Nellcor Puritan Bennett Incorporated

New Sd, Inc.

Michael W Nootbaar

Gerald R Newell

Charles E Porges

Michael J Bernstein

David B Swedlow

Pradeep Bhardwaj

James E Luecke

Robert S Potratz

Robert C Willson

A method and apparatus for conserving power in a medical diagnostic apparatus by using a sleep mode during a monitoring state. The sleep mode allows not only the processor to be put to sleep, but other detection circuitry as well. This is accomplished by not relying on detecting events to awaken the sleeping circuitry, but rather establishing the stability of a physiological parameter before going to sleep. The invention monitors a physiological parameter of the patient and enters a sleep mode only after it has been stable for a predetermined period of time. The apparatus is periodically awakened from the sleep mode to take additional measurements and to ascertain that the stability of the physiological parameter has not changed. In one embodiment, the sleep period is chosen to be consistent with the period in which an alarm condition would need to be generated if a patient's condition started to quickly change.

Medical diagnostic apparatus with sleep mode

A preferred oximeter detects the transillumination by red and infrared light of a portion of an in vivo subject and produces analog signals representative thereof on two channels. Sigma-delta modulators sample the analog signals on each channel. A digital filter processor digitally filters the sample signals from both modulators to produce respective digital signals with multi-bit resolution.

Pulse oximeter with sigma-delta converter

A method and apparatus for conserving power in a medical diagnostic apparatus by using a sleep mode during a monitoring state. The invention monitors physiological parameters of the patient and enters a sleep mode only after they have been stable for a predetermined period of time. The apparatus is periodically awakened from the sleep mode to take additional measurements and to ascertain that the stability of the physiological parameters has not changed.

Crystal oscillator and method which in one embodiment have a crystal element connected in a positive feedback loop with a charge amplifier and an integrator, with the gain of the loop being maintained at a level of unity. Compensation is provided to offset the effects of shunt capacitance in the crystal element, and precise phase control is maintained around the loop. In other embodiments, a crystal element is connected in a series feedback loop with a buffer amplifier, and operation is provided by maintaining the oscillation signal at level at which distortion, clipping, and saturation do not occur. Compensation for shunt capacitance across the crystal element is provided by applying a compensation signal which is equal in amplitude but opposite in phase to the signal passing through the shunt capacitance to the input terminal of the buffer amplifier to cancel the effect of the shunt capacitance. Compensation is also provided to cancel interfering crosstalk signals between oscillators in systems with more than one oscillator.

Crystal oscillator and method with amplitude and phase control

A differential capacitive pickoff detector circuit for measuring the difference in spacing of a pair of differential pickoff capacitor plates. Current sources are provided for each output terminal of each of the pair of differential capacitors so that for each capacitor output terminal a current signal alternates between a first current level and a second current level at a predetermined carrier clock switching rate. The capacitors are varied to provide DSB-LC voltage signals across each of the capacitors. The average value of each of the alternating voltages and their amplitudes are automatically adjusted to predetermined levels. The two DSB-LC voltage signals are combined to provide a DSB-SC signal. The DSB-SC signal is synchronously demodulated using a quadrature reference carrier clock signal to provide an output baseband signal which represents the difference between the spacing of the first and second differential capacitor plates.

Capacitive position detector

A series-feedback crystal oscillator has a crystal element in series with a buffer amplifier. The oscillator maintains a linear oscillation signal by using an amplitude control circuit to hold the oscillation signal to a certain level at which distortion, clipping, or saturation does not occur. A control signal indicative of the amplitude of the oscillation signal linearly multiplies the oscillation signal to control the amplitude of the oscillation signal. Shunt capacitance across the crystal is compensated for by connecting a compensating capacitor to the same input terminal of the buffer amplifier as is connected the crystal. A compensating signal, which is equal in amplitude but opposite in phase to the signal passing through the shunt capacitance of the crystal is fed to the input terminal of the buffer amplifier to cancel the effect of the shunt capacitance. A noninverted tracer signal is injected in the feedback loop and passes through the shunt capacitance. An inverted tracer signal passes through the compensating capacitor to cancel the noninverted tracer signal through the shunt capacitance and thereby compensate for the shunt capacitance of the crystal. Interfering crosstalk signals from one crystal oscillator circuit which are coupled into a second crystal oscillator circuit are reduced by feeding an oppositely phased interfering signal into the second crystal oscillator circuit.

Growing community of inventors

Benicia, CA, United States of America

Michael W Nootbaar