Proximity sensor for portable wireless device
AssigneeSemtech Corporation
InventorsChaouki Rouaissia, Remi Le Reverend
Life of this patent
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Abstract
A proximity sensor for a portable wireless connected device, the sensor being arranged to determine whether a part of a user's body is near the portable connected wireless device. The sensor generates a time-averaged proximity that is alerted when the device is brought near a part of a user's body for a given time and may be periodically reset momentarily during the periods of proximity. An integration time comparable with that used in SAR testing, enables the sensor to reduce the radio power emitted by a portable device when it is near the body. The integration time can be obtained by a sigma/delta modulator configured as rate-compression unit.
Claims14
A proximity sensor for a portable wireless connected device, the sensor being arranged to determine whether a part of a user's body is near the portable connected wireless device, the sensor comprising at least one capacitive input electrode, a circuit configured to determine a capacitance of the at least one capacitive input electrode and generate, based on the capacitance, an immediate proximity status flag that becomes active when a part of a user's body is close to the proximity sensor, characterized by an averaging unit configured to generate a running average of the immediate proximity status flag in a predetermined time window, and by a decision unit generating a time-averaged proximity status flag based on an averaged or accumulated value of the immediate proximity status flag in the time window.
A method of reducing a dose of integrated SAR in a user of a wireless device comprising, in a temporal cycle:
- determine a capacitance of at least one capacitive input electrode;
- obtain an immediate proximity flag indicating whether the wireless portable device is momentarily near the user based on the capacitance;
- compute a running average value of the immediate proximity flag based on present and past values of the proximity flag and determine a time-averaged proximity flag based thereon;
- and
- reduce a power of a radio emission of the wireless device when the time-averaged proximity flag is asserted.
Dependencies are inferred from the claim text.