A propagation experiment for modelling high elevation angle land mobile satellite channels

This paper summarizes the results of a feasibility study for conducting high elevation angle propagation experiments in the European region for land mobile satellite communication. The study addresses various aspects of a proposed experiment. These include the selection of a suitable source for transmission, possibility of gathering narrow and wide band propagation data in various frequency bands, types of useful data, data acquisition technique, possible experimental configuration, and other experimental details

Results of multiband (L, S, Ku band) propagation measurements and model for high elevation angle land mobile satellite channel

Signal propagation in the land mobile satellite (LMS) service is an important consideration due to its critical impact on the overall economic and commercial viability of the system. At frequencies allocated for LMS systems, shadowing of the line-of-sight (LOS) signal as well as multipath propagation phenomena can severely impair the link availability. In particular, as most of the studies have shown, the shadowing of LOS signal causes long and deep fades in a variety of mobile environments due to the inherent nature of the channel between the satellite and a mobile. Roadside obstacles, such as buildings, trees, utility poles etc., in the immediate vicinity of a mobile and the surrounding terrain are major sources of signal shadowing in LMS links. Therefore, a proper knowledge of link degradation is essential for cost-effective planning of a satellite based mobile communication system. The results of a propagation campaign undertaken to characterize the fading nature of LMS channel at high elevation angles is presented. It was envisaged that one of the most important physical variables contributing to the amount of LOS signal shadowing is the elevation angle of the satellite. At higher elevation angles to the satellite, less obstructions in the direct satellite-to-mobile path would therefore amount to statistically better link availability. Narrowband channel measurements were carried out at three RF frequencies corresponding to L (1.3 GHz), S (2.32/2.45 GHz), and Ku (10.4 GHz) bands. The campaign itself was divided into two phases to observe the effects of seasonal variation of foliage on the roadside trees. Phase measurements were carried out in September 1991 and in April 1992. Some important aspects from the statistical analysis of the propagation data are presented

Manganese pigmented anodized copper as solar selective absorber

The study concerns the optical and structural properties of layers obtained by a new efficient surface treatment totally free of chromium species. The process is made up of an anodic oxidation of copper in an alkaline solution followed by an alkaline potassium permanganate dipping post-treatment. Coatings, obtained at the lab and pilot scales, are stable up to 220 °C in air and vacuum, present low emissivity (0.14 at 70 °C) and high solar absorptivity (0.96), i.e. a suitable thermal efficiency (0.84 at 70 °C)

Mobile satellite communications: principles and trends

Madhavendra Richharia, Knowledge Space Ltd., UK.xx, 731 pages : illustrations ; 25 c

Surface analysis of a black copper selective coating

This paper presents the surface analysis of a black copper selective coating using AES and XPS techniques. This study indicates that the textured black copper selective coating is a multiphase system. These surfaces are stable up to 250°C in air and under vacuum conditions. Subsequent annealing of these surfaces to temperatures > 370°C shows significant changes. The external environment exposed surface has indicated no significant change

Study Of Higher Harmonics Of Cosmic Ray Intensity On Quiet Days At Tokyo Station

ABSTRACT The cosmic ray intensity data recorded with TOKYO Neutron Monitoring Station have been investigated on 60 Quiet Days (QD) in a year for studying the higher harmonics of daily variation during solar cycle 21 and 22. It has been observed that inspite of the abrupt change in the amplitude and the phase of the higher harmonics of daily variation in cosmic ray intensity, the amplitude of third harmonic of daily variation on QDs is larger by a factor of two during the period 1983 to 1986, i.e. the declining phase of solar cycle 21, similar to that observed 11-years ago i.e., declining phase of solar cycle 20, at Tokyo station. Thus, 11-year variation in the tri-diurnal anisotropy of cosmic ray intensity is clearly observed at the Tokyo neutron monitoring station. Further, the amplitude of the fourth harmonic of the daily variation on QD during 1987-90 shows an increasing trend continuously in association with phase of fourth harmonic shifting to earlier hours

Effect of solar poloidal magnetic field reversal on diurnal anisotropy of cosmic ray intensity on quiet days

236-240Using the Deep River neutron monitor (NM) data for the period 1964-95 covering three solar cycles, namely 20, 21 and 22, the long term trend and the effect of reversal of polarity of the solar magnetic field (PSMF) on the diurnal anisotropy of cosmic ray (CR) intensity on quiet days (QDs) have been investigated. The phase of the diurnal anisotropy on the QD has started regaining its usual corotational direction after 1976, acquiring it in 1985 and remains statistically invariant till 1991. The phase of the diurnal anisotropy on QD has shown a significant shift to early hours when the PSMF in the northern hemisphere (NH) is positive during the periods 1971-79 and 1992-95 as compared to that during the periods 1964-70 and 1980-89 when the PSMF in the NH is negative, confirming again the earlier results of 22-yr periodicity