Time-Domain Evaluation of Atmospheric Ducting Effects on X-Band Propagation Over Water

The marine atmospheric boundary layer (MABL) is the region of atmosphere that interacts with the ocean surface. The atmospheric variability (i.e. temperature and relative humidity) in this region can result in rapid changes in the refractive index with increasing height from the sea surface. The complex region can result in non-standard propagation of electromagnetic (EM) waves beyond the horizon under atmospheric ducting conditions. However, when ducting layers are not present, EM waves are limited to line-of-sight transmission. Atmospheric ducting research is typically conducted using radio frequencies in the X-band (around 8-12 GHz) due to its impact on performance of marine radars at those frequencies. Studies typically examine levels of received signal power or effects on radar returns in ducting conditions, but often ignore the time-domain effects of ducting which can also affect communications link performance. In collaboration with the Coastal Observing Research and Development Center at Scripps Institution of Oceanography (SIO), the ducting research in this thesis uses a channel sounder that consists of a X-band transmitter which transmits a coded pseudorandom sequence and a software-defined radio (SDR) receiver. Both transmitter and receiver are GPS synchronized so that the time-domain cross-correlation between the TX and RX signals can be found. In theory, if atmospheric ducting is present, there will be multipath propagation, and the TX-RX cross-correlation indicates multiple “peaks”, indicating multiple arrival times. Conversely, if little to no ducting is present, then the cross-correlation indicates a single “peak”. The channel sounding was evaluated over several over-water communications links, involving fixed-path and variable range sea tests with a moving vessel to verify if this hypothesis is true. The expected ducting conditions were determined by in-situ refractive index measurements of the atmosphere. Results from testing showed multiple peaks when strong ducting was expected, but an extensive sea test in strong ducting conditions is needed to distinguish multipath from ducting from that of terrain reflections. Further work is also needed to determine the computational model that accurately models multipath propagation through a duct, which is beyond the scope of this thesis

Refraction interference elimination employing smart arrays at VHF

Radio interference from the Middle East is one of the most significant problems plaguing the local radio services in Cyprus today. The issue is particularly noticeable on the highway, where it affects in-car tuners in all coastal areas of the island when the weather is hot and humid. In this work, the problem of interference from the Middle East was explored in the context of field strength variations versus the type of propagation mechanism favouring the radio waves in Band II, allowing them to travel from the Middle East to beyond the horizon in Cyprus. This problem was significant, since no line of sight exists between the two regions. After in-depth analysis adhering to the ITU (International Telecommunications Union) Recommendations, it was demonstrated that interference is caused by “Tropospheric Ducting”, i.e., trapping of the overseas transmitted signals between two layers of the troposphere at different heights. The upper air data were obtained using the Weather Research Forecasting (WRF-ARW version 3.4) model. The results yielded by the present study confirm that this model provides accurate prediction of interference for up to five days in advance. The interference problem is widely recognized, and therefore many attempts have been made to explicate its causes and provide solutions. The aim of the present study was to present a robust solution based on an innovative receiving antenna design. The antenna is a receiver’s component that collects electromagnetic waves from various directions. The rationale behind focusing on a circular array topology is that its tuning ensures that the receiver processes the desired signal only, while rejecting the unwanted interference. This can presently only be achieved by a large directional external antenna that must be steered mechanically in the desired direction. As this arrangement is not practical, an innovative smart antenna was proposed as an alternative. A circular phased array is a very compact antenna that produces a predicted radiation pattern, whereby it receives maximum energy from the desired direction without the need for mechanical control. Circular arrays exhibit high gain as well as immunity to interference, making them ideal for use in high interference environments. This combination allows the antenna to be incorporated into a commercial deck receiver or installed on vehicles

Marquette Interchange Installation Report

Task three of the Perpetual Pavement Instrumentation Plan for the Marquette Interchange Project called for the installation of the various pavement sensors, data acquisition system, and various other components of the system outlined in the project proposal. The MU-TRC research team has successfully completed the installation of these various components of the system. This report fulfills the requirement of the installation report from task three in the project plan. This report is organized to describe in detail each specific component of the system. Most, but not all, of these details are written in the order they were completed. Not every activity described in this report is associated with the installation of a particular component but have been included because they are thought to have a significant impact on the methodologies and procedures used. This report is intended to describe the installation processes in as much detail as possible. To help accomplish this, many figures, pictures, data, and video were acquired / developed; many of which have obviously been filtered out and only the most pertinent included. All of this material will be compiled into a single archive and will be submitted to WHRP. This report was also written to explain and document any blunders, failures, and/or deviations from any proposed designs regarding this particular project or the Marquette Interchange project itself. These types of details are given so future research can learn from these experiences and make improvements upon them

Evaluation of Mobile GSM Performance under Different Atmospheric Propagation Models

Atmospheric propagation is very effective on the performance of the wireless, mobile, radar, and communication systems. In this paper different atmospheric models are constructed under different atmospheric conditions. The performance of a GSM mobile communication is tested under different atmospheric models. From the obtained results, it is noticed that the coverage of the mobile system antenna is changed highly if the refractive index model of certain country is changed. It is concluded that the atmospheric propagation is very essential parameter to be taken into account when the siting of a mobile GSM network is to be evaluated and designed. This study will be very useful in order to predict the performance of ground radio and airborne systems