Font Size: a A A

Research On Interference And Clutter Suppression Methods In HF Ground Wave Radar

Posted on:2012-01-08Degree:DoctorType:Dissertation
Country:ChinaCandidate:M WuFull Text:PDF
GTID:1228330344451661Subject:Communication and Information System
Abstract/Summary:PDF Full Text Request
As a kind of the Over the horizon radars (OTHR), HF ground wave radar (HFGWR) becomes a new way to get access to the ocean kinetic parameters (such as the current,the wind and the wave etc)and surveille the moving target on the ocean surface for its con-venience and low-cost in the recent 50 years. especially,it is a perfect choice of the real-time and large-coverage surveillance for the 200 sea-mile of a nation. so a lot of nations in the world devote to the research of the HF ground wave radar (HFGWR). Although HFGWR is very important to the military and economic affairs,the develop-ment of HFGWR is quite limited because of the execrable electromagnetic environment in the HF band. There are many kinds of noise.clutter and interference in the HF band. Thereinto,the radio frequency interference,ionospheric clutter and sea clutter have the most significant impact on the HFGWR, and highly degrade the performance of the radar. especially the ionospheric clutter,it is the most serious impediment to the devel-opment in the world for its quite complex and capricious characteristic. Then how to suppress these kinds of interference and clutter is very important to the future of the HFGWR. just based on this background,the thesis research on the method to suppress the radio frequency interference,ionospheric clutter and sea clutter.The main content is as follows:1. The characteristic of the radio frequency interference in signal processing is analyzed in detail.Two effective radio frequency interference suppression method is discussed based on the lots of real interference data received by array and compact radar ,from the spatial and temporal aspect. The suited condition of each method is also discussed. Processing results of many real interference data prove the availability for the array and compact radar system in practice.2. The structure and transformation of the ionosphere is introduced. Some charac-teristic of the ionospheric clutter is analyzed based on the real ionospheric clutter data. Proposing a method using the range/time spectra to get the macroscopical information of the ionosphere (such as the layered structure,the height,the multiple bounce and drifting ionosphere etc)and the horizontal velocity of the drift iono-sphere can be estimated too. The disturbance mode of the ionosphere is detected by the time-frequency analysis. The "S" shape doppler movement induced by the TID(Traveling Ionospheric Disturbance)is captured in real clutter data, at the same time,the amplitude and period of the disturbance is estimated and the irregularity appearance is judged. It is very helpful to the ionosphere forecast. From the obser-vation of lots of the real data,the regular pattern in time-frequency of the Es and F layer is summarized and the reason of the pattern is explained shallowly.3. The method to suppress the ionospheric clutter is investigated from the spatial tem-poral and time-frequency aspects separately according to the different characteristic of the ionospheric clutter. These methods are also validated and compared by pro-cessing the real data. especially, a new method based on EVD using planar array is proposed, which is validated by the processing result of the real data. Processing in temporal and time-frequency domain has no request on the array aperture and quite fit for the small aperture radar system. Unfortunately,there are lots of limitation of these methods:processing in range domain can only remove the strong ionospheric clutter form concentrated area which has a highly correlation in range domain; The method based on wavelets is highly depends on the choice of the mother wavelet function;The method using SM analysis can only detect the target which has a high SNR in the spread ionospheric clutter.4. The mechanism about the sea clutter forming is introduced briefly. The HRR-SVD method is applied to the real sea clutter with synthetic target data,the processing result turn out that the method is effective when the target has high SNR and get near the edge of the bragg peaks. A new method to suppress the sea clutter is proposed based on the real data analysis in range domain.the processing result of the real data prove that the method is effective when the target has a relative high SNR,and out of the position of the center frequency of the bragg resonance.
Keywords/Search Tags:HF ground wave radar (HFGWR), electromagnetic environment, radio frequency interference, ionospheric clutter, sea clutter, suppression method, time frequency analyze, target detection
PDF Full Text Request
Related items