Synthesis of HF ground backscatter spectral characteristics

Earl, G. F.

doi:10.1016/0021-9169(75)90034-3

Cited by 5 publications

(2 citation statements)

References 7 publications

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“…Time changes in the ionosphere must also be taken into account and these can give rise to a spectral width that depends upon pulse length. Many of these effects have been included in a numerical simulation by Earl (1975).…”

Section: Discussionmentioning

confidence: 99%

On the Interpretation of the Doppler Spectra of Ionospherically Propagated Ground Backscatter Echoes

Bennett¹

1975

Aust. J. Phys.

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The mechanism giVing rise to the backscatter Doppler spectrum is discussed by means of a simple model. Attention is focused on the effect of movement of the region contributing to the echo which arises from time changes in the group velocity within the ionosphere. It is shown that the influence of these changes on the spectrum can be separated into two parts: (1) A change in the maximum possible width of the spectrum as a result of the change of the time for which an indiVidual scatterer is contributing to the echo; this effect is independent of the scatterer distribution. (2) A possible narrowing of the spectrum as a result of the way in which the signals from individual scatterers combine; this effect depends upon scatterer distribution. Scatter from a fixed'scattering surface and from dispersive waves (e.g. sea waves) is considered. A tentative extrapolation of the results to a more realistic model suggests that neither effect is likely to be significant in practical highfrequency radio experiments (except at short ranges with highly directional antennas), although they may be significant in acoustic wave simulations of the radio case.

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Section: Discussionmentioning

confidence: 99%

On the Interpretation of the Doppler Spectra of Ionospherically Propagated Ground Backscatter Echoes

Bennett¹

1975

Aust. J. Phys.

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“…The idea is to use the indication of TID activity present in normal OTH radar IDOP measurements to estimate the associated apparent wander of the OTH radar signals and to mitigate this wander. Previous studies of the HF signatures of TIDs were done by Georges and Stephenson [1969] and Earl [1975].…”

Section: Introductionmentioning

confidence: 99%

Range rate–Doppler correlation for HF propagation in traveling ionospheric disturbance environments

2006

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[1] Using ionospheric sounding together with fast computational inverse processing, it is now possible to obtain good real-time ionospheric models for use in geolocation for over-the-horizon (OTH) radar. However, deflection of HF propagation paths by traveling ionospheric disturbances (TIDs) remains a troubling cause of coordinate registration errors. Bandwidth and coverage limitations in ionospheric soundings preclude the ability to model TID structure in real time in most cases. It would be useful if TID-induced path deflections could be related to radar-measurable quantities like Doppler shift. As a first step in studying this possibility, we have considered the relationship between Doppler shift and group range rate for point-to-point HF propagation paths in TID environments. The nature of group range rate-Doppler correlation is exposed in three ways: (1) simple theoretical modeling, (2) ray tracing in simulated TID environments, and (3) analysis of OTH radar measurements of a fixed beacon. It is shown that group range rate and Doppler shift for fixed-point propagation paths are usually proportional with a ratio that depends on whether ionospheric motion or density changes predominate in the TID environment.

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An improved method of synthesizing ground backscatter ionograms for spherical ionospheres

Ong¹,

Bennett²,

Dyson³

1998

Radio Science

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Abstract. Synthesis of ground backscatter ionograms is a useful technique for studying the structure of the ionosphere. By synthesizing backscatter ionograms from a known ionosphere, knowledge can be obtained on how variations in the ionosphere affect the shape of a backscatter ionogram. A method allowing the rapid synthesis of ground backscatter ionograms is presented. The vertical ionospheric profile is represented by a series of smoothly joined quasi-parabolic segments which can accurately reproduce both measured and model profiles. The ionosphere is, however, restricted to being spherically symmetric. The synthesis includes corrections for geometrical and time delay focusing. The speed of the technique is valuable when ionospheric state is to be determined by seeking a match between measured and synthesized backscatter ionograms. The restriction of the synthesis to spherically symmetric ionospheres means that the best choice can only be made from this class. Residual differences can be a useful indication of the significance of departures from spherical symmetry. The calculations involved in the synthesis are closely related to those necessary to establish coordinate registration in the location of targets for over-the-horizon radar.

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Synthesis of HF ground backscatter spectral characteristics

Cited by 5 publications

References 7 publications

On the Interpretation of the Doppler Spectra of Ionospherically Propagated Ground Backscatter Echoes

On the Interpretation of the Doppler Spectra of Ionospherically Propagated Ground Backscatter Echoes

Range rate–Doppler correlation for HF propagation in traveling ionospheric disturbance environments

An improved method of synthesizing ground backscatter ionograms for spherical ionospheres

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