Portable electronic device having self-calibrating proximity sensors

A method of a portable electronic device for self-calibration of a proximity sensor, the method comprising:

• emitting a first source signal by the proximity sensor, the first source signal including a plurality of pulses;
• receiving a first return signal by the proximity sensor corresponding to the first source signal;
• determining whether the first return signal meets or exceeds a predetermined criterion based on timing of the plurality of pulses;
• determining a magnitude measurement of the first return signal based on signal strength of the plurality of pulses;
• adjusting a detection threshold of the proximity sensor based on the magnitude measurement in response to determining that the first return signal meets or exceeds the predetermined criterion;
• emitting a first source signal by the proximity sensor based on the adjusted detection threshold of the proximity sensor;
• and
• receiving a second return signal by the proximity sensor corresponding to the second source signal.