[pt] O uso de dispositivos móveis cresceu exponencialmente nos últimos anos, tornando-se um desafio a melhoria da qualidade de sinal e o pleno atendimento a serviços que exigem altas taxas de dados e baixa latência. A fim de atender a crescente demanda de tráfego, as faixas de freqüências de ondas milimétricas começam a ser exploradas para aplicação à Quinta Geração de Comunicações Móveis. A partir de medições realizadas em ambientes fechados, nas faixas de freqüências de 28 GHz e 38 GHz, foi possível analisar o canal de comunicação com base nos modelos propagação para as faixas de freqüências de ondas milimétricas. / [en] Mobile usage has grown exponentially in recent years, making it a challenge to improve signal quality and fully support to services that require high data rates and low latency. In order to meet the growing traffic demand, millimeter-wave frequency bands are being explored for application to the 5th Generation of Mobile Communications. From measurements performed in indoor environments, in the 28 GHz and 38 GHz frequency range, it was possible to analyze the communication channel based on the propagation models for the millimeter wave frequency bands.

This thesis describes fundamental approaches to quantify rate versus power consumption tradeoffs for cascaded communication systems. The discussion is bolstered by a large number of in-situ channel measurements, which are used in discussions of the power consumption of future massively broadband cellular systems. Chapter one provides an introduction. Chapter two discusses power consumption trends in modern communication systems. Chapter three introduces the consumption factor framework. Chapter four discusses the channel measurement campaign. Chapter five concludes the thesis, and uses the measurement results to estimate power consumption and capacity of future cellular systems. In addition, chapter five extends the consumption factor theory and draws fundamental conclusions about the energy price per bit for a general cascaded communication system. / text

This research focuses on radio wave propagation at millimeter-wave frequencies. A measurement based channel characterization approach is taken in the investigation. First, measurement techniques are analyzed. Three types of measurement systems are designed, and implemented in measurement campaigns: a narrowband measurement system, a wideband measurement system based on Vector Network Analyzer, and sliding correlator systems at 5.8+AH4AXA-mbox{GHz}, 38+AH4AXA-mbox{GHz} and 60+AH4AXA-mbox{GHz}. The performances of these measurement systems are carefully compared both analytically and experimentally. Next, radio wave propagation research is performed at 38+AH4AXA-mbox{GHz} for Local Multipoint Distribution Services (LMDS). Wideband measurements are taken on three cross-campus links at Virginia Tech. The goal is to determine weather effects on the wideband channel properties. The measurement results include multipath dispersion, short-term variation and signal attenuation under different weather conditions. A design technique is developed to estimate multipath characteristics based on antenna patterns and site-specific information. Finally, indoor propagation channels at 60+AH4AXA-mbox{GHz} are studied for Next Generation Internet (NGI) applications. The research mainly focuses on the characterization of space-time channel structure. Multipath components are resolved both in time of arrival (TOA) and angle of arrival (AOA). Results show an excellent correlation between the propagation environments and the channel multipath structure. The measurement results and models provide not only guidelines for wireless system design and installation, but also great insights in millimeter-wave propagation. / Ph. D.

This works demonstrates the feasibility of the inverse-Class-F harmonic tuning approach for mm-wave silicon PAs. This research addresses the challenges and limitations of the high efficiency inverse-Class-F PAs for mm-wave silicon technology. This work proposes different load networks to mitigate the challenges which are verified with implementations at different mm-wave frequencies with the highest power efficiency performances reported so far: PAE= 50% @ 24 GHz, PAE = 43% @ 41 GHz, and PAE = 23% @ 94 GHz. The design methodology and detailed analysis of the proposed load networks presented and verified with implementation and measured results. / Ph. D.