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1991 Vol. 13, No. 1
Display Method:
1991, 13(1): 1-11.
Abstract:
The problem of bearing estimation of coherent signals impinging on an array of arbitrary geometry is studied. Two methods are developed. The first one synthesizes the observed array data imo the outputs of a linear uniform array and then processes them via cnnventional techniques such as spatial smoothing etc.; the second method is based on the invariant subspace rotation operation which is equivalent to the translational displacement of the array, linearly independent signal vectors are obtained thereby to span completely the signal subspace. As compared with the conventional processing techniques, the method based on invariant subspace rotation does not lead to an effective decrease in aperture size and therefore a decrease in resolution capability. The computer simulations are conducted to demonstrate the effectiveness of the presented methods.
The problem of bearing estimation of coherent signals impinging on an array of arbitrary geometry is studied. Two methods are developed. The first one synthesizes the observed array data imo the outputs of a linear uniform array and then processes them via cnnventional techniques such as spatial smoothing etc.; the second method is based on the invariant subspace rotation operation which is equivalent to the translational displacement of the array, linearly independent signal vectors are obtained thereby to span completely the signal subspace. As compared with the conventional processing techniques, the method based on invariant subspace rotation does not lead to an effective decrease in aperture size and therefore a decrease in resolution capability. The computer simulations are conducted to demonstrate the effectiveness of the presented methods.
1991, 13(1): 12-18.
Abstract:
A nonlinear method for detecting the edge of low-SNR image is developed. This method adopts the filtering in large window to smooth the noise and the nonlinear differential operator in small window to detect the edges. A criterion of noise-guided threshold selection is introduced to segment the derivative image so that the threshold can be determined automatically. In large window s filtering, the technique of 2-D convolution implementation by two 1-D convolutions in series is taken to reduce the storage space of the filter. Finally, the performance of this method is evaluated, and experimental results are given.
A nonlinear method for detecting the edge of low-SNR image is developed. This method adopts the filtering in large window to smooth the noise and the nonlinear differential operator in small window to detect the edges. A criterion of noise-guided threshold selection is introduced to segment the derivative image so that the threshold can be determined automatically. In large window s filtering, the technique of 2-D convolution implementation by two 1-D convolutions in series is taken to reduce the storage space of the filter. Finally, the performance of this method is evaluated, and experimental results are given.
1991, 13(1): 19-27.
Abstract:
New classes of real sequences with good autocorrelation and cross correlation are constructed by using sinusoidal functions. The new sequences are better than the FZC and Alltop sequences in two aspects: (1) lower correlations and (2) taking real values. The new sequences can be used in many areas.
New classes of real sequences with good autocorrelation and cross correlation are constructed by using sinusoidal functions. The new sequences are better than the FZC and Alltop sequences in two aspects: (1) lower correlations and (2) taking real values. The new sequences can be used in many areas.
1991, 13(1): 28-34.
Abstract:
A novel planar leaky-wave antenna of conductor modulating periodic structure for millimeter wave application is proposed. Theoretical analysis, numerical calculation and experimental study are tarried out for this kind of antenna, by use of the theory of two-dimensional periodic admittance surface. A planar antenna of conductor modulating periodic structure is realized in 8mm wave band. It has an aperture area of 9090mm2. The measured performances of the amenna are good.
A novel planar leaky-wave antenna of conductor modulating periodic structure for millimeter wave application is proposed. Theoretical analysis, numerical calculation and experimental study are tarried out for this kind of antenna, by use of the theory of two-dimensional periodic admittance surface. A planar antenna of conductor modulating periodic structure is realized in 8mm wave band. It has an aperture area of 9090mm2. The measured performances of the amenna are good.
1991, 13(1): 35-41.
Abstract:
The equations of electrodynamics for a gyrotropic medium by using Maxwell s equations are deduced. Through Fourier transformation, the admittances of TM and TE modes in the electrically gyrotropic substrate and the magnetically gyrotropic substrate are given. Numerical results of the dominant mode in magnetized ferrite-loaled double-layered finlines are- presented which could be used in designing finline ferrite devices.
The equations of electrodynamics for a gyrotropic medium by using Maxwell s equations are deduced. Through Fourier transformation, the admittances of TM and TE modes in the electrically gyrotropic substrate and the magnetically gyrotropic substrate are given. Numerical results of the dominant mode in magnetized ferrite-loaled double-layered finlines are- presented which could be used in designing finline ferrite devices.
1991, 13(1): 42-48.
Abstract:
The Bandpass characteristics of microwave duplexer TR tube have been calcu-lated theoretically. The theoretical model is that the multiple resonant elements with lumped parameter are shunted, and then the susceptances of these element are transposed step by step. Numeral calculation have been carried out on vector computer with FORTRAN language. Numerical results are in agreement with experimental ones. These calculated results will pro-vide useful rcfcrence for designing wide-band TR tube.
