Numbers of deployable antennas which are planned to be borne on satellite have a polyhedron approximated main reflector. The far or near field patterns of the antenna are affected by the approximation. This paper introduces a near field measurement system. Using the system, the near field of a polyhedron approximated antenna are measured. The effects of the approximated reflector on near field are examined. The peaks of the amplitude exist at the facet junctions on the main reflector. In the plane far from the antenna, the effects of the reflector become weak. The analyzed result with a current distribution method coincides with that in the measurement. It has been made clear that a current distribution method is available for the analyzation of the reflected wave from main reflector.

View full abstract

Multimode conical horn antennas composed of several flare sections with different flare angles which have simple structures, mainly provide the far-field radiation patterns having equal beamwidths in the E- and H-planes and low cross-polarization levels by optimizing relative amplitudes and phases between a dominate mode and higher-order modes. In this paper, an analysis method based on generalized telegraphist's equation is presented for the multimode horn antennas with flare-angle changes. In order to obtain rigorous solutions, many modes were taken into account. The validity of the analysis method was confirmed by comparing between calculated results and measured results.

View full abstract

A dynamic programming algorithm based on the principle of optimality was developed by Bellman as a method for a multi-stage decision process in the 1950's. We have made a wide frequency change using a step frequency radar and have achived 3-dimensional laser microvision with a very high-resolution limit; the dynamic programming algorithm was employed as a signal processing method. With this 3D laser microvision, we can see through fine structures three-dimensionally to detect faults in them. The resolution limits of usual methods for this purpose are of the order of 10 μm or wider than about 10μm; a resolution limit narrower than 1μm is needed. Based on the principle of the dynamic programming algorithm we derive the resolution limit of 10^<-2>μm and show some excellent characteristics in comparison with the numerically-calculated results using the MUSIC method.

View full abstract

The Akebono (EXOS-D) satellite launched on February 21, 1989 make successful observations. The objectives of VLF instruments on board the satellite are designed to investigate the behavior of plasma waves associated with accelerated auroral particles, wave-particle interaction mechanisms, and propagation characteristics of whistler-mode waves in the magnetosphere. The instruments are designed to measure not only dynamic spectra of VLF waves, but also their absolute field intensities, wave normal vectors, and Poynting vectors. These measurements have been successfully performed. The present paper describes the instruments in detail.

View full abstract

The Electro-Magnetic Compatibility specifications for the GEOTAIL spacecraft and sub-systems were established to keep high quality measurement of plasma waves. In order to accept this requirements, we had improved various kinds of ways in the sub-systems and the satellite system itself to reduce the electromagnetic radiation and conduction noise from them. In this report, we describe specifications and measurement of the EMC for the GEOTAIL, and show the results of the EMC tests for the sub-systems and spacecraft,introduce a way to reduce the magnetic radiation noise generated by the trangent current in the Solar Cell on the surface of the satellite when a shadow of the extention mast is cast on the surface, and finally report the actual electro-magnetic interferrnce levels observed by the satellite after the launch.

View full abstract

This paper describes the numerical results on a strip element for Circularly Polarized Printed Array antenna composed of Strips and Slots (CP-PASS). The strip element is composed of a strip dipole and a window which increases the frequency bandwidth of the strip element. In this paper, the basic characteristics of the probe has been demonstrated numerically. Using the Prony's method, we can reduce the computation time. We examined on the parallel plate mode generated from the strip element.

View full abstract

A thin film Microwave absorbers with wide absorbing band structure has been required to deminish the useless electromagnetic wave. In this paper, a new scatter type thin film microwave absorber is proposed. A design method of double-layered absorber was provided by means of a transmission line theory. The authours have applied a scatter type method to the dipole Aluminium metal which are put loss dielectric based on a metal. Also, the. operational principle and experimental results are discussed.

View full abstract

高能率を実親できる回路としてE級動作を用い,かつ終段デバイスとしてVHF帯全域をカバ-できるMOS-FETを用いることにより,90MHzにおいてユニット能率として約80%(従来より15ポイント向上,サ-キュレ-タなし),終段ドレ-ン能率として85%を得た.This paper discribes Class E High-Efficiency FM Power Amplifier. Drain efficiency of 85% and module efficiency of 80% are obtained without the circulator at a frequency of 90MHz Using power MISFITS.

View full abstract

In this paper, a mothod of reducting SAR in a cylindrical human model by a shield plate is proposed for RF engineers exposed to strong electromagnetic waves. The shield plate modeled as an arc structure is shown effectively to protect the cylinrdrical human model from the exposed field.

View full abstract

Liking reported formerly, dividing sections the transmission line transmissing digital signal to do as the digital circuit network, digital signal processing method applies for coupling-crosstalk analysis. This time is for (1) mutual conversion between the coupling distribution having different bandwidth (highest frequency). (2) part and application of all kinds of window functions. (3) actually calculating characteristics of time domain and frequency domain of coupling-crosstalk line as digital circuit network and comparing with an measurement values. Because calculation values are about same with an actual measurement values. Validity of this digital signal processing method made it sure.

View full abstract

The multi -layer electromagnetic absorbers of sintered ferrite and ferrite composite membrane were succesfuly applied to anechoic chambers for EMI mesurements at 3 m and 10 m transmission distance. The site attenuation characteristics of the anechoic chambers satisfied the FCC standards concerned. The wall thickness of the anechoic chamber having the novel absorbers could be reduce 1/10 times thinner of less than 90 mm as compared with the conventional absorber having pyramidal urethane carbon absorber put on sintered ferrite. Consequently, the anechoic chambers having the novel absorbers can reduce its installation area. In case of small size anechoic chamber (7m × 3 m × 3 m) for immunity measurement, the uniformity of electric field was improved in the range of 600 MHz 1000 MHz due to the novel absorbers applied.

View full abstract

CISP R measures the R.F. noises from electric machines using the arti ficial mains network composed of resistance. Even if measured noises voltage using CISPR methode is 1mV, the actual noises of electric machine at its mains terminal may be 100v. Then CISPR methode is doubtful. Let us discussion about the artificial mains network composed of wire lines which can be measured the noise power and used for reserch of noise generation and prevention.

View full abstract

Although making a free space by a single fence (anti-reflection screen) is an expedient method, it has a number of problems such as incompleteness when the reflection point shifts as a result of changing the elevation of the transmit or receive point, and necessity of a phisically larger-size fence to minimize diffraction loss to a direct ray of a longer wave length. There is a countermeasure, i.e., multiple array of lower fence to solve this problem, however, it requires to minimize performance degradation due to double reflection between adjacent fences. In this test, the validity of an obliquely arranged threefold fence. 0.9m (height) by 3.6m (width) was confirmed for measuring distances of 3m, 5m and 10m.

View full abstract

Several paper been written Reporting that software erroes frequently occur in the memory chips installed in the aircraft electronic instrument. The established theory attributes the cause to cosmic rays. However our observation of the electromagenetic enviroment inside the aircraft during flight have unveiled the probability that electric field created by static electric charges could be related to the single-event software errors. We measured the electric filed it could continuously be 1.0 to 3.0 V/m. This result did not occur with the conventional electrostatic simulatars capacitor type method. we wound need to have a different kind of simulator designed for the static electricity problems in the field.

View full abstract