In one embodiment, a method for monitoring a structure includes associating a passive sensor with the structure, the sensor being configured to measure a physical parameter of the structure that is indicative of the structure\u27s condition, associating a dual-channel transceiver with the structure, the transceiver having a sensing repeater that operates on a first channel and a reference repeater that operates on a second channel, wherein the sensing repeater is connected to the passive sensor, receiving with a receive antenna of the reference repeater an interrogation signal transmitted from an interrogation device, multiplying a frequency of the received interrogation signal with the reference repeater to generate a reference response signal having a multiplied frequency, and transmitting the reference response signal with the reference repeater to the interrogation device