Research On Doppler Characteristics Of Ionospheric Echo

With the abilities to cover a wide area, work around the clock, be more real-timeand strongly anti-stealth, high frequency surface wave radar (HFSWR) has been widelyused in marine environment monitoring and military field. But HFSWR will beseriously affected by ionospheric clutter in vertical direction because of theimperfection of the antenna. As a time-varying dispersion signal channel, ionospherecan affect the radio wave which propagates in it. This affection shows up as frequencyshift and amplitude attenuation. In the spectrum of HFSWR echo, we can find thationospheric clutter spreads in distance and Doppler field which may cover up parts ofsignal echo, even submerge the signal. To analyze and forecast the properties ofionospheric clutter, the article focuses on the Doppler properties. The research in thepaper mainly consists of the following content:First, this paper introduces the properties of ionosphere and the mechanism ofradio wave propagation in the ionosphere, and then analyzes the features of ionosphericecho which includes multipath effect, Doppler Effect and propagation loss and so on.Second, the paper’s analysis stresses the causes of Doppler shift of ionosphericecho. And we respectively use ionospheric parabolic layer model and InternationalReference Ionosphere model to calculate the Doppler shift in the certain radarconditions. Then the paper points out the differences in calculation accuracy betweentwo models in the light of the results, and analyzes the change characteristics as well.Then the paper introduces two commonest anomaly structures in ionosphere. Theeffects to Doppler shift have been discussed.Third, there are two kinds of propagation loss in the possible path of radio wave,which are ionospheric absorption loss and propagation attenuation of ground-wave. Thepaper introduces both how to calculate the loss of each path and analysis based onsimulation.Finally, after the research and simulation analysis mentioned above, we design thesimulation experiments about ionospheric echoes from HFSWR, then we compare thesimulation results with measured data. And at the same time, we give the whole processof analysis in a Doppler Effect of Ionospheric Echo Analyzing System based on hybridprogramming of C#and FORTRAN on the purpose to help extracting ionosphericclutter from spectrum of radar echo.