PPG Sensor Ambient Noise Cancellation via Time-Multiplexed Sampling

The patent replaces mechanical/optical blocking methods (physical shields, apertures) with an electronic signal processing approach. The system uses the photodetector to capture both the PPG signal and ambient light, then electronically separates these components through timing-based sampling and signal processing, eliminating the need for complex mechanical blocking structures.

The patent introduces an intermediary signal processing stage that acts as a mediator between the photodetector and the final measurement. This intermediary processing layer uses timing information and signal characteristics to separate the useful PPG signal from ambient light interference, allowing both signals to coexist in the same optical path without physical blocking.

The patent performs preliminary action by measuring ambient light levels during specific time intervals when the light source is known to be inactive. This timing-based approach allows the system to capture ambient light information before it interferes with the PPG measurement, enabling subsequent subtraction without causing receiver overload during the actual measurement phase.

The patent employs periodic action by using time-multiplexed sampling at specific intervals within each PPG cycle. The receiver alternates between capturing PPG signal portions and ambient light sample portions, creating a periodic measurement pattern that separates the two functions in time rather than requiring simultaneous measurement.

The patent uses periodic action by implementing time-multiplexed measurement where the single photodetector alternates between capturing PPG signal portions and ambient light sample portions at high frequency. This periodic sampling enables the system to maintain simple hardware while achieving accurate measurements through temporal separation of signal and noise capture.

The patent ensures continuity of useful action by maintaining continuous high-frequency sampling throughout the entire measurement period. Rather than intermittent or averaged sampling, the system continuously captures both PPG and ambient light information at high frequency, ensuring no useful signal information is lost and enabling precise real-time cancellation.

The patent applies preliminary action by measuring and characterizing ambient light levels before they interfere with the PPG signal. By capturing ambient light information during designated time intervals when the light source is inactive, the system prepares ambient cancellation data in advance, allowing clean subtraction without amplifying noise during the critical measurement phase.

The patent implements feedback by continuously monitoring and using the measured ambient light levels to adjust the signal processing parameters. The system uses the ambient light measurements to dynamically characterize and cancel ambient interference, creating a closed-loop system that adapts to varying ambient conditions and maintains optimal signal-to-noise ratio.