Patent ID: 7194292

Claim:
An apparatus for use in determining at least one physiological parameter relating to a patient from at least first and second signals transmitted to a patient tissue site and attenuated thereby, said apparatus comprising: a source system operative to generate the first and second signals and transmit the first and second signals to the patient tissue site; a detector system operative to receive first and second attenuated signals from the patient tissue site corresponding with the first and second signals transmitted to the patient tissue site and provide a composite detector signal based on the first and second attenuated signals; and a signal processing device including: a code generation module operative to drive the source system to multiplex the first and second signals in accordance with first and second frequency orthogonal code division multiplexed excitation waveforms; and a demodulation module operative to demultiplex the composite detector signal using at least one demultiplexing signal said at least one demultiplexing signal including a series of values corresponding with one of the first and second frequency orthogonal code division multiplexed waveforms to obtain demultiplexed information corresponding to each of the first and second attenuated signals, the demultiplexed information being usable in determining the physiological parameter regarding the patient; wherein the first frequency orthogonal code division multiplexed excitation waveform comprises a number of first pattern groups, each first pattern group comprising a plurality of randomly selected values wherein each randomly selected value in a first pattern group corresponds with one of a plurality of pulse patterns selected from a first set of pulse patterns, wherein the second frequency orthogonal code division multiplexed excitation waveform comprises a number of second pattern groups, each second pattern group comprising a plurality of randomly selected values wherein each randomly selected value in a second pattern group corresponds with one of a plurality of pulse patterns selected from a second set of pulse patterns, wherein each of the pulse patterns within the first set of pulse patterns and within the second set of pulse patterns is a digital code comprising a series of high and low values, and wherein the high values in each of the pulse patterns within the first set of pulse patterns do not overlap in time with the high values in each of the pulse patterns within the second set of pulse patterns.