No description available.

This thesis focuses on the design of radio-frequency (RF) mixers, including a broadband downconverter mixer, an upconverter mixer and a downconverter mixer with high linearity. The basic mixer topology used in this thesis was the Gilbert cell mixer, which is the most popular mixer topology in modern communication systems. In order to accommodate different applications, the broadband mixer and the upconverter mixer were designed to be reconfigurable. First, a broadband downconverter mixer with variable conversion gain was designed using 0.13-$\mu m$ CMOS technology. The mixer worked from 2 to 10 GHz. By changing the effective transistor size of the transconductor and the load, the mixer was able to work in three different modes with different conversion gain and power consumption. Second, an upconverter mixer with sideband selection was demonstrated in CMOS 0.13-$\mu$m technology. The transmitted sideband could be chosen to be the upper sideband or the lower sideband. The mixer worked at 5 GHz with a 100 MHz IF. The measured voltage conversion gains were 11.2 dB at 4.9 GHz and 12.4 dB at 5.1 GHz. The best sideband rejection was around 30 dB. Third, a modified derivative superposition (DS) technique was used to linearize a Gilbert cell mixer. Simulation results predicted an IIP3 improvement of 12.5 dB at 1 GHz. After linearization, the noise figure of the mixer increased by only 0.7 dB and the conversion gain decreased by 0.3 dB. The power consumption of the mixer increased by 0.96 mW. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2010-06-18 14:40:35.062

No description available.

No description available.

The design of emergent wireless sensor networks operating near the ground requires channel models that account for previously unconsidered propagation phenomena. Most models used for link planning and radio design of the last century were designed for use in situations where the transmitters were at least tens of meters above the earth surface. However, near the earth surface, the specifics of the ground composition and atmospheric effects have been postulated to play a significant role. This dissertation describes the first set of investigations in this emergent environment. A novel computational electromagnetics model is presented that can calculate electromagnetic fields of a dipole embedded in planar-stratified propagation medium that represents the ground and near-surface atmosphere. It is the first available electromagnetic model to efficiently combine a spectral-domain solution in arbitrary multilayers of lossy-dielectric media with high-order quadrature routines to synthesize the fields of an impressed dipole. For the first time, high-order asymptotic quadrature is used to efficiently obtain solutions at arbitrary ranges from the dipole source. A measurements-based model of the near-ground atmosphere is derived, and results of modeling the atmosphere are used to predict the performance of an ultra-high-frequency radio system operating near the ground surface. Finally, a study is conducted to determine the effects of varying key parameters in the near ground channel, including atmospheric conditions, ground conditions, and frequency. The primary result is that ultra-high-frequency near-earth narrowband channels are largely insensitive to large-scale refractive effects that occur naturally on Earth; however, as the transmitter frequency increases into the super-high-frequency and millimeter wave regimes, refractive effects have significant effects on the radio propagation environment.

xii, 186 leaves : ill., graphs, tables ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1979) from the Dept. of Electrical Engineering, University of Adelaide

Thesis (Ph. D.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 87-98) Also available in print.

Thesis (M Info Tech) -- Auckland University of Technology, 2004. / Also held in print (84 leaves, 30 cm.) in Wellesley Theses Collection (T 658.78 HOU)

Thesis (M.S.)--Oregon State University, 2005. / Printout. Includes bibliographical references (leaves 76-79). Also available on the World Wide Web.

Thesis (M. Eng.)--Carleton University, 2001. / Includes bibliographical references (p. 133-134). Also available in electronic format on the Internet.