Knowledge-Aided Detection Of Low-Altitude Wind Shear

When aircraft detects the wind-shear field in the look-down mode, the useful meteorological signal is often masked by the strong background clutter. The first step of the target detection is clutter suppression. Comparing to the conventional single-antenna radar, by utilized the Space-time Adaptive Processing(STAP) technology, the phased array radar can suppress the clutter in space-time domain, has a superior performance of target detection in strong clutter environment. The conventional STAP technology is usually applied in the homogeneous clutter assumption. In the real world, the clutter is often heterogeneous, which make the performance of conventional STAP degrade. With the development of the high resolution sensors and the research of the characteristic of different target, knowledge aided STAP technology, which can integrate different kinds of information into STAP to improve the performance of the STAP, has attract more and more attention. It has important significance of the research on integrating different kind of information into the detection of low altitude wind-shear field to improve the performance of the airborne weather radar.First of all, starting with the received data mode of the airborne phased array radar, the simulation approach of the wind-shear field echo and background clutter are introduced.Secondly, according to the RTCA/DO-120 criterion, the main wind-shear detection process is introduced. The key technology used in the detection process including wind speed estimation, wind speed gradient estimation, and F factor calculation is discussed in detail.Numerical simulation is conducted to verify the validity of the detection process.Thirdly, digital topographic information bank and surface scattering data bank are used as the prior knowledge in the selection of clutter training samples to achieve the estimation of the clutter covariance matrix in the heterogeneous environment. Meanwhile, the power spectrum feature of the windshear field echo, the spectrum of the wind-shear field echo and the radar's operating parameters are utilized as the prior information in the modeling of the space and time steering vector of the wind-shear field.Fourthly, an architecture of dimension reduction processor that can be applied to detection and parameter estimation of the distributed target such as wind-shear is introduced.The processor adopts a set of Doppler filters to process the receive signal, which transfers the full space-time clutter into directional active jamming of a fixed Doppler channel. Then this jamming is processed in each Doppler channel adaptively to obtain the wind speed. The simulation results show that the proposed method can suppress ground clutter adaptively andaccumulate low-altitude wind-shear signal, thus get accurate estimation of wind speed.At last, by combing STAP and compressive sensing, a novel spectrum moment estimation algorithm of airborne phased array weather radar for low altitude wind-shear is proposed. According to the feather of the wind-shear radar echo signal, a space-time dictionary aimed to distributed source is designed based on the wind speed and the speed spectrum. Then, compressive sensing is applied to reconstruct the wind-shear signal to get the wind speed and speed spectrum. Thanks to the use of compressive sensing, the proposed method is able to estimate the wind speed and the speed spectrum accurately even with limited number of sampling pulses. Meanwhile, fast algorithm based on the non-coupled relationship of the wind speed and speed spectrum is discussed in the end of the chapter. The performance of the proposed algorithm is verified with numerical simulations.