Research On Some Issues Of Radar Signal Long-time Coherent Accumulation

In the modern battlefield, stealth aircraft and radar camouflage bring huge threat tothe survival of radar, so it is very important to enhance the performance of weak targetsdetection. Long-time coherent accumulation is one effective way, but during this periodthe received pulses may become non-coherent caused by migration or other reasons. Soit is important to make effective compensation and complete coherent accumulation.The coherent accumulations for several commonly used signals are researched. Forfixed-frequency signal, linear frequency waveform (LFM) is analyzed as an example.To correct the target migration of LFM signal, an improved method based on Keystonetransform is applied. To overcome the limitation by Doppler ambiguity numbers in thistransform, a new searching algorithm is proposed which obtains the correct numbers ofall targets through once traversal. In this way, targets of different pulses stay in the samerange cell, and then the coherent time can be extended. For variable frequency signal,stepped frequency waveform (SFM) and frequency-agile waveform (FA) are discussed.For the former, started with analysis of the Doppler sensitivity, a phase compensationmethod is used, which combines variable pulse repetition time (PRT) and two-wayfrequency hopping. By changing the PRT, a clear range profile would be got throughIFFT. Then according to the different results of two frequency forms, the real targetdistance and speed information can be worked out. For the FA signal, to solve theproblem in coherent accumulation, the compatibility between FA and moving targetdetection (MTD) is discussed, and one method based on MTD of same frequency isgiven. For fixed-frequency with staggered pulse repetition frequency (SPRF) signal,compensations with different velocities are made to eliminate the effect caused by thechange of PRF. The results of different channel are compared, and the range and speedinformation of target can be got in the end.