The input power of a radio frequency identification tag is monitored. Based on the monitored input power, the input impedance of the tag is adjusted to enhance the tag backscatter energy. In one embodiment of the present invention, the output voltage of the rectifier is monitored. The input power of the tag is determined based on the monitored output voltage. The input impedance of the tag is adjusted based on the input power to enhance the backscatter energy of the tag.