Apparatus for stopping adaptive filtering when valid received signal detected

摘要

A digital signal receiving apparatus includes a detection-judging portion (19) having a first smoothing filter (19a) generating a first smoothed signal (A1(t)) by smoothing an auto-correlation signal (X(t)) and judging a possible presence of a desired signal when a signal level of the first smoothed signal (A1(t)) is greater than a reference level (A2(t)) and an absence of the desired signal when being smaller than the reference level (A2(t)). The smoothing filter(19a) includes a limiting portion (24) limiting a fluctuation width of the first smoothed signal (A1(t)); and an adjusting portion (21) configure to adjust the fluctuation width of the first smoothed signal (A1(t)) limited by the limiting portion (24) to be reduced while an relapsing time after the detection-judging means (19) judges the possible presence of the desired signal is increasing.