This paper, on the basis of the theory of unit impulse function, puts forward an unified theory and method to analyze the practical engineering signal and linear system which makes the research of this field more normalized and distinctive.

Short-time Fourier transform is used for time-frequency analysis of recorded accelerograms,and the inverse transform on adjusted Fourier spectra yields the adjusted time histories;the recorded accelerograms can also be adjusted by adding unit impulse response functions to be compatible with target response spectra.