Accession Number : ADA290208

Title :   A Simulation Study OF HF Direction Finding In The Presence oF F-Region Scattering And Sporadic-E.

Descriptive Note : Technical note,

Corporate Author : COMMUNICATIONS RESEARCH CENTRE OTTAWA (ONTARIO)

Personal Author(s) : Jenkins, R. W.

PDF Url : ADA290208

Report Date : JAN 1994

Pagination or Media Count : 63

Abstract : An HF direction finding (DF) system employing sampled-aperture techniques on high-latitude signals is simulated. The propagation is treated as scatter from moving patches of field-aligned F-region irregularities modelled as vertical 'thin-wire' scatterers in a horizontally stratified ionosphere, plus a weak sporadic-E (ES) reflection from a horizontal mirror-like surface. The resultant simulated received signals are analyzed by plane wave fitting and multiple-signal classification (MUSIC) DF algorithms. Simulations of DF operations on scattered signals, using system parameters similar to those used for actual high-latitude observations, reveal results similar to those observed. The observed directions reflect the locations of the scattering patches rather than the transmitter. The detection of a patch depends strongly on its location, the radio frequency, and the ionospheric parameters. When a patch is seen, the time history of estimated directions indicated its width, as well as its location. MUSIC provides a picture of the width and number of scattering patches present in a short time. Plane-wave fitting tends to give only the directions for the patch having the strongest scattered signal and requires a longer time for the successive direction estimates (spread over the angle subtended by the patch) to indicate the patch width. When too many signal directions are assumed, MUSIC gives false directions which correspond to the steered directions of the array for which the larger sidelobes are pointed toward the strongest signals. When a weaker ES signal is present with the scattered signal, MUSIC can see it clearly and provide a good direction estimate, provided array dimensions are not so large that narrow beamwidths coupled with large-sidelobe effects prevent the weaker ES signal from being seen.

Descriptors :   *ELECTROMAGNETIC SCATTERING, *RADIO DIRECTION FINDERS, SIMULATION, DETECTION, CANADA, ORIENTATION(DIRECTION), ARRAYS, ALIGNMENT, ESTIMATES, SHORT RANGE(TIME), HORIZONTAL ORIENTATION, RADIO SIGNALS, F REGION, HIGH LATITUDES, STRATIFICATION, RADIOFREQUENCY, PLANE WAVES, RADIO INTERFERENCE, SIDELOBES, FITTINGS, IONOSPHERIC DISTURBANCES, NARROW BEAMS(RADIATION).

Subject Categories : Direction Finding
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE