User presence detection systems for control of electronic devices

An electronic device comprising a liquid crystal display (LCD) screen, the electronic device comprising:

• at least one radio frequency (RF) antenna mounted behind a LCD panel of the LCD screen, wherein the at least one RF antenna comprises a directional transmit RF antenna configured to transmit an RF signal forward through the LCD panel to impinge on tissue of a human user, and the at least one RF antenna comprises a receive antenna configured to receive a reflected RF signal that comprises a reflection of the RF signal impinged on tissue of the human user;
• and
• at least one processor configured to process the reflected RF signal to generate a processed signal indicative of presence or absence of the human user, and, responsive to the processed signal, control an operating mode of the electronic device or enable control by the human user of the electronic device;
• wherein the electronic device comprises at least one of the following features (A) to (D):
• (A) the processing of the reflected RF signal comprises at least one of:
• (i) detection of gross motion of the human user as an indicator of presence of the human user, (ii) detection of respiration rate of the human user as an indicator of presence of the human user, and (iii) detection of a cardiac signal of the human user as an indicator of presence of the human user;
• (B) the at least one processor is configured to dynamically adjust sensitivity in the processing of the reflected RF signal to account for attenuation of the reflected RF signal attributable to transmission losses through the LCD panel and path loss to the human user;
• (C) the at least one processor is configured to control an operating mode of the electronic device by at least one of (1) initiating a low power consumption mode or shutdown responsive to the processed signal when the processed signal indicates absence of the human user, and (2) initiating a normal power consumption mode or activation of the electronic device responsive to the processed signal when the processed signal indicates presence of the human user;
• and
• (D) the processing of the reflected RF signal comprises identifying a cardiac signal signature of the human user, and comparing the identified cardiac signal signature to at least one previously stored cardiac signal signature to authenticate the human user, to generate the processed signal indicative of presence or absence of the human user.