A method for adjusting an antenna resonance impedance network, having an impedance matching circuit comprising an adjustable impedance element, of a wireless charging receiver during a wireless charging operation, the wireless charging receiver for being inductively coupled to a wireless charging transmitter, the method comprising: measuring a first output voltage of a rectifier circuit having an input coupled to the output of the impedance matching circuit, and an output for providing a rectifier output voltage; determining if the first output voltage of the rectifier circuit is within an upper limit and a lower limit; if the first output voltage is not within the upper and lower limits: calculating a first error voltage as a difference between the first output voltage and a stored target rectifier voltage; changing the impedance of the adjustable impedance element by a first set amount; measuring a second output voltage of the rectifier circuit; calculating a second error voltage as a difference between the second output voltage and the target rectifier voltage; determining if the second error voltage is lower than the first error voltage; and if it is determined that the second error voltage is not lower than the first error voltage: changing the first set amount to a second set amount, wherein the second set amount has twice the magnitude and opposite sign of the first set amount; and changing the impedance of the adjustable impedance element by the second set amount. measuring a first output voltage of a rectifier circuit having an input coupled to the output of the impedance matching circuit, and an output for providing a rectifier output voltage; determining if the first output voltage of the rectifier circuit is within an upper limit and a lower limit; if the first output voltage is not within the upper and lower limits: calculating a first error voltage as a difference between the first output voltage and a stored target rectifier voltage; changing the impedance of the adjustable impedance element by a first set amount; measuring a second output voltage of the rectifier circuit; calculating a second error voltage as a difference between the second output voltage and the target rectifier voltage; determining if the second error voltage is lower than the first error voltage; and if it is determined that the second error voltage is not lower than the first error voltage: changing the first set amount to a second set amount, wherein the second set amount has twice the magnitude and opposite sign of the first set amount; and changing the impedance of the adjustable impedance element by the second set amount. calculating a first error voltage as a difference between the first output voltage and a stored target rectifier voltage; changing the impedance of the adjustable impedance element by a first set amount; measuring a second output voltage of the rectifier circuit; calculating a second error voltage as a difference between the second output voltage and the target rectifier voltage; determining if the second error voltage is lower than the first error voltage; and if it is determined that the second error voltage is not lower than the first error voltage: changing the first set amount to a second set amount, wherein the second set amount has twice the magnitude and opposite sign of the first set amount; and changing the impedance of the adjustable impedance element by the second set amount. changing the first set amount to a second set amount, wherein the second set amount has twice the magnitude and opposite sign of the first set amount; and changing the impedance of the adjustable impedance element by the second set amount. <EOS>