| The most important problem for ground motion target detection of airborne radar is clutter suppression.For the moving radar platform,the ground clutter has an angle-Doppler coupling relationship.Space-time adaptive processing(STAP)technology is working in the Space-time two-dimensional joint domain for the signal processing.This technology generates a filter which has space and time degree of freedom.The filter can form a two-dimensional notch in the space-time two-dimensional plane.The clutter can be suppressed effectively.This paper focuses on the clutter suppression of forward looking airborne radar using the reduced space-time adaptive processing.For the side looking airborne radar,the clutter form a clear clutter ridge in the angle doppler spectrum.The variation of the clutter ridge is not significant as the distance changes.But there is a great chance that the clutter echo power changes violently between different range unit.However for the forward looking airborne radar,there is not only a very high probability of violent changes in clutter echo power,but also the distribution of ground clutter formed like an elliptic in the angle-Doppler spectrum.Besides the elliptic like distribution of clutter in the space-time domain differs from range unit to range unit.In the range doppler spectrum,the ground clutter echo signal in the close distance form a significant arc(also known as eyebrow line).Because of the problem mentioned above,the contents of this papar are as follows:1?First of all,the echo signals of ground clutter received by the airborne radar under different placement structures are modeled.Then we analyzed the characteristics of clutter distribution of side looking radar and forward looking radar.At the same time,the range ambiguity and the backscattering effects of radar are discussed.Their effect on the space-time distribution of clutter has also been discussed.2?For the forward looking airborne radar,the clutter suppression method under low pulse repetition frequency is studied.These methods mainly aimed at lose range clutter.Two kinds of range depending compensation methods for the clutter is studied.One is local compensation method,another is derivative updating method.The effectiveness of these algorithms has been verified by the simulated data.3 ? The clutter suppression method under medium and high pulse repetition frequency is studied for the forward looking airborne radar.For this part we have prior Information.According to the characteristics of the clutter spectrum of airborne radar,the close range clutter suppression method of forward looking airborne radar based on space-time interpolation is studied.If the receiving array has the pitching degree of freedom,A elevation prefiltering method is used to suppress clutter in the pitch domain.Due to the array error,a robust elevation prefiltering method is studied.The effectiveness of these algorithms has been verified by the simulated data.4?According to the situation that the radar carrier's information is not accurate or unknown,a clutter partitioning method based on the unite of three adjacent Doppler channels to calculate the clutter characteristic is proposed.Combining the result of clutter partition,the iterative generalized inner product is used to weighting the samples.The samples are used to estimate the clutter covariance matrix.We used real measured data to verify this method.The results shows that not only the close range clutter has been suppressed,but also a good restrain effect can be seen from the heterogeneous clutter in the middle and far distance.Compared with the traditional method,the signal to clutter and noise ratio is improved significantly. |
PDF Full Text Request