I'm recording motor cortex NIRS signals from the human brain where the heart rate(~1.5Hz), respiration(~2Hz) and Mayer wave(~0.1Hz) cloud a lot of the motor signal that is desired.
The filtering technique has to be very phase neutral (like FIR not IIR filtering) unlike the filter.m where a dramatic affect occurs in phase shifting.
Filtfilt.m is the usual one that is used that is effectively phase neutral. Another is polynomial fitting.
However neither are very satisfactory or consistantly successful and can differ dramatically in terms of phase. The signal that we are trying to recover is ~0.1Hz.
Is anyone aware of a successful filtering method in matlab for phase critical physiological signals? Even for Physiological signals in general? Or simply a filtering technique used for phase accuracy unrelated to physiological signals?
Any comments, code or suggestions are welcome,