Low Level Range Coverage Performance Prediction for VHF Radar,
FORSCHUNGSINSTITUT FUER HOCHFREQUENZPHYSIK DER EGAN E V WACHTBERG-WERTHHOVEN ( GERMANY F R)
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At VHF radar frequencies the range coverage is not strictly limited by the quasi-optical horizon like at microwave radar frequencies but is extended due to diffraction propagation. This effect, here called beyond-the-horizon BTH detection capability is strongly dependent on the propagation path and thus on the terrain structure. The availability of digital terrain maps gives way to the use of computerised methods for the prediction of radar range coverage in real environment. In combination with wave propagation models suitable for diffraction at terrain structures, digital terrain data can even be used for the prediction of BTH target detectability at VHF radar. Here the digital landmass system DLMS terrain database was used in combination with a multiple-knife-edge diffraction model to predict the diffraction attenuation between the radar and the potential target positions, especially beyond the optical horizon. The DLMS database consists of topographic height data as well as on cultural data describing the built up areas and forested areas according to their height and extension. The propagation paths extracted from the database are modelled as a sequence of diffraction screens suited for the application of a Fresnel-Kirchhoff algorithm yielding the knife-edge-diffraction attenuation. This terrain related propagation model has been verified by a large number of measurements at different frequencies.
- Active and Passive Radar Detection and Equipment