip antenna excited by a probe. The current on the probe is taken to be uniform. Based on free space electric dyadic Green s function, the field expression of a horizontal electric dipole (HED), which is located in any point of multilayer media and in any direction, has been derived. By using this field expression and Richmond reaction equation, an integral equation of electric current on the patch is formulated. By properly choosing basic function for current expansion, this method can be used for an electrically thick microstrip antenna. The theoretical results are very agree with experimental data for an electrically thick circular microstrip antenna with an air gap.
A new method is presented to analyze the multilayer electrically thick circular microstrip antenna excited by a probe. The current on the probe is taken to be uniform. Based on free space electric dyadic Green s function, the field expression of a horizontal electric dipole (HED), which is located in any point of multilayer media and in any direction, has been derived. By using this field expression and Richmond reaction equation, an integral equation of electric current on the patch is formulated. By properly choosing basic function for current expansion, this method can be used for an electrically thick microstrip antenna. The theoretical results are very agree with experimental data for an electrically thick circular microstrip antenna with an air gap.
1989, 11(6): 576-583.
Abstract:
Closed-form expressions for nonunlform currents induced on a perfectly conducting infinite wedge illuminated by a TM plane wave are presented. Results computed by using these expressions are in good agreement with ones of the eigenfunction solution of the wedge.
Closed-form expressions for nonunlform currents induced on a perfectly conducting infinite wedge illuminated by a TM plane wave are presented. Results computed by using these expressions are in good agreement with ones of the eigenfunction solution of the wedge.
1989, 11(6): 584-589.
Abstract:
Imaging of moving targets by inverse synthetic aperture radar (1SAR) is based on range-Doppler processing and motion compensation. High resolution along the range is provided by broad bandwidth of the transmitted signal, while accross the range (azimuth) provided by an aperture induced by the motion of the target. Range alignment and motion compensation are the key techniques of ISAR. ISAR principles are summarized and experimental results are given.
Imaging of moving targets by inverse synthetic aperture radar (1SAR) is based on range-Doppler processing and motion compensation. High resolution along the range is provided by broad bandwidth of the transmitted signal, while accross the range (azimuth) provided by an aperture induced by the motion of the target. Range alignment and motion compensation are the key techniques of ISAR. ISAR principles are summarized and experimental results are given.
1989, 11(6): 590-599.
Abstract:
The partial charge-simulation method is presented to solve the characteristic impedance of transmission line of specific cross-section with offset inner conductors. This method has a higher accuracy due to the accurate satisfaction of the boundary condition on the outer conductor. The combined method of gnass elimination and optimization is used to solve the equation of charge-simulation, and it is an effective method for increasing the accuracy and assuring the convergence. The Green's functions of five transmission lines (i.e.with circular, elliptic, rectangular, trough and slab outer conductor) are given.
The partial charge-simulation method is presented to solve the characteristic impedance of transmission line of specific cross-section with offset inner conductors. This method has a higher accuracy due to the accurate satisfaction of the boundary condition on the outer conductor. The combined method of gnass elimination and optimization is used to solve the equation of charge-simulation, and it is an effective method for increasing the accuracy and assuring the convergence. The Green's functions of five transmission lines (i.e.with circular, elliptic, rectangular, trough and slab outer conductor) are given.
1989, 11(6): 600-606.
Abstract:
The microwave back-scattering characteristics are numerically analysed by the electromagnetic scattering theory, and the sea wave height spectrum that reflects the wind field is rebuilt by comparing the calculated data with some experimental data which are measured by airborne scatter. According to the wave height spectrum, the relationship between the back-scattering coefficients and wind speeds can be obtained. Once the back-scattering coefficients of sea surface are measured, thus the wind speeds on sea surface can proximally be determined. It is useful for the microwave remote sensing in ocean.
The microwave back-scattering characteristics are numerically analysed by the electromagnetic scattering theory, and the sea wave height spectrum that reflects the wind field is rebuilt by comparing the calculated data with some experimental data which are measured by airborne scatter. According to the wave height spectrum, the relationship between the back-scattering coefficients and wind speeds can be obtained. Once the back-scattering coefficients of sea surface are measured, thus the wind speeds on sea surface can proximally be determined. It is useful for the microwave remote sensing in ocean.
1989, 11(6): 607-615.
Abstract:
Small signal analysis and synthesis of a microwave amplifier with shunt feedback are described. The estimation values of all network elements, the closed-loop broadband gain, bandwidth and match quality of both ports are given. The relation between the match quality and gain is studied by graphic method.
Small signal analysis and synthesis of a microwave amplifier with shunt feedback are described. The estimation values of all network elements, the closed-loop broadband gain, bandwidth and match quality of both ports are given. The relation between the match quality and gain is studied by graphic method.
1989, 11(6): 616-620.
Abstract:
Simple approximate formulas of near field for a element current in microstrip structure are derived by using the exact formulas consisting of integrals of Sommerfeld type, results Calculated with these formulas are compared with those obtained by numerically calculating Sommerfeld integrals, and it is shown that these formulas are valid for small p/ and ! have no limitation of layer thickness and loss.
Simple approximate formulas of near field for a element current in microstrip structure are derived by using the exact formulas consisting of integrals of Sommerfeld type, results Calculated with these formulas are compared with those obtained by numerically calculating Sommerfeld integrals, and it is shown that these formulas are valid for small p/ and ! have no limitation of layer thickness and loss.
1989, 11(6): 621-624.
Abstract:
The method of calculating the characteristic impedance of the coaxial transmission line with regular polygonal outer and circular inner conductor is presented. With this method the reliable upper and lower limits of the characteristic impedance are obtained for the transmission lines with equilateral triangular outer, square outer, regular pentagonal outer, regular hexagonal outer and circular inner conductor respectively. The error of this method is low, so it has a certain practical value.
