US Patent 10931148 Waveform design for RF power transfer

A passive tag transponder circuit comprising a receive antenna, reflect antenna, and rectifier network. The receive antenna can be configured to receive an ambient RF signal having a frequency of fc, or, a backscattered RF signal having a frequency of 2fc. The reflect antenna can be configured to receive a rectified output signal from the rectifier network, the rectified output signal having a frequency of 2fc. The reflect antenna can be configured to send a backscattered signal at the frequency of 2fc. The rectifier network can be connected to receive an input corresponding to the ambient RF from the receive antenna and send the rectified output to the reflect antenna.