Most of the R.F. noises which are the sources of disturbance for electronic devices, are caming from their power supply lines. Mains of them are damped oscillation induced in their lines, R.F. noises are generated at opening and closing the circuit. Noise mode are two types, one is normal and other's common. Let discuss the noise generation mechanism at opening case, and shows how to suppress them.
Electromagnetic interference is evaluated to apply metallic lines to digital transmission of ISDN. Especially, the interference on usernetwork interface is investigated in detail, because the unbalance about earth of terminal equipment increases the interference on bus wiring configuration. The interference by induced voltage from radio wave, lowvoltage supply line and analog telephone line is evaluated, and measures against the induced voltages are studied. Consequently, the interferences are eliminated by insertion of common-mode choke coil and improvement of balance of the equipment.
The radiation noise from the harness which is connected to the shield-box was measured with the turned dipole antenna in order to evaluate the shielding effects of the harness used in the electronic apparatus. The directivity of the radiation noise from the harness changes with the measured frequency and depends on the harness length for the fixed frequency.
It is generally difficult to estimate the inside profile of dielectric layers structure using with monocycle pulse which does not obtain a carrier frequency. The reflected wave of monocycle pulse from a dielectric structure consists of many elementary passing through the layers. If we could separate the reflected wave to elementary component, it is easy to presume the inside profile. In this paper, we describe how to separate the reflected wave to elementary component named spectrum separate calculation method, and discussed the properties of this method.
Microwave absorbers produced by painting method are proposed. In this paper, a good impedance matching and a low reflection factor for microwave absorber can be expected resulting from the multi-layer structures. A design method of double-layer absorber was provided by means of trasmission line theory. The authours have developed a painting method absorbing wall using several kinds of magnetic materials which are put loss-less dielectric based on a metal. From the experimental results, it is concluded that the amounts of reflection agree well with results from theoretical calculation.
The present facilities to procedure for electromagnetic shield effectiveness are mainly that only to measure the materials (small sample), and the object itself to be measured is limited to a thin material with the area of about 60cm×60cm maximum. This situation does not allow to measure the joint section of the materials themselves and the connecting sections of buildilng components at the actual construction of a shielded enclosure. In addition, it does not conform to the procedure of MIL-STD-285 which is generally used to evaluate the effctiveness of shielded enclosures. The facility to measure electromagnetic shield effectiveness presented here allows to measure a thick material with a width upto 230cm and a height 180cm having a weight upto 1 ton based on the procedure to the MIL-STD-285. At the construction, three kinds of shielded enclosure construction method wereused. This paper introduces these construction methods in addition to the measurement facility.
A ground resistance reducing material using water-absorbent polymers is superior to the Bentonit treatment material regarding to use amount, labor and corrosion against grounding electrode. Its reducing ground resistance material with only water has long-term stabilities against temperature and underground environment, and its material with a epoxy also has stabilities for ground resistance and compressive strength against such underground environments.