The Quantification of the Influence of Rain Attentuation on Received Power at Ka Band

The Quantification of the Influence of Rain Attentuation on Received Power at Ka Band.

Abstract

The quality of satellite communication link can be seriously affected by variable climatic phenomena such as rain, gases, and scintillation. As the frequency of operation increases

beyond 10GHz, the effect of rain becomes very severe with the growing need for high bandwidth frequencies such as frequencies in the Ku-band and Ka- band hence the need for better fade mitigation becomes necessary.

In order to identify the appropriate rain fade mitigation technique, there is need to quantify the amount of fading experienced due to rain.

This project aims to identify an appropriate rain fade calculation technique for Nigeria.

After the technique is identified, rain rate data is then obtained from Nsukka, Enugu State in Nigeria and used to obtain the rain fade margin.

In performing a link power budget analysis, the fade margin (FM) is a critical component. Often times, the inclusion of a large FM is not cost efficient or technically feasible. Therefore FMTs must be integrated into the overall system design.

This thesis is aimed at presenting a comprehensive review of current and future satellite communication technologies and applications, paving the way for a comprehensive analysis of current and proposed FMTs catering for rain attenuation.

This analysis spans techniques such as; Diversity, Adaptive Signal Processing, Adaptive Source Sharing, Uplink and Downlink Power Control, and others.

Introduction

Background Of Study

As the radiowave propagates through the earth-space link, the nature and composition of the atmosphere introduces impediments which cause a degradation of the signal.

The effect of the atmosphere on the propagating radiowave is a critical concern in the design of a satellite communication link as it can cause variations in signal polarization, phase and amplitude [1].

These effects depend on the geography of the location, climate of the location and frequency of operation of the satellite link.

The frequency of operation is a critical factor in determining what impediments the radiowave would be susceptible to.

The complexity of the atmosphere means that the losses experienced are a combination of losses due to individual components in the atmosphere.

The primary constituents affecting a satellite link are water vapour, gases, rain and clouds.

At frequencies below 3 GHz the ionosphere is the primary source of transmission impairment as a result of background ionization and ionospheric irregularities along the propagation path.

Above 3 GHz, rain is the major impediment impacting on the earth-space link as the raindrops scatter and absorb the radiowave energy causing a reduction in the amplitude of the transmitted signal leading to a situation known as rain attenuation.

At frequencies above 10 GHz and spanning into the Ka-band and beyond, the effect is very significant leading to grossly ineffective links.

References