“…Signal recovery: perform single‐branch recovery on the decomposed coefficients [
27–31], that is, use a 3 to restore the low‐frequency signal d 3 of the third level, and use
to restore the high‐frequency signal of the third level. Since the high‐frequency signal of the second layer restores d 2 to
, and the high‐frequency signal of the first layer restores d 1 to
, the three‐layer decomposition of the S signal can be expressed by formula (8)
…”