Email alert
1987 Vol. 9, No. 2
Display Method:
1987, 9(2): 97-106.
Abstract:
A new scheme of target discrimination based on transient EM-fields is described in detail-in this paper. The fundamental theory and its mathematical deduction for getting scattering fields of single frequency of a excited target are given.We have got some more contented results, when this theory is used to linear target and conducting spheres. Several useful conclusions on calculating impulse response of targets are stated here. A practical and available scheme about measuring impulse response of a target in time domain is proposed Experimental results show that this new theory is useful.
A new scheme of target discrimination based on transient EM-fields is described in detail-in this paper. The fundamental theory and its mathematical deduction for getting scattering fields of single frequency of a excited target are given.We have got some more contented results, when this theory is used to linear target and conducting spheres. Several useful conclusions on calculating impulse response of targets are stated here. A practical and available scheme about measuring impulse response of a target in time domain is proposed Experimental results show that this new theory is useful.
1987, 9(2): 107-115.
Abstract:
The relation between the sample number and the performances of signal detection and paramater estimation in correlative Gaussian noise in fixed time T is investigated. It is pointed out that when the autocorrelation coefficient between the neighbour samples in the range of 0.1-0.2, the general SNR S2[T(XL)] will approach to the limit of SNR S2(T). It is also pointed out that the sample sequences of the solution of a second order differential equation generally is not an AR(2) model. But when the sample interval △0, the sample sequences can be described by AR(2). Therefore, S2(T) can be easily calculated. Finally, the relation between likelihood ratio detection and the maximum likelihood estimation is discussed.
The relation between the sample number and the performances of signal detection and paramater estimation in correlative Gaussian noise in fixed time T is investigated. It is pointed out that when the autocorrelation coefficient between the neighbour samples in the range of 0.1-0.2, the general SNR S2[T(XL)] will approach to the limit of SNR S2(T). It is also pointed out that the sample sequences of the solution of a second order differential equation generally is not an AR(2) model. But when the sample interval △0, the sample sequences can be described by AR(2). Therefore, S2(T) can be easily calculated. Finally, the relation between likelihood ratio detection and the maximum likelihood estimation is discussed.
1987, 9(2): 116-124.
Abstract:
The design method of E/D NMOS chopper-stabilized operatinal amplifier is discussed. The offset factors are analyzed and a new formula is derived. The circuit design is simulated with SPICE-II and the experiment of test chip shows a satisfactory result.
The design method of E/D NMOS chopper-stabilized operatinal amplifier is discussed. The offset factors are analyzed and a new formula is derived. The circuit design is simulated with SPICE-II and the experiment of test chip shows a satisfactory result.
1987, 9(2): 125-134.
Abstract:
The elementary unit of switched-capacitor (SC) network is composed of lossless integrator. According to charge conservation law, the lossless integrator can be equivalently transformed to two independent networks in z-domain. Introducing a storistor having a delay of one half switching period, the discrete time network in z-domain can be transformed to the continue time network in s-domain. Therefore if the circuit simulation program (such as SPICE) has time-delay elements, it is possible to design and analyze the SC network with computer. And a equivalent transformation process for lossless integrator is given. The result of computer analysis is also given. Using this method a five order ellipse lowpass SC filter is designed by SPICE program.
The elementary unit of switched-capacitor (SC) network is composed of lossless integrator. According to charge conservation law, the lossless integrator can be equivalently transformed to two independent networks in z-domain. Introducing a storistor having a delay of one half switching period, the discrete time network in z-domain can be transformed to the continue time network in s-domain. Therefore if the circuit simulation program (such as SPICE) has time-delay elements, it is possible to design and analyze the SC network with computer. And a equivalent transformation process for lossless integrator is given. The result of computer analysis is also given. Using this method a five order ellipse lowpass SC filter is designed by SPICE program.
1987, 9(2): 135-139.
Abstract:
The method of determination of plasma temperature by measuring the deionization time of discharge is proposed. The testing set-up and the experimental results are given. It shows that the obtained results are in good agreement with that obtained by probe method, so this method is useful.
The method of determination of plasma temperature by measuring the deionization time of discharge is proposed. The testing set-up and the experimental results are given. It shows that the obtained results are in good agreement with that obtained by probe method, so this method is useful.
1987, 9(2): 140-148.
Abstract:
The general field solutions are obtained for two kinds of infinitely long multipole electrostatic deflectors. A method is Riven to obtain uniform deflection field near optical axis. Having calculated six forms of the deflectors, the concerned formulas and data are given. The relationship and difference between ihe two kinds of deflectors are analysed.
The general field solutions are obtained for two kinds of infinitely long multipole electrostatic deflectors. A method is Riven to obtain uniform deflection field near optical axis. Having calculated six forms of the deflectors, the concerned formulas and data are given. The relationship and difference between ihe two kinds of deflectors are analysed.
1987, 9(2): 149-155.
Abstract:
Some results in investigating deep levels in Ti-doped silicon are given. Three Ti associated deep levels are found by DLTS. They are two electron trap levels located at Ec- 0.23 eV and Ec - 0.53eV respectively in Ti-doped n-silicon and a hole trap level located at Ev +0.32eVin Ti-doped p-silicon. In order to study these levels further, the method of transient capacitance at constant temperature is used, and the thermal activation energy and capture cross-section in the range of experimental temperature and other related parameters are obtained. According to our experimental results, a brief discussion on the bonding feature of these levels and on their pinning to which band is given.
