System and method for detecting the proximity of a body
A system and method for sensing the proximity of an electronic device, in particular, a radio frequency mobile communication device such as a mobile telephone, wireless modem equipped portable computer, or the like to a body employs an antenna capable of altering its impedance for changing the amount of radio frequency electromagnetic energy reflected by the antenna when the antenna is in proximity to the body. The radio frequency electromagnetic energy reflected by the antenna is measured and used for determining proximity of the antenna to the body.
1. A method for detecting the proximity of a body using an antenna capable of having its impedance altered for changing the amount of radio frequency electromagnetic energy provided to the antenna via an antenna feed and reflected onto the antenna feed when the antenna is in proximity to the body, the method comprising steps of:
sampling radio frequency electromagnetic energy reflected by the antenna within a predetermined frequency band;
measuring the sampled radio frequency electromagnetic energy;
determining proximity of the antenna to the body based on the amount of radio frequency electromagnetic energy measured,
wherein determining proximity of the antenna to the body comprises calculating a reflection coefficient from the radio frequency electromannetic energy reflected by the antenna, the determined reflection coefficient deviating from a predetermined reflection coefficient for the antenna in free space when the antenna is in proximity to the body.
2. The method as claimed in claim 1 , wherein measuring the sampled radio frequency electromagnetic energy comprises measuring the power of the radio frequency electromagnetic energy reflected by the antenna, the power of the radio frequency electromagnetic energy reflected by the antenna being decreased when the antenna is in proximity to the body.
3. The method as claimed in claim 1 , wherein the antenna is detuned when it is not in proximity to the body.
4. The method as claimed in claim 3 , wherein determining proximity of the antenna to the body further comprises comparing the calculated reflection with a threshold reflection coefficient, the antenna being in proximity to the body when the reflection coefficient is less than the threshold coefficient.
5. The method as claimed in claim 1 , wherein determining proximity of the antenna to the body further comprises comparing the reflection coefficient with a lower threshold reflection coefficient and an upper threshold reflection, the reflection coefficient being one of greater than the lower threshold reflection coefficient and less than the upper threshold reflection coefficient when the antenna is not in proximity to the body.
6. The method as claimed in claim 3 , wherein the antenna becomes tuned when in proximity to the body.
7. The method as claimed in claim 6 , wherein the system comprises a mobile telephone or a mobile palmtop computing device or a mobile laptop computer.
8. The method as claimed in claim 1 , further comprising controlling a function of a system when the antenna is determined to be in proximity to the body.
9. The method as claimed in claim 8 , wherein the step of controlling said function comprises reducing power, issuing a warning regarding an unsuitable power level, or lowering a ringer volume, or any combination thereof.
10. The method as claimed in claim 9 , wherein said step of controlling said function of the system is also based on a current traffic mode and/or a current power level needed for maintaining the wireless communication link of the system.