RANGE SIDELOBE SUPPRESSION BY LOCALLY WEIGHTING FILTER

One of the important technologies in the pulsed radar is the pulse com pression by means of chirp signals. This technology simultaneously sat isfies the contradicting requirements of increased search distance, or the increase of the average transmission power, and of range resoluti on. However, the waveform after pulse compression has a range sidelobe in the range direction and a small object existing near an object wit h a large radar cross section is hidden in the range sidelobe so that its detection becomes difficult. To suppress the range sidelobes, a me thod has been considered to provide weights to the frequency character istics of the pulse compression radar. In this paper, the wavelet tran sform as a tool for time frequency analysis is used for the analysis o f pulse compression waveform. A range sidelobe suppression method in w hich a filter with a wavelet localized on the time and frequency axis as an impulse response is placed behind the compression filter is prop osed since the frequency components near the main lobe and near the si delobes are different. In this method, the local weighting is carried out. As a result of the convolution of the pulse compressed waveform w ith the wavelet with a scale corresponding to the frequency components near the main lobe, i.e., the filtering, it is shown by computer simu lation that the correlation is reduced in the range sidelobe region an d the maximum sidelobe level is reduced by about 10 dB. The proposed m ethod can be combined with the weighting of the frequency characterist ics of the pulse compression filter. Further, the de offset of the I/Q signal can be eliminated.