A signal processor which acquires a first signal, including a first
primary signal portion and a first secondary signal portion, and a second
signal, including a second primary signal portion and a second secondary
signal portion, wherein the first and second primary signal portions are
correlated. The signals may be acquired by propagating energy through a
medium and measuring an attenuated signal after transmission or
reflection. Alternatively, the signals may be acquired by measuring
energy generated by the medium. A processor of the present invention
generates a primary or secondary reference signal which is a combination,
respectively, of only the primary or secondary signal portions. The
secondary reference signal is then used to remove the secondary portion
of each of the first and second measured signals via a correlation
canceler, such as an adaptive noise canceler, preferably of the joint
process estimator type. The primary reference signal is used to remove
the primary portion of each of the first and second measured signals via
a correlation canceler. The processor of the present invention may be
employed in conjunction with a correlation canceler in physiological
monitors wherein the known properties of energy attenuation through a
medium are used to determine physiological characteristics of the medium.
Many physiological conditions, such as the pulse, or blood pressure of a
patient or the concentration of a constituent in a medium, can be
determined from the primary or secondary portions of the signal after
other signal portion is removed.