A new method of realizing elliptic ladder-type active bandpass filters is proposed. Comparing with the methods of the same category, it has the advantage of using fewer operational amplifiers, so the power consumption can be reduced. It also has the advantage of ease in adjustment. The low sensitivity property of ladder networks is maintained. The stability and the error of the fundamental circuits are analysed in detail. A sixth-order bandpass circuit is realized with this method and it shows that the evperimental resultsagree pretty well with the theoretical design.

A theoretical analysis of the performances of RF sensor proposed by B. K. Watson et al. (1981) on the Large Satellite is carried out in this paper. By use of the method given here for dealing with the error signals, it makes the EF sensing system be indeed a bigt performance system. Except the case of b=1, γ=0 or π/2, the EF sensor is insensitive to depolarization of the coming waves, and because the horizontal channel does not couple with the vertical one, so it is obvious that the precision of dynamic tracking of the RF sensor on satellite is high and in ground station this RF sensing system will be a good one for tracking righ-speed vehcles.

In this paper the wave impedaa.ee of dielectrie image line as a function of geometry dimensions and frequency is analyzed. Both the necessity and the possihility of impedance matching are studied. An optimal matching element is put forward. Its bandwidth with VSWR≤1.10 can be as wide as10.5 GHz, when it is connected between two dielectrie image lines with an impedance ratio of 4.7. Its properties are obviously better than those of elassical type.

The Obreschkoff approximation for a retardation network is carried out. Some analytic formulas of the Obreschkoff approximation and the relationship between these formulas and those of the Bessel approximation are also given. The characteristic, the frequency response and the time response of the Obreschkoff approximation are ana-lyzed. The results obtained show that the Obreschkoff approximation is more accurate than the Bessel approximation for a retardation network. In the end, a typical example is given to varify the above conclusion.

This paper puts forward a new method of network synthesis. By using the method, the RC two-port networks in which only one port is connected with RC load and those in which one port is eonnected with RC load while another port is connected with RL load can be realized.

On the basis of analyzing the oscillatory frequency of crystal oscillator, the general expression of the frequency deviation of crystal frequency-modulation oscillator is de-rived. The design formulas of the frequency deviation under optimum load condition and under condition of the modulating stage with series negative current feedback are also given.

In this paper, several types of resonant cavities with large transverse cross-section used in gyrotron are briefly reviewed. The method of caleulating the cutoff frequeneies of TE mode of elliptical waveguides with moderate eccentricities is given. From the cal-culated data of cutoff frequencies, it is shown that the gyrotron with elliptical cavity has the following characteristics: (1) a large volume cavity can be used; (2) the dcn-sity of modes which can oscillate is rare; (3) it is allowable to use an electron beam with a large diameter; (4) it is possible to use a cavity mode with low azimuthal number.

The present paper introduces an experimental method for measuring the width of illuminated and short-circuited Ni/a-Si: H Schottky barriers. The current-voltage curves for the Schottky barrier solar cells under AM1, 100 mW/cm² illumination are caleulated by using the parameters determined by experiments. The diffusion length of holes in a-Si:H obtained from the illuminated I-V curve is consistent with the results measured by the author with the surface photovoltage method in 1983. The factors affeeting the fill factor are analysed on the basis of the calculated results. A comparison of the calculated results to the experiment's reveals that the very low fill factor of the solar cells measured is due to series and shunt resistances rather than the low diffusion length of the holes.

In this paper a fast classification algorithm which uses table-look-up method is proposed. Both theoretical and experimental results have shown that (1) in two dimensional case it can reduce the computer time to the same order needed for the data I/O; (2) in the case of more than two dimensions it can save more than half of computer time. The classification accuracy is not affected by the use of table-look-up method. The algorithm is most suitable for computers without floating-point processor while there are many remote-sensed data to be processed.

In this paper, a new type of high-gain circular polarized backfire antenna is presented. It is developed on the basis of equivalent reflector method proposed by the author (1979, 1981). A eircular polarized wave is obtained by use of two orthogonal dipoles. The lengths of the two dipoles are so chosen that the real parts of their input admittances differ in 90°. The transverse dimension of the antenna is 2.24λ, the axial dimension is 2λ, the weight of the complete antenna assembly is only 1.2 kg. The gain measured is 17.5dB, the axial ratio is 0.5 dB, VSWR is 1.18 at centre frequency.