Bistatic Airborne Radar Clutter Suppression Techniques

An accurate mathematical model which expresses the geometrical relationship between the bistatic radars and the clutter scatterers is presented in this dissertation. The dissertation detailedly analyzes that relationship in varying geometrical scenarios, and formulates mathematical expressions to describe the relationship by transformation of coordinate system. There is no constraint condition on the position coordinates of the transmitter and the receiver. The the model can be applied in any geometrical scenarios. The Azimuth-Doppler trajectories are provided with to examine the model and compared with that of observation data. The results prove that the model is accurate. The model is valuable for the modeling of ground clutter and the researching of clutter suppression in bistatic airborne radar systems.Then, the dissertation detailedly analyzes the clutter characteristics of bistatic airborne radar. The effect of bistatic configuration on clutter characteristics is analyzed through the isodops. And it is shown that the clutter Doppler is range-dependent in bistatic airborne radar systems by analyzing the Azimuth- Doppler trajectories and clutter power spectra in various geometrical scenarios. Then the dissertation introduces the modeling and simulation of K amplitude distributed bistatic clutter, and the bistatic clutter is modeled as a spherically invariant random process (SIRP). The simulation results show that the probability density function (PDF) of the generated clutter dovetails nicely with corresponding theoretical PDF. The model is an essential component for assessing the performance of clutter suppression algorithms and is the basic of the researching of clutter suppression in bistatic airborne radar systems.Then the problem of suppressing bistatic clutter by the space-time adaptive processing (STAP) is detailedly analyzed. The first is STAP requires large computational cost, and the second is the effect of the non-stationary of bistatic clutter on the performance of STAP. The dissertation researches the parametric adaptive matched filter (PAMF) methodology for bistatic clutter suppression as it requires significantly less training and computation compared with the traditional STAP. Computer simulations show that PAMF can effectively reject unwanted disturbance. Finally, the dissertation presents non-linear time-varying adaptive weights algorithm to mitigate the clutter Doppler range dependency for improving the clutter suppression performance. The mathematicl expression of non-linear time-varying adaptive weights algorithm is formulated on the basis of linear time-varying adaptive weights algorithm. Non-linear time-varying adaptive weights algorithm is to use STAP weights that vary nonlinearly from range agte to range gate. The performance of non-linear time-varying adaptive weights algorithm is compared with that of linear time-varying adaptive weights algorithm through the simulation. The results show that non-linear time-varying adaptive weights algorithm is closer to ideal STAP performance but computationally more expensive.