A passive radio frequency identification (RFID) sensor includes at least one antenna. The least one antenna has an antenna impedance operable to vary within an environment in which the antenna is placed. The RFID sensor further includes a processing module coupled to the antenna comprising a tuning module coupled to the antenna. The tuning module is operable to vary a reactive component impedance coupled to the antenna in order to change a system impedance, the system impedance includes the antenna impedance and the reactive component's impedance, to produce an impedance value representative of the reactive component's impedance. The RFID sensor further includes a memory module operable to store the impedance value representative of the reactive component's impedance, and a wireless communication module coupled to the processing module, operable to communicate with an RFID reader and to exchange the impedance value representative of the reactive component's impedance with the RFID reader.