Simple automatic antenna tuning system and method

A method for determining the change in impedance of an antenna in a wireless communication device, comprising the steps of:

• separating an antenna signal into an in-band antenna signal and an out-of-band antenna impedance;
• generating an error signal related to the out-of-band antenna impedance;
• and
• applying the error signal to a controller circuit configurable to generate a signal representing the change in impedance of the antenna.

An electronic circuit for determining the change in impedance of an antenna in a wireless communication device, comprising:

• a filter operably connected to the antenna, wherein the filter comprises a diplexer that separates an antenna signal into an in-band antenna signal and an out-of-band antenna impedance;
• an oscillator operably connected to the filter, said oscillator capable of generating a frequency error signal related to the out-of-band antenna impedance;
• and
• a controller operably connected to the oscillator, said controller configurable to generate a signal related to the change in impedance of the antenna in proportion to the frequency error signal.

A wireless communication device comprising:

• an antenna;
• and
• an antenna tuning circuit, comprising:
• a selectively adjustable impedance disposed between an element of the antenna and a ground plane of the wireless communication device;
• a filter operably connected to the antenna, wherein the filter comprises a diplexer that separates an antenna signal into an in-band antenna signal and an out-of-band antenna impedance;
• an oscillator operably connected to the filter, said oscillator capable of generating a frequency error signal related to the out-of-band antenna impedance;
• and
• a controller operably connected to the oscillator, said controller configurable to generate an impedance error signal in proportion to the frequency error signal and to adjust the resonant frequency of the antenna to a desired resonant frequency by applying the impedance error signal to the selectively adjustable impedance.