The Bandpass characteristics of microwave duplexer TR tube have been calcu-lated theoretically. The theoretical model is that the multiple resonant elements with lumped parameter are shunted, and then the susceptances of these element are transposed step by step. Numeral calculation have been carried out on vector computer with FORTRAN language. Numerical results are in agreement with experimental ones. These calculated results will pro-vide useful rcfcrence for designing wide-band TR tube.
1991, 13(1): 49-56.
Abstract:
It is proved that in a regular boundary system of rectangular, cylindrical or spherical coordinate, an arbrtrary Vector function can be separated into three orthogonal parts: TE mode field, TM mode field and irro tational field. Each of these components can be determined fully by a scalas function. On the basis of this theorem, the compltenesa of vector wave function system {L, M, and N} is proved, also. Thus it is explained that a vector furction space can be proiected into three uncrossed subspaces not only in Euclidean space but also in the subspace of vector wave function space.
It is proved that in a regular boundary system of rectangular, cylindrical or spherical coordinate, an arbrtrary Vector function can be separated into three orthogonal parts: TE mode field, TM mode field and irro tational field. Each of these components can be determined fully by a scalas function. On the basis of this theorem, the compltenesa of vector wave function system {L, M, and N} is proved, also. Thus it is explained that a vector furction space can be proiected into three uncrossed subspaces not only in Euclidean space but also in the subspace of vector wave function space.
1991, 13(1): 57-64.
Abstract:
The quantum efficiency of photocathodes which are diffusion type or drift type, or which produce charge amplification effect in high field is analysed. a-Si:H photoemissive model with internal or external electric field is presented. Its structure is p-i-n -Si:H/Bi2S3 or SnO2--Si:H-Al:Cs:O. Its quantum efficiency and photosensitivity are estirnated. They are 1-102 and 103-105 A/lm respectively. The experimental results of the photoemissive model with external electric field show that the structural design is correct.
The quantum efficiency of photocathodes which are diffusion type or drift type, or which produce charge amplification effect in high field is analysed. a-Si:H photoemissive model with internal or external electric field is presented. Its structure is p-i-n -Si:H/Bi2S3 or SnO2--Si:H-Al:Cs:O. Its quantum efficiency and photosensitivity are estirnated. They are 1-102 and 103-105 A/lm respectively. The experimental results of the photoemissive model with external electric field show that the structural design is correct.
1991, 13(1): 65-70.
Abstract:
DLTS technique has becn used to investigate (4 1012cm-2/30keV+5 1012cm-2/ 130keV)Si implanted LEC undoped SI-GaAs annealed by tow-step rapid thermal annealing (RTA) (970℃/9s +750℃/12s). Two electron traps ET1(Ec- 0.53 eV, 2.3 10-16cm2) and ET2(Ec-0.81eV, 9.710-13cm2) are detected. Furthermore, the noticeable variations of trap s concentration and energy level in the forbidden gap with the depth profile of defects induced by ion implantation and RTA processes have been observed, The [Asi VAsAsGa] and [VAsAsiVGaAsGa] are proposed as the possible atomic configurations of ET1,and ET2 respectively to explain their RTA behavior.
DLTS technique has becn used to investigate (4 1012cm-2/30keV+5 1012cm-2/ 130keV)Si implanted LEC undoped SI-GaAs annealed by tow-step rapid thermal annealing (RTA) (970℃/9s +750℃/12s). Two electron traps ET1(Ec- 0.53 eV, 2.3 10-16cm2) and ET2(Ec-0.81eV, 9.710-13cm2) are detected. Furthermore, the noticeable variations of trap s concentration and energy level in the forbidden gap with the depth profile of defects induced by ion implantation and RTA processes have been observed, The [Asi VAsAsGa] and [VAsAsiVGaAsGa] are proposed as the possible atomic configurations of ET1,and ET2 respectively to explain their RTA behavior.
1991, 13(1): 71-77.
Abstract:
The mathematical modei for analysing the temporal process of AC silent dis-charge is established from its physical model. Then, the breakdown characteristics and the de-pendence of discharge current density on time are theoretically calculated in this kind of AC silent discharge. They are compared with the experimental results, and the defference bet-ween the theoretical and experimental results are briefly discussed.
The mathematical modei for analysing the temporal process of AC silent dis-charge is established from its physical model. Then, the breakdown characteristics and the de-pendence of discharge current density on time are theoretically calculated in this kind of AC silent discharge. They are compared with the experimental results, and the defference bet-ween the theoretical and experimental results are briefly discussed.
