Research On Wave Information Inversion Of Bacscatter In Shipborne Wide-band Coherent X-band Radar

Ocean is rich in natural resources, with the development of economic, scientific and technology and the growth of population, human demand for resources increasingly, development of ocean resources has become an inevitable trend. Ocean provides not only a wealth of natural resources, but also protection for country, in addition, ocean is necessary for transportation. Ocean monitoring system can provide support and protection for a variety of marine operations, and therefore is widely studied, in which the X-band radar waves is the core.Because of the advantage of X-band radar such as cheap, high resolution, working around the clock, convenient and flexible, it received special attention.In this paper, the development process of the waves information retrieval algorithm using X-band radar are briefly described. Most researches focused on the X-band non-coherent radar, there is little study about the X-band coherent radar algorithm. Comparing to traditional non-coherent radar, X-band wideband coherent radar has the following two main advantages: firstly, it can obtain radial velocity of the waves; secondly it has a higher radial distance resolution. To take full advantage of it, the paper-based wideband X-band coherent radar, waves information retrieval algorithm and the factors that influence accuracy of the algorithm has been studied.X-band broadband coherent radar inversion algorithm draws part of the traditional method, so firstly the traditional algorithm is studied. This paper adopts numerical simulation methods to generate random waves, on the basis of that and according to radar imaging modulation mechanism, the radar sea clutter simulation images are generated. Subsequently, use conventional X-band radar inversion algorithm inverse ocean wave parameters, obtained simulation results are in good agreement with set values.For coherent radar, obtained radial velocity information can be used to reconstruct the sea wave elevation images. By integrating of the radial velocity along the radial distance, velocity potential function can be obtained, according to the boundary conditions of freedom of the sea, ocean surface wave elevation images can be reconstructed by velocity potential function. Using method of three-dimensional Fourier transform analysis for wave elevation of the ocean surface images can obtain wave spectrum, and then wave parameters are calculated. The algorithm is affected by the resolution of the distance, so the effect of wave elevation images reconstruction and retrieval accuracy under different resolution are studied.For shipborne radars, doppler radial velocity measured by radar is the sum of waves radial velocity and boat sailing speed, to get radial waves velocity, s ailing speed needs to be subtracted from measured Doppler velocity. However, due to existence of ship speed measurement errors which will affect the accuracy of the inversion, so the variation of inversion accuracy under different speed errors is simulated. In addition, under the circumstance of shipborne `radar, the relationship between root of the SNR and significant wave height is simulated and a method for calculating the shipborne radar significant wave height is introduced.