In Japan, the interference against TV channels caused by Duct or Sporadic-E propagation of neighbouring countries'FM or TV broadcast waves is one of the most serious problems. The canceller of this interference was developed and started to use practically in May 1986 at two NHK TV relay stations in Tottori prefecture. The canceller could reduce the beat interference about 40 dB. According to the evaluation of pictures recorded by VTR before and after cancellation, compensation was almost achieved.
Unwanted Radiation from Teletext Receivers by Harmonic waves generated its sampling clock-signal, is possible to give undesirable interference with TV-receivers and other radio receivers. This report presents measuring and considering results of Unwanted Radiation from Teletext receivers.
In the case of connecting the small scale A. C. magnetic switch to the power supply of electronic systems and making and breaking switch, the electrical noises generate and can be the cause of systems malfunction. The main electrical noise may be the saw-tooth noise generated when switch's coil current is cutoff. This paper clarifies the noise generation mechanism and proves the noise suppression method theoretically and experimentally.
Transient response of a transmission line excited by an electromagnetic pulse is developed by the use of Laplace transformation. The response obtained in a form of analytical functions is composed as if it were induced one at both line ends, and also reflected one for mismatched lines. This leads the equivalent circuit represented by a voltage and a current sources at each end. Since the circuit is in a form of cascade, it is available to predict the response for lines in various configurations.
Noise Suppressing Inductors of Amorphous Core have already used as common mode chokes, but they have not used as normal mode chokes. In this paper, normal mode chokes were inserted to several kind of noise sources. It was confirmed that noise suppressing normal mode chokes of Amorphous core were better in effect than chokes of Iron Dust Core.
This paper describes the protection method of IC card against electrostatic discharge. The protective device consists of five silicon avalanche diodes fabricated in a planar structure of 3×1.5×0.25mm^3. The IC card connected in parallel with this device was not degraded by exposure to electrostatic discharge of 15.5 kilovolts.
This report presents the FM-CW radar system for detecting buried bodies in snowpack and the experimental results. From the experimental propagation characteristics of microwave through snowpack, frequency range from 1 to 2.5 GHz was considered to be suitable for detecting the target in snowpack and our radar system employed this frequency range. It is shown that this FM-CW radar system can detect the buried bodies in the snowpack about 1 meter in depth from the surface of snowpack.
The application of the spectral estimation technique to direction finding faces two problems : (1) The available data length is short, and (2) The multipath propagation results in non-stationary process. The authors combine the technique of eigenvector analysis on a spatially smoothed correlation matrix with a robust power estimation formula. The numerical examples demonstrate its excellent performance.
It is necessary to investigate the radio propagation characteristics in snowy regions or snow-capped mountains for mobile communication systems. This report presents the experimental results of radio propagation on roads surrounded by tall snow side walls. The results are compared with calculated ones by Ray theory using a groove shaped model. It is shown that the attenuation constants for horizontally and vertically polarized waves are minimal in a frequency range from 1 to 3 GHz and that theoretical characteristics agree with experimental ones in UHF band.
A general method for theoretical evaluation of site attenuation is developed which can be applicable to test sites with natural ground as well as with metal ground plane. In this method, site attenuation for horizontal antennas is calculated by introducing an effective reflection coefficient. Site attenuation curves are presented for various types of ground conditions.