Fig. 9

The DF result of different sampling rates for one segment of AF signal. a The original signal with fs = 2 kHz. b The signal’s morphology after down sampling to 50 Hz, which is compared with a. c The corresponding frequency spectrum and DF of a. When the signal of a down sampled to 400, 200, 100, 50, and 20 Hz, the spectrum and DFs are shown in d–h