Research Of PN Code Signal Processing

Phase coded radar has a large time bandwidth product characteristic, and it also performs excellently in any other fields,including the detection ability of radar,the anti reconnaissance capability, and the range resolution and velocity resolution ability. Pseudo random code is one kind of the binary phase code, and it is used very popular because of the simple formation, simple digital signal processing procedure.However, pseudo random code’s side-lobe of pulse compression result is too high. Especially under the multi targets environment, the high side-lobe of the target often results that the main lobe of the small target is covered by the bigger one. So the detection accuracy of the environment with multiple targets is under question. Therefore, the reduction of the Pseudo random code’ side-lobe has raised widely concern, and it is also becoming the focus of this graduation study.The application of pseudo random code in radar signal processing is analyzed and showed emphatically in this paper. Then I will use the M sequence code as an example to introduce the pseudo random code’s concept, production procedure, properties, the composition of pseudo random code radar system, and the simulation results of both the pseudo random code radar system emission waveform and echo waveform. Finally, aiming at the disadvantages of the high side-lobe of pseudo random coding pulse compression result and the low accuracy of the multi target recognition, the paper will focus on a new algorithm ——the side-lobe suppression method based on CLEAN algorithm.The CLEAN algorithm mainly processes the result of pseudo random code’s pulse compression, estimate the target’s distance by a method named Interpolation Method,so that we can get the ideal pulse compression result of the target, then use the adjusted ideal pulse compression of the target to cut the actual pulse output, so as to achieve the remarkable performance of the side-lobe suppression for large targets, and let the adjacent small targets can appear. It is needed to explain that the interpolation method is different from the method of estimating distance in the past, and is a method of estimating distance by the center line of the main valve area. Based on the theoretical study of the clean algorithm, finally, I simulated CLEAN algorithm used in the ideal environment and noise environment by MATLAB. It is proved that this method indeed can effectively solve the problem that pseudo random code signal side-lobe is too high, and can enhances the radar’s multi-target detection ability.