Abstract: A Wi-Fi wake-up receiver that receives wake-up signals encoded using orthogonal frequency division multiplexing based on-off keying (OFDM-OOK) modulation includes receiver circuitry having analog envelope detector circuitry configured to non-linearly down-convert an input signal and provide an energy signal for sampling by an analog-to-digital converter (ADC). A wake-up signal for waking up a main radio in a Wi-Fi device can be based on the digitized energy signal. The receiver circuitry can further include, upstream of the envelope detector circuitry and the ADC in the signal chain, an analog mixer for linearly down-converting the input signal and a low-pass filter for attenuating adjacent-channel interferer (ACI) signals prior to the non-linear down-conversion by the envelope detector circuitry. Sampling of the energy signal rather than the higher-bandwidth input signal yield power savings in the ADC and associated circuitry such as a modem.