Signal processing apparatus

In a signal processor for processing at least first and second measured signals S.sub.1 and S.sub.2 each containing a primary signal portion s and a secondary signal portion n, said signals S.sub.1 and S.sub.2 being in accordance with the following relationship:

• S.sub.1 =s.sub.1 +n.sub.1
• S.sub.2 =s.sub.2 +n.sub.2
• where s.sub.1 and s.sub.2, and n.sub.1 and n.sub.2 are related by:
• s.sub.1 =r.sub.a s.sub.2 and n.sub.1 =r.sub.v n.sub.2
• and where r.sub.a and r.sub.v are coefficients,
• a method comprising the steps of:
• determining a value for the coefficient r.sub.a which minimizes correlation between s.sub.1 and n.sub.1 ;
• and
• processing at least one of the first and second signals using the determined value for r.sub.a to significantly reduce n from at least one of the first or second measured signal to form a clean signal.

A physiological monitor comprising:

• a first input configured to receive a first measured signal S.sub.1 having a primary portion, s.sub.1, and a secondary portion n.sub.1 ;
• a second input configured to received a second measured signal S.sub.2 having a primary portion s.sub.2 and a secondary portion n.sub.2, said first and said second measured signals S.sub.1 and S.sub.2 being in accordance with the following relationship:
• S.sub.1 =s.sub.1 +n.sub.1
• S.sub.2 =s.sub.2 +n.sub.2
• where s.sub.1 and s.sub.2, and n.sub.1 and n.sub.2 are related by:
• s.sub.1 =r.sub.a s.sub.2 and n.sub.1 =r.sub.v n.sub.2
• and where r.sub.a and r.sub.v are coefficients;
• a transform module responsive to said first and said second measured signals and responsive to a plurality of possible values for r.sub.a to provide at least one power curve as an output;
• an extremum calculation module responsive to said at least one power curve to select a value for r.sub.a which minimizes the correlation between s and n, and to calculate from said value for r.sub.a a corresponding saturation value as an output;
• and
• a display module responsive to the saturation value output of said extremum calculation module to display said saturation value.

In a signal processor for processing at least firs and second measured signals, each containing a primary signal portion and a secondary signal portion, said first and second signals substantially adhering to a predefined signal model, a method comprising the steps of:

• sampling said first and second signals over a period to obtain a first series of data points representing said first signal over said period and a second series of data points representing said second signal over said period;
• transforming said first series of data points into a first transformed series of points having at least a frequency component and a magnitude component and transforming said second series of data points into a second transformed series of points having at least a frequency component and a magnitude component;
• comparing said first and second transformed series of points to obtain a third series of comparison values having a magnitude component and at least a frequency component;
• selecting at least one of said comparison values that has a magnitude within a selected threshold;
• and
• from said selected at least one comparison value, determining a resulting value consistent with the predefined signal model.

In a signal processor for processing at least first and second measured signals, each containing a primary signal portion and a secondary signal portion, said first and second signals substantially adhering to a signal model for blood constituent saturation, a method comprising the steps of:

• sampling said first and second signals over a period to obtain a first series of data points representing said first signal over said period and a second series of data points representing said second signal over said period;
• transforming said first and second series of data points from time domain to frequency domain to obtain a first transformed series of points and a second transformed series of points, said first and second transformed series of points having a magnitude component and at least a frequency component;
• determining a series of ratios of magnitudes with respect to frequency of ones of said first transformed series of points to ones of said second transformed series of points;
• selecting at least one of the ratios from said series of ratios that has a magnitude within a selected threshold;
• and
• from said selected at least one of the ratios, determining a resulting value consistent with the signal model.