The method of calculating the characteristic impedance of the coaxial transmission line with regular polygonal outer and circular inner conductor is presented. With this method the reliable upper and lower limits of the characteristic impedance are obtained for the transmission lines with equilateral triangular outer, square outer, regular pentagonal outer, regular hexagonal outer and circular inner conductor respectively. The error of this method is low, so it has a certain practical value.
1989, 11(6): 625-629.
Abstract:
The energy conservauon in the radiation process by electron beam in a waveguide with arbitrary cross-section is proved. Some mistakes in Ref. [1] by myself are corrected. And the results are extended to the waveguide system with one shorted end. This result explains that the energy conservation is the intrinsic attributes of the Maxwell's equation set.
The energy conservauon in the radiation process by electron beam in a waveguide with arbitrary cross-section is proved. Some mistakes in Ref. [1] by myself are corrected. And the results are extended to the waveguide system with one shorted end. This result explains that the energy conservation is the intrinsic attributes of the Maxwell's equation set.
1989, 11(6): 630-636.
Abstract:
Making use of the perturbation approach, the large-orbit gyro-klystron was investigated. The expressions of the electron bunching, the beam-wave interaction power and the gain were obtained. Furthermore, it was found that the axial motions of bunching electrons have an unneglected effect on the beam-wave interaction. Taking account of this effect, the corre spending revised expressions of the electron bunching, the beam-wave interaction power and the gain were derived out.
Making use of the perturbation approach, the large-orbit gyro-klystron was investigated. The expressions of the electron bunching, the beam-wave interaction power and the gain were obtained. Furthermore, it was found that the axial motions of bunching electrons have an unneglected effect on the beam-wave interaction. Taking account of this effect, the corre spending revised expressions of the electron bunching, the beam-wave interaction power and the gain were derived out.
1989, 11(6): 637-642.
Abstract:
A new structure of vector classifiers, based upon space partition of voronot region according to a pattern set gem-rated by classed patterns training, is presented. The fact that this structure is an optimal pattern classifier on Euclidean distance is shown. Two decision rules and three kinds of M classes and k-dimension classifier structures on voronoi region are given.
A new structure of vector classifiers, based upon space partition of voronot region according to a pattern set gem-rated by classed patterns training, is presented. The fact that this structure is an optimal pattern classifier on Euclidean distance is shown. Two decision rules and three kinds of M classes and k-dimension classifier structures on voronoi region are given.
1989, 11(6): 643-648.
Abstract:
Three-dimensional (3-D) Markov cubic random mesh models are prorated and proved in the form of two theorems in details. Its applications to the modeling and description of 3-D images are described. The model presented here is the appropriate mathematic tool for the segmentation, modeling, classification and other processing. Finally, an example is given.
Three-dimensional (3-D) Markov cubic random mesh models are prorated and proved in the form of two theorems in details. Its applications to the modeling and description of 3-D images are described. The model presented here is the appropriate mathematic tool for the segmentation, modeling, classification and other processing. Finally, an example is given.
A NEW METHOD FOR MEASURING THE SECONDARY ELECTRON EMISSION OF THERMIONIC CATHODE AND ITS APPLICATION
1989, 11(6): 649-655.
Abstract:
By using correlation-detection technique and improving the structure of test tube, the background noise of thermionic-electrons and space charge effect are restrained. The secondary emission coefficient of thermionic cathode at high temperature have been studied. The of impregnated scandate cathodes increases exponentially with increasing temperature at low energy and current of bombardment electron; at high energy or current of bombardment electron, the temperature has little effect to . The research shows that an enhanced thermionic emission occured when the cathode works in high temperature and at electron bombardment. These phenomena are discussed in terms of internal field model.
By using correlation-detection technique and improving the structure of test tube, the background noise of thermionic-electrons and space charge effect are restrained. The secondary emission coefficient of thermionic cathode at high temperature have been studied. The of impregnated scandate cathodes increases exponentially with increasing temperature at low energy and current of bombardment electron; at high energy or current of bombardment electron, the temperature has little effect to . The research shows that an enhanced thermionic emission occured when the cathode works in high temperature and at electron bombardment. These phenomena are discussed in terms of internal field model.
1989, 11(6): 656-660.
Abstract:
The hydrogen effusion and its temperature dependence in semiconducting amorphous a-si:H/a-SiN,:H multilayer films prepared by PECVD has been studied using IR absorption, nuclear reaction method, SIMS and TEM. Some possible interpretations are presented for out-diffusion of hydrogen in the films.
The hydrogen effusion and its temperature dependence in semiconducting amorphous a-si:H/a-SiN,:H multilayer films prepared by PECVD has been studied using IR absorption, nuclear reaction method, SIMS and TEM. Some possible interpretations are presented for out-diffusion of hydrogen in the films.
1989, 11(6): 661-665.
Abstract:
The composition of released gasses of B-A gauge and Ag tube during degassing and operation are analyzed. The degassing processing of Ag tube at high temperature is suggested by using N2-O2 alternately. In this way, the degassing time of Ag tube is shortened effectively, the degassing vacuum is raised notably and highly pure oxygen permeating through Ag tube is obtained. The effects on the purity of oxygen are discussed in detail.
The composition of released gasses of B-A gauge and Ag tube during degassing and operation are analyzed. The degassing processing of Ag tube at high temperature is suggested by using N2-O2 alternately. In this way, the degassing time of Ag tube is shortened effectively, the degassing vacuum is raised notably and highly pure oxygen permeating through Ag tube is obtained. The effects on the purity of oxygen are discussed in detail.
