Abstract: Described are systems, methods, and apparatus that utilize multiple sensors to conserve battery life of a device, limit potential disruption to a user, and reliably detect whether the device is worn by the user. In one example, a first sensor, such as an infrared sensor, may be activated to determine a proximity of the device to an object. If the device is within a proximity of the object, a second sensor, such as a photoplethysmography (PPG) sensor, may be activated to verify that the device is being worn by the user and then to continue collecting data that may be used to determine biometrics for the user.

Abstract: A method for clutter filtering staggered pulse repetition time data signals is provided. The method comprises the steps of receiving a plurality of staggered pulse repetition time data signals. The data signals may comprise one or more desired signals and one or more clutter signals. The method further comprises separating the staggered pulse repetition time data signals into a first separated data sequence and a second separated data sequence. The first and second separated data sequences comprise equally spaced data samples. The method also comprises the step of filtering the one or more clutter signals from the first and second separated data sequences.