Method for modulating the impedance of an antenna circuit

An electromagnetic transponder comprising:

• an antenna circuit configured to transmit and receive electromagnetic signals;
• a charge pump, wherein the antenna circuit is configured to provide signals to the charge pump, the charge pump comprising a first transistor with a first conduction path coupled between the antenna and a first capacitor;
• and
• a control circuit configured to cause the transponder to:
• transmit a first signal by performing a first retromodulation on a load formed in an electromagnetic field produced by a transmitting terminal, wherein performing the first retromodulation comprises applying a first voltage value to a gate of the first transistor, and
• transmit a second signal by performing a second retromodulation on the load formed in the electromagnetic field produced by the transmitting terminal, wherein performing the second retromodulation comprises applying a second voltage value to the gate of the first transistor, wherein the first transistor conducts a current when the first voltage value is applied to the gate and when the second voltage value is applied to the gate.

A method of receiving uninterrupted wireless power at an electromagnetic transponder that includes an antenna circuit, a load, and a charge pump transistor, the method comprising:

• supplying a first power level from the antenna circuit through the charge pump transistor to the load during a first time period;
• transmitting a first retromodulated signal during the first time period;
• supplying a second power level from the antenna circuit through the charge pump transistor to the load during a second time period;
• and
• transmitting a second retromodulated signal during the second time period, wherein the first and second power levels are operable to supply the load with uninterrupted power.