In this paper, an efficient circuit vector space algorithm is presented for enumerating directed circuits of a directed graph, by which every directed circuit is generated by the ring-sum of a fundamental circuit (directed circuit or semi-circuit) defined by a chord of the-cotree and a subset of the previously obtained directed circuits. At the same time every directed circuit in the digraph can be represented by a linear combination of a selected basic set of directed circuits.

A method is presented for a practical solution of irregular boundary problems. In this method, the irregular boundary is treated as a combination of several simple boundary value problems, which can be solved easily and exactly. To illustrate the application of the method, the characteristic inpedances of some transmission lines with special cross-section are computed. The accuracy of the method is confirmed by comparing the values obtained here with those reported in the literature.

Based on the fundamental solution of a two dimensional Helmholtz equation, the general principle of determing the cut-off frequencies of waveguides filled with two dielectric layers by using the boundary element method is discussed. In terms of the formulae obtained, some numerical results are given for two commonly used configurations. The results show that the me-od is simple and practical, and iis precision is appreciable.

Several equations of the electron-wave synchronous interaction in gyrotron oscillator are-derived, in which the effects of the guiding center drift and the phase of the RF field profile are considered. The electron efficiency is calculated for the second harmonic operation of the TE₀₂₁ mode for a double-cavity gyrotron model, in which the RF field profile and operation parameters of the gyrotron are adjusted. It is shown that the efficiency of 53% can be attained for α=1.5. The characteristic of the double-cavity structure is discussed. The bunching processes of the single and double cavities are compared. The effect of the guiding center drift and the Phase of the RF field profile on the electron-wave interaction in analysed.

The network equations of the cut-set voltage and loop current of the linear active network are formulated, and their solutions are given in terms of the submatrices of the original matrix of the network. Doing so, the matrix order, the storage space, and the computing time are greatly reduced.

After solving the boundary value problem of a waveguide junction, the exact design method of a wide-band duplexing filter for 4 and 6 GHz relay communication is obtained by using the concept of equivalent circuit. The theoretical results are in good agreement with the measured data. This design method can be used for other wide-band duplexer with similar construction.

A design technique for realizing high Q and/or f_s SC bandpass filters with reduced capa-citor spread and total capacitance is proposed. The significant reduction of capacitor spread and toul capacitance is achieved through introducing the partial positive feedback and changing the feed in capacitors in the conventional biquadratic SC filter structures. A design example of a second order high Q(=50) SC bandpass filter is given and a comparison of performance parameters among the different filter structures is given also.

In order to get better output formats for data compressors, the synchronization, efficiency and complexity of encoding and decoding, and the spreading range of error generated in transmission are analysed and discussed. Then theoretical analyses of the preformances of several typical output formats are carried out. Finally, some simulation results are given.

A 1MV 6μ Blumlein transmission line with water-dielectric is presented. Some basic parameters of this equipment are given. Major components and physical processes such as charging by Marx generater and fast pulse-forming, are theoretically analysed and calculated. The obtained results are compared with the experimental ones.

The factors affecting the mixer noise figure are examined. A low noise figure mixer is ahieved by means of GaAs Schottky barrier diode, the cross field mixer structure and recovering the sum frequency. The measured SSB overall noise figure (including IF amplifier noise figure 1.5 dB) is 5.8 dB. It is in agreement with the theoretical calculation.

A new method for accurate Zn diffusion in InP/InGaAs(P) at low temperature is put forward in order to keep the carrier profile in multilayers from redistribution. Several kinds of diffusion sources with different Zn contents are used in the experiment that shows good reprodu-cibility of the method. Using this method, the characteristics of low temperature Zn diffusion in InP, InGaAs and InGaAsP are studied, and it is found for the first time that the Zn diffusion, rate is proportional to the square of the phosphorus content in the materials.