Embodiments of a circuit are described. In this circuit, a receiver includes at least one input node that receives one or more signals from one or more antenna elements. Note that a given signal from a given antenna element may have an associated fixed bandwidth and/or may include directional information corresponding to a region in a space. Moreover, the receiver includes a measurement circuit, coupled to at least the one input node, that determines whether a metric of the given signal exceeds a corresponding threshold. Additionally, control logic in the circuit, which is coupled to the measurement circuit, instructs a communication circuit in the circuit to exit a first power-consumption mode if the metric of at least one of the signals exceeds the corresponding threshold.