System and method for measuring variable impedance elements in a wireless sensor

A wireless remote sensor for sensing a first external parameter and a second external parameter comprising:

• a receiver coil configured to receive power wirelessly from a wireless power transmitter;
• a communication circuit including a voltage controlled oscillator operatively coupled to said receiver coil to receive power from said receiver coil;
• a first variable impedance element coupled to said communication circuit including said voltage controlled oscillator, whereby output oscillations of said communication circuit including said voltage controlled oscillator are dependent on a value of said first variable impedance element, said first variable impedance element is configured to vary in response to changes in a value of a sensed first external parameter, wherein said first variable impedance element is capable of varying independently of power received wirelessly from the wireless power transmitter;
• a second variable impedance element coupled to said communication circuit including said voltage controlled oscillator, whereby said output oscillations of said communication circuit including said voltage controlled oscillator are dependent on a value of said second variable impedance element, said second variable impedance element is configured to vary in response to changes in a value of a sensed second external parameter, wherein said second variable impedance element is capable of varying independently of power received wirelessly from the wireless power transmitter;
• and
• wherein a duty cycle of said output oscillations varies based on variations in said second variable impedance element such that said duty cycle of said output oscillations is affected by variations in the value of the sensed second external parameter that are sensed by said second variable impedance element.

A wireless remote sensor system for sensing a first external parameter and a second external parameter comprising:

• an inductive transmitter with a transmitter coil;
• a wireless remote sensor having:
• a receiver coil configured to receive power wirelessly from a wireless power transmitter;
• a communication circuit including a voltage controlled oscillator operatively coupled to said receiver coil to receive power from said receiver coil;
• a first variable impedance element coupled to said communication circuit including said voltage controlled oscillator such that output oscillations of said communication circuit including said voltage controlled oscillator are dependent on a value of said first variable impedance element, said first variable impedance element is configured to vary in response to changes in a value of a sensed first external parameter, wherein said first variable impedance element is capable of varying independently of power received wirelessly from the wireless power transmitter;
• a second variable impedance element coupled to said communication circuit including said voltage controlled oscillator such that said output oscillations of said communication circuit including said voltage controlled oscillator are dependent on a value of said second variable impedance element, said second variable impedance element is configured to vary in response to changes in a value of a sensed second external parameter, wherein the second variable impedance element is capable of varying independently of power received wirelessly from the wireless power transmitter;
• wherein a duty cycle of said output oscillations varies based on variations in said first variable impedance element such that said duty cycle of said output oscillations is affected by variations in the value of the sensed first external parameter that are sensed by said first variable impedance element;
• and
• a signal receiver configured to wirelessly receive a signal generated from said output oscillations, said signal receiver being configured to determine variations in said first variable impedance element as a function of said signal generated from said output oscillations and variations in said second variable impedance element as a function of said signal generated from said output oscillations.