High frequency multi-beam aerial array

Imperial Users onl

Effects of rain and other phenomena on the received signal of the inmarsat earth-space system

The records of signals from the inmarsat satellite received at low elevation angle at the Singapore Telecom Earth Station at Sentosa were studied to determine the cause of significant fading which had occurred. The three main mechanisms were identified as rain attenuation, ionospheric scintillations, and troposheric effects.RP 34/8

Telecommunication and information techniques and systems II

This research highlights the need to corporate a new addition loss factor in the design of millimetre line-of-sight as well as satellite links especially in equatiorial regions.RGM 13/9

Prediction models for DTV coverage in Singapore

RGM 28/01 is research funded project entitled "Prediction Models for DTV (Digital Television) coverage in Singapore" approved by NTU in December 2001. The scope of the project work was to review the prediction models, quality of service (QOS) parameters and measurement techniques for obtaining QoS of mobile and Fixed DTV in Singapore. With the received signal strength, the objective was to design and package the software for predicting the coverage area for DTV in Singapore using commercial software tools and terrain data together with clutter classification for local environment. From the contents of the report, the research work has developed a suitable QoS parameters and measurement methods, procedures and analysis for verifying the QoS of DTV service in Singapore. The recommendations and technical work within is useful for the broadcast operators in the future. Finally, the research work has proposed several new models for DTV predictions including integrating a software package EDX making use of the terrain data, clutter classification and clutter factor for the local environment

Rain attenuation prediction model for satellite communications in tropical regions

This paper proposes a model for predicting rain attenuation in the tropical region. Slant path rain attenuation measurements were carried out in Singapore by analyzing the beacon signals from two satellites, namely WINDS and GE23, operating at frequencies of 18.9 and 12.75 GHz, respectively. Rainfall rates at the location of the beacon receivers were recorded. The cumulative distributions of the rainfall rate and the corresponding rain attenuation are presented and analyzed. It is found that the cumulative distribution of the measured rainfall rate is close to that predicted by the ITU-R model. Measurement data from a total of nine countries are compared with four existing rain attenuation prediction models, namely the Yamada, DAH, Karasawa, and Ramachandran models. Results show that although three of these models have relatively good prediction capability for the tropical region, they could be improved. Therefore, in this paper, a slant path rain attenuation model suitable for the tropical region is proposed. This is done by using the complementary cumulative distributions of rain attenuation for satellite links measured in Singapore and five other tropical countries. The proposed model is found to outperform exisitng models.Accepted versio

Site diversity gain at the equator : radar-derived results modeling in Singapore

Site diversity is an effective rain attenuation mitigation technique, especially in the tropical region where high rainfall rates are common. According to our previous study, site diversity gain is found to be dependent on the site separation distance and path elevation angle while it is independent of signal frequency, baseline angle and polarization angle. Therefore, using 28 months of Radar data, a simple site diversity gain prediction model is proposed. The proposed model is compared with the existing ITU-R models. The seasonal wind direction, another factor that might affect the site diversity gain prediction model, is shown to have negligible effect on site diversity gain. Triple-site diversity is also investigated and although it is found to provide gain improvement over dual-site diversity, this gain improvement is too little to justify for the cost of setting up an additional site. This study is useful for the implementation of site diversity as a rain attenuation mitigation technique in the tropical region.Accepted versio

Development and fabrication of low noise microwave distributed amplifiers using hybrid techniques for optical fiber receiver applications

304 p.An introduction to the background and achievements of the research project is given in Section I. This is followed by the theory and development of an ultra-wideband distributed amplifier in Section II.RP 42/8