Novel Signal Noise Reduction Method through Cluster Analysis, Applied to Photoplethysmography

Figure 3

The (a) high-pass and (b) low-pass filters. The phase response for the high-pass filter is shown as a dashed red line, showing an increasing nonlinear effect at very low frequencies. The phase for the low pass is linear, such that all frequencies are delayed by the same time.

(a)

(b)