Inductive Power Transfer Uplink Using Rectifier Second-Order Nonlinearity

This work introduces two new uplink schemes for inductive wireless power transfer (IWPT) system with significant rejection on the Tx-to-Rx interference and noise. The second-order nonlinearity of the diode rectifier on the tag (target) is utilized to generate a new frequency component at the second-harmonic (SH) frequency of a continuous-wave (CW) Tx or at the second-order intermodulation (IM2) frequency of the a two-tone Tx. The two new frequencies are distant from the Tx fundamental frequency used for wireless powering, so the undesired Tx interference/noise at the Rx frequency can be filtered at the Tx output without compromising the wireless power transfer. The tag-to-reader uplink can be performed at the new Rx frequencies. PCB implementations for the SH and IM2 uplink are demonstrated with the signal-to-blocker ratio (SBR) largely improved compared to the conventional backscattering uplink. Although the Rx signal is weaker at the new uplink frequencies, the signal-to-noise ratio (SNR) of the SH uplink can out-perform the SNR of the backscattering uplink when a high-power Tx is required. The comparison between the SH, IM2, and the backscattering uplink is provided, in terms of SBR, SNR, and the power conversion efficiency.