2026-09-20T02:58:24Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/69404 2023-07-11 col_2142_5131 col_2142_8888 com_2142_5130 com_2142_8887 com_2142_234

Yeh, K.C., Wagen, Jean-Frederic O. 2014-12-15T19:05:36Z 2014-12-15T19:05:36Z 1988 1988 The communication channel established with HF waves reflected by the ionosphere is investigated. The background ionosphere is modeled by a horizontally stratified medium. This model is superimposed with random irregularities. The resulting channel is characterized by a random transfer function. Each frequency component of this transfer function is determined from the received wave field, knowing the transmitted wave field. The computation of the random fluctuations of the received wave field is performed by using the phase screen-diffraction layer method. This scheme simulates the propagation of an HF wave in the turbulent ionosphere. Based on the forward-scatter approximation, the scheme computes sequentially the effects of phase fluctuations due to the irregularities and the effects of diffraction due to phase mixing. Stepping along the ray path, phase fluctuations are imbedded into a number of phase screens. Diffraction effects are then computed between phase screens using FFT techniques. Special attention is given to the reflection region where the classical WKB approximations are invalid. The simulated received wave field is processed to determine some of the skywave channel characteristics. The computed statistics of the received signal include probability distribution, power spectrum, correlation function and scintillation index. For communication purposes, the pulse distortion is of major interest. The two-frequency mutual coherence function is computed to determine the statistical behavior of the received signal. The coherence bandwidth resulting from this computation is used to assess the ionospheric effects on HF spread spectrum systems. Made available in DSpace on 2014-12-15T19:05:36Z (GMT). No. of bitstreams: 1 8823275.pdf: 8608496 bytes, checksum: 5bd16cff98576866057cbed72b2cf2bd (MD5) Previous issue date: 1988 Embargo set by: Seth Robbins for item 69570 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs Open Restriction set for Item 69570 on 2018-03-05T16:03:10Z with date null by nrhodes3@illinois.edu. Open Restriction set for Item 69570 on 2018-03-05T16:03:11Z with date null by nrhodes3@illinois.edu. Open Restriction set for Item 69570 on 2018-03-05T16:03:22Z with date null by nrhodes3@illinois.edu. Open 279 p. Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988. http://hdl.handle.net/2142/69404 (UMI)AAI8823275 Engineering, Electronics and Electrical Simulation of High Frequency Waves Reflected From a Turbulent Ionosphere for Spread Spectrum Systems text University of Illinois at Urbana-Champaign Dissertation Ph.D. Electrical Engineering Electrical Engineering