This paper offers a comprehensive and integrative overview of all empirical data available from the open literature on the in-tunnel radiowave-communication channel's power loss characteristics, as a function of the tunnel's cross-sectional shape, cross-sectional size, longitudinal shape, wall materials, presence or absence of vehicular/human traffic, and presence/absence of branches. These data were originally presented in about 50 papers in various journals, conferences, and books.

This paper offers a comprehensive and integrative overview of all empirical data available from the open literature on the in-tunnel radiowave-communication channel's power loss characteristics, as a function of the tunnel's cross-sectional shape, cross-sectional size, longitudinal shape, wall materials, presence or absence of vehicular/human traffic, and presence/absence of branches. These data were originally presented in about 50 papers in various journals, conferences, and books.

Natural phenomena such as rainfall are responsible for communication service disruption, leading to severe outages and bandwidth inefficiency in both terrestrial and satellite systems, especially above 10 GHz. Rainfall attenuation is a source of concern to radio engineers in link budgeting and is primarily related to the rainfall mechanism of absorption and scattering of millimetric signal energy. Therefore, the study of rainfall microstructure can serve as a veritable means of optimizing network parameters for the design and deployment of millimetric and microwave links. Rainfall rate and rainfall drop-size are two microstructural parameters essential for the appropriate estimation of local rainfall attenuation. There are several existing analytical and empirical models for the prediction of rainfall attenuation and their performances largely depend on regional and climatic characteristics of interest. In this study, the thrust is to establish the most appropriate models in South African areas for rainfall rate and rainfall drop-size. Statistical analysis is derived from disdrometer measurements sampled at one-minute interval over a period of two years in Durban, a subtropical site in South Africa. The measurements are further categorized according to temporal rainfall regimes: drizzle, widespread, shower and thunderstorm. The analysis is modified to develop statistical and empirical models for rainfall rate using gamma, lognormal, Moupfouma and other ITU-R compliant models for the control site. Additionally, rain drop-size distribution (DSD) parameters are developed from the modified gamma, lognormal, negative exponential and Weibull models. The spherical droplet assumption is used to estimate the scattering parameters for frequencies between 2 GHz and 1000 GHz using the disdrometer diameter ranges. The resulting proposed DSD models are used, alongside the scattering parameters, for the prediction and estimation of rainfall attenuation. Finally, the study employs correlation and regression techniques to extend the results to other locations in South Africa. The cumulative density function analysis of rainfall parameters is applied for the selected locations to obtain their equivalent models for rainfall rate and rainfall DSD required for the estimation of rainfall attenuation. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 138-145). Also available via the Internet.

This thesis reports the results of a thorough study into the effects of rain and ice on the polarization reuse technique for earth-space communications. Precipitation in the form of rain and ice leads to significant depolarization and attenuation of dual polarized signals above about 10 GHz. The depolarization versus attenuation relationship is examined in depth using a rigorous multiple scattering model. This relationship for rain is expressed in the form of a simple function similar to that used by the CCIR. Prediction accuracy using this simple model is quantified by comparisons to measured data and other model values. The impact of depolarization effects on the carrier-to-noise ratio for digital PSK systems is also addressed. Preliminary results for ice layer effects are presented. / Master of Science

Driven by the ever growing consumer wireless electronics market and the need for higher speed communications, the 60-GHz technology gifted with an unlicensed 9 GHz frequency band in the millimeter-wave spectrum has emerged as the next-generation Wi-Fi for short-range wireless communications. High-performance, cost-effective, and small form-factor 60-GHz antenna systems for portable devices are key enablers of this technology. This work presents various antenna architectures built on low-cost organic packages. Planar end-fire switched beam antenna modules that can easily conform to various surfaces inside a wireless device platform are developed. The planar antenna package is realized on thin flexible LCP dielectrics. One design is based on a planar Yagi-Uda antenna element and the second on a tapered slot antenna element. A low-loss microstrip-to-slot via transition is designed to provide wide impedance matching for end-fire antenna paradigms. The novel transition utilizes the slow-wave concept to provide unbalanced to balanced mode conversion as well as impedance matching. It is demonstrated that the planar antenna packages may be even integrated with active circuits that are cavity recessed inside the thin dielectric. A compact switched-beam antenna module is demonstrated. The first-ever integrated mm-wave active antenna module on organic package capable of generating both broadside and end-fire radiation is also developed in this work. Both broadside and end-fire radiators are co-designed and integrated into a single multilayer package to achieve optimal directivity, efficiency and frequency bandwidth and yet maintain excellent isolation between the two radiators. Post-wall cavities, image theory and dielectric slab modes concepts are invoked to optimize these functions. Active circuitry are integrated into the same package to add control functions such as beam switching, and also amplify the packaged-antenna gain when operated either as a transmitter or a receiver. A significant challenge in the design of antenna systems for wireless platforms is the assessment of embedded antenna performance, that is, the proximity effects of the platform chassis on the embedded antenna. Various antennas are mounted at different locations inside a laptop computer chassis: modeling and experimental studies are carried out to characterize this problem that is apparent to an antenna behind a radome. Air traffic control radars usually require cavity filters that can handle high power and low in-band insertion loss while providing enough out-band rejection to prevent interference with neighboring channels. Such radars that operate in the S-band consist of filter banks frequency micro electromechanical systems (RF-MEMS) switches. Evanescent-mode mode cavity resonators are loaded with RF-MEMS tuning capacitance networks to control the resonant frequency of a second-order bandpass filter. The second part is the design of a novel cavity filter architecture for enhanced selectivity near the passband. It is a second-order folded cavity resonator bandpass filter with magnetic source-load cross coupling. This filter can have at least two finite transmission zeros near the passband.

