The Bergeron's method is presented for the numerical transient analysis of the electromagnetic fields. The method is available for the problem containing both the dispersive media and the complicated geometries of boundary. The formulation of the method is briefly introduced. Numerical evaluations of the formula are given as an example for the cold plasma radiated by an cylindrical reflector, and some interesting results are illustrated to show the electric field variation caused by dispersion and reflection on the space-time domain.

Performance of multilevel FM with discriminator detection is studied for digital speech transmission in mobile radio channels. New transmit- and receive-baseband filter configurations in digital FM are considered. The low-pass filters are characterized by a square root of the raised cosine Nyquist filter. The present method is simple as an analog FM and has high immunity against fast fading. It is shown that digital speech can be transmitted with a 4-level FM and a 16 kbit/s adaptive delta modulation under a 25 kHz channel spacing, where the relative interchannel interference power is around -70 dB.

A new voice multiplexing system for subscriber carrier system called "envelope multiplexing" is proposed in this paper. In this scheme, transmission format is composed of a frame in which at most one signal from one subscriber appears. Time slots in a frame can be assigned on statistical multiplexing basis and if all the demand can not be satisfied in a frame, the excessive information will be lost. The design principle and the characteristics of the system are described in this paper.

A fundamental study for labeling and painting of line drawings is described, and its applications to an animation cel and alphabet are exemplified. Multiple closed regions included in binary line drawings are extracted, and they, both enclosed by image pixels and by non-image pixels, are labeled from the outermost boundary into inner boundaries. After that, a set of these labeled regions is transformed into a simple string by using inclusion relation and disjoint relation defined among them. In the method, the contour of every closed region is automatically traced, and the coordinates of the traces points are stored in the memory of a computer. Inclusion relation and disjoint relation among multiple closed regions are obtained by comparing the numbers (areas) of image pixels and non-image pixels.

A novel transversal electro-optical switch using Bi₁₂SiO₂₀ single crystal is proposed and demonstrated. Since the drive voltage of switches of this type is proportional to the crystal thickness, we used a crystal plate with a thickness of only 100 µm to reduce drive voltage. With plate of this thickness, however, the light rays propagated inside the crystal undergo total internal reflection at its upper and lower surfaces. Consequently, the polarization state is scrambled causing crosstalk. A thin three layer interference film of SiO₂-Si:H-SiO₂ was applied to the surfaces of the crystal to maintain the polarization state. By this method, a drive voltage of 390 V with crosstalk of -20 dB was obtained at 1.3 µm wavelength.

We propose a new type light amplifier composed of an integrated twin-guide (ITG) structure and discuss its amplification characteristics. It has two coupled guides: one is an active guide for the light amplification and the other is an output guide which is a loss-less passive guide for input and output of the light. Using a matrix method we derive two expressions of gain for transmission and reflection types of amplification. We obtain the regions of parameter in which the amplifier operates stably. The reflection type gain is usually larger than the transmission type one, because the path of the reflected light is longer than that of the transmitted light in the active guide. Although the amplifier has a resonator, the transmission type gain becomes insensitive to the wavelength of the amplified light under a certain condition. This feature is useful for the stable and wide-band amplification. We also discuss its noise characteristics by regarding only spontaneous emission as a noise sourse and express the signal to noise ratio and the noise temperature. The noise temperature is considered to be the temperature of a black body which emits the same amount of light as the spontaneous emission of the amplifier. As a result of numerical calculation, the temperature is estimated to be over a few 1000 K of a AlGaAs/GaAs laser amplifier, but the signal to noise ratio is expected to be 10-30 dB.

Frequency scaling method, employing the concept of path-averaged raindrop size distribution (D), is successfully applied to predicting the rain attenuation statistics. Experimentally determined Eq. (D)26,000^-0.294 exp (-5.6^-0.283D), (: a path-averaged, rainfall rate) is applicable to the prediction even in the frequency above 80 GHz where Laws and Parsons distribution falls into underestimation.

A time domain formulation for source sound isolation is presented using a new concept of matrix convolution, and is compared with the corresponding frequency domain formulation. Computer simulation suggests that this method is applicable to practical cases.

A compact and accurate large-signal model of bipolar transistors is derived from the original Ebers-Moll model, taking account of the computing efficiency. Since the model including the Early effect and the current-gain factor has a good agreement with the measured current-voltage relationship.