The study of characteristics of the cavity-backed slot antenna in a lossymedium is given by using the moment method and dyadic Green s functions. The Poisson summation formula is used to convert the double series of the elements into a more rapidly converging series, and the integration middle value theorem and elliptic integral are used to simplify the double integral of the elements. Numerical results show the effects of the lossy medium and antenna parameters on input impedance, which could be used in designing cavity-backed slot antenna.

Generally speaking, an accurate mutual coupling correlation is necessaryfor an array antenna to reach ultra-low sidelobe level. If the mutual impedance or mutual coefficient matrix of an array is perfectly known, one can completely compensate the effect of mutual coupling and realize the desired low sidelobe level in theory. However, the mutual impedance matrix obtained whether by calculation 01 by measurement has a limited precision, which limits the availability of the compensation. This paper deals with the requirements on the precision of mutual impedance for compensation. in ultra-low sidelobe array antenna. The relationship between mutual impedance errors and the amplitude and phase errors of channels is derived, by which the relationship between mutual impedance error and the sidelabe level is given.

A novel method proposed in the paper is aimed at reconstructing thecomplex permittivities of inhomogeneous lossy dielectric bodies. The method is based on such a principle that sufficient informations of a dielectric body may be obtained from the scattered fields when the body is illuminated by a group of unrelated incident fields. The formula derivations and the simulation results are presented, and the accurate reconstructed results show that the method proposed has great potentialities in developing the electromagnetic inverse sca- ttering and the microwave imaging.

A general analysis approach to multi-object scattering systems of arbitrarystructure is presented. Through the system scattering equation (SSE), the multi-object problems are first transformed into a series of single-object problems. Then we solve the single-object problems, one-object by one-object, TO yield the unknown coefficients of SSE and finally obtain the complete solution of original multi-object problems. As to the solutions of single-object problems, we use the finite element method for complex scatterers, or simply the moment method for conducting scatterers. We will confine ourself in two-dimensional cases, and show some calculation examples of 3-object conducting cylinder scatterers coated with dieletric material for demonstration.

With the extension of complex ray theory (CRT) from lossless media intolossy ones, the complex ray analysis in lossy media can be constracted, and effectively used in the problems of scattering analysis of objects coated with radar absorbing materials (RAM). This method has advantages, such as simple calculation procedure, clear physical meaning, wide applicanon area etc. As an example, the radar cross-section (RCS) of conducting flat plates coated with RAM is analyzed. The results show that the theoretical predictions agree very well with the experimental results.

The curve moment and curve moment invariants are proposed, which aresuitable to be used not only in the pattern recognition of closed shapes, but also in that of any curved objects. By using the proposed moments, some errors of the known methods are corrected. Finally, a simple algorithm is proposed to calculate curve moments.

A new array processing method is presented. The method is computationally simple and beneficial to real-time processing, because it dose not require eigenvalue de-composition (EVD) and multi-dimensional optimizing processing. The method is also suitable for the coherent case. It is compared with PROJ method and Yeh s method (1987). Simulation results are given.

A new method is presented based on nullor substitution, which is suitablefor detecting single faulty branch with short-circuit or open-circuit on tree type power network. The required current and voltage values of each port are easy to be measured, and the proposed method needs less computations after measurement. It is feasible for single faulty-branch location on tree type powed network with several branches. Simulation by computer shows satisfactory results.

Finding all perfect matchings in a given bipartite graph has importantapplications to the global routing and channel ordering for VLSI building block layout. An algorithm for finding all perfect matchings in a given bipartite graph G(X,Y, E) is presented. First, the definition of marriage tree T(x_i) is proposed and some properties of T(X_i) are discussed. Second, it is proved that anyone of marriage trees, T(x_i), resulted from G(X,Y,E) corresponds to all perfect matchings in G(X,Y,E). Finally, discription of the algorithm is given. The algorithm has been implemented in C language and good results laave been obtain-ed. The algorithm has also been employed as a program block in our VLSI building block layout system which has been developing.

A new type of public key cryptosystem and a new type of auto-authentication cryptosystem over Eisenstein s ring Z[ω] are presented. The security of these two types of cryptosystems depends on the difficulty of integer factoring and logarithmic computation in Z[ω] .

When a linear voltage ramp applied to the gate of an MOS device the C-t transients are observed. Before the voltage ramp is applied the MOS capacitor is biased into strong inversion in order to eliminate the surface generation. From the C-t transient curve obtained experimentally, the minority carrier generation lifetime in semiconductor can be determined. The experimental results show that for the same sample the lifetimes extracted from the C-t curves obtained under different voltage sweep rates are consistent each other, and they are consistent with the lifetimes extracted fdom saturation capacitance method.

The fabrication method of W[111] tip and the operating characteristics ofa field emission gun (PEG) which consists of W[111] tip, first and second anodes are reported. Experimental results show that on condition that the vacuum in the gun chamber is better than 5×10^-7 Pa and acceleration voltage is 30kV, the finite radius of the virtual source of the FEG is 1.6nm, and the brightness of FEG is estimated as 3.8×10⁹ A/cm², sterad; on condition that the field emission current is 1μA, the stability of beam current is better than 5% in 10 min. It is able to be used in scanning electron microscopesand electron probe system etc.

An adaptive dummy spectrum insertion method which can be applied to L. S. Lee s asynchronous speech scrambler is presented. It is concluded that the method shows high-level security and good voice quality.

The analysis of frequency pulling phenomena occurred in mutual inductive coupling oscillator under a sinewave signal injection by using Volterra series method is presented. The frequency pulling width is finally obtained. When the model of a system has been established, one needs only to perform algebraic operations, thereby, the complicated process of solving nonlinear differential equations is avoided.

The propagation of electromagnetic wave in the mirostrip structures is.studied. By using the Sommerfield integral, the expression of the field in the microstrip structure is deduced. This expression is the same as the Sommerfield formula for the half space in limiting case.

A supplement and an expansion of authers previeous work (1990) are presented. The improved perturbation method is used for analyzing the radiation characteristics of the millimeterwave dielectric grating antennas with various groove profiles. A comparison between the results given and those obtained by the rigorous calculations shows that the present analysis yields as highly accurate results as the rigorous method but the calculation procedure is tremendously simplified. Based on this, the effects of groove profiles on the performances of the grating antennas are systemetically studied. The curves given in this paper may be used as reference for designing the dielectric grating antennas.

A method for compensating the amplitude-phase distorfion of ISAR system is described. This system compensation can be separated into two parts; the compensation of the system before mixing and the compensation of the system after mixing. The experimental results of the compensation in microwave dark room are given. It is shown that the method presented is effective.

A accurate expression for the bandgap and a simple formula for the intrinsic carrier concentration at low temperature are presented. The relation between the intrinsic carrier concentration and the temperature and doping concentration in the heavily doped silicon is obtained, under the consideration of the narrowing effect of the bandgap at the heavy doping level. It is indicated that the intrinsic carrier concentration increases more rapidly with increasing the doping concentration at low temperature than at room temperature.

MCP noise caused by nature radioactive isotopes is calculated. The calculated results of MCP noise caused by Rb⁸⁷ and K⁴⁰ are in the order of 10^-13A/cm² and 10^-14A/cm² respectively. They show that in some special applications, MCP free of Rb³⁷ and K⁴⁰ are needed.

The dispenser cathodes are investigated by using modern surface analysistechniques (XPS, APES and ARPES). The surface chemistry and emission properties of the dispenser cathodes activated in situ are obtained, and the experimental results are discussed.