Study Of Extraction Of Ionosphere Height Information Based On High Frequency Ground Wave Radar

High frequency radar transmit high-frequency, vertical-polarized electro-magneticwave which could travel around the surface of the ocean to detect target and sense theocean state. At present time, ionospheric clutter is a vital difficulty for the application ofHF radar in real world, a lot of research has been done to mitigate ionospheric clutter.However, though treated as clutter, ionosphere echo itself contains so many informationof ionosphere; therefore it definitely could be reused. In this thesis, we use current HFradar equipment to get one of the most important parameter in ionosphereresearch-ionosphere virtual height. This research could not only bring a whole new areain the application of HF radar but also increase the amount of ionosphere verticaldetector. This thesis consist the following parts.1. To extract ionosphere virtual height information, in this paper, we first introducethe forming reason of ionosphere and the layer structure of it. Then we apply simpleliner ionosphere model to calculate, what’s more, we modify the current linerionosphere model. Finally, we get the ionosphere height reference based on modifiedliner ionosphere model.2. We discussed the characters of ionosphere echo in Range-Doppler spectrum,then we bring up that the directionality varies with the angle of incidence of ionosphereecho. Then, normalized variance maps are used to extract vertical ionosphere echo.Finally, we apply threshold segmentation, connected region generation and the prioriknowledge of ionosphere virtual height to segment vertical ionosphere echoinformation.3. Finally, we use segmented Range-Doppler spectrum as data source to evaluatethe height of ionosphere and test the result.