An electronic communications device includes a radio frequency (RF) transceiver, an RF antenna, a millimeter wave (mmW) antenna and a processor. The RF antenna has dielectric-object proximity-sensing capability. The processor is a) coupled to the RF antenna to receive capacitance variation signals from the RF antenna; b) coupled to the mmW antenna to receive distance to the object signals from the mmW antenna; and c) coupled to the RF transceiver to produce power reduction signals to the RF transceiver.