Study On Parameters Estimation And Relevant Technique In Microwave Sparse Array Synthetic Impulse And Aperture Radar

Microwave sparse Synthetic Impulse and Aperture Radar (SIAR) uses an sparse-array to transmit FMCWs of multiple carrier-frequencies to ensure the energy emitted covers a rather large sector, and an array or omni-antenna to receive the echoes.Using the Synthetic Impulse and Aperture technique, the narrow-band signals are synthesized to wide-band signal and transmitting and receiving pattern are formed in receiving station. It has the advantages of high range and high bearing resolution. The radar It is considered effective to encounter the threats existing in the modern high-technology war scenario, such as stealth target, anti-radiation missile, active electronic jamming and low-flying target penetration. And it has the advantages of miniaturization, high resolution and high flexibility. Focusing on parameters estimation and relevant technique of this radar, the main content of this dissertation is summarized as follows:1. A brief introduction is given to the radar system and its characteristics. What follows is the processing flow of multi-carrier-frequency FMCW and the waveform parameters selection, with an emphasis on the transmitting and receiving pattern synthesis process when the transmitting and receiving station are uniform plane arrays. The bearing resolution is compared between mono-static system and bi-static system. It can be seen that range-angle coupling is decreased when transmitting station is sparse array. The system synchronization and the array calibration are introduced.2. The principle of the range grating lobe is analyzed in the paper. The amplitude of the range grating lobes is discussed with different Bu andΔf for constant Te and N e. Based on this, two methods are presented to suppress the range grating lobes: weighting method and DFT method, by using which the ratio of main lobe to grating lobe reaches 40dB.3. The moving parameters estimation is discussed in microwave sparse SIAR. The signal model is established when target moves at a constant acceleration. And two methods are given to estimate the moving parameters of the target. One is phase difference method based on Discrete Polynomial-Phase Transform (DPT). The method uses DPT to separate the acceleration and velocity. And then the acceleration and velocity are estimated with phase difference method. The other method is dechirping based on DPT. Firstly the cursory acceleration is estimated with DPT. And the dechirping method is used to search the true velocity and acceleration within a small scope. Therefore the computational complexity is decreased dramatically. A new method for SIAR is presented to resolve velocity ambiguity. The method can work effectively without transmitting multiple PRF (pulse repetition frequency) signals. Consequently the system complexity is decreased.4. The estimation of parameters (range, azimuth and elevation) is studied for high speed targets. The targets moving at a high speed result in range and Doppler migration, which makes MUSIC algorithm invalid. Two methods of parameter estimation are shown in the paper. One is that the range and Doppler migration is corrected using velocity estimation, and MUSIC algorithm is applied to estimate the range and bearing parameters. Under the condition of multi-target, the CLEAN method is used to separate different target on the range and Doppler domain. Finally, all parameters of every target are estimated. The other one is based on the Keystone transform. The Doppler Keystone transform is used for Doppler migration of the target, while the range and Doppler Keystone transform is used for range and Doppler migration of high speed target. Finally the MUSIC algorithm is applied on the transformed signals to estimate the range and bearing parameters.5. The angle estimation based on wide-band focusing is studied. In SIAR the signals after separated have N e frequencies, which makes MUSIC algorithm invalid. This characteristic is the same with wide-band radar. The data of N e frequencies is transformed to the data of the same frequency using focusing transformation, which overcome the Doppler migration, and then the MUSIC algorithm is applied to estimate the angle of the target. The result of simulation indicates the method can estimate angle of the target effectively.6. The target tracking based on monopulse technique is studied when SIAR works in the mode of bi-static and the receiving station is plane array. The tracking mission of SIAR is tracking the rang, azimuth relative to transmitting station, elevation relative to transmitting station, azimuth relative to receiving station, elevation relative to receiving station and forming flight path. The tracing model is given. The digital sum and difference beamforming is done based on monopulse tracking about rang, azimuth relative to transmitting station, elevation relative to transmitting station, azimuth relative to receiving station, elevation relative to receiving station. The flight path tracking indicates the validity of the methods presented in this paper.