People around the globe are immensely trying to connect using light as carrier due to its low power consumption and high data transfer rates. Sound and microwaves are examples of other carriers that can be used, although they aren't nearly as efficient as light. A method of communicating is using light beneath the surface of the water. As the depth of the water increases, the temperature, pressure, and salinity of the water are changed. The refractive index of water is determined by the combination of all of these variable parameters. The goal of this thesis is to establish a relationship between changes in water temperature, salinity, and pressure resulting in changes of the refractive Index of the sea water. This thesis will demonstrate an empirical model of travelling the ultraviolet wave under sea water. We are acknowledging all of the properties that are change as the depth of the water is increasing. MATLAB was used to create a simulation of this scenario. Based on previous model of light traveling which covers the wavelengths between 400-700 nm, we have extended the model to ultraviolet range of light (200-400 nm).We design an experimental set up according to sea water parameters and then the experimental results are compared to the simulation results. The comparison shows the validity of our extension model.

This thesis provides a description of the analysis, design, and tests of an X-band RF Transmitter communication system for small satellites. X-band transmitter systems are becoming popular in the upcoming deep space missions. Most of the deep-space ground stations have been using X-band frequencies to receive or transmit signals. The X-band (<10 GHz) can offer lower atmospheric losses and up to a couple of Mbps data rates for multiple satellite operations. Nowadays, many small satellites have been using frequency bands such as VHF, UHF, L, and S-band frequencies for communication. From deep space to the ground station, the low-frequency ranges are inadequate in providing Mbps level data rates and enough bandwidth for deep space missions. The main focus of this thesis was the development of the subsystems such as gain block amplifier, Mixer, Bandpass Filter, and RF power amplifier. The subsystems were designed separately, then they were connected together to perform an end-to-end system test. One of the thesis aims is to design a manageable, power-efficient, and especially cost-effective X-band RF transmitter system. We presented a transmitter system demonstration in this thesis that can also be used in other orbits such as LEO, MEO, or GEO. Additionally, we presented a whole transceiver architecture. However, we focused on specifically designing transmitter subsystems. Initially, the top-level transmitter system objectives were determined. Then, the link budget was calculated. In the next stage, the RF front-end components were determined. Moreover, we simulated a transmitter system to foresee the output power, EVM, LO and IF frequency requirements, harmonics and spurious signals, cascaded gain and noise figure, and phase noise. From the calculated link budget, we were able to close the link by obtaining a 3 dB link margin. At the end of this calculation, we successfully obtained 1.45 Mbps for uplink data rate and 3.05 Kbps downlink rate. We used modulated signal to evaluate EVM. From the simulated transmitter chain, the output EVM was obtained as 1.456% RMS. From the filter board, we obtained an 8.5 dB insertion loss at 8.45 GHz. From the Mixer board, we’ve got 10 dB conversion loss and greater than 20 dB isolation between LO-RF ports. From the gain block amplifier board, we obtained a +9 dB gain at 8.45 GHz. The bandpass filter, mixer, and gain block amplifier boards were designed by using FR-4 dielectric material. We also designed a 5 W RF power amplifier board. From this board, we successfully obtained +37 dBm output at bias current at 200 mA. We reached almost 30% Power-added efficiency (PAE). In the end, we connected all the subsystems together using male-to-male SMA connectors to observe output by using a spectrum analyzer. We obtained transmitter output as +10.67 dBm at 8.45 GHz with a -10.7 dBm input power level. One benefit of this thesis is that its content has inspired other students in the department to develop similar subsystems. The other benefit of this work might be to inspire the way for next-generation X-band communication systems for use in small satellites, such as for deep space missions. This thesis might also be a reference source for institutions with a limited budget to develop a cost-effective satellite communication subsystem and contribute to space exploration for their educational and research objectives.

The increasing demand for greater capacity of mobile communications has led to the petition of more radio spectrum at 1900 MHz for the new personal communication service (PCS) systems. The PCS spectrum is proposed to coexist with current fixed microwave spectrum. This presents cochannel interference control problems which can be avoided with extensive propagation studies in both measurements and predictions. Currently, there is no readily available tool to predict propagation channels for the small coverage area that PCS operates at 1900 MHz. This thesis presents new methods for propagation prediction without relying on measurements but rather local environment geometries and their electrical properties. The propagation prediction tool developed is based on the principle of geometrical optics and Fresnel-Kirchoff diffraction. Geometrical optics enables computer software to automatically trace the propagation of radio wave energy from the transmitter to the receiver. The ray tracing techniques presented are optimized for speed with a little trade-off in accuracy. Also, efficient techniques were developed to find true diffracting building edges in dense urban environments. The propagation prediction software also rely on other commercial software packages such as AutoCAD and GRASS to maintain and manipulate the environmental database as well as displaying prediction results. The software yielded reasonable accuracy when compared against VT campus propagation measurements at 900 MHz and 1900 MHz. / Master of Science