Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / 1 ill. in back pocket. Vita. Abstract. Includes bibliographical references (leaves 224-228). Also available via the Internet.

The Global System for Mobile communications (GSM), which covers 54% of the world's mobile market, evolved into the General Packet Radio Service (GPRS). The thesis addresses interference suppression using new radio frequency (RF) and microwave design methods for GSM and GPRS. The overall outcome is interference reduction and enhanced network capacity, leading to superior quality of service (QoS) for wider area coverage. The main results can be summarized as follows * Design, manufacturing and characterisation measurements of new compact filters for GSM and GPRS base stations in order to reduce the out-of-band interference. It is shown that filters with novel microstrip resonators - dual mode filters and cross coupled filters - provide both a high degree of miniaturisation and narrow bandwidth. * Development of a new 3-D Finite-Difference Time-Domain (FDTD) design method for new microstrip filters. A non-homogeneous Perfectly Matched Layer (NH-PML) was implemented for Absorbing Boundary Conditions (ABC) to increase the accuracy of the FDTD method. Signal estimation techniques were developed to speed up FDTD computations. A novel design method based on neural networks (NN) and FDTD was implemented to reduce the total design time. * Investigation of High Temperature Superconductors (HTS) thin film resonators and antennas at microwave frequencies. High Q-factor HTS devices considerably enhance both the front-ends sensitivity and selectivity of wireless receivers. * Design, manufacturing and testing of radio frequency (RF) electronics for 16 elements GSM and GPRS Smart Antenna for multipath fading mitigation and for in-band interference including co-channel interference (CCI) suppression.

No description available.

Thesis (Ph. D.)--University of New South Wales, 2003.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 127-130). Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaf 157). Also available via the Internet.

This document describes the theory, design and implementation of a digital receiver designed for the ACTS propagation experiments. The Virginia Tech Satellite Communications Group is designing, constructing and distributing eight ACTS propagation terminals (APTs) under a contract with NASA. The terminals will measure the received signal power from the ACTS satellite beacons (20 GHz, 27.5 GHz) in various climates at different elevation angles. The resulting signal power measurement, radiometer and weather measurement data will be used to characterize atmospheric effects on signal propagation at Ka band. Each APT system will contain two identical, independent digital receivers; one 20 GHz channel and one 27.5 GHz channel. The algorithm implemented on each receiver utilizes the results of multiple fast Fourier transforms to reliably identify the carrier tone amidst neighboring modulation tones. The acquisition procedure, can reliably identify the carrier signal at signal-to-noise ratios down to 10 dB in a 20 Hz bandwidth (23 dBHz in a 1 Hz bandwidth, -26 dB relative to clear air conditions on the APT system) in 2 seconds. The receiver then uses a comb filter, two FIR filters and additional FFTs to produce power measurements accurate to 0.1 dB at signal-to-noise ratios down to 5 dB in a 20 Hz bandwidth (18 dBHz in a 1 Hz bandwidth, -31 dB relative to clear air conditions on the APT system) at 1 Hz and 20 Hz sampling rates. The algorithm also provides several supplemental functions including a software selectable detection bandwidth from 2 Hz to 50 Hz (1 Hz increments), spectrum analyzer type output for a 303.333 kHz bandwidth centered on the current carrier frequency and carrier frequency estimates accurate to ±O. 5 Hz. / Master of Science

Fade and inter-fade duration data obtained from the three beacons at 12, 20, and 30 GHz aboard the OLYMPUS satellite were analyzed. The different types of signal impairments and their causes were highlighted and a literature survey conducted. Twelve months of fade and inter-fade data were analyzed and the results of these statistics are presented in the form of tables and figures. The analysis was done on both the monthly and annual data. These tables and figures show that at the higher fade levels, the number of fade events and the fade time is smaller than at the lower thresholds. For the same fade level the number of fade events and the fade time goes down as the fade duration which it exceeds is increased. Inter-fade durations also showed similar results. The fades exhibited seasonal dependencies. The number of fades (and consequently the fade time) were much higher for the months of May through August and for the months of March and December. The other months showed very little fade activity. A model was also constructed that can predict the fade time as a function of frequency, attenuation level, and fade duration interval. The predicted fade times agree well with the measured fade duration data. An alternate simplified version of the model is also presented. / Master of Science

Frequency scaling of attenuation is the prediction of attenuation at a desired frequency from attenuation values at a base frequency. The attenuation at the base frequency is often known from prior measurements. Frequency scaling of attenuation is of interest because of the eventual need to exploit higher frequency bands. Most satellite communications traffic now use C-band (4-8 GHz) and Ku-band (12-18 GHz). The next approved, yet largely unused, frequency allocation for domestic use is in the K-band (18-27 GHz) to Ka-band (27-40 GHz). At these higher frequencies, however, earth-space radio links suffer atmospherically induced impairments as frequency increases. In particular, rain causes severe fading. Consequently, satellite systems in these higher bands are very susceptible to outages due to rain-induced fades. Reliable frequency scaling models are needed in system design to estimate the effect of these rain-induced fades. Between August 1990 and August 1992, V.P.I. & S.U.'s SATCOM Group performed extensive measurements of slant path attenuation using the 12, 20, and 30 GHz beacon signals (in the Ku/Ka-bands) of the European OLYMPUS experimental satellite. The experimental results are used to evaluate the usefulness of scaling models proposed by other researchers, both for instantaneous and statistical purposes. New models are presented for accurate scaling of attenuation within the Ku/Ka-bands. / Master of Science