An optical fiber amplifier for optical AM-VSS transmission systems has been developed. CNR characteristics was estimated theoretically when using flber amplifiers. It was made clear that the input signal power into a flber amplifier was limited to be more than a certain level for achieving a desired CNR. An optical flber amplifier have been fabricated by using an erbium-doped fiber with high conversion afficiency which we have also developed. The loss budget was improved to be 14dB for CNR of 51dB at the 40 channel transmission.
This paper describes the design and performance of elliptical offset gregorian antenna (2m×1m) for satellite news gathering (SNG). The primary horn of this antenna is a triple mode horn with double flare and has a low cross polarization component. It was confirmed that this antenna with the triple mode horn realized a low sidelobe (29-25log θ dBi). low cross polarization discrimination (35dB) and high efficiency (70%). The results show the effectiveness of this design.
In this paper, for AM/FM B.C. and mobile telephone (MT) in vehicles, a triway antenna with double sleeves has been desined. one of the triway antennas has been analyzed numerically and the results have been compared with experimental results.
A high gain image type antenna combined two and four stacked circular loop antenna with a metal plate is analyzed by a proposed theoretical model. Several computed curves are given, and the values computed for current distributions and radiation characteristics are substantiated by experiments. Computed radiation characteristics are utilized to obtain a desirable configuration, and four stacked image antenna used to UHF TV broadcast is experimentally examined.
Extraordinary increase of operable frequency range is achieved when the cylindrical rod of a monopole antenna is replaced by a circular disc. The radiation patten is omni-directional and the beam width is slightly frequency-dependent. A mesh of wire may also be used instead of a solid disc. The entire broadcast TV channels (VHF and UHF) are covered by a single disc monopole antenna of 500mm diameter.
As the next generation satellite broadcasting system, the system which uses the K-band, such as 22GHz band, have been studied. For the design of this kind of system, it is necessary to have detailed knowledge of the wave propagation characteristics along satellite-to-earth path. In this paper, propagation characteristics ; rain attenuation, cross-polarization discrimination, etc., in the K-band are explained together with mitigation technologies of those effects. One system example of K-band satellite broadcasting is proposed, in which time-diversity technology is introduced to compensate the rain attenuation.
Development of the field strength chart is used for determination of the optimum antenna direction for radio and television propagation. We have an idea of the chart has a constant field intensity characteristic, following the cosecant beams on the propagation. The field intensity characteristic shows constant gradient curves, and the free space field intensity value is shown at horizontal line on the chart. This field strength chart is useful for any praotical measurements for radio and television electromagnetic wave propagation, and we discuss the CCIR propagation characteristics.