Wideband measurements of coherence over an HF skywave link and implication for spread-spectrum communication


  • S. Salous,

  • E. D. R. Shearman


A wideband frequency-modulated, continuous-wave (FMCW) oblique incidence sounder was used in an experiment to measure the coherent bandwidth of a one-hop F2 layer propagated ionospheric path. The experimental data were collected over a 234-km link in the United Kingdom by using frequency sweeps of up to 5 MHz repeated at 10-s intervals. The path had the characteristics of quasi-longitudinal propagation. The results indicated that the limiting factors to the coherent bandwidth are mainly polarization interference and frequency dispersion. Data on the coherent bandwidth and fade depth as a function of frequency and the time variation of the amplitude frequency response are presented.