Research Of Complementary Waveforms Design For Radar Target Detection

The sidelobe suppression and target detection performance of radars can be effectively enhanced by properly designing and choosing radar waveforms under the complex electromagnetic environment.Since it can achieve an impulse function for the sum of autocorrelations,complementary waveforms are promising to be used for the improvement of signal-to-noise ratio after matched filtering and weak target detection.However,this advantage is sensitive to the Doppler-induced mismatch of matched filtering,which results in significant sidelobes in the delay-Doppler map and worsen the target detection performance.The thesis focuses on the research of sidelobe suppression and target detection for complementary waveforms and designs the transmission order and receiving weights of complementary waveforms.The main contributions and results of the thesis are concluded as follows:1.We first analyze the multiple target detection problem of Golay complementary waveforms as a simple case.We propose a signal processing procedure under multiple nonzero Doppler targets by applying a combination of Binomial Design approach and one of the three proposed transmission order design methods(Walsh matrix based method,target Doppler based method and weighted mean Doppler method)via a pointwise minimization processor.The final output of the procedure achieves the range sidelobe suppression around the Doppler of all targets,while retains the Doppler resolution.Then,the computational complexity,the performance of the pointwise minimization processor under a Swerling II target model and the estimation of significant range sidelobe regions in delay–Doppler map are analyzed.Simulation results for both fixed and randomized target detection scenarios are presented to validate the effectiveness of proposed procedure.2.We further research the waveform design method to suppress sidelobes for complementary sets,as an extension case of Golay complementary waveforms.We propose a generalized Binomial Design procedure to be a receiving weights design method for complementary sets,that combine two independent receiving weights design approaches—the Middle Blanked Design approach and the Side Blanked Design approach through a pointwise addition processor.The results of this procedure performs no less than the Binomial Design method for the Golay complementary waveform in sidelobe suppression with similar processing time and Doppler resolution.Moreover,the performance of this procedure is evaluated by the peak to peak-sidelobe ratio and integration loss factor,and we also deduced the sequence pattern of the chosen complementary sets for a better suppression of sidelobes.Numerical simulations are presented to demonstrate the improvement of the proposed procedure.3.The simplified Golay complementary waveforms signal processing procedure for multiple moving targets are validated to be also effective for the elimination of false target returns arising from sea clutter.An S?S distribution is selected to model the sea clutter in our discussion.We also explain the condition of high probability target detection based on a Swerling II target model under the simplified procedure.The results of simulation illustrate the procedure outperforms the scheme using linear frequency modulation waveform under the same parameters in terms of sea clutter suppression and delay resolution,with even less pulse accumulation time.4.Complementary sets for the target detection under distributed multistatic radar is analyzed.Based on the distributed multistatic radar system model using complementary sets,signal separation between antennas is established through complementary sets,which reduce the frequency band requirement as an identical carrier frequency is used in a centralized signal processing environment.In theory,the matched filtering results are free of interference from the phase difference between antennas,as well as range sidelobes.Besides,the model is resilient to the jitter or drift of carrier frequency,while range sidelobes are induced by the significant carrier frequency variation.5.We also discuss the target detection performance under multicarrier Golay complementary waveforms.Golay complementary waveforms are not sensitive to the variation of target Doppler when transmitting a single pulse,which is hopeful to enhance the position and velocity accuracy of high-speed moving targets.The performance of multipulse processing for this waveform scheme is also illustrated.The multi-pulse processing brings acceptable sidelobe suppression effect compared to the Golay complementary waveforms with same pulse number but with single carrier frequency,as well as better velocity resolution,it also significantly increases the bandwidth of system,while does not enhance the delay resolution correspondingly.Therefore,further researches of the waveform design methods for multicarrier Golay complementary waveforms in this discussion with better performance are still needed.In conclusion,the thesis enriches the theory and waveform design methods of complementary waveforms,and also provides an exemplification to the potential application for this waveform scheme.