Abstract: The novel practical method to eliminate the difference of sampling instant which is called the shifted unit impulse response is proposed in this paper. By integrating the process of elimination with the subsequent digital signals processing， the method is equivalent to eliminate the difference of sampling instant with nil-operation. When combined with the matching filter operation of LFM signals， the performance analysis of the novel method is validated. A novel topology which is easy to be implemented can optimize the digital signals process flow， economize the hardware resources and the runtime is presented based on the novel method. The novel topology is suitable for the quadrature demodulation for large TB LFM signal by direct sampling of IF signal on the premise of performance.