The method used in this project is adaptive noise cancellation (ANC) based on neuro fuzzy logic technique. ANC is a process by which the interference signal can be filtered out by identifying a non linear model between a measurable noise source (which is MECG in this case) and the corresponding immeasurable interference (Assaleh, 2007). This is an extremely useful technique when a signal is submerged in a very noisy environment. Usually, the MECG noise is not steady; it changes from time to time. So the noise cancellation must be an adaptive process: it should be able to work under changing conditions, and be able to adjust itself according to the changing environment. The basic idea of an adaptive noise cancellation algorithm is to pass the corrupted signal (abdominal) through a filter that tends to suppress the MECG while leaving the signal unchanged. As mentioned above, this is an adaptive process, which means it does not require prior knowledge of signal or noise characteristics. Figure 1 shows noise cancellation with ANFIS filtering (Swarnalatha et al, 2009)
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Figure 1: Schematic Diagram Of Adaptive Noise Cancellation Using Neuro Fuzzy Technique.
In this project,
represents the FECG signal that is to be extracted from the noisy signal.
is the MECG which is the noise source signal. The noise signal goes through an unknown nonlinear dynamics (f) and generates a distorted noise
, which is then added to
to form the measurable output (abdominal) signal
. The aim is to retrieve
from the measured signal
which consists of the required signal
Σ
Σ
f
ANFIS