脉冲多普勒雷达中补零FFT与折叠FFT的性能比较

摘要

脉冲多普勒雷达中相干脉冲数经常不是2的整数幂,当进行FFT时需要尾部补零或脉冲折叠.本文推导了补零FFT与折叠FFT的解析关系,发现抽取前者的偶数号频点得到后者;计算了两种FFT的跨越损失,因为上述抽取关系,折叠FFT的跨越损失更大.另外,在统计意义上补零FFT的虚警数是折叠FFT的2倍,为使两者的虚警数相同,要求补零FFT的检测门限高于折叠FFT的检测门限.计算发现,两个门限仅相差0.16～0.32 dB.%The number of coherent pulses in the pulse Doppler radar is not often an integer power of 2,so it is required to fill zeros behind the pulses or fold the pulses when fast Fourier transform (FFT) is performed.The analytical relation between the zero-filled FFT and the folded FFT is firstly derived,and it is found that extracting the even frequency points of the zerofilled FFT leads to the folded FFT.Then the spanning losses of two kinds of FFT are computed and the loss of the folded FFT is larger than that of the zero-filled FFT because of the above extraction operation.In addition,in the statistical sense,the number of false alarm of the zero-filled FFT is twice that of the folded FFT,so a higher detection threshold for the zerofilled FFT is required.But it is calculated that the difference of two thresholds is only among 0.16～0.32 dB.