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|Title:||Theoretical and Experimental Investigation and Characterizations of Ionospheric HF Communication Channels|
|Doctoral Committee Chair(s):||Yeh, K.C.,|
|Department / Program:||Electrical Engineering|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Engineering, Electronics and Electrical|
|Abstract:||The ionospheric high frequency channel has been investigated in theory and by experimental measurement. The channel is addressed from the communication perspective. Signal distortions due to both the deterministic dispersive background ionosphere and random electron density fluctuations are studied.
The channel dispersion is characterized in terms of dispersive bandwidth. General expressions are obtained that can be applied to ionospheric model layers or measured ionization profiles. Computations on both cases are carried out. The dispersive bandwidths obtained are plotted for various frequencies and ground distances, which can help a radio operator identify the best operating frequency between different links.
The University of Illinois has put into operation an oblique 5-15 MHz wideband probe capable of measuring the channel transfer function directly. The system's capability, its development process, and some collected data are described. Several measurement examples are shown. Also, the possibility of utilizing this probe's extremely narrow frequency step capability is investigated.
The statistical characterization starts with a general mathematical framework based upon the two-frequency two-time correlation function. The importance of such a characterization is described in terms of channel classification. Two databases are then selected to have a thorough study of the first-order statistics and second-order channel coherency. The results are plotted and summarized in tables which are useful for the selection of the channel model and signaling scheme. The investigation also indicates that a WSSUS channel model may not be applicable in a wideband environment. Its implication on channel modeling and simulator design is noted.
An attempt is also made to establish a connection between the observation and wave scattering theory in random media. In this preliminary study, only general properties are investigated and some agreement is found.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1993.
|Date Available in IDEALS:||2014-12-16|
This item appears in the following Collection(s)
Dissertations and Theses - Electrical and Computer Engineering
Dissertations and Theses in Electrical and Computer Engineering
Graduate Dissertations and Theses at Illinois
Graduate Theses and Dissertations at Illinois