Some results in investigating deep levels in Ti-doped silicon are given. Three Ti associated deep levels are found by DLTS. They are two electron trap levels located at Ec- 0.23 eV and Ec - 0.53eV respectively in Ti-doped n-silicon and a hole trap level located at Ev +0.32eVin Ti-doped p-silicon. In order to study these levels further, the method of transient capacitance at constant temperature is used, and the thermal activation energy and capture cross-section in the range of experimental temperature and other related parameters are obtained. According to our experimental results, a brief discussion on the bonding feature of these levels and on their pinning to which band is given.
1987, 9(2): 156-160.
Abstract:
The diffusion of Zn, Zn-Cd in InxGa1-xAs is investigated using ZnAs2 and ZnAsa+Cd as the diffusion source. The effect of the diffusion temperature, diffusion time, variety of the diffusion source and composition of the material on the relation of the xj-t1/2 is given. The diffusion velocity (xj2/t) of the Zn in InxGa1-xAs is faster than that of the Zn-Cd in InxGa1-xAs. The surface hole concentration of Zn in InxGa1-xAs is 11019-21020 cm-2 at 500-600℃. At the same diffusion condition, the surface concentration of Zn in InxGa1-xAs is higher than that of Zn in InP. Reducing of contact resistance by use of InxGa1-xAs contact layer for 1.3m LED can be expected.
The diffusion of Zn, Zn-Cd in InxGa1-xAs is investigated using ZnAs2 and ZnAsa+Cd as the diffusion source. The effect of the diffusion temperature, diffusion time, variety of the diffusion source and composition of the material on the relation of the xj-t1/2 is given. The diffusion velocity (xj2/t) of the Zn in InxGa1-xAs is faster than that of the Zn-Cd in InxGa1-xAs. The surface hole concentration of Zn in InxGa1-xAs is 11019-21020 cm-2 at 500-600℃. At the same diffusion condition, the surface concentration of Zn in InxGa1-xAs is higher than that of Zn in InP. Reducing of contact resistance by use of InxGa1-xAs contact layer for 1.3m LED can be expected.
1987, 9(2): 161-164.
Abstract:
A Stable surface layer is essential for a high stable long life-span photocathode. Using fluorine instead of oxygen in activating the surface of GaAs substrate, the strong electronegativity of fluorine improved the stability of photocathode. The life-span of reflactive GaAs (Cs, F) photocathode has been up to 8500 hours. Furthermore, its technological reproducibility and anti-contamination ability are better than those of GaAs(Cs, O2) photocathode.
A Stable surface layer is essential for a high stable long life-span photocathode. Using fluorine instead of oxygen in activating the surface of GaAs substrate, the strong electronegativity of fluorine improved the stability of photocathode. The life-span of reflactive GaAs (Cs, F) photocathode has been up to 8500 hours. Furthermore, its technological reproducibility and anti-contamination ability are better than those of GaAs(Cs, O2) photocathode.
1987, 9(2): 172-175.
Abstract:
The problem of two △-function inverse are further discussed. Methods of solving decon-volution difficulties when the Kernel spectrum contains zeroes are presented.
The problem of two △-function inverse are further discussed. Methods of solving decon-volution difficulties when the Kernel spectrum contains zeroes are presented.
1987, 9(2): 176-180.
Abstract:
In this paper a piecewisely linear (with three or four segments) dynamic version for the relaxation oscillations in a circuit with Bidirectional Negative Resistance Transistor (BNRT) is studied. The circuit and the dynamic equations are given and some properties of the relaxation oscillations are discussed. Experimental results agree with the computations, showing that the dynamic model is adequate and useful.
In this paper a piecewisely linear (with three or four segments) dynamic version for the relaxation oscillations in a circuit with Bidirectional Negative Resistance Transistor (BNRT) is studied. The circuit and the dynamic equations are given and some properties of the relaxation oscillations are discussed. Experimental results agree with the computations, showing that the dynamic model is adequate and useful.
1987, 9(2): 181-187.
Abstract:
A practical method for directly designing sequential circuits by use of state transition diagrams is described. This method has many advantages. It is easy to use and especially suitable for multi-input and multi-state conditions.
A practical method for directly designing sequential circuits by use of state transition diagrams is described. This method has many advantages. It is easy to use and especially suitable for multi-input and multi-state conditions.
1987, 9(2): 188-192.
Abstract:
The theory of corrugated conical horn operating at multi-frequency bands is described,. and a practical corrugated conical horn is constructed. It can operate at three frequency bands (4, 6, 11 GHz) at least. The cross poralization peak level is better than-25 dB at 4, 6 GHz frequency bands, and the amplitude pattern at 11 GHz frequency band is also very good It is shown theoratically and experimentally that the corrugated conical horn operating at multi-frequency bands is the best candidate for multi-frequency band feeds.
The theory of corrugated conical horn operating at multi-frequency bands is described,. and a practical corrugated conical horn is constructed. It can operate at three frequency bands (4, 6, 11 GHz) at least. The cross poralization peak level is better than-25 dB at 4, 6 GHz frequency bands, and the amplitude pattern at 11 GHz frequency band is also very good It is shown theoratically and experimentally that the corrugated conical horn operating at multi-frequency bands is the best candidate for multi-frequency band feeds.
1987, 9(2): 165-171.
Abstract:
In 1887, Hertz Discovered the photoemission effect. In memory of the centenary of the discovery of photoemission effect, a condensed review of the development and the existing situation of practical photocathodes are presented in this paper.
In 1887, Hertz Discovered the photoemission effect. In memory of the centenary of the discovery of photoemission effect, a condensed review of the development and the existing situation of practical photocathodes are presented in this paper.
