Time-Frequency Effects in Wireless Communication Systems
Title: | Time-Frequency Effects in Wireless Communication Systems |
Author: | Mazzaro, Gregory James |
Advisors: | J. Keith Townsend, Committee Member Mohammed A. Zikry, Committee Member Kevin G. Gard, Committee Member Michael B. Steer, Committee Chair W. Devereux Palmer, Committee Member |
Abstract: | Time-frequency effects in wireless communication systems caused by narrowband resonances and coupled with device nonlinearities are revealed as new sources of co-site interference, exploited for the metrology of bandpass circuits, and employed to linearize amplitude-modulated transmissions. The transient properties of bandpass filters are found to last much longer than traditional time/bandwidth rules-of-thumb. The cause of this long-tail behavior is attributed to the coupled-resonator structure of the filter circuit. A solution method which uses lowpass prototyping is developed to reduce, by a factor of two, the complexity of the differential equation set describing a narrowband filter's transient response. Pulse overlap caused by the frequency dependence of long tails produced by filters is shown to cause intersymbol interference and intermodulation distortion in RF front-ends during frequency-hopped communications. The same properties which cause the ISI and IMD are used to develop three new transient methods for measuring resonant circuit parameters and a one-port method for extracting the operating band of a filter. A new signal-processing technique which combines time- and frequency-selectivity, Linear Amplification by Time-Multiplexed Spectrum, is developed to reduce IMD associated with amplitude modulation. Distortion reduction is demonstrated experimentally for multisines up to 20 tones. |
Date: | 2009-10-05 |
Degree: | PhD |
Discipline: | Electrical Engineering |
URI: | http://www.lib.ncsu.edu/resolver/1840.16/4523 |
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