Passive tags, and systems and methods for using them

Markers, microwave probes, and related systems and methods are provided for localizing lesions within a patient's body, e.g., within a breast. The marker includes an energy converter e.g., one or more photodiodes, for transforming energy pulses striking the marker into electrical energy, a switch, e.g., FET, coupled to the photodiodes such that light from a probe cause the switch to open and close. A pair of antenna wires are coupled to the switch to provide an antenna, the switch configured to open and close when light strikes the photodiodes to modulate signals from the probe reflected by the antenna back to the probe to identify the location of the marker. The marker also includes an electro static discharge (ESD) protection device coupled to the switch to provide protection against an electrostatic discharge event.