Semtech Corporation
Proximity sensor and mobile wireless device

Abstract:

A capacitive proximity sensor for use in mobile devices such as smartphones and connected tables, in which it is used to switch off a display (70) when the device is brought to the ear, and to reduce selectively the RF power when the device is in close proximity to a body part of a user, in order to fulfil regulatory SAR limits. The capacitive sensor uses two electrodes (60, 30), the first of which may also serve as RF antenna, and the other is preferably on the back of the phone and is opposite the display.