1991, 13(1): 78-82.
Abstract:
The method and procedure for realizing parameter statistical correlation analysis of bipolar analongous integrated circuits are given, and a statistical method of double parame-ters (BF, Rs) with some symmetrical parameters is suggested. Based on the comparision and analysis of the circuits, it is shown that the method can be used to analyse and design bipolar analogous integrated circuits.
The method and procedure for realizing parameter statistical correlation analysis of bipolar analongous integrated circuits are given, and a statistical method of double parame-ters (BF, Rs) with some symmetrical parameters is suggested. Based on the comparision and analysis of the circuits, it is shown that the method can be used to analyse and design bipolar analogous integrated circuits.
1991, 13(1): 83-89.
Abstract:
With the help of the concept of virtual regions and the character of solution curve, a practical algorithm is presented for finding the multiple solutions of DC canonical piecewise-linear resistive networks. The advantage of this algorithm is that there is no repeatedly noneffective iterative procedure throughout the complete operation. Regardless of how many solutions being in the network, the total number of iterative steps is only dependent on the number of the regions made up of the hyperplanes in the Rn.This algorithm is simaple in concept and easy in programing. It can be used to find all solutions of pieewise-linear resistive networks with a common microcomputer.
With the help of the concept of virtual regions and the character of solution curve, a practical algorithm is presented for finding the multiple solutions of DC canonical piecewise-linear resistive networks. The advantage of this algorithm is that there is no repeatedly noneffective iterative procedure throughout the complete operation. Regardless of how many solutions being in the network, the total number of iterative steps is only dependent on the number of the regions made up of the hyperplanes in the Rn.This algorithm is simaple in concept and easy in programing. It can be used to find all solutions of pieewise-linear resistive networks with a common microcomputer.
1991, 13(1): 90-94.
Abstract:
An improved method, which is based on the harmonic-balance technique, for speeding up the convergence of iteration procedure is presented. As example, it is applied to the nonlinear analysis of microwave mixer, in which a simple time domain to frequency domain transformation technique for the mixer diode is introducel. The use of this technique saves computing time dramatically. And the analyzing results are in good agreement with the results published. The improved method can also be extended to the CAA of nonlinear circuits with multi-devices.
An improved method, which is based on the harmonic-balance technique, for speeding up the convergence of iteration procedure is presented. As example, it is applied to the nonlinear analysis of microwave mixer, in which a simple time domain to frequency domain transformation technique for the mixer diode is introducel. The use of this technique saves computing time dramatically. And the analyzing results are in good agreement with the results published. The improved method can also be extended to the CAA of nonlinear circuits with multi-devices.
1991, 13(1): 95-101.
Abstract:
On the basis of Dr. Hoer s (1979) and Dr. Li s work, a new calibration method for the Six-port reflectometer is proposed. The new method is characterized not only by having the advantage of rapidity and simplicity of Dr. Li s method, but also by having the advantage of high precision of Dr. Hoer s method. An example for applying this method to Ku-band Six-port reflectometer is given.
On the basis of Dr. Hoer s (1979) and Dr. Li s work, a new calibration method for the Six-port reflectometer is proposed. The new method is characterized not only by having the advantage of rapidity and simplicity of Dr. Li s method, but also by having the advantage of high precision of Dr. Hoer s method. An example for applying this method to Ku-band Six-port reflectometer is given.
1991, 13(1): 102-107.
Abstract:
The theory and numerical techniques of near-field far-field transformations using spherical-wave expansions are studied. The efficient data processing methods to achieve a high degree of accuracy in transformations and at the same time to reduce the memory capacity are developed. The analytical modei is used to validate the feasibility of the theory and computer software. For an X-Band horn antenna, the far-field pattern computed from near-field data, the measured far-field pattern and the far-field patter from theoretical integral equations are compared, demonstrating the excellent numerical accuracy of the transformation techniques.
The theory and numerical techniques of near-field far-field transformations using spherical-wave expansions are studied. The efficient data processing methods to achieve a high degree of accuracy in transformations and at the same time to reduce the memory capacity are developed. The analytical modei is used to validate the feasibility of the theory and computer software. For an X-Band horn antenna, the far-field pattern computed from near-field data, the measured far-field pattern and the far-field patter from theoretical integral equations are compared, demonstrating the excellent numerical accuracy of the transformation techniques.
1991, 13(1): 108-112.
Abstract:
Calculation of some rotational electostatic defflection fields by the use of one dimensional method is put forward, and the difficulty in singular point has been overcome. The calculation example shows that the method is simple and practical.
Calculation of some rotational electostatic defflection fields by the use of one dimensional method is put forward, and the difficulty in singular point has been overcome. The calculation example shows that the method is simple and practical.
