A method for modulating a signal including operating a circuit in a first arrangement during a first operating interval and switching the circuit between the first arrangement and a second arrangement during a first modulation interval to vary a load on the circuit to produce a first amplitude shift keying (ASK) signal. The method further includes detecting a voltage on the circuit crossing a threshold level and operating the circuit in the second arrangement during a second operating interval. The method also includes switching the circuit between the second arrangement and the first arrangement during a second modulation interval to vary the load on the circuit to produce a second ASK signal.