DWTcanbeimplementedasasetoffilterbanks,comprising a high-pass and low-pass filter. In standard wavelet decomposition, the output from the low-pass filter can then be decomposed further, with the process continuing recursively in this
manner.
(1)
The coefficients dj,k refer to the detail components in signal x(n) and correspond to the wavelet function, whereas aj,k refer to the approximation components in the signal. The functions h(n) and g(n) in the equation represent the coefficients of the high-pass and low-pass filters, respectively, whilst parameters j and k refer to wavelet scale and translation factors. Fig. 2 illustrates DWT schematically.